A secondary die forging forming method of a high-temperature titanium alloy large-size curved surface component with high strength characteristics

Abstract

The present application belongs to the field of hot working of titanium-based materials, and particularly relates to a secondary die forging forming method of high-temperature titanium alloy large-size curved surface components with high strength characteristics. The method comprises applicable alloy types, forming processes, heat treatment methods and other constituent elements and optimized matching thereof. Three main procedures of high-temperature primary forming, medium-temperature secondary forming and low-temperature annealing treatment are adopted. The present application method can be used to prepare near-alpha type titanium alloy large-size curved surface forgings with a weight of 500 kg or more, such as TA15, TA32, TA33, TA37, TA38 and the like, and special effects of a room temperature strength retention rate of 97% and a high-temperature strength retention rate of 95% can be obtained. The high-temperature titanium alloy large-size curved surface components prepared by using the present application technology can be used in the fields of aerospace and the like for integral or split panel or wall plate structures, and meet the application requirements of lightweight high-temperature resistant materials in the fields of aerospace and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of hot working of titanium-based materials, and particularly relates to a secondary die forging forming method for a large-size curved surface component of a high-temperature titanium alloy with high strength characteristics. BACKGROUND

[0002] Different periods of aerospace vehicles have different needs for materials and preparation processes. In the early days, aircraft or spacecraft used aluminum alloy products in large areas to achieve lightweight structures, improve fuel efficiency, speed, load rate, and maneuverability. With the improvement of technical requirements, the strength and temperature resistance of aluminum alloys cannot meet the requirements, so titanium alloys represented by Ti-6Al-4V gradually replace aluminum alloys and become key materials for aircraft structures; the development of high-Mach number aircraft technology makes traditional low-temperature components high-temperature, that is, the parts working at a temperature of 200℃ or even lower for traditional low-Mach number aircraft are generally improved in working temperature under high-Mach number flight conditions, and higher requirements are put forward for the strength and temperature resistance of the materials. In addition, the improvement of aircraft structure and function also needs more efficient overall structure to ensure.

[0003] Most of the traditional large-size curved surface components are formed by plate and rib process, and the plate and rib forming requires the material to have good formability and welding process performance. In addition, the plate and rib forming is limited by material properties and part deformation and surface oxidation, and the heat treatment means for material performance control is limited, so the traditional plate and rib forming process mainly controls the shape, and the performance of the material and the structure is reduced compared with the actual performance level of the material.

[0004] For parts that cannot meet the plate and rib forming or the mechanical properties after plate and rib forming, it is necessary to use the method of overall forming and machining. The biggest advantage of the manufacturing method is to eliminate the inconsistency of the organization performance of different positions of the parts and reduce the weak links, which is of great significance to fatigue structural parts.

[0005] The overall forming + machining process also faces the problem of shape and property matching control. For high-temperature titanium alloys, in order to obtain the best performance matching, it is necessary to use a solid solution and aging treatment system; during the cooling process after solid solution treatment, because of the difference in cooling speed of different positions of the forging, internal stress will be generated in the material, which will cause deformation of the material, thereby being not conducive to the size precision control of the forging; if the solid solution and aging treatment is not used, the performance of the parts is difficult to reach the material design level, and the shape and property control problem is prominent.

[0006] High temperature titanium alloy is a kind of material with specific purpose developed with the development of aero-engine technology in the 1950s, and the current mature application high temperature titanium alloy use temperature range is 350 DEG C~600 DEG C. Compared with other categories of titanium alloy, the most notable feature of high temperature titanium alloy is to require high endurance and creep performance, and the whole machine forming process after forging can maximize the inherent characteristics of high temperature titanium alloy.

[0007] High temperature titanium alloy has three types of partial beta type, alpha + beta type and near alpha type, partial beta type high temperature titanium alloy use temperature is below 450 DEG C, alpha + beta alloy use temperature is in the range of 350 DEG C~550 DEG C, and the existing high temperature titanium alloy above 550 DEG C belongs to near alpha type. The near alpha type high temperature titanium alloy, especially the near alpha type high temperature titanium alloy above 550 DEG C, has a strong and tough matching control problem, and the mechanical properties are sensitive to composition uniformity, impurity element content, forging structure uniformity, heat treatment temperature, time, cooling rate after heat treatment and the like. For large size curved components, because the deformation problem also needs to be considered, the difficulty of matching strength and toughness is higher. SUMMARY

[0008] In view of the application requirement of high temperature titanium alloy large size curved component characteristic performance matching in the field of aerospace, the purpose of the present application is to provide a secondary die forging forming method of high temperature titanium alloy large size curved component with high strength characteristics. The high temperature titanium alloy large size curved component prepared by the present application has a strength level basically equivalent to that of the existing mature process prepared forging, and can be used for whole or split panel or wall plate structure in the field of aerospace and the like, and meets the application requirement of lightweight high temperature resistant material in the field of high technology such as aerospace.

