Process for reducing the number of forging passes of titanium alloy bars

Abstract

The present application belongs to the technical field of titanium alloy material preparation, and particularly relates to a process method for reducing forging fire times of titanium alloy bars. The basic idea of the bar modification forging is to realize three upsetting and three drawing in one fire time below the phase transition point through the design of a special upsetting and drawing device for the bar, so as to ensure the full crushing of the grains and reduce the forging fire times. When the ordinary free forging bar is forged, the height-diameter ratio of the ingot is required to be not greater than 3, and only one upsetting and one drawing can be performed in each fire time below the phase transition point. In order to fully crush the grains, multiple fire times of forging need to be performed. The ordinary forging needs multiple drawing processes, the surface temperature drops greatly, and there are many surface cracks and indentations. When the upsetting and drawing device is used for deformation, the metal is in a three-way compressive stress state, which can reduce the surface cracks and improve the plasticity. The grains can be refined under large deformation, and the operation time of the upsetting and drawing is greatly shortened. Three upsetting and drawing can be realized in one fire time below the phase transition point, the forging fire times are reduced, and the production cost is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material preparation technology, specifically a process method for reducing the number of forging processes for titanium alloy bars. Background Technology

[0002] Titanium alloy bars require multiple forging passes during the forging process, typically 10-12 passes. Each pass involves heating, repeated upsetting and drawing, and grinding, resulting in a long production cycle and high costs. In the single-phase region of ordinary free forging, a maximum of three upsetting and three drawing passes can be completed in one pass, taking 10-12 minutes. In the lower-temperature two-phase region, only one upsetting and one drawing pass is possible per pass, requiring multiple passes to achieve sufficient grain breakage. After forging, the surface temperature of the bar drops by approximately 200°C, resulting in numerous surface cracks. Upsetting and drawing often employs square or hexagonal drawing techniques, leading to uneven deformation and significant grain differences between the core and edges of the bar. Summary of the Invention

[0003] The purpose of this invention is to provide a process method for reducing the number of forging passes for titanium alloy bars, which can obtain uniform fine-grained bars while reducing the number of forging passes for the bars.

[0004] The above-mentioned objective of this invention is achieved through the following technical solution: a process method for reducing the number of forging passes for titanium alloy bars, characterized by comprising the following steps:

[0005] Step 1: Design a special cylinder for bar upsetting and extrusion. The diameters at both ends of the central hole of the cylinder are different, namely R1 and R2. R1 is the final diameter of the required bar, and R2 is the diameter after upsetting deformation designed according to the bar upsetting ratio. The length of the cylinder with diameter R1 is the length of the required bar, and the length of the cylinder with diameter R2 is calculated according to the equal volume method. The connection between the two cylinders is a circular arc transition connection.

[0006] Step 2: Heat the ingot to above 1000℃, lengthen the ingot to a diameter of R1 and a length of H, and place it in a special upsetting and extrusion cylinder. The special upsetting and extrusion cylinder is preheated and sprayed with lubricant. The press applies pressure at end T1, while end T2 is locked. Upset the bar to a diameter of R2. Turn the special upsetting and extrusion cylinder around, lock end T1, and press at end T2 to extrude the bar to a diameter of R1. Repeat the operation three times to complete three upsetting and three drawing operations. After upsetting and drawing, the diameter of the bar is R1. Remove the bar from the special upsetting and extrusion cylinder and let it cool.

[0007] Step 3: Heat the bar obtained in Step 2 to 40°C below the phase transformation point. Place the bar in an upsetting extrusion cylinder. Preheat the upsetting extrusion cylinder and spray it with lubricant. Apply pressure at end T1 of the press. At this time, end T2 is locked. Upset the bar to a diameter of R2. Turn the upsetting extrusion cylinder around and lock end T1. Apply pressure at end T2 of the press and squeeze the bar to a diameter of R1. Repeat the operation three times to complete the three upsetting and three drawing processes.

