CN109563603A - High yield stress steel - Google Patents

Abstract

This disclosure relates to high yield strength steels, wherein the yield strength can be increased without significantly affecting the ultimate tensile strength (UTS), and in some cases, a higher yield strength can be obtained without significantly reducing the ultimate tensile strength and total elongation.

Description

High yield stress steel

Cross reference to related applications

The U.S. Provisional Patent Application Serial No. 62/359,844 and 2017 year 4 submitted this application claims on July 8th, 2016 The equity for the U.S. Provisional Patent Application Serial No. 62/482,954 that the moon is submitted on the 7th is entirely incorporated into herein by reference.

Invention field

This disclosure relates to high yield stress steels.Due to unique tissue and mechanism, the limit can had no significant effect Yield strength and in some cases is improved in the case where tensile strength (UTS), it can be strong in no significant decrease ultimate elongation Higher yield strength is obtained in the case where degree and breaking elongation.These new steel can be strong for wherein desirable relatively high surrender The extensive application (such as passenger compartment of automobile) of degree and relatively high UTS and breaking elongation provides benefit.

Background

Third generation advanced high-strength steel (AHSS) is currently being deployed for mobile applications, and especially car body is answered With.By greater than 700MPa tensile strength with from 4% to 30% elongation percentage classify advanced high-strength steel (AHSS) steel simultaneously And it includes the type as martensite steel (MS), two-phase (DP) steel, transformation induced plasticity (TRIP) steel and complex phase (CP) steel. The example mesh of the 3rd generation AHSS is provided in the Banana Type chart (Fig. 1) by the car body steel published by World Auto Steel Mark.

Tensile property such as ultimate tensile strength (UTS) and breaking elongation are important base for establishing combination of properties It is quasi-.However, usually not by yield strength (YS) come AHSS material of classifying.The yield strength of material also has very automobile designers Big importance, once because part is on active service and if the part by stress is more than surrender, the part becomes permanent (plasticity) Shape.Material ratio with high-yield strength, which has, resists permanent deformation to more high stress water compared with those of low yield strength material It is flat.It is this to change making the structure made of the material be subjected to bigger load before the structure permanent bend and deformation The repellence of shape is useful.Thus material with higher yield strength can be such that automobile designers are thinned by specification to reduce Relevant pts wt maintains the identical repellence to the deformation in part simultaneously.The new appearance of many types of third generation AHSS The trade mark be subjected to low initial yield intensity, although with tensile strength and ductility various combinations.

Based on most of design standards, experience early stage surrenders and is subjected to permanent plastic deformation during normal service Automobile in component will be unacceptable.However, the lower yield strength in collision accident, especially when with Large strain Hardening coefficient can be beneficial when combining.In the front-end and back-end of the passenger compartment of commonly known as buffer area especially in this way 's.In these regions, caused by height originates ductility, the material of the relatively low yield strength with high ductility can lead to height It is deformed during the collision accident that horizontal energy absorbs and strain hardening is to improve intensity.

For other regions of automobile, low yield strength will be unacceptable.Particularly, this will include so-called Automobile passenger compartment.In passenger compartment, the material utilized must have high-yield strength because only allow it is very limited deformation/ It sinks down into passenger compartment.Once penetrating passenger compartment, this can lead to the injury or death of (one or more) occupant.Therefore, right The material for needing that there is high-yield strength in these regions.

The yield strength that many modes improve material can be used on an industrial scale.It can be a small amount of in referred to as smooth technique Ground (drafts < 2%) the cold rolling material.This technique introduces a small amount of plastic strain in the material, and corresponds to smooth The dependent variable that material is undergone during passage slightly improves the yield strength of material.Improve the another kind of yield strength in material Method is the crystal grain sizes by reducing material, is known as Hall-Petch reinforcing.Lesser crystallographic grain improves material Shear stress required for initial bit is mobile in material, and initial deformation has been postponed until higher application load.It can pass through The annealing operation of process modifications such as change is to limit the recrystallization occurred in annealing process after plastic deformation and growth work Grain growth during skill reduces crystallite dimension.The chemical composition modification of alloy is for example added present in solid solution and is closed The yield strength of material also can be improved in alloying element, however adds these alloy elements and must take place at when material is melting simultaneously And it can lead to the cost of raising.

It is possible route from the high-yield strength in the low yield strength version of AHSS exploitation passenger compartment.However, it is difficult to The equably strain hardening fabricated part in many metalworking operations.This means that although the Serious Cold machining area of part has Have much higher surrender, but still will be present compared with low yield strength region, it is then deformable and cause it is unacceptable under It is sink in passenger space.

It is the known route for improving yield strength and tensile strength from full annealing state cold work steel.It can be existed by cold rolling Across the uniformly applied cold working of sheet material to improve yield strength and tensile strength in process.However, this mode is led It causes the reduction of breaking elongation and is usually reduced to the level much smaller than 20%.As elongation percentage reduces, cold forming ability is also reduced, Reducing preparation has the ability of part of complex geometric shapes, and the availability of AHSS is caused to reduce.Usually require that there is minimum The high ductility of 30% breaking elongation is to form complex geometric shapes by cold punching technology.Although can be used such as rolling at The technique of type come from compared with low elongation material generate part, but the complex geometry of the part from these techniques by Limitation.Anisotropy can be also introduced into material by cold rolling, and ability of the material by cold forming at part will be further reduced.

It summarizes

The method for improving yield strength in metal alloy, comprising:

A. supplying metal alloy, the metal alloy is comprising at least 70 atom % iron and selected from Si, Mn, Cr, Ni, Cu or C At least four or more elements melt the alloy, with 10^-4K/s to 10³The rate of K/s is cooling and be solidified to > 5.0mm extremely The thickness of 500mm；

B. the alloy is processed into the first sheet-form, thickness is from 0.5 to 5.0mm, and wherein first sheet material has X₁ Breaking elongation, the Y of (%)₁(MPa) ultimate tensile strength and Z₁(MPa) yield strength；

C. the alloy is permanently deformed into the second sheet-form within the temperature range of 150 DEG C to 400 DEG C, this second Material form shows following tensile property combination one of A or B:

A. (1) breaking elongation X₂=X₁± 7.5%；

(2) ultimate tensile strength Y₂=Y₁±100MPa；With

(3) yield strength Z₂≥Z₁+100MPa。

B. (1) ultimate tensile strength Y₃=Y₁±100MPa；With

(2) yield strength Z₃≥Z₁+200MPa。

Optionally, the second sheet material exposure formed in the step of then can pointing out above tensile property combination A or B (c) Permanent deformation at a temperature of≤150 DEG C.

Therefore, the invention further relates to the methods for improving yield strength in metal alloy, comprising:

A. supplying metal alloy, the metal alloy is comprising at least 70 atom % iron and selected from Si, Mn, Cr, Ni, Cu or C At least four or more elements melt the alloy, with 10^-4K/ seconds to 10³K/ seconds rates are cooling and are solidified to > 5.0mm To the thickness of 500mm；

B. the alloy is processed into the first sheet-form, thickness is from 5.0 to 0.5mm；

C. the alloy is permanently deformed into the second sheet-form within the temperature range of 150 DEG C to 400 DEG C；

D. < 150 DEG C at a temperature of by alloy permanent deformation at the second sheet-form, second sheet-form performance Following tensile property combination out:

(1) breaking elongation=10.0 to 40.0%；

(2) ultimate tensile strength=1150 are to 2000MPa；

(3) yield strength=550 are to 1600MPa.

Metal alloy produced herein connects in vehicle, rolling stock, tank car/trailer, drill collar, drilling rod, casing, tool Special effectiveness is provided in head, well head, compressed gas storage tank or liquefied natural gas container.More particularly, the alloy is white in vehicle Application is found in vehicle body, vehicle frame, chassis or panel.

Brief Description Of Drawings

It is better understood with reference to the drawings described in detail below, provides the attached drawing for illustrative purpose and not by it It is regarded as limiting any aspect of the invention.

The World Auto Steel " Banana Type figure " of Fig. 1 the 3rd generation AHSS destination properties.

Fig. 2 generates the general introduction of the method 1 of high-yield strength in this paper alloy.

Fig. 3 generates the general introduction of the method 2 of high-yield strength and destination properties combination in this paper alloy.

Ultimate tensile strength of Fig. 4 before and after cold rolling in this paper alloy.

Stretch percentage elongation of Fig. 5 before and after cold rolling in this paper alloy.

