Method for producing short-process ti-55531 titanium alloy bar

Abstract

The application discloses a preparation method of short-process Ti-55531 titanium alloy bar, and steps include: step 1, open-die forging: the titanium alloy ingot is heated and kept, and after 1-2 times of forging, the intermediate blank is obtained; step 2, intermediate forging: the intermediate blank is heated and kept, and after 3-6 times of forging, the intermediate bar blank is obtained; step 3, recrystallization heat treatment: the intermediate bar blank obtained in step 2 is heated and kept, and after cooling, the intermediate bar blank with uniform and fine beta structure is obtained; step 4, forming forging: the intermediate bar blank is heated and kept, and after 1-2 times of forging, the finished bar is obtained. The method belongs to the technical field of non-ferrous metal processing, and the Ti-55531 titanium alloy large-size bar prepared by the method has the advantages of small grain size of the titanium alloy intermediate blank, uniform and fine macrostructure, less preparation times, short process and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing technology and relates to a short-process method for preparing Ti-55531 titanium alloy bars. Background Technology

[0002] Ti-55531 titanium alloy, with a nominal composition of Ti-5Al-5Mo-5V-3Cr-1Zr, is a multi-component near-β type titanium alloy. It has the characteristics of high hardenability, low segregation sensitivity, wide range of hot working processes, high strength, and high fracture toughness. It is currently widely used in the manufacture of key components such as aircraft landing gear, wing joints, and suspension joints.

[0003] Because Ti-55531 is a metastable β-type titanium alloy, it has a low heating temperature, high deformation resistance, poor forgeability, and a large deformation dead zone. Traditional forging processes mainly involve repeated upsetting and drawing in the two-phase region to break down the microstructure, resulting in a long bar preparation process, low yield, and high production costs. Furthermore, repeated upsetting and drawing in multiple heats makes process control difficult, hindering the control of microstructure uniformity at different locations and making it challenging to match strength and toughness in mechanical properties. Therefore, reconsidering a shorter process flow during forging to achieve rapid and sufficient refinement of the original grains, uniform deformation of the intermediate billet, shorten the preparation cycle, and reduce overall costs, while ensuring that the finished bars meet the requirements of large aerospace structural components and other industries, has become a major challenge that urgently needs to be addressed for Ti-55531 titanium alloy materials used in the aerospace field.

[0004] Therefore, it is necessary to design and optimize the production process of bars based on traditional forging technology. By controlling the recrystallization temperature and heating time, the microstructure of the billet can be effectively refined. Furthermore, by controlling the heating temperature, holding time, deformation amount, and deformation method, the uniformity of the core and surface microstructure of the billet can be improved. This will enable short-process, large-scale, and stable production of Ti-55531 titanium alloy bars to meet the needs of aerospace and other industries. Summary of the Invention

[0005] The purpose of this invention is to provide a short-process method for preparing Ti-55531 titanium alloy bars, which solves the problems of long bar preparation process, high difficulty in controlling the forging process, poor uniformity of microstructure at different locations, and difficulty in matching mechanical properties and toughness in the existing forging methods.

[0006] The technical solution adopted in this invention is a short-process method for preparing Ti-55531 titanium alloy rods, which is implemented according to the following steps:

[0007] Step 1, billet forging: Heat and hold the titanium alloy ingot, forge it 1-2 times and then cool it to obtain an intermediate billet;

[0008] Step 2, intermediate forging: The intermediate billet is heated and held at that temperature, and then forged 3 to 6 times before being cooled to obtain an intermediate bar billet;

[0009] Step 3, recrystallization heat treatment: The intermediate billet obtained in step 2 is heated, held at the temperature, and then cooled to obtain an intermediate billet with a uniform and fine β structure;

[0010] Step 4, forming and forging: The intermediate billet is heated and held at the temperature, and then forged 1 to 2 times before cooling to obtain the final finished bar.

