CN106134379B

CN106134379B - Microstructure and properties control method of near-α-type titanium alloy under isothermal local loading transition zone

Info

Publication number: CN106134379B
Application number: CN200810076423.6A
Authority: CN
Inventors: 孙志超; 杨合; 樊晓光; 周建华; 苑世剑; 周义刚; 王晓英; 吴跃江
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2008-08-18
Filing date: 2008-08-18
Publication date: 2011-06-01
Anticipated expiration: 2028-08-18

Abstract

The invention is a method for controlling the microstructure and properties of the transition zone under isothermal local loading of a near-α-type titanium alloy. The microstructure and properties of the transition zone are controlled throughout the entire thermal processing process. Process parameters in heat treatment to control the structure and properties of the transition zone. The ingot is water-cooled in the β-phase region, and re-forged at 40-50°C below the phase transition point, and water-cooled after forging. The number of partial loading passes is no more than 2, the heating forging temperature is 20-30°C below the phase transition point, and the deformation speed is 0.01-0.02s ^-1 . After partial loading, press the press for 10 to 15 minutes to finish the forging. Rapid water cooling after forging, using strengthening and toughening heat treatment. The invention can effectively control the microstructure of the transition zone in the local loading forming, and obtain a fine and uniform equiaxed α phase + β transformation structure. The transition zone has no grain coarsening, inhomogeneity and abnormal growth, and has stable structure and mechanical strength. Good performance features.

Description

Nearly alpha titanium alloy isothermal local loads transition region structure property control method

One, technical field

The present invention relates to hot-working field, specifically a kind of nearly alpha titanium alloy isothermal local loads transition region structure propertyControl method.

Two, technical background

Aero-Space have very high requirement with titanium alloy member to microstructure and mechanical property. For nearly alpha titanium alloy,Forging part requires to have the evenly tiny axle α phase+β that waits to change tissue, to realize the matched well of mechanical property. Adopt etc.When temperature local loading is produced titanium alloy part, forging is the distortion of regional area stand under load at each shaping stage, is being shapedIn journey, on forging, there is load deflection district, not loading zone and transition region. Transition region is subject to loading zone and the not impact of loading zoneAnd deform, unhomogeneity of deformation increases, and adds showing tremendous enthusiasm time and process time also more than common die forging simultaneously. These because ofElement causes forging transition region Microstructural Evolution complexity in process, alligatoring and uneven homogenize easily occurs, transition regionAlso corresponding reduction of mechanical property.

In the patent application that is 200710083701.6 at number of patent application, disclose the complicated entirety of titanium alloy large-sized gusset classThe method of member isothermal local loading and shaping, but do not provide the technical scheme of controlling transition region tissue.

Three, summary of the invention

Organize thick, inhomogeneous and the reduction of transition region mechanical property for overcoming the forging transition region existing in prior artDeficiency, the present invention proposes a kind of nearly alpha titanium alloy isothermal local loading and shaping forging transition region structure property controlling partyMethod.

The present invention by the control of transition region structure property through whole hot procedure, by controlled working process hairBase changes forging, preformed blank preparation, local loading process, finishing process and forges the technological parameter in after-baking,Realize transition region tissue and Properties Control, detailed process is as follows:

The first step, blank change forging

Titan alloy casting ingot is in the above cogging of transformation temperature, and ingot casting is heated to T_β+ (50～100 DEG C), deflection is greater than 50%,Water-cooled after forging, to improve the metallurgical quality of material, improves the microstructure and composition uniformity of material; Then by the hair obtainingBase is heated to T_βThe two-phase section of-(40～50 DEG C) changes forging, and deflection is greater than 50%, and water-cooled after forging is tiny etc. to obtainAxle tissue or bifurcation tissue.

Second step, preformed blank preparation

By the blank appearance parcel adiabatic cotton changing after forging, be heated to T_β-40 DEG C, adopt open die forging and loose tooling forging to carry out base,Time bases as how fiery in need, and melt down again heating after blank being wrapped up to adiabatic cotton after each fire processing. Can increase like thisEvery fiery deflection, reduces processing fire, suppresses microstructure coarsening.

The 3rd step, isothermal local loading and shaping

In local loading, workpiece is divided into two to three loading zones, mould is divided into corresponding several accordingly. OftenIndividual loading passage is divided into two and loads step, in each loading step, utilizes the mould of piecemeal to enter successively different loading zonesRow local loading, after all loadings complete, proceeds to next and loads passage, repeats the loading side of a loading passageMethod, until arrive total deflection.

