A warm forming process for titanium alloy elongated rods

Abstract

The application relates to the technical field of titanium alloy profile machining, and particularly discloses a warm forming machining method for a titanium alloy slender rod, which comprises rod part manufacturing, upsetting head manufacturing and groove manufacturing, the rod part, the upsetting head and the groove of the titanium alloy slender rod are respectively manufactured by using a warm extrusion die, a warm upsetting die and a warm roll pressing die, and the screw rod blank and the die are preheated before being put into the die. The scheme can solve the problem that the existing TB9 titanium alloy machining process is difficult to be applied to the machining of a slender rod structure.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy profile processing technology, specifically to a warm forming process for slender titanium alloy rods. Background Technology

[0002] Titanium and titanium alloys are the preferred structural materials in the aerospace field due to their high specific strength, non-magnetic properties, low coefficient of linear expansion, and corrosion resistance. With the development of shipbuilding, chemical, and medical fields, titanium and titanium alloys are gradually becoming the preferred materials in other areas as well. TB9 (Ti-3Al-8V-6Cr-4Mo-4Zr) titanium alloy is a metastable β-type high-strength titanium alloy. β-titanium alloys have good resistance to crack propagation and fatigue performance, while also possessing good variability and weldability. Currently, TB9 alloy is widely used in aerospace and automotive fields, primarily for springs and bolts, exhibiting excellent high strength and corrosion resistance.

[0003] TB9 alloy has a high content of β-stabilizing elements, resulting in high tensile strength and yield strength. However, in actual forming processes, if cold forming is used, the material properties of TB9 titanium alloy make it difficult for the metal to flow. Furthermore, for the slender rod products that our company needs to produce, compared to spring products, the stepped structure increases the difficulty of cold working. The high material hardness during cold working hinders material flow, easily leading to cracks and low yield rates. For machining the head of the slender rod, traditional cutting methods are wasteful due to material removal. Moreover, the lack of material flow during cutting does not improve the quality of the head formation. Additionally, the strength of the titanium alloy increases the technical requirements for cutting tools and parameters, resulting in significant tool wear and potentially uneven mechanical marks on the cutting surface. Furthermore, existing processes for cold forming the rod and cutting the head involve transferring the workpiece between different machines, resulting in a long and complex process. Therefore, a new forming method suitable for machining slender rod structures using TB9 titanium alloy is proposed. Summary of the Invention

[0004] The present invention provides a warm forming process for slender titanium alloy rods to solve the problem that the existing TB9 titanium alloy processing technology is difficult to apply to the processing of slender rod structures.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a warm forming process for a slender titanium alloy rod, comprising rod fabrication, upsetting head fabrication, and groove fabrication;

[0006] The fabrication of the shaft includes the following steps:

[0007] S1: Prepare TB9 titanium alloy wire blanks with specifications and quality of 103~105% of the finished workpiece;

[0008] S2: Heat the wire blank to 770℃-850℃, and preheat the warm extrusion die, warm upsetting die, and warm rolling die to 380~420℃;

[0009] S3: The heated wire blank is placed into a warm extrusion die for warm extrusion, and the first stepped shape is formed by the first extrusion die.

[0010] S4: The second stepped shape is formed by the second extrusion die, so that the stepped part of the slender rod is completely formed;

[0011] The construction of the pier head includes the following steps:

[0012] S5: Reheat the intermediate blank of the rod part to 770℃-850℃, put it into the warm upsetting mold, the head of the intermediate blank extends out of the warm upsetting mold, the head is upset, and the first upper mold is used to form a drum-shaped head, the height of the drum-shaped head is the same as the height of the formed slender rod head;

[0013] S6: The head is hot-forged again through the second upper mold so that the slender rod completely fills the second upper mold;

[0014] The groove creation process includes the following steps:

[0015] S7: The intermediate blank made by the head is reheated to 770℃-850℃ and placed in a warm rolling mold to form the groove on the stepped surface of the slender rod. The groove is formed by circumferential extrusion of the stepped surface by the first rolling roller and the second rolling roller.

[0016] The basic principle of this scheme is as follows: Warm forming technology heats the production parts, which are at room temperature, to a suitable temperature. The phase transformation point of TB9 alloy is 735℃. Above the β phase transformation point, its microstructure is a single β phase. By heating it to a temperature higher than the phase transformation point, the α phase of TB9 material easily transforms into the β phase, leading to an increase in the strength and hardness of the titanium alloy. Simultaneously, the mold preheating temperature is lower than the workpiece temperature. The selection of the mold temperature prioritizes mold lifespan, meaning it cannot operate at high temperatures for extended periods. Furthermore, the workpiece material undergoes a slow cooling process within the mold, which is beneficial for the surface hardness of the formed material. Because the mold preheating temperature is lower than the workpiece heating temperature, demolding issues are largely avoided. External force is applied to the raw material, causing it to form within the pre-set mold. The extrusion between steps one and two in the rod production process must be continuous, as must the extrusion between steps three and four in the head production process.