[0011] The beneficial effects of this invention are that it abandons the traditional process of repeatedly upsetting and drawing in the two-phase region to break the microstructure. In the billet forging stage, large deformation upsetting is used to refine the original coarse cast grains to obtain a β microstructure with a grain size of 10mm to 20mm. After the intermediate forging stage, a recrystallization heat treatment stage is added to achieve rapid refinement of the billet microstructure. This solves the problem of increased deformation inhomogeneity caused by repeated upsetting and drawing in the traditional forging process, improves the microstructure uniformity at different positions of the billet, and obtains a uniform and fine β microstructure with a grain size of 1mm to 2mm. In the forming stage, the direct drawing forging method is combined with a smaller forging ratio and appropriate reheating in the furnace, which not only ensures uniform flow and deformation of the metal in all directions during the forging process, but also facilitates the control of the forging process. The large-size Ti-55531 titanium alloy bars prepared by the method of this invention effectively reduce the grain size of the titanium alloy intermediate billet, resulting in a uniform and fine microstructure at low magnification, and mechanical properties that meet the requirements of aerospace material standards. At the same time, the preparation process requires fewer firing steps, a shorter process, and less energy consumption, which can meet the requirements of large-scale industrial production. Attached Figure Description

[0012] Figure 1 This is a low-magnification microstructure image of the rod prepared according to Example 1 of the method of the present invention;

[0013] Figure 2 This is a low-magnification microstructure image of the rod at R / 2 prepared according to Example 1 of the method of the present invention;

[0014] Figure 3 This is the β-annealed microstructure of the edge of the bar prepared according to Example 1 of the method of the present invention;

[0015] Figure 4 This is the β-annealed microstructure at R / 2 of the bar prepared by the method of Example 1 of the present invention;

[0016] Figure 5 This is the β-annealed microstructure of the core of the bar prepared according to Example 1 of the method of the present invention;

[0017] Figure 6 This is the solution-treated and aged microstructure of the edge of the bar prepared according to Example 1 of the method of the present invention;

[0018] Figure 7 This is the solution-treated and aged microstructure at R / 2 of the rod prepared according to Example 1 of the method of the present invention;

[0019] Figure 8 This is the solution-treated and aged microstructure of the core of the bar prepared according to Example 1 of the method of the present invention;

[0020] Figure 9 This is a low-magnification microstructure image of the rod prepared by the method in Example 2 of the present invention;

[0021] Figure 10 This is a low-magnification microstructure image of the rod at R / 2 prepared by the method of Example 2 of the present invention;

[0022] Figure 11 This is the β-annealed microstructure of the edge of the bar prepared in Example 2 of the present invention;

[0023] Figure 12 This is the β-annealed microstructure at R / 2 of the bar prepared by the method of Example 2 of the present invention;

[0024] Figure 13 This is the β-annealed microstructure of the core of the bar prepared according to Example 2 of the method of the present invention;

[0025] Figure 14 This is the solution-treated and aged microstructure of the edge of the bar prepared according to Example 2 of the method of the present invention;

[0026] Figure 15 This is the solution-treated and aged microstructure at R / 2 of the rod prepared according to Example 2 of the method of the present invention;

[0027] Figure 16 This is the solution-treated and aged microstructure of the core of the bar prepared according to Example 2 of the method of the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] The raw material for the preparation method of this invention is a 4000kg to 6000kg Ti-55531 titanium alloy ingot with a diameter of Ф690mm. After sawing, the weight of the ingot is 1300kg to 3000kg. The processing is divided into four parts: billet forging → intermediate forging → recrystallization heat treatment → forming forging. The final product bar has a diameter of Ф150mm to Ф400mm and a length of not less than 1000mm, which fully meets the production requirements of Ti-55531 titanium alloy bars required by aerospace and other industries.

[0030] The preparation method of the present invention is carried out according to the following steps:

[0031] Step 1, billet forging: Heat and hold the titanium alloy ingot, forge it 1-2 times and then cool it to obtain an intermediate billet;

[0032] The specific process is as follows: For large-size Ti-55531 titanium alloy ingots, 1 to 2 forging cycles (i.e., upsetting and drawing forging) are performed at 250℃ to 350℃ above the phase transformation point. Each forging cycle completes 2 to 3 upsetting and drawing operations to obtain a β structure with a grain size of 10mm to 20mm. The cumulative forging ratio per cycle is 7.2 to 12.8. The forging methods are upsetting, rounding, and octagonal forging. After air cooling, the surface cracks of the material are ground off. The initial forging temperature of each cycle is 50℃ to 150℃ above the phase transformation point, and the final forging temperature is 20℃ to 100℃ below the phase transformation point to obtain an intermediate billet.