The specific implementation process of local loading and shaping is:

First loads work step: blank is heated to T_β-(30～40 DEG C), mold heated is to T_β-50 DEG C, with piecemeal mould pairWorkpiece carries out local loading, and pressing speed is 0.2～0.4mm/s, and relative deformation equals total deformation or total deformation55%～65%. As more mold exchange of need, by blank depanning water-cooled.

Second loads work step: blank obtained in the previous step is heated to T_β-(30～40 DEG C), mold heated is to T_β-50℃，By other parts of piecemeal die forming workpiece, pressing speed is 0.2～0.4mm/s, and relative deformation equals total deformationOr total deformation 55%～65%.

In local loading, main technological parameter has passage and each pass deformation of loading, heating-up temperature, loading velocity,The type of cooling. For controlling the microstructure of transition region, the selection of main technologic parameters should meet following some: 1. localLoading passage is no more than twice. The preferential a time that adopts loads, and can not be shaped as a time loads, and can select twice timeLoad. While adopting two passages to load, each pass deformation must be greater than the critical strain amount of material generation recrystallization,The first pass deformation is that the 55%～65%, second pass deformation of total deformation is total deformation 45%～35%.2. the heating-up temperature of blank is T_β-(30～40 DEG C), the heating-up temperature of mould is T_β-50 DEG C. 3. each loads work step, materialStrain rate 0.01～the 0.02s of material^-1, corresponding deformation velocity is 0.2～0.4mm/s. 4. while needing more mold exchange, will forgePart depanning water-cooled.

The 4th step, finishing

Finishing is carried out after last fire that completes local loading and shaping is inferior. Now, each piecemeal mould is depressed simultaneously.Finishing adopts forcing press pressurize to complete, and during due to bulk deformation, required plastic force generally will exceed the equipment scope of forcing press,Its maximum that can provide is provided the tonnage of forcing press pressurize, and the dwell time is 10min～15min. In this conditionUnder, mainly there is superplasticity flow deformation in material, can reduce forming defects.

The 5th step, heat treatment

After forging, take out immediately workpiece water-cooled, then adopt the Technology for Heating Processing of solid solution recrystallization annealing, workpiece is heatedTo T_β-(20～30 DEG C), insulation 1～2h, water-cooled; Then workpiece is heated to recrystallization temperature, insulation 2～3h, air cooling.

The 6th step, Non-Destructive Testing

Adopt technical scheme of the present invention, can effectively control the microstructure of transition region in local loading and shaping, obtainThe tiny uniform axle α phase+β that waits changes tissue. Transition region macrostructure is fuzzy crystalline substance, and mirco structure does not have blocky α phaseExist. Compared with each loading zone, the axle α phase volume fractions such as transition region and crystallite dimension differ in 5%, mechanicsPerformance is close with each loading zone. Transition region microstructure Evolution is stable, there is no grain coarsening, uneven homogenize and abnormal growthPhenomenon.

Four, brief description of the drawings

Accompanying drawing 1 is the block diagram that nearly alpha titanium alloy isothermal local loads transition region structure property control method.

Five, detailed description of the invention

Embodiment mono-:

The TA15 whole titanium alloy gusset member that the present embodiment Shi Mou iron company produces, adopts by internal mold and external mold structureBecome the isothermal local of patrix to load die forming, internal mold Forming Workpiece mid portion, external mold Forming Workpiece both sides, workpieceThe position that upper internal mold and external mold line of demarcation are corresponding and adjacent area thereof are transition region. This TA15 titan alloy casting ingot adopts threeInferior vacuum consumable arc-melting, transformation temperature T_βIt is 990 DEG C. Concrete operations are as follows:

The first step, blank change forging. TA15 titan alloy casting ingot is heated to T in resistance furnace_β+ 100 DEG C, insulation 2h,Upsetting pull in quick forging machine, deflection 50%～60%, water-cooled after forging; Then blank is heated in resistance furnace to T_β-40℃，Insulation 1.5h, upsetting pull repeatedly in quick forging machine, total deformation is 50～60%, water-cooled after forging.

Second step, preformed blank preparation. By the blank appearance parcel adiabatic cotton changing after forging, be heated to T_β-40 DEG C, protectTemperature 2h, adopts open die forging and loose tooling forging to carry out base, after every fire completes, melts down heating at blank surface parcel adiabatic cotton,Heating-up temperature T_β-40 DEG C, insulation 2h, totally six fire complete base.

The 3rd step, isothermal local load. On 8000 tons of isothermal forging hydraulic presses, carry out isothermal local loading. Adopt togetherInferior local loading, drafts is 28mm, average deformation amount 50%, point two loadings have walked.