[0017] The warm forming process can be regarded as a processing method that does not remove material, so the volume before and after forming remains basically unchanged. Two stepped shafts are made by two vertical extrusions in the warm extrusion direction, and then the head is warm-forged a second time in the vertical direction to make a full-filled head. Finally, the slender rod is placed horizontally between the rolling rollers to form a groove.

[0018] The beneficial effects of this solution are as follows: 1. Compared with cutting, the warm forming process of slender rods has high production efficiency, high material utilization, high forming quality and simple process, which can save a lot of materials. The material utilization rate reaches about 97%. The extrusion and upsetting process strengthens the material to a certain extent and increases the service life of the formed parts.

[0019] 2. Compared to traditional cutting, the head produced by warm upsetting using the extrusion process has a longer service life than the head produced by cutting. It greatly avoids the problem of stress concentration and damage at the upsetting head of slender rods during use. This warm upsetting process fully considers the flow characteristics of TB9 titanium alloy metal material, and divides the forming process with large deformation into two steps, so that the metal material is completely filled in the mold cavity, improving the forming quality of slender rods and avoiding slender rods.

[0020] 3. Compared with cutting, roll forming can save materials, strengthen the grain size of the extruded surface, and make the formed parts more durable and have a longer life. At the same time, roll forming has high production efficiency. Therefore, this method is suitable for batch or large-scale production. From the point of view of economic rationality in actual production, roll forming has more prominent advantages in mass production.

[0021] Furthermore, the warm extrusion die includes an upper extrusion die that can reciprocate up and down, and a fixed lower extrusion die. The lower extrusion die has a cylindrical cavity that vertically penetrates the lower die. The lower extrusion die includes a first lower extrusion die and a second lower extrusion die. The lower cavity of the first lower extrusion die is divided into a first stage and a second stage from low to high. The inner diameter of the first stage is smaller than the inner diameter of the second stage. The first stage of the second lower extrusion die is the same as that of the first lower extrusion die. The second stage of the second lower extrusion die is divided into a second stage and a third stage from low to high. The inner diameter of the third stage is larger than the inner diameter of the second stage.

[0022] Furthermore, the warm upsetting mold includes a warm upsetting upper mold that can move up and down, and a warm upsetting lower mold fixed on the frame. The warm upsetting lower mold has a lower mold cavity that can accommodate the rod below the upsetting head of the slender rod. The lower mold cavity vertically penetrates the warm upsetting lower mold. The warm upsetting upper mold includes a first upper mold and a second upper mold. The bottom surface of the first upper mold is a plane, and the bottom surface of the second lower mold has an upper mold cavity that can accommodate the upsetting head. The bottom surface of the upper mold cavity is rounded.

[0023] Furthermore, the warm rolling die includes rolling rollers, which include a first rolling roller and a second rolling roller. The first rolling roller and the second rolling roller are arranged horizontally along the axis. A support roller that can lift and receive the workpiece is provided between the two rolling rollers. The two rolling rollers and the workpiece are arranged parallel to each other and their central axes pass through the same horizontal plane. The outer wall of the rolling roller is provided with outwardly protruding annular patterns. The two rolling rollers are fixed on the main shaft of an external drive device, and one of the rolling rollers can move horizontally along the radial direction of the workpiece.

[0024] Furthermore, both the warm extrusion die and the warm upsetting die are mounted on the warm upsetting machine. The warm extrusion die and the warm upsetting die are designed to be interchangeable within a single warm upsetting machine, facilitating their use.

[0025] Furthermore, the warm rolling die is mounted on the rolling mill. The rolling mill deforms the groove by controlling the rotational speed and lateral feed speed of the rolling die.

[0026] Furthermore, the diameter of the titanium alloy wire blank is the same as the diameter of the largest end of the slender rod stepped section. A single extrusion directly forms one section of the stepped shaft, and a second extrusion forms two sections of the stepped shaft.

[0027] Furthermore, S7 is followed by S8: inserting a slender rod into the corresponding cleaning line to remove surface contaminants.

