CN115464114B - Thixotropic rotary extrusion method and device for shaft sleeve part - Google Patents

Abstract

The invention discloses a thixotropic rotary extrusion method and a device for shaft sleeve parts, which are used for transferring metal slurry heated to a semi-solid temperature range into a die with a flange. The motor controls the rotation speed of the male die, the male die starts to rotate when the male die is about to contact the slurry, and the maximum rotation speed is reached when the slurry is about to be filled; when the upper end of the ejector rod is flush with the upper end of the female die, the shaft sleeve is completely ejected, and the ejected extruded shaft sleeve part is taken out and subjected to rapid water quenching; and carrying out T6 heat treatment on the shaft sleeve part after water quenching. The method is a near-net forming technology, axial force of pressing down of the male die and shearing force generated by rotation in the extrusion process can fully crush and refine crystal grains, the adopted male die can inhibit and refine the crystallized crystal grains in a variable speed rotation mode, and the material organization performance is further improved, so that the utilization rate of the produced part material is high, the product quality is high, and the production efficiency is high; the die has simple and stable structure, and is easy to realize mechanical and automatic production.

Description

A thixotropic rotation extrusion method and device for axle sleeve parts

Technical Field

The invention relates to a thixotropic rotation extrusion method and a device for a shaft sleeve part, belonging to the field of semi-solid forming.

Background Art

Metal sleeve parts have the functions of supporting rotating shafts, guiding and positioning, and are often used in many fields such as machinery, chemical industry, aerospace, and automobiles. Since the metal semi-solid forming technology was proposed in the 1970s, it has developed rapidly. Compared with traditional casting or forging, it has the characteristics of low forming temperature, less pores, dense organization, and high material utilization rate. Therefore, the use of semi-solid forming method to prepare sleeve parts is expected to solve the problems of low material utilization rate, low mechanical properties, long production cycle, and many defects in the existing sleeve production. In the process of preparing sleeve parts by semi-solid thixoforming, it is often necessary to reheat the prepared blank to the semi-solid range and then transfer it to the mold for extrusion forming. During the forming process, there is often uneven distribution of components at the upper and bottom ends of the parts, which affects the product quality. Semi-solid billets are prone to solid-liquid separation, which causes the solid and liquid phases in the organization after extrusion to have different degrees of segregation, which ultimately affects the performance of the product and has a greater impact on the product quality, especially when preparing semi-solid alloy parts with a higher liquid phase ratio. Especially in the fields of aerospace and automobile, the bushing is a key part, so the requirements for its mechanical properties are high. How to improve the performance of bushing parts is of great research significance.

Summary of the invention

The purpose of the present invention is to provide a thixotropic rotary extrusion method for sleeve parts, which aims to solve the problem of solid-liquid separation of semi-solid slurry during the transfer of the blank in the existing semi-solid sleeve preparation method, resulting in uneven organization of the product after extrusion, coarse organization of the parts, and low product performance. The method uses semi-solid forming technology and uses a rotating convex head to fully stir the slurry during the extrusion process, so that the inner and outer walls of the product generate a large shear force to refine the organization; at the same time, the punch is pressed down, and the axial force and shear force work together to achieve a significant grain refinement effect. The method is used to form and prepare sleeve parts with high material utilization, high production efficiency, and excellent mechanical properties, which specifically includes the following steps:

(1) transferring the metal slurry heated to a semi-solid temperature into a preheated mold;

(2) The punch rotates and presses down quickly. The punch rotation process is a variable speed process. When the punch is about to contact the slurry, it starts to rotate at a low speed. The punch continues to press down and accelerates the rotation. When the slurry is fully filled, the punch rotation speed reaches the maximum. After maintaining the maximum rotation speed for 2-4 seconds, it stops rotating and maintains pressure. The rotation speed is:

v＝0.3f _s (x ³ +1)

In the formula: v is the rotation speed rps/min, _fs : solid phase ratio, x: pressing process (mm), where _fs is determined by different materials and performance requirements.

(4) Rapid water quenching of the extruded sleeve parts.

