Die and forging forming method for thick-core thin-arm type forgings with large size cross configuration

Abstract

The application discloses a large-size cross-shaped thick-core thin-arm type forging die and a forging forming method, and belongs to the field of plastic processing of difficult-to-deform material forging forming. The die comprises a forging upper die, a forging lower die and a ejector rod which are used in a matched mode. The forging upper die is provided with a cross-shaped upper die cavity. The forging lower die is provided with a cross-shaped lower die cavity. The shape of the cavity after die closing is consistent with the shape of the thick-core thin-arm type titanium alloy forging. The forging forming method comprises the following steps: bar pretreatment, free forging upsetting, positioning forging, free forging blanking, die forging forming and forging demolding. The die adopts a lock buckle type structure design, has low cost, simple structure and large operation space, guarantees the service life of the thick-core thin-wall type titanium alloy forging die, reduces the die manufacturing cost, and improves the material utilization rate, reduces the forging fire times, shortens the forging production cycle, and realizes efficient blanking and high-quality forming of the large-size special-shaped titanium alloy forging.

Description

Technical Field

[0001] This invention relates to the field of forging and plastic processing of difficult-to-deform materials, and particularly to a forging die and forging method for large-sized cross-shaped thick-core thin-arm forgings. Background Technology

[0002] The number of helicopter rotor blades significantly impacts the design of the central component forgings for its rotor system. For a 4-bladed rotor system central component forging, adopting a design method similar to that for 5-bladed or more rotor system central component forgings would inevitably result in a huge waste of raw materials with existing forging technology. However, a cross-shaped forging design can solve this problem. On the other hand, the core of large-sized cross-shaped forgings needs to be heightened and thickened to ensure its fatigue life meets the alternating loads under the complex operating conditions of the helicopter rotor system. Titanium alloys are difficult to deform, which greatly increases the forming difficulty of large-sized cross-shaped thick-core thin-arm (ratio greater than 2:1) titanium alloy forgings. Summary of the Invention

[0003] The purpose of this invention is to provide a large-size cross-shaped thick-core thin-arm forging mold and forging method to solve the problems of high cost of forging mold, low raw material utilization, difficulty in forging, and severe clamping damage in actual production.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention relates to a large-size cross-shaped thick-core thin-arm forging die, comprising a forging upper die, a forging lower die, and an ejector pin. The forging upper die has a cross-shaped upper mold cavity, and the forging lower die has a cross-shaped lower mold cavity. The ejector pin is located at the lower part of the forging lower die. After the forging upper die and the forging lower die are closed, the shape of the cavity formed by the upper mold cavity and the lower mold cavity is consistent with the shape of the cross-shaped thick-core thin-arm titanium alloy forging.

[0006] Furthermore, the upper forging die and the lower forging die are locked and positioned by a locking structure. The locking structure includes a cooperating arc-shaped boss and an arc-shaped groove. The arc-shaped boss is disposed on the top surface of the upper forging die, and the arc-shaped groove is disposed on the top surface of the lower forging die.

[0007] Furthermore, there are four arc-shaped protrusions and four arc-shaped grooves. The four arc-shaped protrusions are evenly distributed around the circumference. The size of one arc-shaped protrusion is smaller than the size of the other three arc-shaped protrusions, and the size of one arc-shaped groove is smaller than the size of the other three arc-shaped grooves. The positions of the arc-shaped grooves correspond one-to-one with the positions of the arc-shaped protrusions.

[0008] Furthermore, the locking angle S1 is 1-3°, the gap distance A1 between the locking sidewalls is 1-2mm, the concave radius R1 at the locking point is 10mm, the convex radius R2 at the locking point is 15mm, and the gap distance A2 between the upper and lower parts of the locking point when closed is 1-2mm, with the non-locking area as the mold closing surface.

[0009] Furthermore, the upper and lower model cavities adopt a gradient bridge width design, with the bridge width ratio between the vertical cross position and the included angle position of the cavity being 1:2, and the corresponding hopper width ratio being 1:3.

[0010] Furthermore, the top rod includes a first rod segment and a second rod segment, with a guide segment provided between the first rod segment and the second rod segment. The guide segment has a length of 30 to 60 mm, and the angle between the ridge line of the guide segment and the center line of the first rod segment is 120 to 150°.