[0009] The technical scheme of the present application is:

[0010] A secondary die forging forming method of high temperature titanium alloy large size curved component with high strength characteristics, comprising three main processes of high temperature primary forming, medium temperature secondary forming and low temperature annealing treatment, and the applicable materials include TA15, TA32, TA33, TA37 or TA38 high temperature titanium alloy materials, and the specific steps are as follows:

[0011] 1) high temperature primary forming

[0012] The forging blank is heated to 10 DEG C~50 DEG C below the alpha + beta / beta phase transition point in the heating equipment, and the heat penetration is kept for 1~4h; after the end of the heat preservation, the forging blank is transferred into the forging die, and is formed by water pressure machine forging;

[0013] 2) medium temperature secondary forming

[0014] Forming heating temperature 750℃-850℃, after heating, the quenched forging blank is loaded into the electric furnace, and after hot penetration, it is kept for 20min-120min; after the end of the keeping, the forging blank is transferred into the forging die, and the water pressure machine is used for secondary forging forming treatment;

[0015] 3) Low temperature annealing treatment

[0016] After the secondary forming at medium temperature, the forging blank is transferred into the air for air cooling to room temperature; or is cooled in the air to a temperature below 650℃, and then is directly transferred into the electric furnace for annealing treatment, the annealing temperature is 650℃-750℃, and the annealing treatment time is 2-50h after hot penetration keeping.

[0017] The secondary die forging forming method of the large-size curved surface member of the high-temperature titanium alloy with high strength characteristics, the cooling mode after the end of the high-temperature primary forming is quenching treatment.

[0018] The secondary die forging forming method of the large-size curved surface member of the high-temperature titanium alloy with high strength characteristics, the forging blank is directly transferred into the quenching tank for quenching treatment to room temperature after the end of the high-temperature primary forming.

[0019] The secondary die forging forming method of the large-size curved surface member of the high-temperature titanium alloy with high strength characteristics, the forging blank is transferred into the air for air cooling to below 800℃, and high-temperature solid solution treatment is carried out: the forging blank after primary forming is loaded into the furnace below 800℃, is heated to 10℃-50℃ below the alpha+beta / beta phase transition point, is kept for 1-3h after hot penetration, and is quenched in the water tank or oil tank after being taken out of the furnace to room temperature.

[0020] The secondary die forging forming method of the large-size curved surface member of the high-temperature titanium alloy with high strength characteristics, after the end of the low-temperature annealing treatment in step 3), the forging blank is taken out of the furnace and air cooled to room temperature; or is cooled at a controlled temperature or is cooled in the furnace after power-off to below 400℃, and is taken out of the furnace and air cooled to room temperature.

[0021] The secondary die forging forming method of the large-size curved surface member of the high-temperature titanium alloy with high strength characteristics, the curved surface member has a single weight of greater than or equal to 500kg, a thickness of 30-100mm, and a projection area of greater than or equal to 2m 2 , the raw material used is a forged or rolled forging blank, and the macrostructure meets the requirements of 1-3 levels of fuzzy crystal of GJB 2220A-2018 standard.

[0022] The design idea of the application is:

[0023] In order to realize the high strength and high dimensional accuracy requirements of large size curved surface forgings, the following main influencing factors are considered: one is the equipment capacity, under the condition of certain material deformation resistance, the pressure required for forging forming is proportional to the projection area, in order to avoid the problem of insufficient equipment capacity, the design adopts the forging blank with good low-multiplication organization as the forming blank, the purpose of die forging is forming rather than deformation, so that the forgings with the largest possible size can be formed under the premise of limited equipment tonnage; two is the forming process. The conventional production process of high-temperature titanium alloy forgings is forging forming + solid solution aging heat treatment. For large size curved surface forgings, if the conventional process is used for production, the forging is prone to large-scale deformation during the solid solution treatment and subsequent quenching cooling process; if the unconventional means is used, the mechanical properties of the forging, especially the strength level, are difficult to guarantee. In order to solve the above problems, the present application proposes a secondary die forging forming + annealing process. The first forming is required to be completed below 10℃-50℃ of the α+β / β phase transition point, the heating temperature, holding time and cooling rate after forming are strictly controlled, the volume fraction of primary α phase is about 10-40% of the duplex structure, so as to ensure that the forging has high initial strength; the second forming temperature is required to be in the range of 750℃-850℃, the holding time is strictly controlled, so as to prevent the α phase grains from being excessively coarsened and causing the strength level to be greatly reduced; the low-temperature annealing process not only adapts to the first and second forming, but also pays attention to the reasonable matching of annealing temperature and time, so as to make the α2 phase and silicide of different scales appropriately precipitate in the forging structure, make up for the strength loss caused by the second hot medium-temperature forming, and realize the good compromise of high strength and high dimensional accuracy of large size forgings.

[0024] The advantages and beneficial effects of the present application are:

[0025] 1. The present application can form large size curved surface components of high-temperature titanium alloy with high deformation resistance characteristics, the technical bottleneck of the limited size of traditional high-temperature titanium alloy forgings is effectively broken through, and the typical forging blanks and part shapes suitable for the present application are shown in Figure 1 and Figure 2 .

[0026] 2. The high-multiplication organization of the large size curved surface component is duplex structure, the volume fraction of primary α phase is required to be controlled between 10% and 40%, Figure 3 is a typical organization with a volume fraction of primary alpha phase of about 15%, and after low-temperature annealing, the α2 phase is generated in the strip-shaped α phase Figure 5 , so that the mechanical properties of the forging, especially the strength level, can be effectively guaranteed.

[0027] 3. The large size curved surface component of high-temperature titanium alloy of the present application can realize a strength retention rate of more than 96%, and the dimensional accuracy control is good.

[0028] 4. The method of the present application has high operability and is conducive to engineering application.

[0029] 5、The method of the present application includes deformation mode, process, annealing system and other components to obtain forgings with high strength characteristics to meet the application requirements of high strength high temperature titanium alloy curved forgings in aerospace. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a schematic diagram of the typical curved forging blank geometry of the present application.

[0031] Figure 2 It is a schematic diagram of the typical curved part geometry of the present application.

[0032] Figure 3 It is a typical high magnification structure after two forming of the curved forgings of the present application.

[0033] Figure 4 It is a typical high magnification structure obtained by using traditional process under shape control constraint.

[0034] Figure 5 It is the dispersed alpha2 phase generated after low temperature annealing of the curved forgings of the present application. DETAILED DESCRIPTION

[0035] In the specific implementation process, the present application proposes a secondary die forging forming method of high temperature titanium alloy large size curved component with high strength characteristics, which includes applicable alloy type, hot working process and heat treatment method and other components, including the following steps:

[0036] 1) The die forging blank is selected from high temperature titanium alloy forgings with a thickness of 30-100 mm, and the original state is required to be forged, and the macrostructure needs to meet the 1-3 level blurred crystal requirement of GJB2220A-2018 standard;

[0037] 2) The forging is formed in two steps, the first step is high temperature primary forming, and the second step is medium temperature secondary forming, the high temperature primary forming undertakes main deformation, and the medium temperature secondary forming mainly realizes local deformation to realize high precision control of the forging size;

[0038] 3) High temperature primary forming: heat the forging blank in the electric furnace to a certain temperature in the range of 10-50℃ below the alpha+beta / beta phase transition point, heat through and keep for 1-4h; after the end of the heat preservation, transfer to the forging die, and form by using the water pressure machine; then transfer to the air and air cool below 800℃, and then execute the step 4); or transfer to the quenching tank (water quenching tank or oil quenching tank) for quenching treatment, at this time, skip the step 4) and directly execute the step 5) operation;

[0039] 4) High temperature solid solution treatment: after the primary forming, the forging blank is loaded into the furnace below 800℃, heated to a certain temperature in the range of 10-50℃ below the alpha+beta / beta phase transition point, heat through and keep for 1-3h, and after taking out of the furnace, transfer to the water quenching tank for quenching treatment;

[0040] 5) Medium temperature secondary forming: the electric furnace is heated to a temperature in the range of 750-850°C, after the temperature is reached, the forged blank after quenching is loaded into the electric furnace, and after the hot penetration, the blank is kept for 20-120 min; after the keeping, the blank is transferred into the forging die, and the secondary forming treatment is performed by using the hydraulic press;

[0041] 6) Low temperature annealing: after the secondary forming is finished, the forged piece is transferred into the air to be air cooled to room temperature; or after being cooled to 550-650°C, the forged piece is directly transferred into the electric furnace for annealing treatment, the annealing treatment temperature is 650-750°C, after the hot penetration, the blank is kept for 2-50 h. After the keeping, the blank is taken out of the furnace and air cooled to room temperature, or is cooled to below 400°C (preferably 300°C) in the furnace, and then is taken out of the furnace and air cooled to room temperature.