Yield strength of Fig. 6 before and after cold rolling in this paper alloy.

Fig. 7 magnetic phase volume percentage in this paper alloy before and after cold rolling.

The tensile stress-strain curve of alloy 2 after the various drafts cold rollings of Fig. 8.

The back scattering SEM micrograph of microscopic structure in the torrid zone (hot band) of the Fig. 9 from alloy 2: a) low times magnification Number image；B) high-amplification-factor image.

The light field TEM microphoto of microscopic structure in the torrid zone of the Figure 10 from alloy 2: a) low magnification image；B) high Amplification factor image.

Figure 11 shows the TEM microphoto of nanoscale precipitate in the torrid zone from alloy 2.

The back scattering SEM micrograph of Figure 12 microscopic structure in the cold rolling sheet material of alloy 2: a) low magnification figure Picture；B) high-amplification-factor image.

The TEM microphoto of Figure 13 microscopic structure in the cold rolling sheet material of alloy 2: a) low magnification image；B) high Amplification factor image.

Figure 14 is shown in the TEM microphoto of the nanoscale precipitate found after cold deformation in 2 sheet material of alloy.

The engineering tensile load-deformation curve of alloy 2 after Figure 15 uses 20% drafts to roll at different temperatures.

The change of Figure 16 magnetic phase volume percentage (Fe%) in alloy 2 during extension test.

Engineering stress-strain curve of alloy 7 after Figure 17 uses 20% drafts to roll at different temperatures.

Engineering stress-strain curve of alloy 18 after Figure 18 uses 20% drafts to roll at different temperatures.

Engineering stress-strain curve of alloy 34 after Figure 19 uses 20% drafts to roll at different temperatures.

Engineering stress-strain curve of alloy 37 after Figure 20 uses 20% drafts to roll at different temperatures.

Figure 21 is rolled to representative engineering stress-strain curve of the alloy 2 of various roll reductions at 200 DEG C.

The surrender of Figure 22 alloy 2 and ultimate tensile strength with roll reduction at 200 DEG C variation.

The yield strength of Figure 23 alloy 2 and breaking elongation with roll reduction at 200 DEG C variation.

The influence to the phase transition for deforming induction in alloy 2 is rolled at 200 DEG C of Figure 24 with the variation of roll reduction.

The back scattering SEM micrograph of microscopic structure in the torrid zone of the Figure 25 from alloy 2: a) low magnification image；b) High-amplification-factor image.

Figure 26 is rolling to the back scattering SEM micrograph of microscopic structure in alloy 2 after 30% drafts at 200 DEG C: A) low magnification image；B) high-amplification-factor image.

Figure 27 is rolling to the back scattering SEM micrograph of microscopic structure in alloy 2 after 70% drafts at 200 DEG C: A) low magnification image；B) high-amplification-factor image.

Figure 28 is at 200 DEG C with the light field TEM microphoto of microscopic structure in alloy 2 after the rolling of 10% drafts: a) Low magnification image and b) high-amplification-factor image.

Figure 29 is at 200 DEG C with the light field TEM microphoto of microscopic structure in alloy 2 after the rolling of 30% drafts: a) Low magnification image and b) high-amplification-factor image.

Figure 30 is at 200 DEG C with the light field TEM microphoto of microscopic structure in alloy 2 after the rolling of 70% drafts: a) Low magnification image and b) high-amplification-factor image.

Engineering stress-strain curve that Figure 31 passes through the alloy 2 of the Combined machining of milling method.

Engineering stress-strain curve that Figure 32 passes through the alloy 7 of the Combined machining of milling method.

Engineering stress-strain curve that Figure 33 passes through the alloy 18 of the Combined machining of milling method.

Engineering stress-strain curve that Figure 34 passes through the alloy 34 of the Combined machining of milling method.

The engineering stress for 2 sheet material of alloy that Figure 35 is processed by distinct methods and their combination-strain curve comparison.

Figure 36 stretch percentage elongation and magnetic phase volume percentage in the post-tensioning sample specification of beta alloy 2 at different temperatures Than.

Figure 37 magnetic phase volume percentage with the roll reduction at room temperature and at 200 DEG C variation.

Figure 38 rolls engineering stress-strain curve example of the annealed sheet of the two preparation by cold rolling and at 200 DEG C.

Figure 39 the roll reduction limit and rolling temperature for alloy 2.

Detailed description

Fig. 2 represents the general introduction of preferred method 1, and this method, which passes through, to be caused as appointed in two kinds of conditions providing in condition 3a or 3b A kind of route is from low yield strength developing material high-yield strength.In the step 1 of method 1, initial conditions are to provide metal Alloy.This metal alloy is by least four or more comprising at least 70 atom % iron and selected from Si, Mn, Cr, Ni, Cu or C Kind element.Melted alloy chemical composition and preferably with 10^-4K/s to 10³The rate of K/s is cooling and be solidified to > 5.0mm extremely The thickness of 500mm.It is (including ingot casting casting, square billet casting, continuously casting, sheet billet casting, thick that various techniques can be used Slab casting, thin strip casting, belt casting etc.) complete casting process.Preferred method will be by sheet billet casting, slab The continuously casting in the form of a sheet of base casting and thin strip casting.Preferred alloy will in from 150 to 400 DEG C of temperature ranges At least 10 percents by volume are shown up to austenite (γ-Fe) score of 100 percents by volume and all increments therebetween.

In the step 2 of method 1, alloy is preferably processed into the sheet-form having from 0.5 to 5.0mm thickness.This Step 2 may include hot rolling or hot rolling and cold rolling.If hot rolling, preferred range will be in 700 DEG C and less than the alloy Tm at a temperature of.If using cold rolling, it should be understood that such temperature is at room temperature.Pay attention to hot rolling or hot rolling and cold rolling it Afterwards, additionally sheet material can be heat-treated, preferably from 650 DEG C at a temperature of to less than the alloy melting point (Tm) temperature In the range of.

Therefore the step of preparing sheet material from casting product may depend on specific manufacture route and specific target and change. As example, consider that heavy slab is cast into obtain a kind of process route of the sheet material with this target thickness.To preferably it lead to It crosses water cooling mold and alloy is cast into the thickness range that thickness is usually 150 to 300mm.Then cooling will preferably be prepared Casting spindle afterwards is used for hot rolling, may include some surface treatments to remove surface defect (including oxide).Spindle is then It will may include several passages by roughing mill hot roll, and generate central strip (transfer of the thickness usually from 15 to 100mm Bar) slab.This central strip then will be by continuous/concatenated hot finishing mill to prepare tropical coiled material, and thickness is usual For from 1.5 to 5.0mm.It is thinned if necessary to other specification, it can be in various drafts per pass, the road number of variation and difference Milling train (including tandem mill, Z- milling train and reversible mill) in complete cold rolling.The thickness of normally cold rolling will for 0.5 to 2.5mm thick.Preferably, material of the annealing through cold rolling in the temperature range from 650 DEG C to less than the alloy melting point (Tm) temperature Material is to restore in the ductility from cold-rolled process partly or completely total loss.

Another example will be that cast material is preferably processed by sheet billet casting technique.In this case, After the mold by being cooled down by water is usually formed 35 rolling to 150mm thickness, the slab newly formed passes directly to heat It rolls, without making slab directly rise to target temperature with the cooling of liaison tunnel furnace or application induction heating.Then directly in Duo Tai (multi-stand) hot rolling slab in finishing mill (its preferred amount is from 1 to 10).After hot rolling, by strip-rolling at tool Have with a thickness of from 1 to 5mm typical thickness tropical coiled material.If necessary to be further processed, then can be used and side like above Formula applies cold rolling.Notice that square billet casting will be similar to that above example but may be cast as the bigger thickness of the usually thickness from 200 to 500mm Degree, and first cogging (initial breaker) step is needed to reduce initial cast thickness to allow it to pass through hot rolling Roughing mill.

Although sheet material is from 0.5mm to 5.0mm once being formed from the founding materials in step 1 to the special process of step 2 Preferred scope in, then sheet material will show X₁Breaking elongation, the Y of (%)₁(MPa) ultimate tensile strength and Z₁(MPa) bend Take intensity.Preferred property for this alloy will be ultimate tensile strength value from 900 to 2050MPa, from 10 to 70% breaking elongation, and yield strength is within the scope of from 200 to 750MPa.