[0011] A forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging, comprising the following steps, using a large-sized, cross-shaped, thick-core, thin-arm forging die as described above:

[0012] Step 1: Bar stock pretreatment. After cutting the bar stock to the required specifications and dimensions, use a lathe to mill the end face of the titanium alloy bar stock flat and chamfer it.

[0013] Step 2, free forging upsetting: After heating the titanium alloy bar on the high-speed forging machine, it is placed in the preheated forging die for multiple passes of local constraint upsetting, so that the total height of the bar is reduced by 1 / 2, and the thick core part of the forging is pre-formed.

[0014] Step 3, positioning forging: After heating the above-mentioned billet on a large die forging hydraulic press, it is placed in the preheated upper forging die and the lower forging die for 1 to 2 passes of positioning forging to achieve positioning of the thin arm part of the cross-shaped forging.

[0015] Step 4: Free forging billet. Using an arc-shaped tool on a high-speed forging machine, the billet obtained in step 3 is shaped at the cross angle position. This is completed in 1 to 2 passes, driving the billet to flow to the thin arm position of the cross configuration.

[0016] Step 5, die forging: The blank obtained in step 4 is heated on a large die forging hydraulic press and then placed in the preheated upper and lower forging dies for 1 to 3 passes of die forging to obtain a cross-shaped thick core thin arm titanium alloy forging.

[0017] Step six: Demolding the forging. The large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging is ejected from the lower forging die using the ejector pin.

[0018] Furthermore, in step two, when upsetting the bar stock, free upsetting is performed first. Before the final upsetting, a stepped circle no larger than the deepest part of the lower mold cavity needs to be forged at the lower end of the billet. Then, it is placed in the lower forging mold to maintain constraint and perform the final upsetting to obtain forging billets with different cross-sectional dimensions.

[0019] Furthermore, in steps two through five, the heating temperature of the titanium alloy bar and the forging billet is at T... β The temperature range is selected from 40 to 60 degrees Celsius. The cold material holding time is calculated as 0.6 to 0.8 min × effective cross-sectional thickness of the billet (mm), and the hot material holding time is calculated as 0.4 to 0.5 min / mm × effective cross-sectional thickness of the billet (mm). During the forging in steps three and five, the large die forging hydraulic press adopts a low pressing rate of 1 to 3 mm / s.

[0020] Furthermore, before implementing step five, the billet needs to be preheated in a heating furnace to 200±50℃ and kept at that temperature for 20 to 40 minutes. After being taken out, it is sprayed with a special forging lubricant for titanium alloys.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] The mold of this invention adopts a locking structure design, eliminating the need for guide pillars. This results in low cost, simple structure, and ample operating space for workers during the forging process. It ensures the lifespan of the mold for thick-core, thin-walled titanium alloy forgings while effectively reducing mold manufacturing costs. The alternating forging method of die forging and free forging provided by this invention solves problems such as difficult billet preparation, long processing steps, and severe clamping damage in large-sized, cross-shaped, thick-core, thin-arm titanium alloy forgings. It improves material utilization while reducing the number of forging passes, significantly shortening the forging production cycle and achieving efficient billet preparation and high-quality forming of large-sized, irregularly shaped titanium alloy forgings. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] Furthermore, other figures can be obtained based on these figures.

[0025] Figure 1 This is a three-dimensional structural diagram of the forging die of the present invention;

[0026] Figure 2 This is a three-dimensional structural diagram of the forging die of the present invention;

[0027] Figure 3 This is a cross-sectional view of the mold of the present invention in the mold-closed state;

[0028] Figure 4 This is a partial cross-sectional view of the locking structure after the mold is closed according to the present invention;

[0029] Figure 5 This is a three-dimensional structural diagram of the push rod of the present invention;

[0030] Figure 6 A three-dimensional structural schematic diagram of a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging produced using the forging die provided in this embodiment of the invention;

[0031] Figure 7 This is a three-dimensional structural diagram of the arc-shaped tooling of the present invention;

[0032] Figure 8 This is a three-dimensional structural diagram of the arc-shaped tooling of the present invention;

[0033] Figure 9 This is a schematic diagram showing the usage status of the upper and lower arc-shaped tooling in step four of the present invention;

[0034] Figure 10 This is a schematic diagram of the forging blank obtained in step four of the present invention;

[0035] Figure 11 This is a low-magnification microstructure image of a large-sized cross-shaped thick-core thin-arm titanium alloy forging in an embodiment of the present invention;

[0036] Figure 12 This is a microstructure diagram of a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to an embodiment of the present invention.