[0042] The preparation method has the following characteristics: the primary and secondary forming are mainly aimed at "controlling the shape", and do not require the forged blank to have a compression deformation in the thickness direction, that is, the purpose of the die forging is to shape rather than to deform. By using the method, the titanium alloy large-size curved forged piece with a weight of more than 500 kg, such as TA33, TA37 or TA38, etc., and a projection area of more than 2 m 2 , can be prepared, and the special effects of a room temperature strength retention rate of 97% and a high temperature strength retention rate of 95% can be obtained.

[0043] The application will be further described in detail through the following examples.

[0044] Example 1

[0045] The experimental material is a TA38 alloy forged or rolled slab with a size of 3200 mm x 660 mm x 80 mm, a nominal composition of Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C, a weight of 780 kg, an α+β / β phase transition temperature of 1035°C, and a low-magnification cross-section microstructure of 2-grade fuzzy crystal. The preparation process route mainly includes three steps of primary forming → secondary forming → annealing treatment:

[0046] 1) Primary forming: the heating temperature of the forged blank is 1005°C, and the preheating temperature of the forging die is 300°C. The forged blank is heated by using the electric furnace conforming to GJB 904A Class II, the blank is loaded into the furnace at 800°C, the hot penetration time is 50 min after the temperature is raised to 1005°C, and the keeping time is 120 min; after the keeping, the blank is taken out of the furnace and transferred into the forming forging die, and the blank is formed by using the die forging press, and then is transferred into the water quenching tank for quenching treatment to room temperature;

[0047] 2) Secondary forming: forging blank heating temperature 750°C, forging die preheating temperature 300°C. The forging blank is heated in an electric furnace in accordance with GJB 904A Class III, 750°C charging, after the temperature is re-raised to 750°C, the hot penetration time is 50 min, the holding time is 120 min; after the holding is completed, the furnace is discharged and transferred to the forming forging die, the forging is formed by a die forging press, the forging is left in the die for 10 min, and then transferred to the atmospheric environment for air cooling to room temperature;

[0048] 3) Annealing treatment: annealing temperature 650°C. The forging is heated in an electric furnace in accordance with GJB 904A Class III, 500°C charging, the temperature is raised to 650°C at a rate of 5°C / min, the hot penetration time is 50 min, the holding time is 240 min; after the holding is completed, the furnace is naturally cooled to 300°C and discharged, and then air cooled to room temperature.

[0049] Example 2:

[0050] The experimental material is a TA38 alloy forged or rolled plate blank with a size of 2800 mm x 1000 mm x 90 mm, a nominal composition of Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C, a weight of 1160 kg, an α+β / β phase transition temperature of 1035°C, and a low-magnification cross-section microstructure of 2-grade fuzzy crystal. The preparation process route is divided into three steps of primary forming → secondary forming → annealing treatment:

[0051] 1) Primary forming: forming temperature 1020°C, forging die preheating temperature 300°C. The forging blank is heated in an electric furnace in accordance with GJB 904A Class II, 800°C charging, after the temperature is raised to 1020°C, the hot penetration time is 60 min, the holding time is 120 min, after the holding is completed, the furnace is discharged and transferred to the forming forging die, the forging is formed by a die forging press, and the forging blank is transferred to a water quenching tank for quenching treatment to room temperature after forming;

[0052] 2) Secondary forming: forming temperature 800°C, forging die preheating temperature 300°C. The forging blank is heated in an electric furnace in accordance with GJB 904A Class III, 800°C charging, after the temperature is re-raised to 800°C, the hot penetration time is 30 min, the holding time is 40 min; after the holding is completed, the furnace is discharged and transferred to the forming forging die, the forging is secondarily formed by a die forging press, the forging is left in the die for 10 min after unloading, and then transferred to the atmospheric environment for air cooling to room temperature;

[0053] 3) Annealing treatment: annealing temperature 700℃. The electric furnace in accordance with GJB 904A class III is used for heating, the furnace is loaded at 500℃, the temperature is raised to 700℃ at a rate of 5℃ / min, the hot penetration time is 40min, the holding time is 240min; after the holding time ends, the furnace is cooled to 300℃ and then the furnace is unloaded, and then the air cooling is performed to room temperature.

