A method for preparing large-size and high-uniformity Ti650 high-temperature titanium alloy slab

Abstract

The present invention belongs to the technical field of titanium alloy preparation, and specifically discloses a method for preparing a large-size, high-uniformity Ti650 high-temperature titanium alloy slab. The whole forging process is carried out by using asbestos wrapping, which avoids the risk of cracking caused by the temperature reduction of the billet. In the specific preparation, the large-size grains of the alloy ingot are fully broken and the deformation dead zone is eliminated by repeated upsetting and forging of the billet for 2 fires; then the billet is continuously refined under the premise of maintaining uniform structure through "low-high" cycle forging; finally, a high-uniformity Ti650 high-temperature titanium alloy slab with a specification of δ80mm to δ360mm is prepared through upsetting and forming with multiple frequencies and small feeds in the two-phase region. The preparation method of the present invention effectively solves the problems of Ti650 titanium alloy single weight, easy damage, and non-uniform structure. The Ti650 high-temperature titanium alloy slab prepared by the method fully meets the requirements of the aviation manufacturing industry for large size, integration, and high performance of materials.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy preparation, and specifically relates to a method for preparing a large-size high-uniformity Ti650 high-temperature titanium alloy slab, which is mainly used for preparing Ti650 high-temperature titanium alloy slabs with a specification of δ80mm to δ360mm. Background Art

[0002] Ti650 titanium alloy belongs to the Ti-Al-Sn-Zr-Mo-Si-Nb-Ta-WC series multi-component solid solution strengthened 650℃ near-α-type high-temperature titanium alloy. It has the characteristics of low density, high specific strength and good high-temperature performance. It can serve for a long time in a working environment of 650℃. It is mainly used to manufacture key components such as integral blades, blades and hot end components of aircraft engine compressors and high Mach aircraft. It can meet the needs of my country's high thrust-to-weight ratio and low energy consumption turbofan and turboshaft engines, and is a key material to break through the bottleneck of domestic engines.

[0003] The Al equivalent of the alloy is 7.8, and the β stability coefficient K β As high as 0.55, the mechanical properties of the alloy are not only affected by alloying elements, grain size, organizational morphology, and the size and content of α and β phases, but are also relatively greatly affected by the uniformity of texture distribution. As a near-α-type high-temperature titanium alloy dominated by close-packed hexagonal α phase, the alloy has few independent slip systems in the close-packed hexagonal α phase, which makes it difficult to plastically deform and is more likely to produce strong deformation texture and anisotropy, which has an important impact on the performance of the material. Considering the heredity of organizational properties, the uniformity of the slab organization will directly affect the consistency of the organization and performance of the subsequent rolled plate or die forging, and will also affect the grain grade and anisotropy of the plate or die forging; in addition, with the development of aviation models, the large size and integration of materials have posed some challenges, so it is very important to prepare a large-scale, high-performance, and high-uniformity Ti650 slab.

[0004] In addition, due to the narrow processing window of the material and poor processability, the forging process is prone to damage. At the same time, with the increase of billet size and unit weight, the forging permeability of the material deteriorates and the deformation "dead zone" increases. Especially in the two-phase zone, the forging temperature is low and the deformation resistance is large, which can easily cause "deformation temperature rise" and increase the difficulty of controlling the uniformity of organizational properties.

[0005] In view of this, the inventors propose a method for preparing a large-scale and high-uniformity Ti650 high-temperature titanium alloy slab based on the processing characteristics of high-temperature titanium alloy. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing large-scale and high-uniformity Ti650 high-temperature titanium alloy slabs, which effectively solves the problems of Ti650 titanium alloy's single piece weight, easy damage and structural heterogeneity.

