CN103842550A - Method for producing almgsi aluminum strip - Google Patents

Abstract

The invention relates to a method for producing a strip made of an AlMgSi alloy, in which a rolling ingot made of an AlMgSi alloy is cast, the rolling ingot is subjected to homogenization, the rolling ingot having been brought to rolling temperature is hot-rolled and is optionally cold-rolled to the final thickness thereafter. The problem of providing an improved method for producing aluminum strip made of an AlMgSi alloy, with which AlMgSi strips having very good shaping behaviour can be produced reliably, is solved in that immediately after exit from the final rolling pass, the hot strip has a temperature of between more than 130 DEG C, preferably 135 DEG C, and at most 250 DEG C, preferably at most 230 DEG C, and the hot strip is wound up at this temperature.

Description

Manufacturing method of AlMgSi aluminum strip

technical field

The invention relates to a method for producing a strip from an AlMgSi alloy, in which method the AlMgSi alloy is cast into rolled blanks, the rolled blanks are subjected to a homogenization treatment, the rolled blanks adjusted to the rolling temperature are subjected to Hot rolling, followed by optional cold rolling to final gauge and solution annealing and quenching of the final rolled strip. Furthermore, the invention relates to the advantageous use of correspondingly produced AlMgSi aluminum strips.

Background technique

Sheets made of aluminum alloys are mainly used in automobile construction but also in other fields of application, such as aircraft construction or rail vehicle construction, and are not only characterized by particularly high strength values but also very good formability and High degree of deformation. Typical areas of application in automotive construction are body and chassis components. For visible, painted structural parts, such as exterior, visible body panels, the shaping of the material must be carried out in such a way that the surface is not affected by, for example, scratches or wrinkle-like deformations (bumps) after painting. This is particularly important, for example, when aluminum alloy sheets are used for the production of bonnets or other body parts of motor vehicles. This however limits the material options for aluminum alloys. In particular, the AlMgSi alloy, whose main alloy components are magnesium and silicon, has relatively high strength in the T6 temper, and at the same time has good formability in the T4 temper and has excellent corrosion resistance. AlMgSi alloys are alloy types AA6XXX, for example alloy types AA6016, AA6014, AA6181, AA6060 and AA6111. Aluminum strip consisting of an AlMgSi alloy is usually produced by casting a rolled stock, homogenizing the rolled stock, hot rolling the rolled stock and cold rolling the hot rolled strip. The homogenization of the rolled slab is carried out at a temperature of 380 to 580° C. for more than one hour. The strip in the T4 temper can be obtained by a final solution annealing, typically at a temperature of 500° C. to 570° C., followed by quenching and cold aging approximately at room temperature for at least three days. The T6 temper is adjusted by thermal aging at temperatures between 100°C and 220°C after quenching.

The problem is that in the hot-rolled aluminum strip of AlMgSi alloy there are coarse Mg ₂ Si precipitates, which are broken up and become smaller during the subsequent cold-rolling process due to a high degree of deformation. Hot-rolled strip of AlMgSi alloy is generally produced in a thickness of 3 mm to 12 mm and sent to cold rolling with a high degree of deformation. Due to the very slow passage through the temperature region where the AlMgSi phase is formed during conventional hot rolling, this phase forms very coarsely. The temperature region used to form the above phases is alloy dependent. However, this temperature range is between 230° C. and 550° C., ie in the range of hot rolling temperatures. From experiments it can be confirmed that coarse phases in the hot-rolled strip negatively affect the elongation of the final product. That is, the formability of aluminum strips composed of AlMgSi alloys has not been sufficiently obtained so far.

According to the published European patent registration EP 2270249A1 belonging to the applicant, the AlMgSi alloy strip has a temperature of up to 130° C. immediately after the final hot rolling process and is wound at this temperature or lower. By quenching the hot-rolled strip using this method, an aluminum strip in the T4 temper can be produced which has an elongation at break A ₈₀ higher than 30% or a uniform elongation A _g higher than 25%. Furthermore, very high elongation at break values are also achieved in the T6 temper. However, it has been pointed out that this temperature range out of the final hot-rolling process leads to problems with regard to the flatness of the hot-rolled strip, so that the subsequent final steps are affected. Furthermore, the prescribed cooling rates can only be achieved with reduced production speeds.