First loads in step, blank is heated in chamber type electric resistance furnace to T_β-30 DEG C, insulation 1h; Mold heated arrives T_β-50 DEG C. By the mid portion of internal mold Forming Workpiece, in shaping, internal mold presses down with the speed of 0.2mm/s, depressesAmount is 28mm. After internal mold has loaded, forging is taken out to water-cooled.

Second loads in step, first external mold is installed and is heated to T_β-50 DEG C. Forging is heated in chamber type electric resistance furnace T_β-30 DEG C, be incubated 1 hour, put into subsequently mould and be shaped. External mold loading velocity 0.2mm/s, drafts 28mm.

The 4th step, finishing. On 8000 t hydraulic press, carry out. Interior external mold is depressed simultaneously, and forcing press pressurize tonnage is8000 tons, the time is 15min. After forging, take out fast forging water-cooled.

The 5th step, heat treatment. Forging heat treating regime is 970 DEG C × 1h water-cooled+840 DEG C × 3h air cooling.

The 6th step, Non-Destructive Testing.

Embodiment bis-:

The first step, blank change forging. TA15 titan alloy casting ingot is heated to T in resistance furnace_β+ 50 DEG C, insulation 3h, soonUpsetting pull on forging machine, deflection 50%～60%, water-cooled after forging; Then blank is heated in resistance furnace to T_β-40℃，Insulation 1.5h, upsetting pull repeatedly in quick forging machine, total deformation is 50～60%, water-cooled after forging.

Second step, preformed blank preparation. By the blank appearance parcel adiabatic cotton changing after forging, be heated to T_β-40 DEG C, protectTemperature 2h, adopts open die forging and loose tooling forging to carry out base, after every fire completes, melts down heating at blank surface parcel adiabatic cotton,Heating-up temperature is T_β-40 DEG C, insulation 2h, totally four fire complete base.

First loads in step, blank is heated in chamber type electric resistance furnace to T_β-30 DEG C, insulation 1h; Mold heated arrives T_β-50 DEG C. By the mid portion of internal mold Forming Workpiece, in shaping, internal mold presses down with the speed of 0.4mm/s, depressesAmount is 28mm. After internal mold has loaded, forging is taken out to water-cooled.

The 4th step, finishing. On 8000 t hydraulic press, carry out. Interior external mold is depressed simultaneously, and forcing press pressurize tonnage is8000 tons, the time is 12min. After forging, take out fast forging water-cooled.

The 5th step, heat treatment. Forging heat treating regime is 960 DEG C × 2h water-cooled+840 DEG C × 2h air cooling.

The 6th step, Non-Destructive Testing.

Embodiment tri-:

The TA15 whole titanium alloy gusset member that the present embodiment Shi Mou iron company produces, adopts by left, center, right threeThe isothermal local that individual piecemeal mould forms patrix loads die forming, intermediate module Forming Workpiece mid portion, left and right mouldPiece motion Forming Workpiece simultaneously both sides, corresponding position and the phase thereof in the line of demarcation of intermediate module and left and right module on workpieceNeighbouring region is transition region. This TA15 titan alloy casting ingot adopts three vacuum consumable arc-meltings, transformation temperature T_βIt is 990 DEG C.Concrete operations are as follows:

The first step, blank change forging. Ingot casting is heated to T in resistance furnace_β+ 50 DEG C, insulation 3h, upsetting pull in quick forging machine,Deflection 50%～60%, water-cooled after forging; Then blank is heated in resistance furnace to T_β-50 DEG C, insulation 1.5h,Upsetting pull repeatedly in quick forging machine, total deformation 50～60%, water-cooled after forging.

Second step, preformed blank preparation. By the blank appearance parcel adiabatic cotton changing after forging, be heated to T_β-40 DEG C, protectTemperature 2h, adopts open die forging and loose tooling forging to carry out base, after every fire finishes, melts down heating at blank surface parcel adiabatic cotton,Heating-up temperature T_β-40 DEG C, insulation 2h, totally four fire complete base.

The 3rd step, isothermal local load. On 8000 tons of isothermal forging hydraulic presses, carry out isothermal local loading. Adopt twiceInferior local loading, overall reduction is 28mm, average deformation amount 50%. The first reduction in pass 18mm, secondInferior drafts 10mm.

The first passage loads point two loadings and has walked. First loads step, first blank is heated in chamber type electric resistance furnaceTo T_β-40 DEG C, insulation 1h; Mold heated is to T_β-50 DEG C. By the mid portion of intermediate module Forming Workpiece, be shapedIn, intermediate module presses down with the speed of 0.4mm/s, and drafts is 18mm. After loading completes, forging is taken out to waterCold. Second loads step, first left module and right module is installed and is heated to T_β-50 DEG C. Forging is added at chamber type electric resistance furnaceHeat is to T_β-40 DEG C, insulation 1h, puts into subsequently mould and is shaped. Left module and right module are depressed simultaneously, loading velocityFor 0.4mm/s, drafts is 18mm. After the first passage completes, forging is taken out to water-cooled, and pull down external mold.