[0028] Furthermore, S8 is followed by S9: flaw detection of slender rods to detect whether the product has microscopic defects. Attached Figure Description

[0029] Figure 1 This is an assembly diagram of an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of a warm extrusion die and a warm upsetting die in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of a warm rolling die in an embodiment of the present invention;

[0032] Figure 4 for Figure 3 Cross-sectional view of the intermediate rolling roller;

[0033] Figure 5 for Figure 4 Detailed illustration of the central ring pattern;

[0034] Figure 6 This is a schematic diagram of the workpiece formed by each process in this embodiment. Detailed Implementation

[0035] The following detailed description illustrates the specific implementation method:

[0036] The reference numerals in the accompanying drawings include: guide sleeve 1, upper extrusion die 2, lower die pressure plate 3, guide post 4, lower die cavity 5, lower die base 6, lower die pad 7, ejector rod 8, first lower extrusion die 91, second lower extrusion die 92, bolt 10, upper die base 11, upper extrusion die pad 12, pressure sleeve 13, upper die pressure plate 14, first upper die 20, second upper die 21, upper die cavity 211, warm upsetting lower die 22, lower die cavity 23, annular step 24, workpiece 25, key 16, support roller 17, plane 171, workpiece to be rolled 18, rolling roller 19, main shaft hole 191, keyway 192, annular groove 193, and drive shaft 020.

[0037] The basic implementation examples are as follows: Figure 1 As shown:

[0038] Processes one and two are warm extrusion processes used for rod fabrication; processes three and four are warm upsetting processes used for upsetting heads; and process five is warm rolling processes used for groove fabrication.

[0039] Warm forming processing dies include warm extrusion dies, warm upsetting dies, and warm rolling dies. Warm extrusion dies and warm upsetting dies are installed on warm upsetting machines, while warm rolling dies are installed on rolling machines.

[0040] S1: Prepare TB9 titanium alloy wire blanks with specifications and quality of 103~105% of the finished workpiece;

[0041] S2: Heat the wire blank to 770℃-850℃, preferably 800℃ in this embodiment; preheat the warm extrusion die, warm upsetting die, and warm rolling die to 380~420℃, preferably 400℃ in this embodiment.

[0042] S3: The heated wire blank is placed into a warm extrusion die for warm extrusion, and the first stepped shape is formed by the first extrusion die.

[0043] S4: The second stepped shape is formed by the second extrusion die, so that the stepped part of the slender rod is completely formed;

[0044] Specifically, after fixing the first extrusion die 91 on the warm upsetting machine, the slender rod is inserted into the lower die cavity 5 of the first extrusion die 91 and contacts the ejector rod 8. The warm upsetting machine is started, and the upper die presses down to extrude the slender rod, making the diameter of the bottom part of the slender rod smaller and becoming a stepped shaft. The workpiece 25 after processing is ejected by the ejector rod 8. Then, the second extrusion die 92 is installed to extrude the slender rod again, making the diameter of the lower end of the slender rod smaller again and becoming a second-order stepped shaft.

[0045] The extrusion die 2 is cylindrical, with large diameters at both ends and small diameters in the middle. The upper end of the extrusion die 2 is a conical section, and the lower end of the extrusion die 2 is a cylindrical section. The extrusion die 2 is fixed inside the upper die base 11, which is plate-shaped. Vertical guide sleeves 1 pass through the left and right ends of the upper die base 11, and vertical guide posts 4 pass through the guide sleeves 1. The guide posts 4 are fixed on the horizontally placed lower die base 6. The upper die base 11 and the lower die base 6 are respectively fixed on the warm upsetting machine. The hydraulic system of the warm upsetting machine is used to realize the reciprocating up and down movement of the extrusion die 2.

[0046] One end of the upper die holder 11 where the extrusion die 2 is mounted is machined with a downward-facing mounting groove. A pad for the extrusion die 2 is placed at the bottom of the mounting groove. The extrusion die 2 is then passed from top to bottom through a cylindrical pressure sleeve 13. The inner wall of the pressure sleeve 13 is a conical surface that fits against the upper end of the extrusion die 2, thereby limiting the extrusion die 2 within the pressure sleeve 13. The pressure sleeve 13 is installed inside the mounting groove. An upper die pressure plate 14 covering the entire top surface of the mounting groove is installed outside the pressure sleeve 13. Downward-facing threaded blind holes are machined on both sides of the mounting groove. Bolts 10 pass through the upper die pressure plate 14 and are threadedly connected to the blind holes of the upper die holder 11, thus allowing the extrusion die 2 to be installed inside the upper die holder 11.

[0047] The lower die includes a first extrusion lower die 91 and a second extrusion lower die 92, both of which are rectangular blocks with a vertically penetrating lower die cavity 5 at the central axis. The lower die cavity 5 of the first extrusion lower die 91 is divided into a first stage and a second stage from low to high, with the diameter of the first stage being smaller than that of the second stage. The lower die cavity 5 of the second extrusion lower die 92 further divides the second stage, with the upper end of the second stage forming a third stage, the diameter of which is larger than that of the second stage.