Contents of the invention

Based on this prior art, the object of the present invention is to provide an improved method for producing aluminum strips from AlMgSi alloys, with which AlMgSi alloys with very good formability in the T4 temper can be reliably produced. aluminum strip.

According to the first teaching of the invention, the hot-rolled strip has a temperature above 130° C., preferably 135° C. up to 250° C., preferably 135° C. up to 230° C. The material is wound at this temperature so that the proposed object for the method is achieved.

Compared to known methods with particularly low winding temperatures, it has surprisingly been shown that the mechanical properties with regard to the uniform elongation _Ag , which determines the formability, do not change or only change when the winding temperature changes. Make small changes. The AlMgSi alloy strips produced according to the invention in the T4 temper also exhibit a uniform elongation of more than 25% in a tensile test according to DIN EN. Furthermore, this strip shows very good curing properties in the T6 temper, as is known from applicant's previous applications. Of course, this manufacturing method can be significantly stabilized and achieves higher production speeds.

According to an advantageous embodiment of the method according to the invention, the cooling process is carried out in the last two hot rolling steps, i.e. within seconds, at most within five minutes, to temperatures above 130° C., preferably 135° C. to a maximum of 250° C., preferably Temperatures from 135°C to a maximum of 230°C. It has been shown that increased uniform elongation values in the T4 temper and improved curing properties in the T6 temper are achieved particularly reliably with conventional strength values and elongation limit values in this operating method.

According to a further embodiment of the method according to the invention, reliable cooling of the hot-rolled strip is thereby achieved by self-quenching the hot-rolled strip by using at least one slab cooling device and a hot-rolling process with emulsion to winding temperature. The slab cooling device consists of a structure of coolant or lubricant nozzles which spray rolling emulsion onto the aluminum strip. The slab cooling device can be present in the hot rolling tool, so that the rolled hot strip is cooled to the rolling temperature before hot rolling and enables higher production speeds.

A further embodiment of the method according to the invention achieves that after the quenched There are particularly small Mg ₂ Si precipitates in the hot-rolled strip, since the largest proportions of the alloy components, magnesium and silicon, are present in the molten state in the aluminum matrix at this temperature. This favorable state of the hot-rolled strip is practically "frozen" by quenching.

According to another configuration of the method according to the invention, the temperature of the hot-rolled strip after the penultimate rolling step is 290° C. to 310° C. It has been shown that this temperature not only achieves sufficient freezing of the precipitates but at the same time allows the final rolling process to be carried out without problems.

If the rolled hot strip has a temperature of 200°C to 230°C as it comes out directly after the final hot rolling process, an optimum operating speed can be achieved during the hot rolling process without damaging the produced aluminum belt performance.

The thickness of the obtained hot-rolled strip is 3 mm to 12 mm, preferably 5 mm to 8 mm, so that conventional cold rolling equipment can be applied to the cold rolling of the present invention.

The aluminum alloy used is preferably of alloy type AA6XXX, preferably AA6014, AA6016, AA6060, AA6111 or AA6181. All alloy types AA6XXX have in common that this type of alloy has particularly good formability, for example after thermal aging at 205°C/30min, characterized by high elongation values in the T4 temper and high strength and elongation in the T6 temper limit.

According to a further embodiment of the method according to the invention, the rolled aluminum strip is subjected to a heat treatment, wherein the aluminum strip is heated after solution annealing and quenching to above 100° C. temperature for winding and aging. This embodiment of the method according to the invention allows the aluminum strip to be adjusted to the T6 state in the strip or sheet after cold aging by means of a short heating phase at a lower temperature, in which state the sheet to be formed into a structural part is used or strip. For this purpose, the fast-curing aluminum strip is only heated for 20 min to a temperature of approximately 185° C. in order to achieve a high yield limit value in the T6 temper.