In the step 3 of method 1, permanent (i.e. plasticity) deforms the alloy within the temperature range of from 150 DEG C to 400 DEG C. Such permanent deformation can be provided by rolling and causing thickness to be thinned.This for example can be in the terminal stage of coil of strip material development Middle completion.The raising temperature rolling now preferably completed in 150 to 400 DEG C of target temperature range, rather than at room temperature The sheet material of beginning carries out traditional cold rolling and is thinned for final specification.A kind of method will heat sheet material before through cold-rolling mill To target temperature range.Can by various methods (including by tunnel milling train, pharoid, resistance heater or induction plus Hot device) heat the sheet material.Another method will directly heat thinned roll.Third example for explanation will be low temperature batch Then annealed sheet is simultaneously sent to (or multiple) cold-rolling mill in target temperature range.Alternatively, it may be used at There is provided the various techniques of permanent deformation during manufacture part by various methods, (including rolling and forming, metal stamping, metal are led Drawing, hydro-forming etc.) in raised temperature range sheet material is deformed into part.

Although the special process for making alloy be permanently deformed within the temperature range of 150 to 400 DEG C, can form two different Condition is shown in Fig. 2 with condition 3a and condition 3b.In condition 3a, the institute of comparison in step 2 and after step 3 Alloy is stated, breaking elongation and ultimate tensile strength are relatively unaffected but yield strength improves.Particularly, breaking elongation X₂Deng In X₁± 7.5%, tensile strength Y₂Equal to Y₁± 100MPa and yield strength Z₂≥Z₁+100MPa。

Preferred property will be ultimate tensile strength value (Y for alloy this in condition 3a₂) from 800 to 2150MPa, Stretch percentage elongation (X₂) from 2.5% to 77.5% and yield strength (Z₂)

≥300MPa.It is highly preferred that yield strength can be fallen into the range of 300 to 1000MPa.

In condition 3b, the comparison alloy in step 2 and after step 3, ultimate tensile strength relatively not by Still yield strength is influenced to improve.Particularly, ultimate tensile strength Y₃Equal to Y₁± 100MPa and yield strength Z₂≥Z₁+ 200MPa.Preferred property will be ultimate tensile strength value (Y for alloy this in condition 3b₃) from 800 to 2150MPa, With yield strength (Z₃)≥400MPa.It is highly preferred that yield strength can be fallen into the range of 400 to 1200MPa.In addition, with item Part 3a is different, and breaking elongation decline is greater than 7.5%, i.e., breaking elongation (X in stepb₃) be limited to it is following: X₃<X₁- 7.5%.

As will be by the way that shown in various case embodiments, using normal deformation, metallic alloy be hard by strain hardening/processing Change.This for example passes through σ=K ε between stress (σ) and strain (ε)ⁿStrain hardening exponent (n) in relationship is shown.Its result It is when material permanent deformation, basic material property changes.Compare primary condition and final condition display is typical and expected Behavior, wherein yield strength and tensile strength improve and total ductility accordingly reduces.Specific case embodiment is provided to illustrate Then this effect simultaneously compares this effect with the new material behavior mentioned in this disclosure.

Fig. 3 confirms the general introduction of the method 2 of present disclosure.3 steps of foremost are identical as method 1 in method 2, step Rapid 4 be additional step for method 2.Step 4 can be applied as shown to the alloy for being in condition 3a or condition 3b herein.

Presenting as before, in the description of fig. 2, various property (i.e. breaking elongations, pole are provided to every kind of condition 3a or 3b Limit tensile strength and yield strength) combination.As will be further illustrated in detailed description and subsequent case embodiment, it is in The alloy of condition 3a or 3b can also be characterized by their specific organization.This then also allow by using from environment to≤ The further optional step at a temperature of 150 DEG C or more preferably making alloy be permanently deformed in 0 DEG C to 150 DEG C of temperature range To customize final properties.This can for example be completed by adding another step in coil of strip material preparation process such as illustrated in fig. 3. Step 4 (can also be used in surface quality improvement for the skin rolling of from 0.5 to 2.0% drafts sometimes in this case Or smooth knobble passage) or from > 2% to 50% compared with heavy reduction with develop special properties combination.It can be such as Alternate mode is carried out in the sheet material manufacture part by processing by method 1.In the optional step 4 of method 2, it can be used Sheet material is subsequently formed into part by various modifications method (including rolling and forming, metal stamping, metal drawing, hydro-forming etc.).Though Step 4 in right exact method Activiation method 2 can develop final properties with the alloy, it is expected that showing to have from 10 To 40% stretch percentage elongation, from 1150 to 2000MPa ultimate tensile strength and from 550 to 1600MPa yield strength property.

Alloy

Cause the tissue of the new technology route for developing high-yield strength and mechanism to depend in table 1 in the application to be mentioned For the following chemical composition of alloy.

Table 1

The chemical composition (atom %) of alloy

Such as can as seen from Table 1, this paper alloy is the metal alloy based on iron, has the Fe greater than 70 atom %.In addition, can Understand this paper alloy be it is such, they include Fe and at least four or more selected from Si, Mn, Cr, Ni, Cu or C or five Kind or more or six kinds of elements.Accordingly, with respect to four kinds or more or five kinds selected from Si, Mn, Cr, Ni, Cu or C or more The presence of multiple element, such element exist in atomic percent noted below: Si (0 to 6.13 atom %), Mn (0 To 15.17 atom %), Cr (0 to 8.64 atom %), Ni (0 to 9.94 atom %), Cu (0 to 1.86 atom %) and C (0 to 3.68 atom %).Most preferably, this paper alloy is such, they include with the Fe and Si of 70 atom % or bigger levels, Mn, Cr, Ni, Cu and C are substantially made of the Fe and Si, Mn, Cr, Ni, Cu and C of 70 atom % or bigger levels, or by 70 The Fe and Si, Mn, Cr, Ni, Cu and C of atom % or bigger level are formed, wherein the impurity level of every other element is from 0 To 5000ppm.

Laboratory slab casting

According to the atomic ratio in table 1, the commercially available iron additive with known chemical composition is used (ferroadditive) it is 3400 grams of chargings that powder and basic steel raw material, which weigh alloy,.As mentioned above, depending on being used Raw material, impurity can exist at various levels.Impurity element will typically include following element: Al, Co, Mo, N, Nb, P, Ti, V, W and S will be preferred with 0 to 500ppm from 0 to 5000ppm in (parts per million) range if there is impurity element In range.

The silica for the coated with zirconia being placed in Indutherm VTC800V vacuum overturning casting machine will be fitted into In crucible.Then before casting machine will cast chamber and melt chamber evacuate and with argon be perfused to atmospheric pressure twice to prevent The only oxidation of melt.Melt is using the heating of 14kHz RF induction coil until melting completely, about from 5 to 7 minutes, depends on Composition of alloy and charging quality.Make its heating and continuous 30 to 45 second additionally to provide after the solid melts of observation to the end It overheats and ensures melt uniformity.Then chamber is evacuated and is overturn crucible and pours into melt in the cooling copper mould of water by casting machine 50mm it is thick, 75 to 80mm wide and the deep channel 125mm in, and the step 1 in Fig. 2 and 3 will be represented.The process can be made to adapt to Yu Cong > 5.0 to 500mm range preferred as-cast condition thickness.Make melt true before with argon filled chamber to atmospheric pressure Sky is lower 200 seconds cooling.

Laboratory hot rolling

It is preferred that this paper alloy is processed into lab sheet.The processing of research and development laboratory alloy is to simulate from passing through continuously casting The torrid zone of the slab of preparation prepares and will represent the step 2 in Fig. 2 and 3.By heating slab in continuous tunnel furnace to target temperature Degree, then from 700 DEG C until slab is made to pass through reversible mill or how desk-top in the preferred range of alloy melting point (Tm) Any or both the combination of milling train carries out industrial hot rolling to reach goal standard.Caused by heat loss to air and work roll On any rolling mill type in the operation of rolling slab temperature steady decrease, so the final torrid zone is at a temperature of much reduced.This In the lab by being heated between 1100 DEG C and 1250 DEG C then hot rolling in continuous tunnel furnace to simulate.Laboratory milling train ratio Industrial rolling mills are slow, and bigger heat loss is caused in each hot rolling pass, so reheating slab between passage 4 minutes to reduce The reduction of temperature, the final temperature when leaving laboratory milling train at goal standard is typically in DEG C range from 1000 DEG C to 800 It is interior, depend on furnace temperature and final thickness.