[0033] In step 1, upsetting with a large deformation amount can refine the coarse cast grains in the original material; rounding and octagonal operations can improve the forging penetration of the core and the deformation uniformity at each position.

[0034] Step 2, intermediate forging: The intermediate billet is heated and held at that temperature, and then forged 3 to 6 times before being cooled to obtain an intermediate bar billet;

[0035] The specific process is as follows: To obtain an alloy billet with a uniform microstructure, the intermediate billet after the initial forging is subjected to 2-4 heating cycles (i.e., upsetting and drawing) at temperatures ranging from 70°C below the phase transformation point to 150°C above it. This is divided into two heating cycles at temperatures between 30°C and 70°C below the phase transformation point, and another two heating cycles at temperatures between 30°C and 150°C above the phase transformation point. The forging ratio per cycle is 2.8-5.2. The forging process includes upsetting, drawing square, drawing flat square, and inverted octagonal forging. The cooling method after forging is air cooling. After air cooling, the surface cracks of the material are ground to ensure uniform deformation of all parts of the billet. In the two-phase zone, the initial forging temperature for each forging is 60℃~150℃ below the phase transformation point, and the final forging temperature is 150℃~250℃ below the phase transformation point. In the single-phase zone, the initial forging temperature for each forging is 30℃~80℃ above the phase transformation point, and the final forging temperature is 60℃~150℃ below the phase transformation point.

[0036] The billet that has undergone the above forging is reheated at 30℃~70℃ below the phase transformation point and held for 6~9 hours. Then, it is forged 1~2 times, with a forging ratio of 1.6~2.8 per forging. The forging methods are upsetting and octagonal forging. After forging, it is air-cooled. The initial forging temperature of each forging is 60℃~150℃ below the phase transformation point, and the final forging temperature is 150℃~250℃ below the phase transformation point to obtain an intermediate billet.

[0037] Step 3, recrystallization heat treatment: The intermediate billet obtained in step 2 is heated, held at the temperature, and then cooled to obtain an intermediate billet with a uniform and fine β structure;

[0038] The specific process is as follows: the intermediate billet obtained in step 2 is directly heated, the heat treatment temperature is 60℃~90℃ above the phase transformation point, the holding time is 6~9h, and then it is taken out of the furnace and air-cooled to obtain an intermediate billet with a uniform and fine β structure with a grain size of 1mm~2mm.

[0039] Step 4, forming and forging: The intermediate billet is heated and held at the temperature, and then forged 1 to 2 times before cooling to obtain the final finished bar.

[0040] The specific process is as follows: The intermediate billet obtained in step 3 is heated to 30℃~60℃ below the phase transformation point and held for 6~9 hours; then it is forged 1~2 times with a forging ratio of 1.0~2.0. The forging methods are straight drawing, chamfering and rounding. The billet shape changes from an octagonal billet to a round billet. The forging process can be appropriately reheated in the furnace. After air cooling, the surface cracks of the material are polished. The initial forging temperature of each forming forging is 80℃~200℃ below the phase transformation point, and the final forging temperature is 150℃~300℃ below the phase transformation point.

[0041] After further machining and finishing, finished bars with diameters ranging from Ф150mm to Ф400mm are finally obtained.

[0042] In step 4, the forging methods of straight drawing, chamfering, and rounding are adopted. Combined with a small forging ratio and appropriate reheating in the furnace, this not only ensures uniform flow and deformation of the metal in all directions during the forging process, but also facilitates the control of the forging process.