Furthermore, the elongation at break value A ₈₀ of the aluminum strip produced by this embodiment of the method according to the invention is slightly lower than 29% in the T4 temper. However, the aluminum strip produced according to the invention after aging in the T4 temper is also characterized by a very good uniform elongation A _g of more than 25%. The uniform elongation _Ag refers to the maximum extension of the sample at which the sample does not shrink in the tensile test. That is, the sample stretches uniformly in a region of uniform extension. Uniform elongation values for similar materials have so far been as high as 22% to 23%. The uniform elongation significantly affects the formability, because the uniform elongation determines the maximum deformation of the material in practice. In this respect, with the aid of the method according to the invention it is possible to provide aluminum strips with very good formability, which can also be converted to the T6 temper by accelerated thermal aging (185° C./20 min).

Aluminum alloys of the type AA6016 have the following alloy compositions shown in weight percent:

0.25%≤Mg≤0.6%,

1.0%≤Si≤1.5%,

 Fe≤0.5%,

Cu≤0.2%,

Mn≤0.2%,

Cr≤0.1%,

Zn≤0.1%,

Ti≤0.1%

and the remaining Al and unavoidable impurities (total maximum 0.15%, individual maximum 0.05%).

At magnesium contents below 0.25% by weight, the strength of the aluminum strip designed for structural applications is too low, while at magnesium contents above 0.6% by weight, the formability deteriorates. The combination of silicon and magnesium essentially determines the hardening properties of the aluminum alloy and thus also the high strength which can be achieved during application, for example after the coating has been baked. In the case of Si contents below 1.0% by weight, the curability of the aluminum strip is reduced so that only a low strength is provided in the application. Si contents higher than 1.5% by weight do not lead to an improvement in the solidification properties of the alloy. The Fe content should be limited to a maximum of 0.5% by weight in order to avoid coarse precipitates. Limiting the copper content to a maximum of 0.2% by weight results primarily in improved corrosion resistance of aluminum alloys in certain applications. Manganese contents below 0.2% by weight reduce the tendency to form coarser manganese precipitates. Although chromium contributes to the formation of a fine structure, it is limited to 0.1% by weight, also to avoid coarse precipitates. On the other hand, the presence of manganese improves the weldability by reducing the cracking tendency and quenching sensitivity of the aluminum strip according to the invention. A reduction of the zinc content to a maximum of 0.1% by weight improves in particular the corrosion resistance of aluminum alloys and finished sheet metal in various applications. Titanium, while contributing to grain refinement during casting, should be limited to a maximum of 0.1% by weight to ensure excellent castability of the aluminum alloy.

Aluminum alloys of the type AA6060 have the following alloy compositions shown in weight percent:

0.35%≤Mg≤0.6%,

0.3%≤Si≤0.6%,

0.1%≤Fe≤0.3%,

Cu≤0.1%,

Mn≤0.1%,

Cr≤0.05%,

Zn≤0.10%,

Ti≤0.1% and

Remaining Al and unavoidable impurities (total max. 0.15%, individual max. 0.05%).

The combination of a precisely defined magnesium content and a reduced Si content compared to the first embodiment and a strictly limited Fe content results in an aluminum alloy in which the method according to the invention can prevent particularly good _Mg2Si precipitates are then formed, making it possible to provide sheets with improved elongation and a high elongation limit compared to conventionally produced sheets. A lower upper limit for the alloy components Cu, Mn and Cr additionally enhances the effect of the method according to the invention. The influence of the upper limit of Zn and Ti can refer to the design of the first embodiment of the aluminum alloy.

Aluminum alloys of the type AA6014 have the following alloy compositions shown in weight percent:

0.4%≤Mg≤0.8%,

0.3%≤Si≤0.6%,

 Fe≤0.35%,

Cu≤0.25%,

0.05%≤Mn≤0.20%,

Cr≤0.20%,

Zn≤0.10%,

0.05%≤V≤0.20%,

Ti≤0.1% and

Remaining Al and unavoidable impurities (total max. 0.15%, individual max. 0.05%).

Aluminum alloys of the type AA6181 have the following alloy compositions shown in weight percent:

0.6%≤Mg≤1.0%,

0.8%≤Si≤1.2%,

 Fe≤0.45%,

Cu≤0.10%,

Mn≤0.15%,

Cr≤0.10%,

Zn≤0.20%,

Ti≤0.1% and

Remaining Al and unavoidable impurities (total max. 0.15%, individual max. 0.05%).