Before hot rolling, laboratory slab is preheated in Lucifer EHS3GT-B18 heating furnace.Depending on alloy Point in fusing point and hot rolling technology, furnace set point change between 1100 DEG C to 1250 DEG C, wherein initial temperature is set higher It is larger thinned to promote, and subsequent temperature is set lower so that the surface oxidation on the torrid zone is minimum.Make plate before hot rolling Base homogeneous heat treatment 40 minutes with ensure they reach target temperature and then from continuous tunnel furnace be pushed out to Fenn Model061 2 from In dynamic milling train (high rolling mill).Make to pass through milling train for 5 to 10 roads of 50mm casting hot rolling before its air is cooling It is secondary.Final thickness range is preferably from 1.8mm to 4.0mm after hot rolling, can be changed per pass the range of drafts from 20% to 50%.

After hot rolling, slab thickness has been thinned to the tropical final thickness from 1.8mm to 2.3mm.Change can be passed through Hot rolling amount and/or addition cold rolling step are come the preferred thickness range that adjusts processing conditions to prepare from 0.5 to 5.0mm.Use line EDM cuts tensile sample from the laboratory torrid zone.Utilize Instron's in Instron mechanical test frames (model 3369) Bluehill control and analysis software measure tensile property.The tensile property of alloy under hot-rolled condition, the conjunction are listed in table 2 Gold has been machined to the thickness from 1.8 to 2.3mm.

Ultimate tensile strength value can change from 913 to 2000MPa, and stretch percentage elongation from 13.8 to 68.5% changes.It bends Intensity is taken within the scope of from 250 to 711MPa.From this paper steel alloy the torrid zone engineering properties depend on alloy composition, Processing conditions and the material mechanical of processing conditions is responded.

Table 2

The tensile property of alloy under hot-rolled condition

Case embodiment

Compare normal response of the case embodiment #1 to rolling under environment temperature

For comparative purposes, the torrid zone of this paper alloy listed in table 1 is cold-rolled to 1.2mm by multiple cold rolling passes Final goal gauge thickness.Tensile sample is cut from each cold rolling sheet material using line EDM.In Instron mechanical test frames Tensile property is measured using the Bluehill control of Instron and analysis software in (model 3369).All tests are in environment temperature It is run in degree bottom offset control.

The tensile property of this paper alloy is listed in Table 3 below after cold rolling.As can be seen, yield strength is significant in tropical range It improves, maximum value is 711MPa (table 2).Yield strength changes from 1037 to 2000MPa after cold rolling.The limit is drawn after cold rolling Intensity value is stretched within the scope of from 1431 to 2222MPa.However, having recorded stretching for each this paper alloy after cold rolling The decline of elongation percentage, variation from 4.2 to 31.1%.Illustrate cold rolling to the tensile property of this paper alloy in fig. 4 to fig. 6 The general trend of influence.

Table 3

The tensile property of alloy under final specification after cold rolling

Phase is measured by Feritscope for each this paper alloy being listed in Table 4 below in the torrid zone and after cold rolling To magnetic phase content and it is illustrated in Figure 7 selected alloy.In the torrid zone 0.1 to 56.4Fe% magnetic phase volume percentage improve to Range after cold rolling from 1.6 to 84.9Fe%, it is thus identified that the phase transition in deformation process.

Table 4

Magnetic phase volume percentage (Fe%) after the cold rolling in alloy

This control case embodiment shows that the surrender in this paper alloy can be improved by cold rolling (i.e. at ambient temperature) Intensity.Ultimate tensile strength also improves but cold rolling leads to the significant of the alloy ductility as pointed by the decline of stretch percentage elongation It reduces, in some applications can be limiting factor.Strengthen as shown in the raising by ultimate tensile strength and is related to as passed through The austenite of the measurement description of magnetic phase volume percentage before and after cold rolling is to ferritic phase transition.

Compare case embodiment #2: influence of the cold roling reduction to yield strength in alloy 2

Alloy 2 is processed into the torrid zone with 4.4mm thickness.Then (existed with different drafts by multiple cold rolling Under environment temperature) the passage cold rolling torrid zone.After cold rolling, with intermediate annealing heat treated sample 10 minutes at 850 DEG C.This is represented For the initial conditions of every kind of alloy, the full annealing condition for removing first cold working is represented.From this initial conditions, apply Add as provided in table 5 under different weight percentage (i.e. 0%, 4.4%, 9.0%, 15.1%, 20.1%, 25.1% and 29.7%) Subsequent cold rolling make the final specification for extension test will be for the target constant thickness of 1.2mm.With the cold rolling of raising Lower amount shows that the correspondence of material yield strength mentions by the tensile stress-strain curve in Fig. 8 as the final step after annealing It is high.The tensile property for carrying out self-test is listed in Table 5 below.The yield strength of alloy 2 is improved to from 666 to 1140MPa range, is depended on In thinned horizontal (table 5) compared with the initial value under annealed condition.Equally, as shown in table 5 and in an annealed state The initial value of 1.0Fe% is compared, and is improved by the magnetic phase volume percentage of Feritscope measurement until 12.9Fe%.It should be noted that bending Taking intensity raising is to be reduced to cost with stretch percentage elongation after cold rolling with alloy ductility to realize.

Table 5

Tensile property and magnetic phase volume percentage in alloy 2 after the cold rolling

This control case embodiment #2 shows to change by cold roling reduction the yield strength of this paper alloy to realize Relatively high yield strength value, and tensile strength improves but ductility reduction.Apply higher cold roling reduction, then realizes more Simultaneously lower stretch percentage elongation is recorded in high yield strength.

Compare structural transformation of the case embodiment #3 in tropical process of the cold rolling from alloy 2

By multiple cold rolling passes at 850 DEG C intermediate annealing 10 minutes by the heat from alloy 2 with 4mm thickness Band is cold-rolled to the final thickness of 1.2mm.Pass through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) the research torrid zone With the microscopic structure of cold rolling sheet material.

It in order to prepare SEM sample, is cut and workpiece and is embedded in epoxy resin by EDM, and with 9 μm, 6 μm and 1 μm diamonds Suspended matter solution is simultaneously finally polished with 0.02 μm of silica step by step.In order to prepare TEM sample, with EDM from sheet material cutting sample, And then by every time with the pad grinding of reduced size to be thinned.By outstanding with 9 μm, 3 μm and 1 μm diamonds respectively Floating object solution polishes to complete further to be thinned to 60 to 70 μ m-thicks.Diameter is gone out from foil and is the disk of 3mm, and is used Last polishing is executed using the electrobrightening of double spray polishing instrument.Used chemical solution is blended in methanol-based bottom 30% nitric acid.In the case where insufficient thin region for tem observation, the accurate ion polishing system of Gatan can be used (PIPS) ion beam milling TEM sample.Ion beam milling is usually completed at 4.5keV, and inclination angle is reduced to 2 ° from 4 ° to open Thin region.TEM is completed using the JEOL2100 high resolution microscope to work at 200kV to study.

The sem analysis of torrid zone tissue discloses the relatively large austenite grain (Fig. 9) with straight boundary.Light field TEM image Display torrid zone tissue is straight and sharp (Figure 10) containing considerably less dislocation and crystal boundary, is typical for recrystallized structure 's.TEM research is additionally shown in microscopic structure that there are nano-scaled precipitate (Figure 11).

When the torrid zone is subjected to cold rolling, under stress in the selected region of the torrid zone tissue austenite phase transition to refining iron Ferritic phase.The presence (Figure 12) of the tissue and deformation twins of back-scattered SEM image display transformation and the refinement of cold rolling sheet material.Such as figure TEM image is shown in 13, high dislocation density is generated in retained austenite crystal grain, and formed with 200 to 300nm size Fining ferrite grains.Also deformation twins are observed in retained austenite crystal grain.It is also observed in cold-rolled process as phase (Figure 14) is precipitated in the other nanometer of transition process a part.

This case embodiment shows to pass through in cold-rolled process from the Microstructures Evolvement of initial tropical austenite structure By phase transition at caused by the ferrite being precipitated with nanometer crystal grain refinement and dislocation density improves and deformation twins are to leading It causes alloy strengthening (raising of ultimate tensile strength).

Influence of the case embodiment #4 rolling temperature to the yield strength of alloy 2

Starting material is the torrid zone from alloy 2 with about 2.5mm thickness, passes through the laboratory of hot rolling 50mm thickness Block preparation, to imitate the processing in the preparation of the business torrid zone.Average ultimate tensile of the starting material with 1166MPa is strong Degree, 53.0% average tensile elongation percentage and the average yield strength of 304MPa.Starting material also has the magnetic phase body of 0.9Fe% Product percentage.