[0054] Example 3:

[0055] The experimental material is TA38 alloy forged or rolled slab with a size of 3100mmx1600mmx75mm, a nominal composition of Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C, a weight of 1660kg, an α+β / β phase transition temperature of 1042℃, and a low-magnification microstructure of the cross section of the forging blank being 3-grade blurred crystal. The preparation process route includes three steps of primary forming→secondary forming→annealing treatment:

[0056] 1) Primary forming: forming temperature 1025℃, preheating temperature of the forging die 300℃. The electric furnace in accordance with GJB 904A class II is used for heating, the forging blank is loaded into the furnace at 800℃, the temperature is raised to 1025℃, the hot penetration time is 40min, and the holding time is 120min; after the holding time ends, the furnace is unloaded, the forging blank is transferred into the forming die, the die forging press is used for forging forming, and the forged blank is transferred into the water quenching tank for quenching treatment to room temperature after forming;

[0057] 2) Secondary forming: forming temperature 850℃, preheating temperature of the die 300℃. The electric furnace in accordance with GJB 904A class III is used for heating to 850℃, the furnace is loaded when the temperature reaches, the hot penetration+holding time is 60min; after the holding time ends, the furnace is unloaded, the forging blank is transferred into the forming forging die, and the die forging press is used for hot pressing forming; after the press is unloaded, the forging is kept in the die for 10min, and then the air cooling is performed to 600℃ in the atmospheric environment, and the forging is reheated into the furnace for annealing treatment;

[0058] 3) Annealing treatment: annealing temperature 680℃. The electric furnace in accordance with GJB 904A class III is used for heating, the furnace is loaded at 500℃, the temperature is raised to 680℃ at a rate of 5℃ / min, the hot penetration time is 40min, and the holding time is 300min; after the holding time ends, the furnace is cooled to 300℃ and then the furnace is unloaded, and then the air cooling is performed to room temperature.

[0059] Example 4:

[0060] The experimental material is a TA38 alloy forged or rolled slab with a size of 3100mmx1600mmx75mm, a nominal composition of Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C, a weight of 1660kg, an α+β / β phase transition temperature of 1042℃, and a low-magnification structure of a 3-grade blurred crystal in the cross section of the forging blank. The preparation process route comprises four steps of one-time forming, high-temperature heat treatment, two-time forming, and annealing treatment:

[0061] 1) One-time forming: forming temperature 992℃, preheating temperature of the forging die 300℃, heating by a GJB 904A III-class electric furnace, 800℃ charging, after the temperature is raised to 992℃, heat penetration time 40min, holding time 60min, after the holding ends, discharging, transferring into the die, forming by a die forging press, after forming, transferring into the air to cool to room temperature;

[0062] 2) High-temperature solid solution treatment: target temperature 1020℃, heating by a GJB 904A II-class electric furnace, 800℃ charging, after the temperature is raised to 1020℃, heat penetration time 40min, holding time 120min; after the holding ends, discharging, transferring into a water quenching tank to cool to room temperature;

[0063] 2) Two-time forming is the same as in Example 2;

[0064] 3) Annealing treatment: annealing temperature 700℃. Heating by a GJB 904A III-class electric furnace, 500℃ charging, heating at a rate of 5℃ / min to 700℃, heat penetration time 40min, holding time 120min; after the holding ends, cooling in the furnace to 650℃, holding for 40h, then cooling to 300℃ to discharge, and then air cooling to room temperature.

[0065] The mechanical properties that can be reached by the components described in Examples 1-4 are shown in Tables 1 and 2. In the tables, Comparative Example 1 is the mechanical property of a 160kg weight, 80mm thickness forged piece after water quenching after solid solution treatment, which is the mechanical property under the ideal condition of the material, and Comparative Example 2 is the mechanical property of a 500mm length, 200mm width, 80mm thickness forged piece after air cooling treatment, which is the mechanical property of the traditional heat treatment means under the condition of shape control constraint. It can be seen that by using the process described in the application, the room temperature and tensile strength retention rate reaches more than 95% of the ideal level of the material, which is significantly higher than the level that can be reached by the traditional shape control process.