[0037] Explanation of reference numerals in the attached drawings: 1. Upper forging die; 101. Upper die cavity; 102. Arc-shaped boss; 2. Lower forging die; 201. Lower die cavity; 202. Arc-shaped groove; 3. Push rod; 301. First rod segment; 302. Second rod segment; 303. Guide segment; 4. Forging; 5. Arc-shaped tooling; 5-1. Upper arc-shaped tooling; 5-2. Lower arc-shaped tooling; 5-1-1. First forming block; 5-1-2. First support rod; 5-2-1. Second forming block; 5-2-2. Second support rod;

[0038] R1, concave fillet of the latch; R2, convex fillet of the latch; S1, latch slope; A1, gap distance between the side walls of the latch; A2, gap distance between the upper and lower parts of the latch when the mold is closed. Detailed Implementation

[0039] like Figure 1-12As shown, a large-sized cross-shaped thick-core thin-arm forging die includes a forging upper die 1, a forging lower die 2, and an ejector pin 3. The forging upper die 1 has a cross-shaped upper mold cavity 101, and the forging lower die 2 has a cross-shaped lower mold cavity 201. The ejector pin 3 is located at the lower part of the forging lower die 2. After the forging upper die 1 and the forging lower die 2 are closed, the shape of the cavity formed by the upper mold cavity 101 and the lower mold cavity 201 is consistent with the shape of the cross-shaped thick-core thin-arm titanium alloy forging.

[0040] Unlike traditional forging die designs, to reduce die height and increase the effective forging stroke and operating space of the equipment, the upper forging die 1 and the lower forging die 2 are locked together using a locking structure. Figure 1 , 2 As shown, the locking structure includes cooperating arc-shaped bosses 102 and arc-shaped grooves 202. The arc-shaped bosses 102 are disposed on the top surface of the upper forging die 1, and the arc-shaped grooves 202 are disposed on the top surface of the lower forging die 2. There are four arc-shaped bosses 102 and four arc-shaped grooves 202. The four arc-shaped bosses 102 are evenly distributed in a circle, and the positions of the arc-shaped grooves 202 correspond to the positions of the arc-shaped bosses 102. The size of one arc-shaped boss 102 is smaller than the size of the other three arc-shaped bosses 102. Correspondingly, the size of one arc-shaped groove 202 is smaller than the size of the other three arc-shaped grooves 202. By differentiating the four locking points of the die, it is convenient for workers to effectively identify them during production.

[0041] The invention employs a locking structure for die forging. To reduce frictional damage at the locking positions of the guide pillar-less die, extend die life, and minimize circumferential misalignment of the forgings, the invention utilizes a locking structure. Figure 4 As shown, the upper and lower mold locking concave fillet R1 is set to R10mm, the convex fillet R2 is set to R15mm, the locking angle S1 is 1~3°, the locking sidewall gap distance A1 is 1~2mm, the locking concave fillet R1 is 10mm, the locking convex fillet R2 is 15mm, and the upper and lower gap distance A2 at the locking point is 1~2mm when closed, with the non-locking area as the mold closing surface.

[0042] The upper mold cavity 101 and the lower mold cavity 201 adopt a gradient bridge width design. The bridge width ratio between the vertical cross position and the included angle position of the cavity is 1:2, and the corresponding material bin width ratio is 1:3. This can solve the problem of large differences in the flow capacity of billets in different areas of cross-shaped titanium alloy forgings.

[0043] like Figure 5As shown, the push rod 3 includes a first rod segment 301 and a second rod segment 302. A guide segment 303 is provided between the first rod segment 301 and the second rod segment 302. The length of the guide segment 303 is 30-60mm, and the angle between the ridge line of the guide segment 303 and the center line of the first rod segment 301 is 120-150°. By setting the push rod 3, the effective demolding of large-sized irregular forgings can be achieved.