The media grit blast torrid zone is to remove oxide and put into Yamato DKN810 mechanical convection baking oven before rolling Continue at least 30 minutes so that plate reaches temperature.It is rolled on 061 milling train of Fenn Model in the roller gap with steady decrease Heat band, and between passage will the torrid zone put into furnace in continue at least 10 minutes with ensure in order to 20% overall reduction of target for Constant initial temperature (i.e. 50,100,150,200,250 DEG C, 300 DEG C, 350 DEG C and 400 for each subsequent rolling pass ℃).According to ASTM E8 standard geometrical shapes, EDM cutting sample.It is utilized in Instron mechanical test frames (model 5984) The Bluehill of Instron is controlled and analysis software measures tensile property.All extension tests Bit andits control at ambient temperature Middle operation, wherein bottom jig is kept fixed and top clamp is mobile；Pressure sensor is attached to top clamp.

Confirmation at a temperature of rolling after the tensile property of alloy 2 be listed in Table 6 below.Depending on rolling temperature, with the torrid zone In 250 to 711MPa value compare (table 2), yield strength improves to the range from 589 to 945MPa.The ultimate elongation of alloy 2 Intensity changes from 1132 to 1485MPa and stretch percentage elongation from 21.2 to 60.5% changes.Example load-deformation curve is shown in figure In 15.As can be seen, the at a temperature of torrid zone of the rolling from alloy 2 at 200 DEG C shows to surrender with the consistent raising of step 3a in Fig. 3 Intensity and a possibility that ductility and ultimate strength minimum change.

Magnetic phase volume percentage (Fe%) is measured after rolling, is reported in table 7 away from fracture in stretching specification At least 10mm.As can be seen, with magnetic phase volume percentage (18.0Fe%, table 4) phase after cold rolling alloy 2 at ambient temperature Than, 100 DEG C or more at a temperature of rolling after magnetic phase volume percentage it is significantly lower, from 0.3 to 9.7Fe% range It is interior.At a temperature of rolling and extension test after measure in alloy 2 magnetic phase volume percentage significantly improve (table 7, figure 16).After extension test, depend on rolling temperature, sample stretch specification in magnetic phase volume percentage from 25.2 to 52.1Fe% variation.

Table 6

At different temperatures~20% after roll reduction alloy 2 tensile property

Table 7

Magnetic phase volume percentage (Fe%) is with rolling temperature before and after the extension test of alloy 2

Variation

This case embodiment shows thus reduce austenite to ferritic phase by rolling at elevated temperatures Transformation is to improve the yield strength in this paper alloy.Being remarkably decreased for Fe% occurs when rolling temperature is greater than 100 DEG C.In addition, The torrid zone from this paper alloy is rolled at a temperature of 150 DEG C to 400 DEG C shows that (i.e. change is limited not significantly changing ductility System is in positive or negative 7 percent points five (± 7.5% stretch percentage elongations)) and maintain ultimate tensile strength in about the same level The ability that yield strength is improved in the case where (± 100MPa i.e. comparing with intial value) (such as improves yield strength to more than initial It is worth at least 100MPa or bigger value).

Influence of the case embodiment #5 rolling temperature to the yield strength of alloy 7, alloy 18, alloy 34 and alloy 37

Starting material is that have about 2.5mm original depth from every kind in alloy 7, alloy 18, alloy 34 and alloy 37 The torrid zone, by the preparation of the laboratory coin slab of hot rolling 50mm thickness, to imitate commercial processing.By at 1100 DEG C and At a temperature of between 1250 DEG C hot rolling and then media grit blast to remove oxide to which alloy 7,18,34 and 37 is processed into tool There is the torrid zone of about 2.5mm thickness.It is listed in Table 2 below before the tensile property of tropical material.The media grit blast torrid zone is to go deoxygenation Continue at least 30 minutes so that plate reaches expectation in compound and before rolling threading Yamato DKN810 mechanical convection baking oven Temperature.It is clean the torrid zone caused by rolling on 061 milling train of Fenn Model in the roller gap with steady decrease, And the torrid zone is put into furnace between passage and continues at least 10 minutes to ensure stationary temperature.By hot strip rolling to 20% target Drafts and carry out EDM cutting sample according to ASTM E8 standard geometrical shapes.In Instron mechanical test frames (model 5984) tensile property is measured using the Bluehill control of Instron and analysis software on.All extension tests are in environment temperature It is run in bottom offset control, wherein bottom jig is kept fixed and top clamp is mobile；Pressure sensor is attached to top folder Tool.

The response of every kind of alloy, especially their elongation percentage, surrender are monitored on the entire scope of investigated temperature by force Degree and ultimate tensile strength.Every kind of alloy is tested after rolling under from minimum 100 DEG C to 400 DEG C of temperature ranges of highest.For For alloy 7, the range of stretch percentage elongation is from 14.7% to 35.5% in the temperature range investigated, ultimate tensile strength Range be from 1218MPa to 1601MPa, and the range of yield strength is and the Fe% number from 557MPa to 678MPa (table 8) Range is from 29.9 to 41.7 before extension test, and is 57.7 to 65.4 (tables 9) after testing.For alloy 18 Speech, from 150 to 400 DEG C, the range of stretch percentage elongation is from 43.0% to 51.9%, the range of ultimate tensile strength be from 1083MPa to 1263MPa, and the range of yield strength is from 772MPa to 924MPa (table 10), and in 150 to 400 DEG C of models Enclosing interior Fe% number range before extension test is from 6.8 to 12.3, and is 31.5 to 39.6 (tables 11) after testing.For For alloy 34, within the scope of 150 to 400 DEG C, the range of stretch percentage elongation is from 21.1% to 31.1%, ultimate tensile strength Range be from 1080MPa to 1140MPa, and the range of yield strength is and the Fe% from 869MPa to 966MPa (table 12) Number range before extension test is from 0.4 to 1.0, and is 0.8 to 2.1 (table 13) after testing.For alloy 37, Within the scope of 150 to 400 DEG C, the range of stretch percentage elongation is from 1.5% to 9.0%, the range of ultimate tensile strength be from 1537MPa to 1750MPa, and the range of yield strength is from 1384MPa to 1708MPa (table 14), and and Fe% number is stretching Range is from 74.5 to 84.3 before test, and is 71.1 to 85.6 (tables 15) after testing.

Table 8

At different temperatures~20% after roll reduction alloy 7 tensile property

Table 9

Fe% before and after alloy 7 tested under different temperatures

Table 10

At different temperatures~20% after roll reduction alloy 18 tensile property

Table 11

Fe% before and after alloy 18 tested under different temperatures

Table 12

At different temperatures~20% after roll reduction alloy 34 tensile property

Table 13

Fe% before and after alloy 34 tested under different temperatures

Table 14

At different temperatures~20% after roll reduction alloy 37 tensile property

Table 15

Fe% before and after alloy 37 tested under different temperatures

The representative curve of every kind of this paper alloy is shown in Figure 17 to Figure 20, wherein from testing the torrid zone and being cold-rolled to phase Reference curve after about 20% same drafts for comparing in parallel.

This case embodiment shows that the yield strength in this paper alloy can be improved, although when at 100 DEG C or it is bigger until Austenite to ferritic phase transition reduces when rolling at a temperature of 400 DEG C.Both step 3a and 3b in Fig. 2 is provided The example changed in terms of yield strength, ultimate tensile strength and stretch percentage elongation.

Influence of the drafts that case embodiment #6 is rolled at 200 DEG C to the yield strength of alloy 2

Alloy 2 is processed into the torrid zone with about 2.5mm thickness by laboratory casting.After hot rolling, rolled at 200 DEG C Alloyage 2 is to range in the variation roll reduction from about 10% to 40%.Between rolling pass, by 2 sheet material material of alloy Expect to continue 10 minutes in the convection furnace being placed at 200 DEG C to maintain temperature.When realizing desired roll reduction, pass through line EDM cutting ASTM E8 stretches sample and tests.