[0008] Step 4: Heat the bar obtained in Step 3 to 40°C above the phase transformation point. Place the bar in a special upsetting and extrusion cylinder. Preheat the special upsetting and extrusion cylinder and spray it with lubricant. Apply pressure at end T1 of the press, while end T2 is locked. Upset the bar to a diameter of R2. Turn the special upsetting and extrusion cylinder around, lock end T1, apply pressure at end T2 of the press, and extrude the bar to a diameter of R1. Repeat the operation three times to complete the three upsetting and three drawing processes.

[0009] Step 5: Repeat step 3 to finally obtain a bar with a diameter of R1.

[0010] The preheating temperature of the upsetting cylinder in step two is 400-500℃.

[0011] R1 is the diameter of the final required bar material, where 50mm ≤ R1 ≤ 500mm.

[0012] The diameter of the ingot is ≥R1.

[0013] R2 is

[0014] The lubricant mentioned in step two is a high-temperature lubricant Ti-1.

[0015] The lubricant used in steps three to five is a medium-temperature lubricant, Ti-7.

[0016] The deformation rate of the upsetting process in steps two to five is 5 to 10 mm / s.

[0017] Technical advantages of this invention: The basic idea of ​​this invention for bar forging is to design a special tooling for bar upsetting and extrusion, which can achieve three upsetting and three drawing operations in one pass below the phase transformation point, ensuring sufficient grain breakage and reducing the number of forging passes. In ordinary free forging of bars, the height-to-diameter ratio of the ingot is required to be no greater than 3, and only one upsetting and one drawing operation can be performed per pass below the phase transformation point. To fully break the grains, multiple forging passes are required. Ordinary forging requires multiple drawing passes, resulting in large surface temperature drops and numerous surface cracks and indentations. With this upsetting and extrusion device, the metal is under triaxial compressive stress during deformation, which can reduce surface cracks, improve plasticity, and refine grains under large deformation. Simultaneously, because the upsetting and drawing operation time is significantly shortened, three upsetting and drawing operations can be achieved in one pass below the phase transformation point, reducing the number of forging passes and greatly reducing production costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an upsetting extrusion cylinder.

[0019] Figure 2 This is a schematic diagram of the bar upsetting process.

[0020] Figure 3 This is a schematic diagram of the bar extrusion process.

[0021] In the diagram: 1-Pressure head a, 2-Bar stock to be upset, 3-Upsetting cylinder, 4-Quick fastening pressure plate, 5-Hydraulic device, 6-Pressure head b, 7-Bar stock to be extruded Detailed Implementation

[0022] To better understand the purpose, technical solution, and advantages of this invention, the following detailed description is provided in conjunction with embodiments.

[0023] A process for reducing the number of forging passes in titanium alloy bars includes the following steps:

[0024] Step 1: Design a special cylinder for bar upsetting and extrusion, such as... Figure 1 The two ends of the cylinder have different diameters, R1 and R2, respectively. R1 is the final diameter of the required bar stock, and R2 is the diameter after upsetting deformation designed according to the upsetting ratio of the bar stock. The length of the cylinder with diameter R1 is the length of the required bar stock, and the length of the cylinder with diameter R2 is calculated according to the equal volume method. The connection between the two cylinders of different diameters is a circular arc transition connection. The design of the variable diameter upsetting extrusion device can realize the upsetting and extrusion of round bars into round bars, eliminating the deformation dead zone caused by the square or hexagonal elongation during the free forging upsetting process, and reducing the unevenness of bar deformation; R1 is the final required bar stock diameter, 50mm≤R1≤500mm, the diameter of the ingot ≥R1, and R2 is √2R1~√10R1 / 4.