(5) Perform T6 heat treatment on the sleeve parts after water quenching.

Preferably, in step (1) of the present invention, the mold preheating temperature is 400-500°C.

Preferably, the extrusion speed of the punch of the present invention is 10-15 mm/s.

Preferably, _fs described in the present invention is derived as follows:

Combining (Ⅰ) and (Ⅱ), we can get:

Where: _Cs is the solid phase solute concentration, _CL is the liquid phase solute concentration, _TS is the solidus temperature, _TL is the liquidus temperature, and _k0 is the equilibrium distribution coefficient.

Another object of the present invention is to provide a thixotropic rotary extrusion device for a sleeve part, comprising an upper die fixing plate 1, a punch 3, a die 11, and a lower die fixing plate 13; a punch 3 is fixed under the upper die fixing plate 1, and a die 11 is fixed on the lower die fixing plate 13, characterized in that: a motor 8 is fixed under the upper die fixing plate 1, a pulley 2 is fixed on the punch 3, and the output shaft of the motor 8 is connected to the pulley 2 through a belt; a flange 4 is provided on the die 11, and a cavity formed by the punch 3 and the die 11 after the die 11 is closed corresponds to the shape of the sleeve part, and the flange 4 prevents liquid splashing while extending a small section into the die to assist in the formation of the sleeve shoulder.

The upper mold fixing plate 1 of the present invention is provided with guide rods 9 on both sides, springs are sleeved on the guide rods 9, the lower ends of the guide rods 9 are fixed on the flange 4, the flange 4 is fixed to the guide rods 9, and the flange is also lifted up when the mold is opened, and then the ejector rod ejects the product.

The punch 3 of the present invention is fixed under the upper mold fixing plate 1 through a punch fixing member 7. The lower end of the punch fixing member 7 is provided with an L-shaped groove, which cooperates with the T-shaped protrusion on the top of the punch 3 so that the punch 3 can rotate in the punch fixing member 7.

The present invention provides a push rod 6 below the concave die 11 , and the push rod 6 is fixed on a push rod fixing plate 12 , and the push rod fixing plate 12 is connected to the hydraulic press.

The material of the punch 3 and the die 11 of the present invention is H13 die steel.

Beneficial effects of the present invention:

(1) The present invention adopts a thixotropic rotary extrusion method to prepare semi-solid sleeve parts. The semi-solid slurry rubs against the outer wall of the punch by rotating the punch, and the lateral shear force fully breaks and refines the grains. The structure is dense with few pores, the mechanical properties of the parts are high, the forming speed is fast, the production efficiency is greatly improved, the production cost of the parts is greatly reduced, and the production cycle is shortened.

(2) The present invention adopts a thixotropic rotary extrusion method to prepare semi-solid sleeve parts. The punch rotates and moves downward rapidly to fully stir the slurry. After forming, the solid and liquid phases in the semi-solid structure are evenly distributed, and the mechanical properties are better.

(3) The present invention can produce products with higher mechanical properties. By adjusting the rotation speed of the punch, it can be applied to the semi-solid forming of different metals. The performance of the product can be adjusted, making it easier to realize customized production of parts.

(4) The rotation of the punch is a variable speed process. When it contacts the slurry, it rotates at a low speed to prevent the liquid from splashing onto the wall of the die and causing macro segregation. The punch continues to press down and accelerates its rotation, so that the semi-solid slurry can fill the mold smoothly. When the slurry filling is completed, the maximum rotation speed is reached. This process can fully inhibit the growth of spherical semi-solid grains, refine the grains, and improve the mechanical properties of the material.

(5) A flange is added to the die to prevent liquid splashing, and together with the male and female dies, it forms the sleeve cavity.

(6) The present invention is rapidly water quenched after extrusion forming, and the sleeve parts are subjected to T6 heat treatment after water quenching to further improve the uniformity of the structure and enhance the mechanical properties.

(7) The mold of the present invention has a reasonable structure and can be installed on a vertical extruder. It occupies a small area and is easy and convenient to operate, thus realizing mechanized and automated production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the die structure of the thixotropic rotary extrusion molding of the present invention.