Table is listed in using the tensile property of alloy 2 after the rolling of different roll reductions (0.0 to 70.0%) at 200 DEG C 16, it further include the data before any rolling experiment.Figure 21 is shown with the alloy that roll reduction changes at 200 DEG C 2 representative stress strain curve.Observe the drafts with raising, the yield strength of material improves rapidly, and until 30% pressure Lower amount does not change ultimate tensile strength (change of i.e. positive or negative 100MPa).Figure 22 is provided with the rolling pressure at 200 DEG C The comparison of the yield strength of variation and the trend of ultimate tensile strength is measured, although display yield strength raising is relatively rapid, All change with step 3a property in Fig. 2 consistent and rolled 39.0% until 30.4% roll reduction ultimate tensile strength changes Change unanimously at drafts processed with step 3b property.

The breaking elongation of alloy 2 is drawn in Figure 23 with the variation of roll reduction at 200 DEG C.Although it shows 200 As the yield strength of additional drafts alloy 2 improves in the operation of rolling at DEG C, but prolong up to > 30% drafts is available Malleability does not reduce rapidly.Notice that this is using laboratory rolling simulation, and (including tandem mill rolls business milling method System, Z- mill milling and reversible mill rolling) it will extraly apply strap tension during the rolling process, so exact be thinned The changeable thus ductility reduction of amount is changeable.

To after being rolled at 200 DEG C and stretching in specification after the extension test (be present in tensile sample again Thinned specification part) sample using Fischer Feritscope FMP30 measurement magnetic phase volume percentage (Fe%).Show What these measurement results in table 17 showed to occur in alloy in rolling process and during subsequent extension test Deformation induces the amount of phase transition.The amount that deformation induces phase transition in alloy 2 after rolling and extension test is shown in Figure 24.It can be seen that Deformation induces phase transition and is largely suppressed at 200 DEG C, and only slightly with the roll reduction magnetic phase volume percentage of raising Micro- raising.Show that deformation during rolling at 200 DEG C also to extension test induces phase transition and has an impact, wherein that improves rolls Drafts processed inhibits the transformation amount in material.

Table 16

The average tensile property of alloy 2 after various drafts is rolling at 200 DEG C

* it is applied with different processing: alloy 2 being processed into the torrid zone with about 9.3mm thickness at 1250 DEG C, then Media grit blast is to remove oxide and then be rolling at 200 DEG C 4.6mm (~50% drafts).Then it is moved back at 850 DEG C Fiery material continues 10 minutes and is rolling to the drafts of about 50.4,60.1 and 70% at 200 DEG C.

Table 17

Magnetic phase volume percentage (Fe%) with roll reduction variation

Roll reduction (%)	Fe% after rolling	Stretch the Fe% in specification
			0.0	0.9	42.6
10.7	3.0	46.7
			20.1	4.2	37.9
30.4	5.8	26.7
			39.0	5.1	16.2
50.4	2.5	15.3
			60.1	2.4	13.5
70.0	2.3	16.1

This case embodiment shows can be by (as shown here right in the at a temperature of variation roll reduction for being greater than environment By being rolled at 200 DEG C for alloy 2) to customize the yield strength of alloy described herein.In the wide of present disclosure Under general background, as provided in the case embodiment before table 7, temperature range is expected between 150 DEG C to 400 DEG C. In this operation of rolling, modification deformation path makes that relatively limited deformation induction phase transition occurs, and causes to keep a large amount of Ductility simultaneously maintains ultimate tensile strength while improving the ability of Cold Rolled Strip lower yield strength.Rolling parameter can be optimized as a result, To improve the yield strength of material without losing ductility or ultimate tensile strength.

Microscopic structure in alloy 2 after case embodiment #7 is rolled at 200 DEG C

By laboratory casting by alloy 2 be processed into 9mm thickness the torrid zone to imitate business the torrid zone preparation in plus Work.With the 50% drafts cold rolling torrid zone and annealing continues 10 minutes at 850 DEG C and air is cooling to simulate in commercial movie Cold rolling processing in material preparation.Using media grit blast to remove the oxide formed in annealing process.Then cold rolling is closed again Gold is until failure or rolling limit drafts.Sample is heated before cold rolling in convection oven and continues at least 30 minutes to 200 DEG C To ensure that they are in uniform temperature, and is reheated between passage and continue 10 minutes to ensure stationary temperature.First With 30% 2 sheet material of drafts cold rolling alloy and then to 70% maximum reduction.It is ground by scanning electron microscopy (SEM) Study carefully initial tissu and microscopic structure after rolling.In order to prepare SEM sample, workpiece is cut by EDM and is embedded in epoxy resin In, and finally polished with 9 μm, 6 μm and 1 μm diamond suspension solution and step by step with 0.02 μm of silica.

Figure 25 is shown in the back-scattered SEM image of microscopic structure before cold rolling, be mainly austenite in micro-dimension crystalline substance The annealing twin in intragranular portion.As shown in Figure 26 using 30% drafts cold rolling after, can with different orientation not With see in region band tissue.It is assumed that have the band that is similarly oriented be deformation twins in an austenite grain without Equidirectional band is the twin in another crystal orientation crystal grain.Some crystal grain refinements can be observed in selected region.

After roll reduction is improved to 70%, band is no longer visible, and the thinning microstructure in volume can be seen (Figure 27).As shown in the high-amplification-factor image in Figure 27 b, the tiny island with size much smaller than 10 μm can be distinguished. In view of height applied in stable austenite in rolling process deforms, austenite can be refined significantly and usually be existed In the range of 100 to 500nm.Feritscope measurement points out that austenite is stable at 200 DEG C, and keeps after rolling Close to 100% austenite.

This case embodiment shows even to close herein in the operation of rolling of 70% high roll reduction at 200 DEG C Stabilization of austenite (resist be converted to ferrite) in gold and when being converted to when ferrite refines by austenite and The austenitic microstructure refinement that cold rolling is compared.Case embodiment #8 at 200 DEG C roll reduction to micro- group in alloy 2 The influence knitted

At a temperature of rolling cause the yield strength of alloy 2 to significantly improve while maintaining high stretch percentage elongation.At 200 DEG C TEM research has been carried out on the alloy 2 of rolling to analyze the variation that change in organization strains with rolling in the operation of rolling at 200 DEG C. In this case embodiment, the laboratory coin slab of hot rolling 50mm thickness, and the then heat obtained by rolling at 200 DEG C first Band is to different strains.In order to show microstructure evolution, micro- group of rolled sheet is studied by transmission electron microscopy (TEM) It knits.In order to prepare TEM sample, using line EDM from sheet material cutting sample, and then by every time with the pad of reduced size Grinding is to be thinned.It is arrived by being completed further to be thinned to 60 respectively with the polishing of 9 μm, 3 μm and 1 μm diamond suspension solution The sample of 70 μ m-thicks.The disk that diameter is 3mm is gone out from foil, and is executed by using the electrobrightening of double spray polishing instrument Last polishing.Used chemical solution is 30% nitric acid being blended in methanol-based bottom.For the insufficient of tem observation In the case where thin region, accurate ion polishing system (PIPS) the ion beam milling TEM sample of Gatan is used.Ion beam milling is usual It is completed at 4.5keV, and inclination angle is reduced to 2 ° from 4 ° to open thin region.Use the JEOL to work at 200kV 2100 high resolution microscopes complete TEM research.

Figure 28 is shown at 200 DEG C with the light field TEM image of the microscopic structure in the alloy 2 of 10% drafts rolling.It can See that the dislocation of entanglement fills up austenite grain, and shows dislocation born of the same parents tissue.However, since relatively low rolling strains, just Beginning austenite grain boundary is still visible.Notice that austenite in the operation of rolling is stable at 200 DEG C.Electronic diffraction points out Austria Family name's body is main phase, also consistent with Feritscope measurement result.It will averagely be bent at 200 DEG C with the rolling of 10% drafts Intensity 303MPa from the torrid zone is taken to improve to 529MPA (referring to table 16).When sheet material is rolling to 30%, TEM is qualitatively shown The higher dislocation density (as shown in Figure 29) in crystal grain, and show clearly dislocation born of the same parents tissue.In addition, in austenite crystal Intragranular sees some deformation twins.Austenite phase is maintained as confirmed by electronic diffraction similar to 10% rolled sample. However, the initial crystal boundary of austenite is no longer visible.Average yield strength is resulted in the rolling of 30% drafts at 200 DEG C For 968MPa (table 16).With 70% drafts rolling after (Figure 30), can see from TEM qualitative high bit dislocation density after It is continuous, and dislocation born of the same parents are similar to the dislocation born of the same parents (Figure 29) in 30% rolled sample.In addition, dislocation twin exists in sample In.Similar to 30% rolled sample, confirm that austenite still maintains stable during the rolling process by electronic diffraction.