[0043] The working principle of this invention is as follows: During the forging process, the optimal microstructure refinement deformation process is determined based on the alloy microstructure evolution law. A combination of deformation methods, such as flattened square drawing, square drawing, and inverted octagonal drawing, is used to improve the material uniformity. The required alloy microstructure and mechanical properties are obtained through the shortest deformation process, ensuring material quality under short processing conditions. The preparation method of this invention includes billet forging → intermediate forging → recrystallization heat treatment → forming forging. Based on the recrystallization theory of titanium alloys, the heating temperature, deformation amount, deformation method, initial forging temperature, and final forging temperature are rationally designed to precisely control the heating and forging process. This solves the problem of increased deformation inhomogeneity caused by repeated upsetting and drawing, reduces the number of forging passes in traditional processes by 4-6, lowers processing costs, and increases the bar yield by 5%-7%. During the initial forging process, large deformation upsetting is used to refine the original coarse cast grains, resulting in a β microstructure with a grain size of 10mm to 20mm. During intermediate forging, square drawing, flat drawing, and inverted octagonal forging methods are used to ensure uniform deformation of all parts of the billet. Subsequently, recrystallization heat treatment is used to rapidly refine the billet microstructure, solving the problem of increased deformation inhomogeneity caused by repeated upsetting and drawing in traditional forging processes. This improves the microstructure uniformity at different locations of the billet, resulting in a uniform and fine β microstructure with a grain size of 1mm to 2mm. During the finished product forging process, the direct drawing forging method is combined with a smaller forging ratio and appropriate reheating in the furnace. This not only ensures uniform flow and deformation of the metal in all directions during forging but also facilitates the control of the forging process. Through the above measures, this invention achieves fully uniform and refined alloy grains with fewer firing cycles, resulting in finished bars with good microstructure and performance consistency. The preparation process is short, the yield is high, and the processing cost is low. It is suitable for industrial production of Ti-55531 titanium alloy bars with diameters of Ф150mm to Ф400mm and lengths of not less than 1000mm.

[0044] Example 1

[0045] Finished bars with a diameter of Φ250mm were prepared using the method of the present invention.

[0046] Step 1, Forging the billet:

[0047] The Ti-55531 titanium alloy ingot has a diameter of 690mm and a weight of 5400kg. After sawing, the ingot weighs 1800kg. The phase transformation point is 840℃. It undergoes a two-stage forging process, with each stage involving three upsetting and three drawing operations. The cumulative forging ratio per stage is controlled between 7.8 and 10.6. The forging methods are upsetting, rounding, and octagonal shaping. After air cooling, surface cracks are removed by grinding. The initial forging temperature for each stage is 950℃, and the final forging temperature is 850℃, yielding an intermediate billet.

[0048] Step 2, Intermediate Forging:

[0049] The intermediate billet was forged in two passes, with the heating settings as follows: the first pass was heated to 50°C below the phase transformation point, and the second pass was heated to 80°C above the phase transformation point. The forging ratio per pass was 3.2–4.8, and the forging methods included upsetting, square drawing, flattened square drawing, and inverted octagonal forging. After air cooling, surface cracks were removed by grinding. In the two-phase region, the initial forging temperature was 720°C and the final forging temperature was 620°C per pass; in the single-phase region, the initial forging temperature was 820°C and the final forging temperature was 720°C per pass.

[0050] The material is reheated to 60°C below the phase transformation point and held for 7 hours. It is then forged in one pass with a forging ratio of 1.8 to 2.4. The forging methods are upsetting and octagonal forging. After forging, it is air-cooled. The initial forging temperature of the first pass is 720°C, and the final forging temperature is 620°C, resulting in an intermediate billet.

[0051] Step 3, recrystallization heat treatment:

[0052] The billet that has completed intermediate forging is directly returned to the furnace and held at 70°C above the phase transformation point for 7 hours before being removed from the furnace and air-cooled to obtain an intermediate billet with a uniform and fine β structure with a grain size of 2 mm.

[0053] Step 4, Forming and Forging:

[0054] The intermediate billet is heated to 50°C below the phase transformation point and held for 7 hours. It is then forged in one pass with a forging ratio of 1.1 to 1.8. The forging methods include straight drawing, chamfering, and rounding. The forging process involves reheating in the furnace. The initial forging temperature for forming is 700°C, and the final forging temperature is 600°C. After machining, a finished bar with a diameter of Ф250mm is obtained.