[0025] Step 2: Heat the ingot to above 1000℃ for billet preparation. Lengthen the ingot to a diameter of R1 and a length of H. Place it in a variable-diameter upsetting device. Preheat the upsetting device. Apply pressure at end T1 while end T2 is locked. Upset the bar to a diameter of R2. Turn the upsetting device around, lock end T1, and apply pressure at end T2 to extrude the bar to a diameter of R1. Repeat this process three times to complete three upsetting and three drawing operations. After upsetting and drawing, the bar diameter is R1. Remove the bar from the upsetting device and let it cool. When metal is under triaxial compressive stress, surface cracks can be reduced, plasticity can be improved, and grains can be refined under large deformation. One-pass three-stage upsetting and drawing forging can fully break the grains, and grain refinement can be achieved with fewer passes. Preheating of the upsetting and extrusion device can ensure that the surface temperature drop of the billet is reduced, thereby improving surface quality and reducing cracks. The preheating temperature of the upsetting and extrusion device is 400-500℃, and the lubricant is a high-temperature lubricant Ti-1.

[0026] Step 3: After removing surface micro-cracks, heat the bar obtained in Step 2 to 40°C below the phase transformation point. Place the bar in the upsetting device, which is preheated to 400-500°C. Apply pressure at end T1, while end T2 is locked. Upset the bar to a diameter of R2. Turn the upsetting device around, lock end T1, and apply pressure at end T2 to extrude the bar to a diameter of R1. Repeat this process three times to complete the three upsetting and three drawing operations.

[0027] Step 4: After removing surface micro-cracks, heat the bar obtained in Step 3 to 40°C above the phase transformation point. Place the bar in an upsetting extrusion device, preheating it to 400-500°C. Apply pressure at end T1, while end T2 is locked. Upset the bar to a diameter of R2. Turn the upsetting extrusion device around, lock end T1, and apply pressure at end T2 to extrude the bar to a diameter of R1. Repeat this process three times to complete the three upsetting and three drawing operations.

[0028] Step 5: Repeat step 3 to obtain a bar with a diameter of R1.

[0029] The lubricant used in steps three to five is the medium-temperature lubricant Ti-7.

[0030] The deformation rate of the upsetting process described in steps two to five is 5 to 10 mm / s.

[0031] Example:

[0032] Step 1: Design special tooling for bar upsetting and extrusion, such as... Figure 1 The R1 of the upsetting device is 330mm, and the R2 is 470mm.

[0033] Step 2: Heat the ingot with a diameter of 380 mm and a length of 490 mm to 1140℃, spray high-temperature lubricant Ti-1 in the upsetting device, and lengthen the ingot to a diameter of 330 mm and a length of 649 mm to obtain the bar 2 to be upset. Place the bar 2 in the upsetting device with a variable diameter. Preheat the upsetting cylinder 3, pressure head a1 and pressure head b6 to 400℃. Press the press at end T1 with pressure head a1 at a pressing speed of 5 mm / s. At this time, lock the T2 end with quick-fastening pressure plate 4 to upset the bar to a diameter of 470 mm to obtain the bar 7 to be extruded. Turn the upsetting device around, lock the T1 end with the quick-fastening pressure plate 4 and the hydraulic device 5, and press the T2 end with the pressure head b6 at a pressing speed of 5 mm / s to extrude the bar to a diameter of 330 mm. Repeat the operation three times to complete the three upsetting and three drawing. After the upsetting and drawing are completed, the diameter of the bar is 330 mm. Remove the bar from the upsetting device and let it cool.

[0034] Step 3: Heat the bar obtained in Step 2 to 810℃, place the bar in the upsetting device, preheat the upsetting cylinder 3, pressure head a1, and pressure head b6 to 400℃, apply lubricant Ti-7 to the upsetting cylinder 3, and press the press at end T1 with pressure head a1 at a pressing speed of 5mm / s. At this time, end T2 is locked with quick-fastening pressure plate 4 and hydraulic device 5, upsetting the bar to a diameter of 470mm to obtain bar 7 to be extruded. Turn the upsetting device around, lock end T1 with quick-fastening pressure plate 4 and hydraulic device 5, and press the press at end T2 with pressure head b6 at a pressing speed of 5mm / s, extruding the bar to a diameter of 330mm. Repeat the operation three times to complete the three upsetting and three drawing processes.