Figure 2 shows the direction of punch rotation.

FIG. 3 is a schematic diagram showing the speed variation during the rotation of the punch of the present invention.

FIG4 compares the hardness properties of semi-solid alloys in different embodiments.

FIG5 compares the tensile strength of semi-solid alloys in different embodiments.

In Figure 1: 1-upper mold fixing plate; 2-pulley; 3-punch; 4-flange; 5-metal slurry; 6-push rod; 7-punch fixing piece; 8-motor; 9-guide rod; 10-spring; 11-die; 12-push rod fixing plate; 13-lower mold fixing plate.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

The mold structure used in the embodiment of the present invention is shown in Figure 1, including an upper mold fixing plate 1, a pulley 2, a punch 3, a flange 4, a metal slurry 5, a push rod 6, a punch fixing part 7, a motor 8, a guide rod 9, a spring 10, a die 11, a push rod fixing plate 12, and a lower mold fixing plate 13; the hydraulic press controls the punch 3 to move up and down; when the punch 3 and the motor 8 move downward at the same time during mold closing, the single-chip microcomputer controls the speed of the motor 8, the punch 3 is driven by the motor 8 belt, the speed sensor monitors and feeds back the rotation speed of the punch 3, and the motor 8 adjusts the speed of the punch. After the mold closing is completed, the punch keeps the speed for 2-4s and then stops rotating; when the mold is opened, the hydraulic press is unloaded, the punch is lifted, and the upper mold reaches the maximum When in the high position, it returns to the initial position under the action of the spring 10; the spring 10 is sleeved outside the guide rod 9; the punch 3 and the flange 4, the flange 4 and the die 11 are clearance-matched; the inner wall of the punch 3 of the mold and the lower die boss are set with a draft angle of 1°; the cavity formed after the punch 3, the flange 4 and the die 11 are combined corresponds to the shape of the sleeve part; the upper die fixing plate 1 is bolted to the punch fixing piece 7, and the upper die fixing plate 1 is fixed to the top position of the hydraulic press by a T-plate; the lower die fixing plate 13 is bolted to the die 11, and the lower die fixing plate 13 is fixed to the working table position of the hydraulic press by a T-plate, and remains fixed during the extrusion process; the material of the punch 3 and the die 11 is H13 die steel.

The use process of the mold described in the present invention is as follows: before the shaft sleeve part is extruded and formed, the hydraulic press controls the upper mold to retreat to the top of the hydraulic press; spray graphite release agent on the surfaces of the punch 3 and the die 11; pour the metal slurry 5 into the die 11, and the spring 10 is in a relaxed state; start the motor 8 and drive the punch to rotate by belt transmission, and control the punch rotation speed by controlling the power of the motor through the single-chip microcomputer; drive the hydraulic press to make the entire upper mold move vertically downward, and the convex movement speed is controlled by the hydraulic press, and the motor 8 stops rotating 2-4 seconds after the punch 3 and the die 11 are closed, and the pressure is maintained for a period of time; then control the hydraulic press to make the entire upper mold retreat to the top of the hydraulic press, the spring 10 is in a relaxed state, the push rod pushes out the shaft sleeve part and then takes it out, and finally performs T6 heat treatment; in the entire extrusion forming process, the mold structure is simple, it is easy to realize mechanized and continuous production, and the shaft sleeve part finally obtained has good comprehensive mechanical properties.

Example 1

The present embodiment describes a thixotropic rotary extrusion forming method for a copper alloy sleeve part, the die structure is shown in FIG1 , and the specific steps are as follows:

(1) The material of this embodiment is ZCuSn10P1 copper alloy. The solidus temperature of ZCuSn10P1 copper alloy is measured to be 876.1°C and the liquidus temperature is 1024.2°C.

(2) Preheat the lower die boss to 450°C, and then place the semi-solid ZCuSn10P1 slurry into the lower die.

(3) The upper die is driven to extrude the metal slurry at a speed of 10 mm/s, and the punch is driven by a motor to rotate, and the speed v is shown in Table 1. After the extrusion is completed, the pressure is maintained for 15 seconds.