[0055] Figure 1 This is a low-magnification microstructure image of the rod prepared in Example 1; Figure 2 This is a low-magnification microstructure image of the rod at R / 2 prepared in Example 1; Figure 3 The microstructure of the edge of the bar prepared in Example 1 is in the β-annealed state. Figure 4 The microstructure of the bar at R / 2 prepared in Example 1 is in the β-annealed state. Figure 5 This is the β-annealed microstructure of the core of the bar prepared in Example 1; Figure 6 This is the solution-treated and aged microstructure of the edge of the bar prepared in Example 1; Figure 7 This is the solution-treated and aged microstructure at R / 2 of the rod prepared in Example 1; Figure 8 This refers to the solution-treated and aged microstructure of the core of the rod prepared in Example 1; R / 2 refers to the midpoint of any radius R of the rod, from... Figures 1-8 As can be seen, the microstructure of all parts is uniform and the performance is consistent. The room temperature properties of the Ti-55531 titanium alloy prepared in Example 1 after β annealing and solution aging are shown in Tables 1 and 2, showing good strength and toughness matching.

[0056] Table 1. Room temperature properties of Ti-55531 titanium alloy Φ250mm bars in the β-annealed state

[0057]

[0058] Table 2. Room temperature properties of Ti-55531 titanium alloy Φ250mm bars in solution-treated and aged state

[0059]

[0060] Example 2

[0061] Finished bars with a diameter of Φ350mm were prepared using the method of the present invention.

[0062] Step 1, Forging the billet:

[0063] The Ti-55531 titanium alloy ingot has a diameter of 690mm and a weight of 4800kg. After sawing, the ingot weighs 1600kg. Its phase transformation point is 835℃. It undergoes a two-stage forging process, with each stage involving three upsetting and three drawing operations. The cumulative forging ratio per stage is controlled between 9.2 and 11.8. The forging methods are upsetting, rounding, and octagonal shaping. After air cooling, surface cracks are removed by grinding. The initial forging temperature for each stage is 940℃, and the final forging temperature is 800℃, yielding an intermediate billet.

[0064] Step 2, Intermediate Forging:

[0065] The intermediate billet after the initial forging was subjected to four intermediate forging passes. The heating settings were as follows: first pass at 50°C below the phase transformation point, second pass at 110°C above the phase transformation point, third pass at 50°C below the phase transformation point, and fourth pass at 60°C above the phase transformation point. The forging ratio per pass was 3.2–4.8, and the forging methods were upsetting, square drawing, flattened square drawing, and inverted octagonal forging. After air cooling, surface cracks were removed by grinding. In the two-phase region, the initial forging temperature was 700°C and the final forging temperature was 600°C per pass. In the single-phase region, the initial forging temperature was 800°C and the final forging temperature was 700°C per pass.

[0066] The material is reheated to 60°C below the phase transformation point and held for 8 hours. It is then forged in one pass with a forging ratio of 1.6 to 2.8. The forging methods are upsetting and inverted octagonal forging. After forging, the material is air-cooled. The initial forging temperature of each pass is 700°C and the final forging temperature is 600°C, resulting in an intermediate billet.

[0067] Step 3, recrystallization heat treatment:

[0068] The billet that has completed intermediate forging is directly returned to the furnace and held at 60°C above the phase transformation point for 6 hours before being removed from the furnace and air-cooled to obtain an intermediate billet with a uniform and fine β structure with a grain size of 1.5 mm.

[0069] Step 4, Forming and Forging:

[0070] The billet is heated to 50°C below the phase transformation point and held for 6 hours. It undergoes a single-pass forging process with a forging ratio of 1.0–2.0. The forging methods include drawing, chamfering, and rounding, transforming the octagonal billet into a round bar. The forging process involves reheating in a furnace. The initial forging temperature is 650°C, and the final forging temperature is 550°C. After machining, a finished bar with a diameter of Ф350mm is obtained.