[0007] The purpose of the present invention is to be solved by the following technical solutions:

[0008] The present invention provides a method for preparing a large-size and high-uniformity Ti650 high-temperature titanium alloy slab, comprising the following steps:

[0009] Step 1: Forging

[0010] Select qualified ingots, heat and keep them warm, and perform two-stage forging to ensure that large-sized as-cast grains are fully broken to obtain intermediate billets;

[0011] Step 2: Forging of intermediate billet

[0012] The intermediate billet obtained in step 1 is first heated and kept warm, and then subjected to multiple-fire forging to further refine and homogenize the structure of the billet to obtain an intermediate forging billet;

[0013] Step 3: Finished product forging

[0014] After the intermediate forging blank obtained in step 2 is subjected to multi-frequency, small-feed upsetting and drawing forming, a large-size, high-uniformity Ti650 high-temperature titanium alloy slab is obtained.

[0015] Furthermore, during the blank forging in step 1, the ingot is first heated to 100°C to 150°C above the phase transformation point, kept warm for 400min to 600min, and the first fire forging is performed, and air-cooling is performed after forging; then, the ingot is heated to 80°C to 150°C above the phase transformation point, kept warm for 400min to 600min, and the second fire forging is performed, and the final forging temperature is not lower than 800°C. After forging, the blank is air-cooled to obtain an intermediate blank.

[0016] Furthermore, in the step 1, when the blank forging is performed twice, repeated upsetting and drawing and asbestos wrapping are adopted, and the upsetting ratio is controlled at 1.3-1.8, and the drawing deformation is controlled at 20%-40%.

[0017] Furthermore, in the step 2, the intermediate billet forging is performed by "low-high" cycle forging and asbestos coating, and a total of 4 fire forgings are performed.

[0018] Furthermore, the specific process of the 4-fire forging in step 2 is as follows:

[0019] The first fire is heated to 30℃~60℃ below the phase transformation point, kept warm for 400min~600min, then upsetting and air cooling; then heated to 30℃~80℃ above the phase transformation point, kept warm for 200min~400min, forging for the second fire and air cooling; the third fire cold material is heated to 30℃~60℃ below the phase transformation point, kept warm for 400min~600min, then upsetting and air cooling; then heated to 30℃~80℃ above the phase transformation point, kept warm for 200min~400min, forging for the fourth fire, air cooling after forging; the above final forging temperatures are not lower than 700℃ to obtain the intermediate forging billet.

[0020] Furthermore, during the 4-time forging in step 2, the upsetting ratio is controlled at 1.3-1.8, and the drawing deformation is controlled at 25%-45%.

[0021] Furthermore, before forging the finished product in step three, the intermediate forging blank is first heated to 30° C. to 60° C. below the phase transformation point.

[0022] Furthermore, in step three, the finished product forging is divided into 3 to 5 upsetting and drawing processes in total.

[0023] Furthermore, during the upsetting and drawing forming in step three, the drawing deformation in each pass is controlled at 20% to 45%, the final forging temperature is not lower than 700° C., and air cooling is performed after forging.

[0024] Furthermore, the preparation method is used to prepare Ti650 high-temperature titanium alloy slabs with a specification of δ80mm to δ360mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The preparation method provided by the present invention adopts asbestos wrapping in the whole forging process, thereby avoiding the risk of cracking caused by the reduction of the billet temperature. Specifically, during the preparation, the large-sized grains of the alloy ingot as-cast are fully broken and the deformation dead zone is eliminated by repeated upsetting and drawing forging of the billet for two fires; then, the billet is continuously refined while maintaining uniform structure through "low-high" cycle forging; finally, a highly uniform Ti650 high-temperature titanium alloy slab with a specification of δ80mm-δ360mm is prepared through multi-frequency and small-feed upsetting and drawing in the two-phase region. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 is a flow chart of the preparation method of the present invention;

[0030] Figure 2 This is a physical picture of a slab with a specification of δ360 mm prepared in Example 1 of the present invention;

[0031] Figure 3 This is a low-magnification structure diagram of the slab head prepared in Example 1 of the present invention;

[0032] Figure 4 This is a low-magnification microstructure diagram of the tail of the slab prepared in Example 1 of the present invention;

[0033] Figure 5 This is a high-magnification microstructure diagram of the edge of the slab prepared in Example 1 of the present invention;

[0034] Figure 6 This is a high-magnification microstructure diagram of the slab 1 / 4ST prepared in Example 1 of the present invention;