[0048] The lower mold base 6 is convex in shape. A groove with an upward opening is machined in the middle of the lower mold base 6 to accommodate the lower mold. A lower mold pad 7 is placed at the bottom of the groove. A through hole for the ejector pin 8 to pass through is machined at the central axis of the lower mold pad 7. A ring platform is machined on the outer edge of the top surface of the lower mold. A lower mold pressure plate 3 that can cover the ring platform and the entire top surface of the lower mold base 6 is installed on the top surface of the lower mold base 6. An upward-opening threaded blind hole is machined at the upper end of the lower mold base 6. The lower mold pressure plate 3 is fixed to the top surface of the lower mold base 6 by bolts 10.

[0049] The construction of the pier head includes the following steps:

[0050] S5: Place the prepared intermediate blank of the rod into the warm upsetting mold to upset its head, and form a drum-shaped head through the first upper mold. The height of the drum-shaped head is consistent with the height of the formed slender rod head.

[0051] S6: The head is hot-forged again through the second upper mold so that the slender rod completely fills the second upper mold;

[0052] Specifically, the first upper die 20 of the warm upsetting upper die is installed on the upper jacket of the warm upsetting machine, and the warm upsetting lower die 22 is fixed in the lower die base 6 of the warm upsetting machine. The worker puts the slender rod processed in the previous process into the lower die cavity 23, starts the warm upsetting machine, and drives the first upper die 20 to press down the upsetting head of the slender rod. The upsetting head flows freely in the radial direction to form a drum shape. The second upper die 21 replaces the first upper die 20, and the warm upsetting machine is started again. The upper die cavity 211 of the second upper die 21 completely accommodates the upsetting head. Under the extrusion action, the upsetting head completely fills and fits the upper die cavity 211 to form a cylindrical upsetting head.

[0053] The lower upsetting mold 22 has a vertically penetrating lower mold cavity 23. The shape of the lower mold cavity 23 is the same as the outline of the slender rod except for the head. In this embodiment, the lower mold cavity 23 is cylindrical, and its inner diameter decreases stepwise along the length of the slender rod, forming two steps. After the lower upsetting mold 22 is placed in, the upsetting head of the lower upsetting mold 22 is exposed at the top.

[0054] Both the first upper mold 20 and the second upper mold 21 are hourglass-shaped with larger outer diameters at both ends and smaller outer diameters in the middle. The lower end of the second upper mold 21 is machined to form a downward-opening upper mold cavity 211. The upper mold cavity 211 is cylindrical and can accommodate the upsetting head. The bottom of the upper mold cavity 211 is rounded, resulting in a smooth transition between the bottom wall and the side walls, allowing the slender rod head after upsetting to be directly and integrally formed with smooth edges. The upper mold cavity 211 and the lower mold cavity 23 are coaxially arranged.

[0055] The groove creation process includes the following steps:

[0056] S7: Place the intermediate blank made of the abutment into the warm rolling mold to form the groove on the stepped surface of the slender rod. The groove is formed by circumferentially pressing the stepped surface with the first rolling roller and the second rolling roller.

[0057] Specifically, during the rolling process, the workpiece 25, which has been processed in the previous process, is placed horizontally on the support roller 17. The two rolling rollers 19 start to rotate, and the movable rolling roller 19 feeds radially along the workpiece 25. The side wall of the workpiece 25 contacts the annular groove 193 on the side wall of the rolling roller 19, causing the material of the workpiece 25 to flow and form an annular groove, thus completing the processing of the entire slender rod.

[0058] The rolling roller 19 includes a first rolling roller 19 and a second rolling roller 19, both of which have the same structure. Taking the first rolling roller 19 as an example, the outer wall of the first rolling roller 19 has two protruding annular patterns 193. The convex surface of the annular patterns 193 is a semi-circular arc surface, the diameter of which can be set according to processing requirements. The first rolling roller 19 has a spindle hole 191 at its center, and a through keyway 192 is formed on the inner wall of the spindle hole 191. The first rolling roller 19 is sleeved on the drive shaft 020 of the external drive device through the spindle hole 191. The first rolling roller 19 is fixed to the drive shaft 020 by inserting a key 16 into the keyway 192. The speed of the first rolling roller 19 can be controlled by controlling the rotational speed of the drive shaft 020. The drive shaft 020 is axially horizontal, so the first rolling roller 19 can rotate vertically in the horizontal direction.