This case embodiment shows to maintain Ovshinsky at 200 DEG C with this paper alloy in the at most 70% drafts operation of rolling Body tissue.The raising for leading to yield strength after rolling at 200 DEG C with the change in organization of twin is formed including dislocation born of the same parents.

The process route that case embodiment #9 is combined by milling method

Alloy 2, alloy 7, alloy 18 and alloy 34 are processed into the torrid zone with~2.7mm thickness, by its media grit blast To remove oxide and be rolling at 200 DEG C 20% drafts.Divide the material and then at ambient temperature with a series of Drafts rolling.ASTM E8 stretching sample is cut by line EDM and utilizes Instron's on 5984 frame of Instron Bluehill software is tested.

The tensile property of selected alloy is listed in table 18 to table 21 after combination rolling.With tropical state or only 200 It is thinned at DEG C with the thinned rolling of rolling thickness~20% and at room temperature subsequent rolling and is compared later, in all three alloys Observe that yield strength significantly improves after milling method combination.Yield strength is recorded up to for alloy 2 1216MPa (yield strength in the torrid zone is 803MPa after being 309MPa and rolling at 200 DEG C), in alloy 7 up to 1571MPa (yield strength in the torrid zone is 575MPa after being 333MPa and rolling at 200 DEG C), in alloy 18 up to 1080MPa (torrid zone in yield strength be 390MPa and at 200 DEG C roll after be 834MPa) and alloy 34 in up to 1248MPa (yield strength in the torrid zone is 1120MPa after being 970MPa and rolling at 200 DEG C).Figure 31 to Figure 34 difference Display corresponding stress strain curve for alloy 2,7,18 and 34.The limit after cold rolling is also observed in all alloys herein The raising of tensile strength and the reduction of stretch percentage elongation (referring to table 18 to 21).Under the conditions of every kind of inspection (extension test it It is preceding and later) analysis of the magnetic phase volume percentage of alloy selected by this paper is listed in table 22 to table 25.Cold rolling causes from herein Higher Fe% in the working sheet of alloy, then caused by the transformation occurred during extension test, Fe% is further mentioned It is high.

The tensile property of the alloy 2 after milling method combination of table 18

The tensile property of the alloy 7 after milling method combination of table 19

The tensile property of the alloy 18 after milling method combination of table 20

The tensile property of the alloy 34 after milling method combination of table 21

Magnetic phase volume percentage (Fe%) of the table 22 after milling method combines in alloy 2

Magnetic phase volume percentage (Fe%) of the table 23 after milling method combines in alloy 7

Magnetic phase volume percentage (Fe%) of the table 24 after milling method combines in alloy 18

Magnetic phase volume percentage (Fe%) of the table 25 after milling method combines in alloy 34

This case embodiment shows to generate the path of different third group combination of properties, can be by the way that alloy to be processed into 0.5mm then (is rolled by deforming in a passage at the temperature within the scope of 150 DEG C to 400 DEG C to the sheet material of 5.0mm thickness System) and thickness thinning, and then realized in subsequent be thinned of the at a temperature of thickness of temperature≤150 DEG C.Observe this with it is only cold Roll compared to providing relatively high yield strength, and with only at a temperature of rolling compared to the higher tensile strength of offer.

The instance method of case embodiment #10 tailored properties combination

According to fig. 2 with the step of offer in Fig. 3 by this paper to the distinct methods of higher yield strength and combination of properties Sheet material is processed into the torrid zone from alloy 2.Casting alloy 2 and then by hot rolling at sheet material first, for from 2.5 to 2.7mm thick.It is compared for stretching, be before test hot-rolled down to reference torrid zone material~1.8mm to be to be thinned specification.For Fig. 2 (20% is rolled at 200 DEG C) for example, roll the torrid zone at 200 DEG C with 20% drafts.Before rolling, 200 It is heated before rolling 20% at DEG C up to 200 DEG C continue 30 minutes and 10 minutes between rolling pass reheat to tie up Hold temperature.(20% simultaneously then 10% cold rolling at ambient temperature is rolled i.e. at 200 DEG C) for Fig. 3 example, repeat work Skill step comprising the additional step of 10% environment temperature roll reduction of 20% drafts and application at 200 DEG C.Use line EDM cuts tensile sample from the sheet material processed by every kind of method.It is utilized in Instron mechanical test frames (model 5984) The Bluehill of Instron is controlled and analysis software measures tensile property.All tests are at ambient temperature in Bit andits control Operation.

It shows in Figure 35 close to the optimal representative stress-with the combination of properties realized in every kind of processing method Strain curve.As can be seen, yield strength (i.e. 469MPa raising) can be significantly improved by rolling at 200 DEG C, change with minimum Become alloy ultimate tensile strength (i.e. 34MPa raising) and elongation percentage (i.e. 1.8% reduces).This is mentioned by example condition 3a in Fig. 2 For.For in addition sample that the initial conditions from step 3 roll at ambient temperature with 10%, then this will meet in Fig. 3 Step 4.As can be seen, in this case, this is higher yield strength (i.e. 688MPa raising) and tensile strength (i.e. 224MPa Improve) path but reduction (i.e. 25.1% reduce) with breaking elongation.Paying attention to meeting the step 4 in Fig. 3 can also pass through Such as completed by various technique cold stamping parts, thus the region in punching parts will undergo higher yield strength and drawing The lower ductility stretching intensity and matching, the part depletion in forming part.

This case embodiment shows by providing various intensity/elongation percentage combination from this paper alloy resulting sheet Various methods or their combination realize high-yield strength in this paper alloy.

Influence of the case embodiment #11 test temperature to the tensile property of alloy 2

By hot rolling and it is cold-rolled to target thickness and subsequent annealing and is prepared into alloy 2 with 1.4mm thickness by slab Sheet-form.Tensile sample is cut from 2 sheet material of alloy using line EDM.Different temperatures within the scope of from -40 DEG C to 200 DEG C Lower measurement tensile property.

The tensile property of 2 sheet material of alloy is listed in table 26 at different temperatures.It is surveyed at each temperature using Feritscope The magnetic phase volume percentage measured in stretching sample specification after examination is also listed in table 26.As can be seen, with test temperature is improved, Surrender and ultimate tensile strength reduce and stretch percentage elongation improves.Stretch percentage elongation and magnetic phase volume percentage (Fe%) are with test The variation of temperature is drawn on Figure 36, although elongation percentage is higher at elevated temperatures for display, stretches sample after a test Close to zero after magnetic phase volume percentage is remarkably decreased and tests at 200 DEG C in specification.Sample rule are stretched after a test The reduction of magnetic phase volume percentage points out that higher stabilization of austenite inhibits Ovshinsky under stress at elevated temperatures in lattice Body is converted to ferrite.The tensile property for the alloy 2 that table 26 is tested at different temperatures

This case embodiment shows that the multi-component alloys of this paper alloy lead to significantly improving simultaneously for stabilization of austenite And compared with the cold rolling clearly provided in last column such as in table 26, display inhibits during the rolling process at elevated temperatures It is converted to ferrite.Its provide itself higher ductility during the rolling process and the operation of subsequent sheet forming (such as punching press, Drawing etc.) in higher mouldability.

Being thinned to goal standard in case embodiment #12 procedure of processing

Alloy 2 is processed into the torrid zone with 4.4mm thickness.Then two sections of torrid zones are rolled, one section at room temperature and one Section is at 200 DEG C.The plate heated in mechanical convection baking oven at 200 DEG C before rolling continues 30 minutes and between passage Reheating continues 10 minutes to ensure steady temperature.

It in the case where rolling at ambient temperature, fails under about 42% drafts, however works as and reach milling train 70% drafts is applied more than when the limit in the operation of rolling at 200 DEG C without failing.Fenn is being worked as in the generation of the milling train limit 061 milling train of model can not generate significant be thinned again per pass in cold-rolled process and still there is material further rolling to be thinned When ability.

Magnetic phase volume is measured by Feritscope under the drafts of different level in the operation of rolling at cold rolling and 200 DEG C Percentage (Fe%).Data are shown in Figure 37.As can be seen, (the material rolling limit is caused to be in being thinned at ambient temperature ~42%), magnetic phase volume percentage (Fe%) improves rapidly.In the case where rolling at 200 DEG C, or even in > 70% maximum Magnetic phase volume percentage (Fe%) is maintained at 3Fe% or less under roll reduction.