[0071] Figure 9 This is a low-magnification microstructure image of the rod prepared in Example 2; Figure 10 This is a low-magnification microstructure image of the rod at R / 2 prepared in Example 2; Figure 11 The microstructure of the edge of the bar prepared in Example 2 is in the β-annealed state. Figure 12 This is the β-annealed microstructure at R / 2 of the bar prepared in Example 2; Figure 13 This is the β-annealed microstructure of the core of the bar prepared in Example 2; Figure 14 This is the solution-treated and aged microstructure of the edge of the bar prepared in Example 2; Figure 15 This is the solution-treated and aged microstructure at R / 2 of the rod prepared in Example 2; Figure 16 This is the solution-treated and aged microstructure of the core of the bar prepared in Example 2. R / 2 refers to the midpoint of any radius R of the bar. From... Figures 9-16 As can be seen, the microstructure of all parts is uniform and the performance is consistent. The room temperature properties of the Ti-55531 titanium alloy prepared in Example 2 after β-annealing and solution aging are shown in Tables 3 and 4, showing good strength and toughness matching.

[0072] Table 3. Room temperature properties of Φ350mm Ti-55531 titanium alloy bars in the β-annealed state.

[0073]

[0074] Table 4. Room temperature properties of Ti-55531 titanium alloy Φ350mm bars in solution-treated and aged state

[0075]

[0076] Example 3

[0077] Finished bars with a diameter of Φ230mm were prepared using the method of the present invention.

[0078] Step 1, Forging the billet:

[0079] The Ti-55531 titanium alloy ingot has a diameter of 650mm and a weight of 5000kg. After sawing, the ingot weighs 2000kg. The phase transformation point is 840℃. It undergoes a two-stage forging process, with each stage involving three upsetting and three drawing operations. The cumulative forging ratio per stage is controlled between 9 and 12. The forging methods are upsetting, rounding, and octagonal shaping. After air cooling, surface cracks are removed by grinding. The initial forging temperature for each stage is 920℃, and the final forging temperature is 820℃, yielding an intermediate billet.

[0080] Step 2, Intermediate Forging:

[0081] The intermediate billet was forged in three passes, with the heating settings as follows: first pass at 50°C below the phase transformation point, then at 80°C above the phase transformation point, and finally at 60°C below the phase transformation point. The forging ratio per pass was 3.0–4.2, and the forging methods included upsetting, square drawing, flattened square drawing, and inverted octagonal forging. After air cooling, surface cracks were removed by grinding. In the two-phase region, the initial forging temperature was 750°C and the final forging temperature was 650°C per pass; in the single-phase region, the initial forging temperature was 850°C and the final forging temperature was 750°C per pass.

[0082] The material is reheated to 50°C below the phase transformation point and held for 9 hours. It is then forged in one pass with a forging ratio of 2–2.8. The forging methods are upsetting and octagonal forging. After forging, it is air-cooled. The initial forging temperature of the first pass is 750°C, and the final forging temperature is 650°C, resulting in an intermediate billet.

[0083] Step 3, recrystallization heat treatment:

[0084] The billet that has completed intermediate forging is directly returned to the furnace and held at 90°C above the phase transformation point for 9 hours before being removed from the furnace and air-cooled to obtain an intermediate billet with a uniform and fine β structure with a grain size of 1.8 mm.

[0085] Step 4, Forming and Forging:

[0086] The intermediate billet is heated to 40°C below the phase transformation point and held for 9 hours. It is then forged in one pass with a forging ratio of 1.3 to 2. The forging methods include straight drawing, chamfering, and rounding. The forging process involves reheating in the furnace. The initial forging temperature for forming is 750°C, and the final forging temperature is 650°C. After machining, a finished bar with a diameter of Ф200mm is obtained.

[0087] Due to space limitations, the data list and micrographs of Example 3 are omitted.