Aluminum alloys of the type AA6111 have the following alloy compositions shown in weight percent:

0.5%≤Mg≤1.0%,

0.7%≤Si≤1.1%,

 Fe≤0.40%,

0.50%≤Cu≤0.90%,

0.15%≤Mn≤0.45%,

Cr≤0.10%,

Zn≤0.15%,

Ti≤0.1% and

Remaining Al and unavoidable impurities (total max. 0.15%, individual max. 0.05%). Alloy AA6111 exhibits substantially higher strength values in the application state T6 due to the increased copper content, but has no corrosion resistance.

All indicated aluminum alloys are suitable for different applications with their specific alloy composition. As already mentioned, the strips produced from these aluminum alloys by using the method according to the invention show particularly high values for the uniform elongation in the T4 temper and a particularly pronounced , The improvement of extension limit. Aluminum strips in the T4 temper also have these properties after heat-treated solution annealing.

Due to the excellent combination of good formability in the T4 state, high corrosion resistance and a high value for the limit of elongation Rp0.2 in the applied state (T6 state), the aforementioned objects are thus achieved according to the second teaching of the invention , that is, the use of AlMgSi alloy strips prepared according to the method of the present invention for structural parts, chassis parts or structural parts and structural plates in automobile construction, aircraft construction or rail vehicle construction, especially as components, chassis parts, automotive An outer or inner panel under manufacture, preferably as a body structural component. High elongation limit Rp0.2 with good surface properties even after molding with a high degree of deformation, which is especially advantageous for visible body parts such as bonnets, fenders, etc. and the exterior of rail vehicles or aircraft layer widget.

Therefore, a rapidly solidified AlMgSi alloy ribbon having excellent formability can be provided by the aluminum alloy ribbon which is continuously subjected to solution annealing and heat treatment after manufacture according to the present invention. As already mentioned, the alloy strip has a uniform elongation A _g of more than 25% in the T4 temper, for example at an elongation limit Rp0.2 of 80 to 140 MPa. This variant makes it possible to provide an AlMgSi alloy strip which solidifies rapidly and at the same time is very well formable. In order to obtain the T6 state, thermal aging can be carried out at 185 ° C for 20 minutes to obtain the required increase in the extension limit.

According to another design solution, the aluminum alloy strip produced according to the present invention has a uniform elongation _Ag higher than 25% along the rolling direction, transverse to the rolling direction and diagonal direction along the rolling direction, so it can be particularly Formed homogeneously.

The aluminum strip produced according to the invention preferably has a thickness of 0.5 mm to 12 mm. Aluminum strips with a thickness of 0.5 mm to 2 mm are preferably used, for example, for body parts in automobile construction, while aluminum strips with a greater thickness of 2 to 4.5 mm are used for chassis parts in automobile construction. Individual components can also be produced in cold-rolled strip with a thickness of up to 6 mm. Furthermore, aluminum strips with a thickness of up to 12 mm can also be used in certain applications. Such aluminum strips of great thickness are usually only obtained by hot rolling.

Description of drawings

Next, the present invention is further explained according to multiple embodiments in conjunction with the accompanying drawings.

In the single FIG. 1 there is shown a schematic flow diagram of an exemplary embodiment of the method according to the invention for the production of strip from MgSi aluminum alloys, the method having the steps a) producing and homogenizing the rolled blank, b) Hot rolling, c) cold rolling and d) solution annealing with quenching.

Detailed ways

First cast into a rolling blank 1 from an aluminum alloy having the following

Alloy composition than shown:

0.25%≤Mg≤0.6%,

1.0%≤Si≤1.5%,

 Fe≤0.50%,

Cu≤0.20%,

Mn≤0.20%,

Cr≤0.10%,

Zn≤0.20%,

Ti≤0.15%

and the remaining Al and unavoidable impurities (total maximum 0.15%, individual maximum 0.05%).

The rolled blank thus obtained is homogenized in the furnace 2 at a homogenization temperature of approximately 550° C. for 8 h, so that the alloy components to be fused are dispersed particularly uniformly in the rolled blank, as shown in Fig. 1a ).