(4) The extruded sleeve part is quickly water quenched, then heated to 550°C and kept warm for 60 min, and then air-cooled to room temperature to obtain the sleeve part.

In this embodiment, the upper mold rotation speed v (rps/min) satisfies the formula v=0.3f _s (x ³ +1), where f _s is 0.91, the pressing process is 0-14 mm, and the pressing speed is 10 mm/s. The specific parameters are shown in Table 1;

Table 1 ZCuSn10P1 copper alloy rotary reverse extrusion process 2

The copper alloy shaft sleeve part prepared in this embodiment has a smooth surface, precise size, and no defects such as scratches and cracks. Compared with the shaft sleeve part prepared by the common reverse extrusion method (preheating the lower die boss to 450°C, then placing the semi-solid ZCuSn10P1 slurry into the lower die, and then driving the upper die to extrude the metal slurry at a speed of 10 mm/s, maintaining the pressure for 10 seconds after the extrusion, and quickly quenching the shaft sleeve part after extrusion, and then heating to 550°C and keeping the temperature for 60 minutes, and then air cooling to room temperature to obtain the shaft sleeve part), the mechanical properties are improved, as shown in Figures 4 and 5.

Example 2

The present embodiment describes a 7075 aluminum alloy shaft sleeve part thixotropic rotary extrusion forming method, the preparation process is shown in FIG1 , and the specific steps are as follows:

(1) The material of this embodiment is 7075 aluminum alloy, and the solid-liquid phase temperature range of 7075 aluminum alloy is measured to be 540-638°C.

(2) The lower die boss is preheated to 400°C, and then the semi-solid 7075 aluminum alloy slurry is placed into the lower die.

(3) Then the upper die is driven to extrude the metal tube at a speed of 15 mm/s. The punch is driven by a motor to rotate, and the speed v is shown in 2. After the extrusion is completed, the pressure is maintained for 10 seconds.

(4) The extruded sleeve part is quickly water quenched, then heated to 380°C and kept warm for 30 min, and then air-cooled to room temperature to obtain the sleeve part.

In this embodiment, the upper mold rotation speed v (rps/min) satisfies the formula v=0.3f _s (x ³ +1), where f _s is 0.95, the pressing process is 0-14 mm, and the pressing speed is 15 mm/s. The specific parameters are shown in Table 2;

Table 2 7075 aluminum alloy rotary reverse extrusion process 2

The aluminum alloy shaft sleeve part prepared in this embodiment has a smooth surface, precise size, and no defects such as scratches and cracks. Compared with the shaft sleeve part prepared by the ordinary reverse extrusion method (preheating the lower die boss to 400°C, and then placing the semi-solid 7075 aluminum alloy slurry into the lower die. Then drive the upper die to extrude the metal slurry at a speed of 15mm/s, and maintain the pressure for 10s after the extrusion. The extruded shaft sleeve part is quickly quenched in water, then heated to 380°C and kept warm for 30min, and then air-cooled to room temperature to obtain the shaft sleeve part), the mechanical properties are improved, as shown in Figures 4 and 5.

Example 3

The present embodiment describes a thixotropic rotary extrusion forming method for an AZ91D magnesium alloy sleeve part, the preparation process is shown in FIG1 , and the specific steps are as follows:

(1) The material of this embodiment is AZ91D magnesium alloy, and the solidus-liquidus temperature range of AZ91D magnesium alloy is measured to be 470-595°C.

(2) The lower die boss is preheated to 350°C, and then the semi-solid AZ91D magnesium alloy slurry is placed into the lower die.

(3) The upper die is driven to extrude the metal slurry at a speed of 13 mm/s. The punch is driven by a motor to rotate, and the speed v is shown in Table 3. After the extrusion is completed, the pressure is maintained for 7 seconds.

(4) The extruded sleeve part is quickly water quenched, then heated to 320°C and kept warm for 90 min, and then air-cooled to room temperature to obtain the sleeve part.