By the way that rolling the two prepares the piece from alloy 2 with 1.2mm final thickness using cold rolling and at 200 DEG C Material.In the case where cold rolling, rolling is recycled with intermediate annealing to restore alloy ductility and realize in final milling step The target thickness of 29% drafts.Have 1.2mm thick from the two preparation in 135 seconds of annealing by milling method and at 1000 DEG C It spends sheet material EDM cutting and stretches sample.The Bluehill of Instron is utilized in Instron mechanical test frames (model 3369) Control and analysis software measure tensile property.All tests are run in Bit andits control at ambient temperature, wherein bottom jig It is kept fixed and top clamp is mobile；Pressure sensor is attached to top clamp.

Engineering stress-strain curve example of the annealed sheet of both rollings preparation is shown through cold rolling and at 200 DEG C In Figure 38.As can be seen, the final properties of sheet material are classes after anneal although different milling methods are towards target thickness As.

This case embodiment shows that (wherein austenite as shown here is steady for rolling at 200 DEG C for alloy 2 It is fixed and be not converted to ferrite) rolling power that improves this paper alloy significantly, it will allow to subtract in procedure of processing It is as thin as target web gauge.Therefore, it can be used this raising temperature rolling to reach with high cold roling reduction (such as this example Middle offer > 70%) approximate final goal specification.Then this approximate final specification material can be annealed to restore to originate property (i.e. primary condition).It then, can be by rolling then in from 150 to 400 DEG C provided in this application of temperature range in Fig. 2 Or the step and process in Fig. 3 are to obtain final goal specification.

The change of case embodiment #13 limit roll reduction

The torrid zone is prepared by the alloy 2 with about 9mm thickness.200 to 250 DEG C are heated to continue 60 minutes and roll To about 4.5mm, 10 minutes are reheated between rolling pass to ensure steady temperature.Once being in 4.5mm, it is segmented simultaneously It anneals 10 minutes at 850 DEG C and keeps its air cooling.The media grit blast material is to remove oxide and heat before rolling To desired constant temperature at least 30 minutes, and 10 minutes were reheated to ensure steady temperature between passage.Rolling stock Until failure (visible cracking), is characterized in that such visible crack propagates at least 2 inches from the end of sheet material.In about 70% drafts milling train is difficult to realize load necessary to the material is thinned and rolls stopping, this is the equipment limit rather than material The limit.Control material for room temperature rolling is the torrid zone of 4.4mm thickness, and rolling is until failure at room temperature.In table 27 and figure The result that maximum roll reduction changes with rolling temperature is provided in 39.

This case embodiment shows to improve for this paper alloy as temperature improves limit roll reduction.Therefore It can be seen that, it is contemplated that this paper alloy allows to have before disabling when being heated to the temperature fallen within the scope of 150 DEG C to 400 DEG C big In the permanent deformation that 20% thickness is thinned.It is highly preferred that this paper alloy is such, it is contemplated that when the quilt within the scope of such temperature They can have before disabling when heating is greater than the permanent deformation that 40% thickness is thinned.This for mill operation (including processing Industrial materials are to reach goal standard) much bigger potential deformation is provided.Biggish be thinned means to need before cracking Less step (i.e. cold rolling and recrystallization annealing) is to reach the specific goal standard during steel is standby.In addition, increasing At a temperature of indicated larger mouldability would be beneficial for it is (including punching press, rolling and forming, drawing, hydraulic from various forming operations Molding etc.) manufacture part.

Table 27 the roll reduction limit and rolling temperature for alloy 2

Temperature (DEG C)	The roll reduction limit
		23	41.4%
100	53.8%
		150	68.6%
200	> 70%
		250	> 70%

Claims (19)

1. the method for improving yield strength in metal alloy, comprising:

A. supplying metal alloy, the metal alloy include at least 70 atom % iron and selected from Si, Mn, Cr, Ni, Cu or C at least Four kinds or more elements, melt the alloy, with 10^-4K/ seconds to 10³K/ seconds rates are cooling and be solidified to > 5.0mm extremely The thickness of 500mm；

B. the alloy is processed into the first sheet-form, thickness is from 0.5 to 5.0mm, and wherein first sheet material has X₁(%'s) Breaking elongation, Y₁(MPa) ultimate tensile strength and Z₁(MPa) yield strength；

C. the alloy is permanently deformed into the second sheet-form, the second sheet material shape within the temperature range of 150 DEG C to 400 DEG C Formula shows following tensile property combination one of A or B:

A. (1) breaking elongation X₂=X₁± 7.5%；

(2) ultimate tensile strength Y₂=Y₁±100MPa；With

(3) yield strength Z₂≥Z₁+100MPa

B. (1) ultimate tensile strength Y₃=Y₁±100MPa；With

(2) yield strength Z₃≥Z₁+200MPa。

2. the method for claim 1 wherein the alloys to contain at least 70 atom % iron and selected from Si, Mn, Cr, Ni, Cu or C Five kinds or more elements.

3. the method for claim 1 wherein the alloys to contain at least 70 atom % iron and Si, Mn, Cr, Ni, Cu and C.

4. the method for claim 1 wherein the alloys formed in step (b) to show 10.0 to 70.0% X₁Value, The Y of 900MPa to 2050MPa₁The Z of value and 200MPa to 750MPa₁Value.

5. the method for claim 1 wherein tensile property combination A is as follows: X₂=2.5% to 77.5%, Y₂=800MPa is extremely 2150MPa and Z₂≥300MPa。

6. the method for claim 1 wherein tensile property combination B is as follows: Y₃=800MPa is to 2150MPa and Z₃≥ 300MPa。

7. it is described by what is formed in step (c) that the method for claim 1 wherein the thickness by the way that the first alloy sheet material is thinned First sheet material is permanently deformed into the second alloy sheet material.

8. the method for claim 1 wherein the fusing point (Tm) of 700 DEG C of temperature to less than the alloy at a temperature of carry out step (b)。

9. the method for claim 1 wherein after the step (b) in 650 DEG C of temperature to less than the temperature of the fusing point (Tm) of the alloy The alloy is heat-treated under degree.

10. thickness, which is thinned, to be greater than the method for claim 1 wherein the alloy is permanently deformed before disabling in step (c) 20%.

11. the method for claim 1 wherein the methods by rolling and forming, metal stamping, metal drawing or hydro-forming to walk Suddenly first sheet material formed in (c) is permanently deformed into the second alloy sheet material.

12. the method for claim 1 wherein the alloys formed with the thickness of > 5.0mm to 500mm to contain greater than 10 volumes The austenite of percentage.

13. the method for claim 1 wherein in step (c) 150 DEG C to 400 DEG C within the temperature range of by the alloy forever It is deformed into after the second sheet material long, be permanently deformed second sheet material under≤150 DEG C of temperature range.

14. the method for improving yield strength in metal alloy, comprising:

A. supplying metal alloy, the metal alloy include at least 70 atom % iron and selected from Si, Mn, Cr, Ni, Cu or C at least Four kinds or more elements, melt the alloy, with 10^-4K/ seconds to 10³K/ seconds rates are cooling and be solidified to > 5.0mm extremely The thickness of 500mm；

B. the alloy is processed into the first sheet-form, thickness is from 5.0 to 0.5mm；

C. the alloy is permanently deformed into the second sheet-form within the temperature range of 150 DEG C to 400 DEG C；

D. < 150 DEG C at a temperature of by the alloy be permanently deformed at the second sheet-form, second sheet-form show with Lower stretching combination of properties:

(1) breaking elongation=10.0 to 40.0%；

(2) ultimate tensile strength=1150 are to 2000MPa；

(3) yield strength=550 are to 1600MPa.

15. the method for claim 14, wherein the fusing point (Tm) of 700 DEG C of temperature to less than the alloy at a temperature of walked Suddenly (b).

16. the method for claim 14, wherein in the fusing point (Tm) of 650 DEG C of temperature to less than the alloy after step (b) At a temperature of be heat-treated the alloy.

17. the method for claim 14, wherein the step of permanent deformation includes rolling and forming, metal stamping, metal drawing Or the method for hydro-forming.

18. the part of the method for claim 14, the permanent deformation wherein formed in step (d) is placed on vehicle frame In frame, vehicle chassis or vehicle panel.

19. the method for claim 14, wherein the part of the permanent deformation in step (d) is placed on drill collar, drilling rod, set In pipe, tool-joint, well head, compressed gas storage tank, tank car/one of tank trailer or liquefied natural gas container.