[0035] Figure 7 This is a high-magnification microstructure diagram at 1 / 2ST of the slab prepared in Example 1 of the present invention;

[0036] Figure 8 This is a physical picture of a slab with a specification of δ260 mm prepared in Example 2 of the present invention;

[0037] Fig. 9 This is a low-magnification structure diagram of the slab head prepared in Example 2 of the present invention;

[0038] Fig.10 This is a low-magnification microstructure diagram of the tail of the slab prepared in Example 2 of the present invention;

[0039] Fig.11 This is a high-magnification microstructure diagram of the edge of the slab prepared in Example 2 of the present invention;

[0040] Fig.12 This is a high-magnification microstructure diagram at 1 / 4ST of the slab prepared in Example 2 of the present invention;

[0041] Fig.13 This is a high-magnification microstructure diagram at 1 / 2ST of the slab prepared in Example 2 of the present invention;

[0042] Fig.14 This is a physical picture of a slab with a specification of δ160 mm prepared in Example 3 of the present invention;

[0043] Fig.15 This is a low-magnification structure diagram of the slab head prepared in Example 3 of the present invention;

[0044] Fig.16 This is a low-magnification microstructure diagram of the tail of the slab prepared in Example 3 of the present invention;

[0045] Fig.17 This is a high-magnification microstructure diagram of the edge of the slab prepared in Example 3 of the present invention;

[0046] Fig.18 This is a high-magnification microstructure diagram of the slab 1 / 4ST prepared in Example 3 of the present invention;

[0047] Fig.19 This is a high-magnification microstructure diagram of the slab at 1 / 2ST prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0048] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with some aspects of the present invention as detailed in the appended claims.

[0049] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0050] like Figure 1 As shown, the present invention provides a method for preparing a large-scale high-uniformity Ti650 high-temperature titanium alloy slab, which specifically includes the following steps:

[0051] Step 1: Forging

[0052] Select qualified ingots, heat them to 100°C to 150°C above the phase transformation point, keep them warm for 400min to 600min, perform the first forging, and air cool them; then heat them to 80°C to 150°C above the phase transformation point, keep them warm for 400min to 600min, and perform the second forging; during upsetting, the forging ratio is controlled at 1.3 to 1.8, the drawing deformation is controlled at 20% to 40%, the final forging temperature is not lower than 800°C, and they are air cooled after forging. During the forging process, repeated upsetting and drawing and asbestos coating are used to ensure that temperature drop is avoided, deformation dead zone is eliminated, and cast grains are fully refined and broken to obtain intermediate billets.

[0053] Step 2: Forging of intermediate billet

[0054] Adopting the "low-high" cycle forging and asbestos packaging method, a total of 4 fire forgings are carried out, and the organization is continuously refined under the premise of maintaining uniform organization. Specifically, the first fire is heated to 30℃~60℃ below the phase transformation point, and the temperature is kept for 400min~600min before upsetting and air cooling; then heated to 30℃~80℃ above the phase transformation point, kept for 200min~400min, and then the second fire forging is carried out, and air cooling is carried out; the third fire cold material is heated to 30℃~60℃ below the phase transformation point, kept for 400min~600min, and then upsetting and air cooling is carried out; then heated to 30℃~80℃ above the phase transformation point, kept for 200min~400min, and then the fourth fire forging is carried out; the forging ratio is controlled at 1.3~1.8 during upsetting, the elongation deformation is controlled at 25%~45%, the final forging temperature is not less than 700℃, and air cooling is carried out after forging to obtain the intermediate forging blank.

[0055] Step 3: Finished product forging

[0056] The intermediate forging billet is heated to 30°C to 60°C below the phase transformation point, and subjected to 3 to 5 upsetting and drawing processes with multiple frequencies and small feeds. The drawing deformation is controlled at 20% to 45%, and the final forging temperature is not lower than 700°C. After forging, it is air-cooled to obtain a slab with high uniformity of δ80mm to δ360mm.