[0035] Step 4: Heat the bar obtained in Step 3 to 890℃, place the bar in the upsetting extrusion device, preheat the upsetting extrusion device to 400℃, spray the upsetting extrusion device with medium-temperature lubricant Ti-1, and press the press at end T1 with pressure head a1 at a pressing speed of 5mm / s. At this time, end T2 is locked with quick-fastening pressure plate 4 and hydraulic device 5, upsetting the bar to a diameter of 470mm, obtaining bar 7 to be extruded. Turn the upsetting extrusion device around, lock end T1 with quick-fastening pressure plate 4 and hydraulic device 5, and press the press at end T2 with pressure head b6 at a pressing speed of 5mm / s, extruding the bar to a diameter of 330mm. Repeat the operation three times to complete the three upsetting and three drawing processes.

[0036] Step 5: Repeat step 3 to finally obtain a bar with a diameter of 330mm.

Claims

1. A process for reducing the number of forging passes for titanium alloy bars, characterized in that, Includes the following steps: Step 1: Design a special cylinder for bar upsetting and extrusion. The diameters at both ends of the central hole of the cylinder are different, namely R1 and R2. R1 is the final diameter of the required bar, and R2 is the diameter after upsetting deformation designed according to the bar upsetting ratio. The length of the cylinder with diameter R1 is the length of the required bar, and the length of the cylinder with diameter R2 is calculated according to the equal volume method. The connection between the two cylinders is a circular arc transition connection. Step 2: Heat the ingot to above 1000℃, lengthen the ingot to a diameter of R1 and a length of H, and place it in a special upsetting and extrusion cylinder. The special upsetting and extrusion cylinder is preheated and sprayed with lubricant. The press applies pressure at end T1, while end T2 is locked. Upset the bar to a diameter of R2. Turn the special upsetting and extrusion cylinder around, lock end T1, and press at end T2 to extrude the bar to a diameter of R1. Repeat the operation three times to complete three upsetting and three drawing operations. After upsetting and drawing, the diameter of the bar is R1. Remove the bar from the special upsetting and extrusion cylinder and let it cool. Step 3: Heat the bar obtained in Step 2 to 40°C below the phase transformation point. Place the bar in an upsetting extrusion cylinder. Preheat the upsetting extrusion cylinder and spray it with lubricant. Apply pressure at end T1 of the press. At this time, end T2 is locked. Upset the bar to a diameter of R2. Turn the upsetting extrusion cylinder around and lock end T1. Apply pressure at end T2 of the press and squeeze the bar to a diameter of R1. Repeat the operation three times to complete the three upsetting and three drawing processes. Step 4: Heat the bar obtained in Step 3 to 40°C above the phase transformation point. Place the bar in a special upsetting and extrusion cylinder. Preheat the special upsetting and extrusion cylinder and spray it with lubricant. Apply pressure at end T1 of the press, while end T2 is locked. Upset the bar to a diameter of R2. Turn the special upsetting and extrusion cylinder around, lock end T1, apply pressure at end T2 of the press, and extrude the bar to a diameter of R1. Repeat the operation three times to complete the three upsetting and three drawing processes. Step 5: Repeat step 3 to finally obtain a bar with a diameter of R1.

2. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, The preheating temperature of the upsetting cylinder in step two is 400-500℃.

3. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, R1 is the diameter of the final required bar material, 50mm≤R1≤500mm.

4. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, The diameter of the ingot is ≥R1.

5. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, R2 is 6. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, The lubricant mentioned in step two is the high-temperature lubricant Ti-1.

7. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, The lubricant used in steps three to five is the medium-temperature lubricant Ti-7.

8. The process method for reducing the number of forging passes for titanium alloy bars according to claim 1, characterized in that, The deformation rate of the upsetting process described in steps two to five is 5 to 10 mm / s.

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