[0044] A forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging, comprising the following steps, using a large-sized, cross-shaped, thick-core, thin-arm forging die as described above:

[0045] Step 1: Bar stock pretreatment. After cutting the bar stock to the required specifications and dimensions, use a lathe to mill both ends of the titanium alloy bar stock flat (80% exposed to light), and chamfer the edges and corners to R10~R30mm to avoid bending or damage during the next upsetting process.

[0046] Step 2, free forging upsetting: After heating the titanium alloy bar on the high-speed forging machine, it is placed in the preheated forging die 2 for multi-pass local constraint upsetting, so that the total height of the bar is reduced by 1 / 2, and the thick core part of the forging is pre-formed.

[0047] Unlike the general free forging process, the key technical point of step two is that when upsetting the bar stock, free upsetting is performed first, and before the final upsetting is carried out, a stepped circle no larger than the deepest part of the lower mold cavity 201 needs to be forged at the lower end of the billet. Then, it is placed in the lower forging mold 2 to maintain the constraint and carry out the final upsetting to obtain forging billets with different cross-sectional dimensions.

[0048] Step 3, positioning forging: After heating the above-mentioned billet on a large die forging hydraulic press, it is placed in the preheated upper forging die 1 and the lower forging die 2 for 1 to 2 passes of positioning forging to achieve positioning of the thin arm part of the cross-shaped forging.

[0049] Step four, free forging of the billet, such as Figure 9 As shown, the billet cross angle position obtained in step three of the forming process is achieved using an arc-shaped tooling on a high-speed forging mill. This is completed in 1-2 passes, driving the billet to the thin arm position of the cross configuration, reducing material loss during die forging, and obtaining... Figure 10 The forging blank shown;

[0050] The arc-shaped fixture 5 has two structures: the upper arc-shaped fixture 5-1 and the lower arc-shaped fixture 5-2, as follows: Figure 7 , 8As shown, the upper arc-shaped fixture 5-1 includes a first forming block 5-1-1, with a first support rod 5-1-2 connected to the center of the first forming block 5-1-1. The first support rod 5-1-2 is connected to the hammer anvil of the high-speed forging machine. The piston rod of the high-speed forging machine drives the first forming block 5-1-1 to descend and shape the upper part of the billet. The lower arc-shaped fixture 5-2 includes a second forming block 5-2-1, with two second support rods 5-2-2 connected to the second forming block 5-2-1. The second support rods 5-2-2 are connected to the worktable of the high-speed forging machine. During operation, the first forming block 5-1-1 descends and, together with the second forming block 5-2-1, shapes the cross-angle area of ​​the billet. After one shaping is completed, the billet is rotated 90°, and the other two sides of the billet are shaped in the same way.

[0051] Step 5, die forging: The blank obtained in step 4 is heated on a large die forging hydraulic press and then placed in the preheated upper forging die 1 and lower forging die 2 for 1 to 3 passes of die forging to obtain a cross-shaped thick core thin arm titanium alloy forging.

[0052] In steps two through five, the heating temperature of the titanium alloy bar and the forging billet is within T. β The temperature range is selected from -40 to 60℃. The cold material holding time is calculated as 0.6 to 0.8 min × effective cross-sectional thickness of the billet (mm), and the hot material holding time is calculated as 0.4 to 0.5 min / mm × effective cross-sectional thickness of the billet (mm). At the same time, in order to maximize the material utilization rate, during the forging in steps three and five, the large die forging hydraulic press adopts a low pressing rate, which is 1 to 3 mm / s, to avoid poor local filling effect of the forging due to rapid material flow.

[0053] To further improve the lubrication environment of the billet during die forging and enhance the filling capacity of difficult-to-deform materials, before implementing step five, the billet needs to be preheated to 200±50℃ in a heating furnace and kept at that temperature for 20 to 40 minutes. After taking it out, spray it with a special titanium alloy forging lubricant (lubricant: water weight ratio = 1:1 to 1:2) until it is visually uniform.

[0054] Step six: Demolding the forging. The large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging is ejected from the lower forging die 2 using the ejector pin 3.

[0055] The forging method described above will be explained below with reference to specific embodiments.