[0057] In order to further verify the efficacy of the preparation method of the present invention, Ti650 titanium alloy with a phase transition point of 1045±10°C is selected for the following example description:

[0058] Example 1 (Preparation of Ti650 high temperature titanium alloy slab with a thickness of δ360 mm)

[0059] The embodiment of the present invention provides a method for preparing a large-sized and highly uniform Ti650 high-temperature titanium alloy slab with a thickness of δ360 mm, which is specifically implemented according to the following steps:

[0060] 1) Billet forging

[0061] The qualified ingot is first heated to 1170℃, kept warm for 450min, and then taken out of the furnace for the first upsetting and drawing deformation. The forging ratio is controlled at 1.6 during upsetting, the deformation is controlled at 35% during drawing, and air cooling is used to remove scratches. Then it is heated to 1120℃ and kept warm for 400min, and then the second upsetting and drawing is carried out. The forging ratio is controlled at 1.6 during upsetting, the deformation is controlled at 35% during drawing, and the billet specification after forging is □780mm (□ in the text represents square material), the final forging temperature is controlled at above 800℃, and air cooling is used for cooling.

[0062] 2) Intermediate billet forging

[0063] The intermediate billet forging is completed in 4 passes.

[0064] Specifically, the heating temperature of the first fire is 1010℃~990℃, and it is upsetting and drawing after keeping warm for 450min, and air cooling and cleaning is performed; then it is heated to 1080℃~1100℃, and it is upsetting and drawing after keeping warm for 400min, and air cooling and grinding and cleaning are performed; the third fire upsetting and drawing forging is performed, and the heating temperature is 1010℃~990℃, and it is upsetting and drawing after keeping warm for 450min, and air cooling and cleaning is performed; it is heated to 1080℃~1100℃, and it is upsetting and drawing after keeping warm for 400min, and upsetting and drawing is performed for the fourth fire; the final forging temperature of the above fires is controlled at above 700℃, the forging ratio of upsetting is controlled at 1.6, the deformation during drawing is controlled at 30%~35%, and the specification after the fourth fire forging is □780mm.

[0065] 3) Finished product forging

[0066] The finished product forging is completed in 4 fires, the heating temperature is 1010℃~990℃, the deformation method adopts multi-frequency, small feed upsetting and drawing, the drawing deformation is controlled at 20%~35%, the final forging temperature is controlled at above 700℃, and air cooling is adopted for cooling. The planer and milling machine adds δ360mm thickness of the slab.

[0067] Example 2 (Preparation of Ti650 high temperature titanium alloy slab with a thickness of δ260 mm)

[0068] The embodiment of the present invention provides a method for preparing a large-sized Ti650 high-temperature titanium alloy slab with a thickness of δ260 mm and high uniformity, which is specifically implemented according to the following steps:

[0069] 1) Billet forging

[0070] The qualified ingot is first heated to 1170℃, kept warm for 450min, and then taken out of the furnace for the first upsetting and drawing deformation. The forging ratio is controlled at 1.5 during upsetting, the deformation is controlled at 30% during drawing, and air cooling is used to remove scratches. Then, after being kept warm at 1120℃ for 400min, the second upsetting and drawing is carried out. The forging ratio is controlled at 1.5 during upsetting, the deformation is controlled at 30% during drawing, and the billet specification after forging is □650mm. The final forging temperature is controlled at above 800℃, and air cooling is used for cooling.

[0071] 2) Intermediate billet forging

[0072] The intermediate billet forging is completed in 4 passes.

[0073] Specifically, the heating temperature of the first fire is 1010℃~990℃, and it is upsetting and drawing after keeping warm for 450min, and air cooling and scratch removal are carried out; then it is heated to 1080℃~1100℃, and it is upsetting and drawing after keeping warm for 350min for the second fire, and the material is air cooled after forging, and polished and scratch removal is carried out; the third fire upsetting and drawing forging is carried out, the heating temperature is 990℃~1010℃, and it is upsetting and drawing after keeping warm for 450min, and air cooling is carried out; then it is heated to 1080℃~1100℃, and it is upsetting and drawing after keeping warm for 350min for the fourth fire upsetting; the final forging temperature of the above fires is controlled at above 700℃, the forging ratio of upsetting is controlled at 1.6, the deformation during drawing is controlled at 30%~35%, and the specification after the fourth fire forging is 680mm in square.