[0088] In summary, the preparation method of this invention, used in a short process (reducing the number of firing cycles by 4-6 compared to traditional processes), enables mass production of Ti-55531 titanium alloy bars with specifications ranging from Ф150mm to Ф400mm and a length of not less than 1000mm. The bar processing cost is low, and the yield can be increased by approximately 5%-7%. Simultaneously, the β-annealed Ti-55531 titanium alloy exhibits Rm ≥ 1200 MPa, A ≥ 10%, and K... IC ≥85MPa·m 1 / 2 Solution-treated and aged Ti-55531 titanium alloy has an Rm ≥ 1300 MPa and an elongation of A ≥ 5%, K IC ≥40MPa·m 1 / 2 The bar stock has a good balance of strength and toughness, meets the requirements of aerospace material standards, and is suitable for industrial production.

Claims

1. A short-process method for preparing Ti-55531 titanium alloy rods, characterized in that, Follow these steps: Step 1, Initial Forging: The titanium alloy ingot is heated and held at that temperature, then forged 1-2 times before cooling to obtain an intermediate billet. The specific process is as follows: For large-sized titanium alloy ingots of Ti-55531, 1-2 forging cycles are performed at 250℃~350℃ above the phase transformation point. Each forging cycle completes 2-3 upsetting and drawing operations, with a cumulative forging ratio of 7.2~12.8 per cycle. The forging methods are upsetting, rounding, and octagonal forging. After air cooling, the surface cracks of the material are polished. The initial forging temperature of each cycle is 50℃~150℃ above the phase transformation point, and the final forging temperature is 20℃~100℃ below the phase transformation point, resulting in an intermediate billet. Step 2, Intermediate Forging: The intermediate billet is heated and held at that temperature, then forged 3-6 times before cooling to obtain the intermediate bar billet. The specific process is as follows: The intermediate billet is forged in 2-4 passes at temperatures ranging from 70°C below the phase transformation point to 150°C above the phase transformation point. This is divided into two passes: one where the heating temperature is 30°C-70°C below the phase transformation point, and another where the heating temperature is 30°C-150°C above the phase transformation point. The forging ratio per pass is 2.8-5.

2. The forging methods are upsetting, drawing, drawing flattened square, and inverted octagonal. Air cooling is used after forging, and surface cracks are removed after air cooling. In the two-phase region, the initial forging temperature is 60°C-150°C below the phase transformation point, and the final forging temperature is 150°C-250°C below the phase transformation point. In the single-phase region, the initial forging temperature is 30°C-80°C above the phase transformation point, and the final forging temperature is 60°C-150°C below the phase transformation point. The billet that has undergone the above forging is reheated at 30℃~70℃ below the phase transformation point and held for 6~9 hours. Then it is forged 1~2 times, with a forging ratio of 1.6~2.8 per forging. The forging methods are upsetting and octagonal forging. After forging, it is air-cooled. The initial forging temperature of each forging is 60℃~150℃ below the phase transformation point, and the final forging temperature is 150℃~250℃ below the phase transformation point to obtain an intermediate billet. Step 3, recrystallization heat treatment: The intermediate billet obtained in Step 2 is heated, held at that temperature, and then cooled to obtain an intermediate billet with a uniform and fine β structure. The specific process is as follows: The intermediate billet obtained in step 2 is directly heated at a heat treatment temperature of 60℃~90℃ above the phase transformation point and held for 6~9 hours. Then it is removed from the furnace and air-cooled to obtain the intermediate billet. Step 4, Forming and Forging: The intermediate billet is heated and held at that temperature, then forged 1-2 times and cooled to obtain the final finished bar. The specific process is as follows: The intermediate billet obtained in step 3 is heated to 30℃~60℃ below the phase transformation point and held for 6~9 hours; then it is forged 1~2 times with a forging ratio of 1.0~2.

0. The forging methods are straight drawing, chamfering and rounding. The billet shape changes from an octagonal billet to a round billet. The forging process is carried out by reheating in the furnace. After air cooling, the surface cracks of the material are polished. The initial forging temperature of each forming forging is 80℃~200℃ below the phase transformation point, and the final forging temperature is 150℃~300℃ below the phase transformation point. After further machining and finishing, finished bars with diameters ranging from Ф150mm to Ф400mm are finally obtained.

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