[0066] Table 1 is the room temperature tensile property

[0067] Sample state [R m , MPa [R p0.2 , MPa A，％ Z，％ Example 1 1095 1000 9.5 20 Example 2 1074 987 9.5 20 Example 3 1064 975 11.5 19 Example 4 1082 988 12.0 19 Comparative Example 1 1111 1022 7.5 11 Comparative Example 2 1029 923 12.0 15

[0068] Table 2 is the 650℃ tensile property

[0069] Sample state [R m , MPa [R p0.2 , MPa A，％ Z，％ Example 1 634 530 24.5 48 Example 2 632 515 17.5 49 Example 3 621 503 18.5 49 Example 4 624 500 37.5 60 Comparative Example 1 661 532 22.5 62 Comparative Example 2 603 476 24.0 34

[0070] As shown in Figure 3 , the typical high-magnification structure of the curved forging after twice forming of the application is a dual-state structure, and there are fine flaky secondary alpha phases inside the original beta grains, which is relatively easy to obtain in the case of small forging size, without or less considering shape control, but for large projection area and complex shape forgings, in order to control the size accuracy, the conventional process will obtain coarse secondary alpha phase, which will significantly weaken the strengthening effect, as shown in Figure 4 .

[0071] As shown in Figure 5 , the dispersed alpha2 phase generated after low-temperature annealing of the curved forging of the application can be seen that under the process conditions of the application, the precipitation of alpha2 phase at high temperature is fully inhibited, so that most of the alpha2 phase is mainly generated during the low-temperature annealing process, the number of alpha2 phase is more, the particle is finer, and the strengthening effect is more obvious.

[0072] In summary, on the basis of theoretical analysis and experimental research, according to the application requirements of higher strength and high-temperature titanium alloy large-size curved surface products in the fields of aviation and aerospace, a twice die forging forming method of high-temperature titanium alloy large-size curved surface component with high strength characteristics is proposed, which can realize the full consideration of the size accuracy and mechanical properties of high-temperature titanium alloy large-size curved surface forgings, and can be applied to TA32, TA33, TA37 or TA38 high-temperature titanium alloy materials, used for the production of high-temperature structure of aircraft or spacecraft, and has broad application prospect.

Claims

1. A method for secondary die forging of large-size curved surface components made of high-temperature titanium alloy with high strength characteristics, characterized in that, The process includes three main steps: high-temperature one-time forming, medium-temperature two-time forming, and low-temperature annealing. Applicable materials are TA32, TA33, TA37, or TA38 high-temperature titanium alloys. Curved components must weigh ≥500kg, have a thickness of 30~100mm, and a projected area ≥2m². 2 The specific steps are as follows: 1) High-temperature one-time molding The forging billet is heated in a heating device to 10℃~50℃ below the α+β / β phase transformation point, and held at that temperature for 1~4 hours after heat penetration. After holding, the forging billet is transferred to a forging die and formed by hydraulic press. The cooling method after high-temperature one-time forming is to transfer the forging billet directly to a quenching tank for quenching to room temperature; or, after high-temperature one-time forming, the forging billet is transferred to air-cooled to below 800℃ and subjected to high-temperature solution treatment. After one-time forming, the forging billet is loaded into the furnace at a temperature below 800℃, heated to 10℃~50℃ below the α+β / β phase transformation point, held at that temperature for 1~3 hours after heat penetration, and then transferred to a water tank or oil tank for quenching to room temperature after removal from the furnace. 2) Medium-temperature secondary forming The forming heating temperature is 750℃~850℃. After reaching the temperature, the quenched forging billet is placed into the electric furnace and heated through. After heating, it is held at the temperature for 20min~120min. After the holding time is completed, the forging billet is transferred to the forging die and subjected to secondary forging forming using a hydraulic press. 3) Low-temperature annealing treatment After the forging billet is formed in the medium temperature secondary process, it is cooled in the air to a temperature below 650℃, and then directly transferred to an electric furnace for annealing. The annealing temperature is 650℃~750℃, and the annealing time is 2~50h after heat penetration. After the low temperature annealing treatment is completed, it is taken out of the furnace and air-cooled to room temperature, or cooled with the furnace to below 400℃ after power is cut off and then air-cooled to room temperature.

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