[0074] 3) Finished product forging

[0075] The finished product forging is completed in 3 fires, the heating temperature is 1010℃~990℃, the deformation method adopts multi-frequency, small feed upsetting and drawing, the drawing deformation is controlled at 20%~35%, the final forging temperature is controlled at above 700℃, and air cooling is adopted for cooling. The planer and milling machine adds δ260mm thickness of the slab.

[0076] Example 3 (Preparation of Ti650 high temperature titanium alloy slab with a thickness of δ160 mm)

[0077] The embodiment of the present invention provides a method for preparing a Ti650 high-temperature titanium alloy slab with a thickness of δ160 mm and high uniformity, which is specifically implemented according to the following steps:

[0078] 1) Billet forging

[0079] The qualified ingot is first heated to 1170℃, kept warm for 450min, and then taken out of the furnace for the first upsetting and drawing deformation. The forging ratio during upsetting is controlled at 1.5, the deformation during drawing is controlled at 30%, and air cooling is performed; then it is heated to 1120℃ and kept warm for 400min, and then the second upsetting and drawing is performed. The forging ratio during upsetting is controlled at 1.5, the deformation during drawing is controlled at 30%. The specification of the billet after forging is □580mm, the final forging temperature is controlled at above 800℃, and air cooling is used for cooling.

[0080] 2) Intermediate billet forging

[0081] The intermediate billet forging is completed in 4 steps.

[0082] Specifically, the heating temperature of the first fire is 1010℃~990℃, and it is upsetting and air-cooling after being kept warm for 450min; then it is heated to 1080℃~1100℃, and it is upsetting and air-cooling after being kept warm for 300min; then it is heated to 1080℃~1100℃, and it is upsetting and air-cooling after being kept warm for 300min; after the forging, the material is air-cooled and polished to remove scratches; the third fire upsetting forging is carried out, the heating temperature is 1010℃~990℃, and it is upsetting and air-cooling after being kept warm for 450min; then it is heated to 1080℃~1100℃, and it is upsetting and air-cooling to remove scratches after being kept warm for 300min; the final forging temperature of the above fires is controlled at above 700℃, the forging ratio of upsetting is controlled at 1.6, the deformation during drawing is controlled at 30%~35%, and the specification after the fourth fire forging is 550mm in all directions.

[0083] S3, finished product forging

[0084] The finished product forging is completed in 4 fires, the heating temperature is 1010℃~990℃, the deformation method adopts multi-frequency, small feed upsetting and drawing, the drawing deformation is controlled at 20%~35%, the final forging temperature is controlled at above 700℃, and air cooling is adopted for cooling. The planer and milling machine adds δ160mm thickness of the slab.

[0085] Result analysis:

[0086] Figure 2 This is a physical picture of a δ360 mm slab prepared by forging using the process of the present invention in Example 1. Figure 3 , Figure 4 The macrostructures of the head and tail of the corresponding slabs show that there is no delamination, cracks, pores, segregation, metal and non-metal inclusions and other metallurgical defects visible to the naked eye in the macrostructures. The microstructures are uniform and fuzzy. Figure 5 , Figure 6 , Figure 7 The microstructures of the edge, 1 / 4ST and 1 / 2ST parts of the corresponding slabs are shown in Figure 2. The microstructure of the slab is a processed structure in the α+β two-phase region, all the original β grain boundaries are fully broken, there is no continuous and straight grain boundary α phase, and the microstructure is uniform and consistent.