In this embodiment, the upper mold rotation speed v (rps/min) satisfies the formula v=0.3f _s (x ³ +1), where f _s is 0.98, the pressing process is 0-14 mm, and the pressing speed is 13 mm/s. The specific parameters are shown in Table 3.

Table 3 AZ91D magnesium alloy rotary reverse extrusion process 3

The copper alloy shaft sleeve part prepared in this embodiment has a smooth surface, precise size, and no defects such as scratches and cracks. Compared with the shaft sleeve part prepared by the ordinary reverse extrusion method (preheating the lower die boss to 350°C, and then placing the semi-solid AZ91D magnesium alloy slurry into the lower die; driving the upper die to extrude the metal slurry at a speed of 13mm/s, and maintaining the pressure for 7s after the extrusion. The shaft sleeve part after extrusion is quickly quenched in water, then heated to 320°C and kept warm for 90min, and then air-cooled to room temperature to obtain the shaft sleeve part), the mechanical properties are improved, as shown in Figures 4 and 5.

Claims (7)

1. A thixotropic rotary extrusion method for a sleeve part, characterized in that the device used in the method comprises an upper die fixing plate (1), a punch (3), a die (11), and a lower die fixing plate (13); a punch (3) is fixed below the upper die fixing plate (1), and a die (11) is fixed on the lower die fixing plate (13); characterized in that: a motor (8) is fixed below the upper die fixing plate (1), a pulley (2) is fixed on the punch (3), an output shaft of the motor (8) is connected to the pulley (2) via a belt, and the motor is connected to a controller for controlling the rotation speed of the motor; a flange (4) is provided on the die (11), and a cavity formed by the punch (3) and the die (11) and the flange (4) after the punch (3) and the die (11) are clamped corresponds to the shape of the sleeve part; The method comprises the following steps: (1) Transferring the metal slurry heated to a semi-solid temperature into a preheated mold; (2) The punch rotates and presses down quickly. The punch rotation process is a variable speed process. When the punch is about to contact the slurry, it starts to rotate at a low speed. The punch continues to press down and accelerates the rotation. When the slurry is fully filled, the punch rotation speed reaches the maximum. After maintaining the maximum rotation speed for 2 to 4 seconds, it stops rotating and maintains pressure. The rotation speed is: ; Where: v is the rotation speed rps/min, : solid phase ratio, x: pressing process (mm), where Determined by different materials and performance requirements; (3) Rapid water quenching of the extruded sleeve parts; (4) Perform T6 heat treatment on the sleeve parts after water quenching; The derivation is as follows: (I); (II); Combining (I) and (II), we get: (III); Where: is the solid solute concentration, is the liquid solute concentration, is the solidus temperature, is the liquidus temperature, is the equilibrium distribution coefficient. 2. The thixotropic rotary extrusion method for a sleeve part according to claim 1 is characterized in that: in step (1), the mold preheating temperature is 400-500°C. 3. The thixotropic rotary extrusion method for sleeve parts according to claim 1 is characterized in that the extrusion speed of the punch is 10-15 mm/s. 4. The thixotropic rotary extrusion method for a sleeve part according to claim 1 is characterized in that guide rods (9) are provided on both sides of the upper die fixing plate (1), springs (10) are sleeved on the guide rods (9), and the lower ends of the guide rods (9) are fixed on the flange (4). 5. The thixotropic rotary extrusion method for sleeve parts according to claim 1 is characterized in that: the punch (3) is fixed to the bottom of the upper die fixing plate (1) by a punch fixing member (7), and the lower end of the punch fixing member (7) is provided with an L-shaped groove, which cooperates with the T-shaped protrusion on the top of the punch (3) so that the punch (3) can rotate in the punch fixing member (7). 6. The thixotropic rotary extrusion method for a sleeve part according to claim 1 is characterized in that a push rod (6) is provided below the die (11), the push rod (6) is fixed on a push rod fixing plate (12), and the push rod fixing plate (12) is connected to a hydraulic press. 7. The thixotropic rotary extrusion method for a sleeve part according to claim 1, characterized in that the material of the punch (3) and the die (11) is H13 die steel.