[0059] The second rolling roller 19 is arranged parallel to the side of the first rolling roller 19, and the line connecting the centers of the two rolling rollers 19 passes through the same horizontal line. The difference between the second rolling roller 19 and the first rolling roller 19 is that the second rolling roller 19 is sleeved on a drive device that can be fed laterally.

[0060] A support roller 17 is horizontally fixed to the side of the first rolling roller 19 near the second rolling roller 19. The support roller 17 is arranged along the circumferential axis of the rolling roller 19, and its upper end is machined into a plane 171. When the workpiece 1825 to be rolled is placed parallel to the plane 171, the workpiece 1825 to be rolled and the central axis of the two rolling rollers 19 pass through the same horizontal plane 171.

[0061] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for warm forming of a slender titanium alloy rod, characterized in that: This includes rod fabrication, upsetting head fabrication, and groove fabrication; The fabrication of the shaft includes the following steps: S1: Prepare TB9 titanium alloy wire blanks with specifications and quality of 103~105% of the finished workpiece; S2: Heat the wire blank to 770℃-850℃, and preheat the warm extrusion die, warm upsetting die, and warm rolling die to 380~420℃; S3: The heated wire blank is placed into a warm extrusion die for warm extrusion, and the first stepped shape is formed by the first extrusion die. S4: The second stepped shape is formed by the second extrusion die, so that the stepped part of the slender rod is completely formed; The construction of the pier head includes the following steps: S5: Reheat the intermediate blank of the rod part to 770℃-850℃, put it into the warm upsetting mold, the head of the intermediate blank extends out of the warm upsetting mold, the head is upset, and the first upper mold is used to form a drum-shaped head, the height of the drum-shaped head is the same as the height of the formed slender rod head; S6: The head is hot-forged again through the second upper mold so that the slender rod completely fills the second upper mold; The groove creation process includes the following steps: S7: Reheat the intermediate blank made of the head to 770℃-850℃, put it into the warm rolling mold to form the groove of the stepped surface of the slender rod, and form the groove by circumferentially pressing the stepped surface with the first rolling roller and the second rolling roller. The warm extrusion die includes an upper extrusion die that reciprocates up and down and a fixed lower extrusion die. The lower extrusion die has a cylindrical cavity that vertically penetrates the lower die. The lower extrusion die includes a first lower extrusion die and a second lower extrusion die. The lower cavity of the first lower extrusion die is divided into a first stage and a second stage from low to high. The inner diameter of the first stage is smaller than the inner diameter of the second stage. The first stage of the second lower extrusion die is the same as that of the first lower extrusion die. The second stage of the second lower extrusion die is divided into a second stage and a third stage from low to high. The inner diameter of the third stage is larger than the inner diameter of the second stage. The upsetting mold includes an upper upsetting mold that moves up and down and a lower upsetting mold fixed on the frame. The lower upsetting mold has a lower mold cavity that accommodates the rod below the upsetting head of the slender rod. The lower mold cavity vertically penetrates the lower upsetting mold. The upper upsetting mold includes a first upper mold and a second upper mold. The bottom surface of the first upper mold is flat. The bottom surface of the second lower mold has an upper mold cavity that accommodates the upsetting head. The bottom surface of the upper mold cavity is rounded. The warm rolling die includes rolling rollers, which include a first rolling roller and a second rolling roller. The first rolling roller and the second rolling roller are arranged horizontally along the axis. A support roller for lifting the workpiece to be processed is provided between the two rolling rollers. The two rolling rollers and the workpiece to be processed are arranged parallel to each other and their central axes pass through the same horizontal plane. The outer wall of the rolling roller is provided with outwardly protruding annular patterns. The two rolling rollers are fixed on the main shaft of an external drive device, and one of the rolling rollers can move horizontally along the radial direction of the workpiece.

2. The warm forming method for a slender titanium alloy rod according to claim 1, characterized in that: Both the warm extrusion die and the warm upsetting die are installed on the warm upsetting machine.

3. The warm forming process for a slender titanium alloy rod according to claim 1, characterized in that: The warm rolling die is installed on the rolling machine.

4. The warm forming process for a slender titanium alloy rod according to claim 1, characterized in that: The diameter of the titanium alloy wire blank is the same as the diameter of the maximum end of the slender rod stepped section.

5. The warm forming method for a slender titanium alloy rod according to claim 4, characterized in that: The process after S7 includes S8: inserting a slender rod into the corresponding cleaning line to remove surface dirt.

6. The warm forming method for a slender titanium alloy rod according to claim 5, characterized in that: S8 is followed by S9: performing flaw detection on the slender rod to detect whether the product has microscopic defects.

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