[0056] Take the preparation of a large-sized cross-shaped thick-core thin-arm titanium alloy forging (outer dimensions: φ1135×410mm, forging weight: 573kg, material grade: TB6) as an example.

[0057] Step 1: Bar stock pretreatment. Use TB6 titanium alloy bars with dimensions of φ350×1550mm. After milling both ends flat (80% exposed to light), chamfer the edges and corners to R10~R30mm.

[0058] Step two, free forging upsetting: Following the free forging upsetting method described above, the bar stock is subjected to three rounds of free upsetting on a free forging high-speed forging machine. The stock is then divided at a distance of 160mm from the end, pressing out a stepped circle of φ350±5×290±20. A final round of locally constrained upsetting is then performed. During the upsetting process, the lower end of the bar stock is placed within the lower mold cavity 201 for constraint. Table 1 lists the forging parameters for the free forging upsetting process.

[0059] Table 1

[0060]

[0061]

[0062] Step 3, positioning forging: After the upsetting billet is heated, it is placed in a preheated mold (300±50℃, held for 12h) and subjected to two rounds of positioning forging on a large die forging hydraulic press to achieve positioning of the thin arm part of the cross-shaped forging. Table 2 lists the forging parameters of the positioning forging process.

[0063] Table 2

[0064]

[0065] Step four: Free forging of the billet. After heating the above billet, return it to the free forging high-speed forging mill for further processing. Figures 7-9 The special arc-shaped tooling 5 and processing method shown are used to perform two passes of cross-angle shaping to produce a blank, and to obtain the blank as shown in the figure. Figure 10 The forging blank shown is illustrated. Table 3 lists the forging parameters for its free forging process.

[0066] Table 3

[0067]

[0068] Step 5: Die forging. The rough mold obtained in the previous step is heated and placed in a preheated mold (300±50℃, held for 12h). It is then die forged in three passes on a large die forging hydraulic press to obtain a large-sized cross-shaped thick-core thin-arm titanium alloy forging that meets the dimensional requirements of the drawings in this embodiment. Table 4 lists the forging parameters of its die forging process.

[0069] Table 4

[0070]

[0071] Step 6: Demold the forging by using the guide pin 3 to eject it from the lower mold cavity of the forging.

[0072] Due to the poor hardenability of titanium alloys, as large-sized forgings, the forgings obtained in this embodiment need to be thinned in non-part areas before heat treatment to ensure the consistency of the microstructure and properties of the forgings after heat treatment.

[0073] Finally, the forgings are treated according to the following heat treatment regime:

[0074] a) Heat at 760±10℃ for 120 minutes, then remove from the furnace and cool in water;

[0075] b) Heat at 515±5℃ for 500 minutes, then remove from the furnace and air cool.

[0076] Figure 6 The image shows a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging 4, manufactured using the forging mold and method provided in this embodiment of the invention.

[0077] Figure 11 , Figure 12 They are respectively Figure 6 The low-magnification and microstructures of the forging shown are illustrated. As can be seen from the figures, the low-magnification microstructure of the forging is free of metallurgical defects and exhibits good flow lines; the microstructure consists of a β matrix and spherical or strip-shaped primary α phases, meeting the forging standard requirements.

[0078] Table 5 shows the room temperature tensile strength, fracture toughness and other properties of the forgings obtained in the above embodiments, and all of their properties meet the relevant technical requirements.

[0079] Table 5

[0080]

[0081]