The second passage loads also divides two loadings to walk. First loads step, first forging is added in chamber type electric resistance furnaceHeat is to T_β-40 DEG C, insulation 1h; Mold heated is to T_β-50 DEG C. By the mid portion of intermediate module Forming Workpiece, becomeIn shape, intermediate module presses down with the speed of 0.4mm/s, and drafts is 10mm. After loading completes, forging is taken outWater-cooled. Second loads step, first left module and right module is installed and is heated to T_β-50 DEG C. By forging at chamber type electric resistance furnaceBe heated to T_β-40 DEG C, insulation 1h, puts into subsequently mould and is shaped. Left module and right module are depressed simultaneously, load speedDegree is 0.2mm/s, and drafts is 10mm.

The 3rd step, finishing. On 8000 tons of isothermal forging hydraulic presses, carry out. Three of left, center, right module is depressed simultaneously,Forcing press pressurize tonnage is 8000 tons, and the dwell time is 10min. After forging, take out fast forging water-cooled.

The 5th step, heat treatment. Forging heat treating regime is 970 DEG C × 1.5h water-cooled+850 DEG C × 2h air cooling.

The 6th step, Non-Destructive Testing.

Claims

1. A method for controlling the microstructure and performance of a near-α-type titanium alloy isothermal local loading forming forging transition zone, including controlling blank forging, preform blank preparation and local loading process conditions, finishing process conditions and post-forging heat treatment, characterized in that The control of the structure and performance of the transition zone runs through the entire thermal processing process. By controlling the process parameters in the process, the control of the structure and performance of the transition zone is realized. The specific process is as follows:

The first step, rough forging: the titanium alloy ingot is opened above the phase transition point, the ingot is heated to T _β + (50 ~ 100 ℃), the deformation is greater than 50%, water cooling after forging; the obtained blank is heated to T _β -(40～50℃) two-phase area modified forging, the deformation is more than 50%, water cooling after forging;

Step 2: Preparation of preformed blank: Wrap the surface of the reforged blank with thermal insulation cotton, heat it to T _β -40°C, and use free forging and tire die forging to make the blank; After the first-fire processing, the blank is wrapped with insulation cotton and then returned to the furnace for heating;

The third step, isothermal local loading forming:

a. Divide the workpiece into several loading areas, and divide the mold into corresponding pieces; in each loading pass, use the divided mold to perform partial loading on different loading areas in turn; after all the loading is completed, transfer to The next loading pass, that is, repeat the loading method of the previous loading pass until the total deformation is reached;

b. Each loading pass is two working steps:

In the first loading step, the blank is heated to T _β - (30-40°C), the mold is heated to T _β -50°C, and the workpiece is partially loaded with a block mold, and the pressing speed is 0.2-0.4mm/s. The relative deformation is equal to the total deformation or 55% to 65% of the total deformation; if the mold needs to be replaced, the blank should be water-cooled;

In the second loading step, the blank obtained in the previous step is heated to T _β -(30～40°C), the mold is heated to T _β -50°C,

Use block molds to form other parts of the workpiece, the pressing speed is 0.2-0.4mm/s, and the relative deformation is equal to the total deformation or 55%-65% of the total deformation;

The fourth step, finishing: finishing is carried out after the last fire of partial loading forming, and the pressure is maintained by a press, and the pressure maintaining time is 10 minutes to 15 minutes;

The fifth step, heat treatment: take out the workpiece immediately after forging and water cooling, and then use the heat treatment process of solid solution and recrystallization annealing to heat the workpiece to T _β - (20～30℃), keep it warm for 1～2h, and water cool; heat the workpiece to Recrystallization temperature, keep warm for 2 to 3 hours, and air cool;

The sixth step is non-destructive testing.

2. As claimed in claim 1, a method for controlling the microstructure and properties of the transition zone of a near-α-type titanium alloy formed by isothermal local loading, wherein when the isothermal local loading is used for two-pass loading, the amount of deformation in each pass is greater than that of the material. The critical deformation of crystallization, the deformation of the first pass is 55% to 65% of the total deformation, and the deformation of the second pass is 45% to 35% of the total deformation; the heating temperature of the blank is T _β -(30 ~40℃), the heating temperature of the mold is T _β -50℃; in each loading step, the strain rate of the material is 0.01～0.02s ^-1 , and the corresponding deformation speed is 0.2～0.4mm/s; when the mold needs to be replaced, the The forgings are water-cooled when they are released from the mold.