[0087] Figure 8 This is a physical picture of a δ260 mm slab prepared by forging using the process of the present invention in Example 2. Fig. 9 , Fig.10 The macrostructures of the head and tail of the corresponding slabs show that there is no delamination, cracks, pores, segregation, metal and non-metal inclusions and other metallurgical defects visible to the naked eye in the macrostructures. The microstructures are uniform and fuzzy. Fig.11 , Fig.12 , Fig.13The microstructures of the edge, 1 / 4ST and 1 / 2ST parts of the corresponding slabs are shown in Figure 2. The microstructure of the slab is a processed structure in the α+β two-phase region, all the original β grain boundaries are fully broken, there is no continuous and straight grain boundary α phase, and the microstructure is uniform and consistent.

[0088] Fig.14 This is a physical picture of a slab with a size of 160 mm prepared by forging using the process of the present invention in Example 3. Fig.15 , Fig.16 The macrostructures of the head and tail of the corresponding slabs show that there is no delamination, cracks, pores, segregation, metal and non-metal inclusions and other metallurgical defects visible to the naked eye in the macrostructures. The microstructures are uniform and fuzzy. Fig.17 , Fig.18 , Fig.19 The microstructures of the edge, 1 / 4ST and 1 / 2ST parts of the corresponding slabs are shown in Figure 2. The microstructure of the slab is a processed structure in the α+β two-phase region, all the original β grain boundaries are fully broken, there is no continuous and straight grain boundary α phase, and the microstructure is uniform and consistent.

[0089] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0090] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a large-scale, high-uniformity Ti650 high-temperature titanium alloy slab, characterized in that: The following steps are involved: Step 1: Forging Select qualified ingots, heat and keep them warm, and perform two-stage forging to ensure that large-sized as-cast grains are fully broken to obtain intermediate billets; Step 2: Forging of intermediate billet The intermediate billet obtained in step 1 is first heated and kept warm, and then subjected to multiple-fire forging to further refine and homogenize the structure of the billet to obtain an intermediate forging billet; Step 3: Finished product forging After the intermediate forging blank obtained in step 2 is subjected to multi-frequency, small-feed upsetting and drawing forming, a large-size, high-uniformity Ti650 high-temperature titanium alloy slab with a thickness of δ80mm to δ360mm is obtained; In the step 2, the intermediate billet forging is carried out by "low-high" cycle forging and asbestos packaging, and a total of 4 fire forgings are carried out. The specific process is as follows: The first fire is heated to 30℃~60℃ below the phase transformation point, kept warm for 400min~600min, then upsetting and air cooling; then heated to 30℃~80℃ above the phase transformation point, kept warm for 200min~400min, then forging for the second fire, then air cooling; the third fire is heated to 30℃~60℃ below the phase transformation point, kept warm for 400min~600min, then upsetting and air cooling; then heated to 30℃~80℃ above the phase transformation point, kept warm for 200min~400min, then forging for the fourth fire, then air cooling; the above final forging temperature is not less than 700℃, and the intermediate forging billet is obtained; and the upsetting ratio of each fire is controlled at 1.3~1.8, and the drawing deformation is controlled at 25%~45%; Before forging the finished product in step 3, the intermediate forging blank is first heated to 30°C to 60°C below the phase transformation point. The finished product forging in step 3 is divided into 3 to 5 upsetting and drawing processes in total. During the upsetting and drawing process, the elongation deformation of each drawing process is controlled at 20% to 45%. The final forging temperature is not lower than 700°C, and air cooling is performed after forging.

2. The method for preparing a large-sized and high-uniformity Ti650 high-temperature titanium alloy slab according to claim 1, characterized in that: During the blank forging in step 1, the ingot is first heated to 100°C to 150°C above the phase transformation point, kept warm for 400min to 600min, and then forged in the first fire, and then air-cooled; then heated to 80°C to 150°C above the phase transformation point, kept warm for 400min to 600min, and then forged in the second fire, the final forging temperature is not less than 800°C, and the blank is air-cooled after forging to obtain an intermediate blank.

3. The method for preparing a large-sized and high-uniformity Ti650 high-temperature titanium alloy slab according to claim 2, characterized in that: When the blank forging is performed twice in step 1, repeated upsetting and drawing and asbestos wrapping are adopted, and the upsetting and forging ratio is controlled at 1.3-1.8, and the drawing deformation is controlled at 20%-40%.

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