In FIG. 1 b ) it is shown how, in the illustrated embodiment of the method according to the invention, a rolling stock 1 is reversibly hot-rolled by means of a hot-rolling plant 3 , wherein the rolled stock 1 has 400 during the hot-rolling process. to a temperature of 550°C. In this embodiment, the hot-rolled strip 4 preferably has a temperature of at least 400°C, preferably 470-490°C, after leaving the hot-rolling installation 3 and before the penultimate hot-rolling process. Quenching of the hot-rolled strip 4 is preferably carried out at this hot-rolling temperature by using the slab cooling device 5 and the work rolls of the hot-rolling plant 3 . The hot-rolled strip is preferably cooled to a temperature of 290°C to 310°C before the final hot-rolling process. In addition, only schematically shown, the slab cooling device 5 sprays the cooled rolling emulsion on the hot-rolled strip 4 and accelerates the cooling of the hot-rolled strip 4 to the above-mentioned temperature. The work rolls of the hot rolling plant 3 are also applied with emulsion and the hot strip 4 is further cooled in the final hot rolling process. In the present embodiment, after the final rolling process, the hot strip 4 has a temperature of 200° C. to 230° C. at the outlet of the slab cooling device 5 ′ and is subsequently wound at this temperature by the coiler 6 .

By hot rolling the strip 4 immediately at the exit of the last hot rolling process to a temperature of 135° C. to 250° C., preferably 200° C. to 230° C. The work rolls of the hot rolling plant 3 are brought to said temperature, so that the hot strip 4 has a frozen crystal structure state even at the increased winding temperature, which results in a very good T4 state of more than 25%. Uniform elongation property A _g . Even faster and better processing of the strip is possible at increased winding temperatures. A hot-rolled strip having a thickness of 3 to 12 mm, preferably 5 to 8 mm, is wound up by means of a coiler 6 . As mentioned earlier, the winding temperature in this embodiment is preferably 135°C to 250°C.

In the method according _to the invention, no or only small amounts of coarse Mg ₂ Si precipitates are formed in the wound hot-rolled strip 4 . The hot-rolled strip 4 has a crystalline state that is very favorable for further processing and can be uncoiled by the uncoiler 7 , eg conveyed to a cold rolling plant 9 and rewound on the coiler 8 , as in FIG. 1 c ).

The resulting cold-rolled strip 11 is wound up. The strip is then solution annealed at a temperature of 520° C. to 570° C. and quenched 10 , FIG. 1 d ). For this purpose the strip is unwound again from the coil 12 , is solution annealed and quenched in the furnace 10 and is wound up again into the coil 13 . The strip is then cold-aged in the T4 temper at room temperature for maximum formability. Optionally (not shown), the aluminum strip 11 can be split into individual sheets which are in a T4 temper after cold aging.

In the case of larger aluminum strip thicknesses, for example in chassis applications or components such as brake base plates, optional single-piece annealing and subsequent hardening of the sheet metal is also possible.

The aluminum strip or sheet is subjected to thermal aging at 100° C. to 220° C. in the T6 temper to obtain the maximum elongation limit value. Thermal aging can also be performed, for example, at 205° C./30 min.

The aluminum strip produced according to the illustrated embodiment has a thickness of, for example, 0.5 to 4.5 mm after cold rolling. Strip thicknesses of 0.5 to 2 mm are typically used for body applications and strip thicknesses of 2.0 mm to 4.5 mm are typically used for chassis components in automotive manufacturing. In both fields of application, improved uniform elongation values have important advantages during the manufacture of components, since, although high strength is required in the finished application state (T6), most of the sheet metal Great deformation.

Table 1 lists the alloy compositions of the aluminum alloys used to manufacture the conventional aluminum strips or the aluminum strips according to the invention. In addition to the stated contents of the alloy composition, the remaining composition of the aluminum strip also includes aluminum and impurities, wherein the individual contents of impurities are a maximum of 0.05% by weight and the total amount of impurities is a maximum of 0.15% by weight.

Table 1

Strips (samples) 251 and 252 were produced by the method according to the invention, in which the hot-rolled strips were heated from about 470°C to 490°C in the last two hot-rolling steps by using a slab cooling device and hot rolling by itself Cool to 135°C to 250°C and wind up. The measurements for this strip are identified in Table 2 as "Inv." Cold rolling was then performed to obtain a final thickness of 0.865 mm.