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging, characterized in that: A large-sized, cross-shaped, thick-core, thin-arm forging die is used for forging. The large-size cross-shaped thick-core thin-arm forging mold includes a matching forging upper mold (1), forging lower mold (2), and ejector pin (3). The forging upper mold (1) is provided with a cross-shaped upper mold cavity (101), and the forging lower mold (2) is provided with a cross-shaped lower mold cavity (201). The ejector pin (3) is located at the lower part of the forging lower mold (2). After the forging upper mold (1) and the forging lower mold (2) are closed, the shape of the cavity formed by the upper mold cavity (101) and the lower mold cavity (201) is consistent with the shape of the cross-shaped thick-core thin-arm titanium alloy forging. Includes the following steps: Step 1: Bar stock pretreatment. After cutting the bar stock to the required specifications and dimensions, use a lathe to mill the end face of the titanium alloy bar stock flat and chamfer it. Step 2, free forging upsetting: After heating the titanium alloy bar on the high-speed forging machine, it is placed in the preheated forging die (2) for multiple passes of local constraint upsetting, so that the total height of the bar is reduced by 1 / 2, and the thick core part of the forging is pre-formed. Step 3, positioning forging: After heating the billet on a large die forging hydraulic press, place it in the preheated upper forging die (1) and lower forging die (2) for 1 to 2 passes of positioning forging to achieve positioning of the thin arm part of the cross-shaped forging. Step 4: Free forging billet, using arc tooling (5) on a fast forging machine to shape the cross angle position of the billet obtained in step 3, completed in 1 to 2 passes, driving the billet to flow to the thin arm position of the cross configuration. Step 5, die forging: The blank obtained in step 4 is heated on a large die forging hydraulic press and then placed in the preheated upper forging die (1) and lower forging die (2) for 1 to 3 passes of die forging to obtain a cross-shaped thick core thin arm titanium alloy forging. Step 6: Demolding the forging. The large-sized cross-shaped thick-core thin-arm titanium alloy forging is ejected from the forging lower die (2) using the ejector rod (3).

2. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 1, characterized in that: The upper forging die (1) and the lower forging die (2) are locked and positioned by a locking structure. The locking structure includes an arc-shaped boss (102) and an arc-shaped groove (202) for use. The arc-shaped boss (102) is located on the top surface of the upper forging die (1), and the arc-shaped groove (202) is located on the top surface of the lower forging die (2).

3. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 2, characterized in that: There are four arc-shaped protrusions (102) and four arc-shaped grooves (202). The four arc-shaped protrusions (102) are evenly distributed around the circumference. The size of one arc-shaped protrusion (102) is smaller than the size of the other three arc-shaped protrusions (102), and the size of one arc-shaped groove (202) is smaller than the size of the other three arc-shaped grooves (202). The position of the arc-shaped groove (202) corresponds one-to-one with the position of the arc-shaped protrusion (102).

4. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 3, characterized in that: The locking angle S1 is 1-3°, the gap distance A1 between the locking sidewalls is 1-2mm, the concave radius R1 at the locking point is 10mm, the convex radius R2 at the locking point is 15mm, and the gap distance A2 between the upper and lower parts of the locking point when closed is 1-2mm. The non-locking area is the mold closing surface.

5. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 1, characterized in that: The upper mold cavity (101) and the lower mold cavity (201) adopt a gradient bridge width design. The bridge width ratio between the vertical cross position and the included angle position of the cavity is 1:2, and the corresponding hopper width ratio is 1:

3.

6. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 1, characterized in that: The top rod (3) includes a first rod segment (301) and a second rod segment (302). A guide segment (303) is provided between the first rod segment (301) and the second rod segment (302). The length of the guide segment (303) is 30-60mm. The angle between the ridge line of the guide segment (303) and the center line of the first rod segment (301) is 120-150°.

7. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 1, characterized in that: In step two, when upsetting the bar stock, free upsetting is performed first. Before the final upsetting, a stepped circle no larger than the deepest part of the lower mold cavity (201) needs to be forged at the lower end of the billet. Then, it is placed in the lower forging mold (2) to maintain the constraint and perform the final upsetting to obtain forging billets with different cross-sectional dimensions.

8. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 1, characterized in that: In steps two through five, the heating temperature of the titanium alloy bar and the forging billet is selected within the range of Tβ - (40–60)℃. The cold material holding time is calculated as 0.6–0.8 min × effective cross-sectional thickness of the billet, and the hot material holding time is calculated as 0.4–0.5 min / mm × effective cross-sectional thickness of the billet, where the unit of effective cross-sectional thickness of the billet is millimeters. During forging in steps three and five, the large die forging hydraulic press adopts a low pressing speed, which is 1–3 mm / s.

9. The forging method for a large-sized, cross-shaped, thick-core, thin-arm titanium alloy forging according to claim 1, characterized in that: Before implementing step five, the billet needs to be preheated in a heating furnace to 200±50℃ and kept at that temperature for 20 to 40 minutes. After being taken out, it is sprayed with a special forging lubricant for titanium alloys.

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