Strips (samples) 491-1 and 491-11 were produced by conventional hot and cold rolling and are designated "Konv."

The mechanical properties results presented in Table 2 clearly show the differences in the uniform elongation values Ag that can be obtained.

Table 2

To obtain the T4 temper the strip was solution annealed followed by quenching and then cold aged at room temperature for 8 days. The T6 temper is achieved by thermal aging at 205°C for 30 minutes after cold aging.

The samples marked L were cut along the rolling direction, the samples marked Q were cut transverse to the rolling direction and the samples marked D were cut diagonally to the rolling direction. Samples 491-1 and 491-11 were measured transversely to the rolling direction, respectively.

The results show that the advantageous structure obtained in the strips 251 and 252 by the method according to the invention enables a significantly increased uniform elongation A _g at the same elongation limit Rp0.2 and strength Rm. In the strip produced according to the invention, the uniform elongation A _g transverse to the rolling direction is increased from 23.0% to a maximum of 26.6% compared to conventionally produced strip.

The structures obtained by the method according to the invention lead to a particularly favorable combination of a high uniform elongation A _g of more than 25% and a very high elongation limit value Rp0.2 of 80 to 140 MPa. In the T6 state, the elongation limit Rp0.2 increases to at least 185MPa, and the uniform elongation _Ag still remains above 12%. Curability of 97 or 107 MPa in ΔRp0.2 of tapes made according to the invention is still very good.

In the T6 temper, the increase in the uniform elongation, _Ag , is almost maintained relative to the conventionally produced strip.

The elongation at break values A _g and A ₈₀ , the elongation limit value Rp0.2 and the tensile strength value Rm in the table are measured according to DIN EM.

Claims (9)

1. manufactured the method for band by AlMgSi alloy for one kind, in described method, pour into rolling blank by AlMgSi alloy, described rolling blank is subject to homogenizing processing, the rolling blank that is adjusted to rolling temperature is carried out to hot rolling, selectively be cold-rolled to subsequently final thickness and be subject to solution annealing and quenching through the finished product band of rolling, it is characterized in that, hot rolled band have immediately after out from last hot-rolled process higher than 130 ℃ to the highest 250 ℃, preferably the highest 230 ℃ temperature and hot rolled band is wound around with described temperature.

2. method according to claim 1, is characterized in that, by the hot-rolled process that uses at least one slab refrigerating unit and be added with emulsion make hot rolled band voluntarily quench cooled to temperature out.

3. method according to claim 1 and 2, is characterized in that, before the cooling operation carrying out in course of hot rolling starts, the temperature of described hot rolled band is higher than 400 ℃.

4. according to the method described in any one in claims 1 to 3, it is characterized in that, after penultimate rolling process, the temperature of hot rolled band is higher than 250 ℃.

5. according to the method described in any one in claim 1 to 4, it is characterized in that, after last rolling process and before being wound around, the temperature of hot rolled band is 200 ℃ to 230 ℃.

6. according to the method described in any one in claim 1 to 5, it is characterized in that, the thickness of finished product hot rolled band is 3mm to 12mm, is preferably 5mm to 8mm.

7. according to the method described in any one in claim 1 to 6, it is characterized in that, aluminium alloy is the types of alloys of AA6XXX, is preferably AA6014, AA6016, AA6060, AA6111 or AA6181.

8. according to the method described in any one in claim 1 to 7, it is characterized in that, the aluminium strip that rolling completes is subject to thermal treatment, in described thermal treatment aluminium strip be heated to more than 100 ℃ in solution annealing with after quenching and subsequently with higher than 55 ℃, be preferably wound around and ageing treatment higher than the temperature of 85 ℃.

9. by the application of the aluminium strip that makes according to the method described in any one in claim 1 to 8, described aluminium strip is applied to vehicle chassis component or structure unit and the structural slab in structural part, automobile making, aircraft manufacturing or rail vehicle manufacture, particularly as the outside plate in integral part, vehicle chassis component, automobile making or inner panel, preferably as body structure parts.

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