Back pressure thixotropic extrusion forming method and device for shaft sleeve part

Abstract

The invention discloses a back pressure thixotropic extrusion forming method and device for a shaft sleeve part, and belongs to the technical field of semi-solid forming. Firstly, a semi-solid blank is reheated to a semi-solid temperature interval, heat preservation is conducted for a period of time, semi-solid slurry is obtained and then transferred into a mold cavity, a hydraulic machine and hydraulic cylinders connected with the upper back pressure ring and the lower back pressure ring are controlled to enable the semi-solid slurry to obtain follow-up back pressure provided by the upper back pressure ring and the lower back pressure ring in the extrusion process, and the semi-solid blank is extruded. And when the die is closed, the upper and lower back pressure rings apply back pressure to the shaft sleeve part and then eject the shaft sleeve part to obtain a semi-solid extrusion shaft sleeve part. According to the method, the shaft sleeve part is prepared through the semi-solid forming technology and the hydraulic control system, and the method has the advantages that the technological process is short, near-net forming can be achieved, the production cost is low, and the prepared shaft sleeve part is compact in structure, uniform in solid-liquid phase distribution and good in mechanical property.

Description

Technical Field

[0001] The invention belongs to the technical field of semi-solid forming, and in particular relates to a back-pressure thixotropic extrusion forming method and device for a shaft sleeve part. Background Art

[0002] With the development of aerospace, military and transportation, the demand for high performance of metal materials is growing. How to prepare materials with high specific strength and excellent plasticity has always been a hot topic and frontier in the field of materials science. In this context, it is particularly important to develop a reasonable and advanced forming method and device.

[0003] Bushing parts are used in various mechanical systems and have supporting, rotary guiding and precise positioning functions. Traditional bushing parts are generally formed by liquid forming methods such as centrifugal casting and liquid die forging. In the macroscopic aspect, the blanks produced by this forming method require a lot of subsequent machining, which increases the waste of materials to a certain extent, resulting in low utilization rate and high production cost. In the microscopic aspect, a lot of machining will cause a lot of residual stress in the parts themselves, making the products prone to failure during service. In addition, the blanks obtained by the liquid forming method are mostly crisscrossed coarse dendrites with poor mechanical properties. In addition, during the forming process, it is inevitable that there will be defects such as pores, shrinkage cavities and shrinkage in the organization, resulting in a short service life of the parts.

[0004] The metal semi-solid forming method is a process with the advantages of short production flow, smooth production process, simple operation, low cost and high yield rate. It is a near-net forming method. The obtained product requires no or only a small amount of subsequent machining. However, the parts obtained by traditional semi-solid forming methods and molds have disadvantages such as loose structure, resulting in low overall product performance.

[0005] The present invention directly performs back pressure extrusion forming on the semi-solid slurry, and controls the hydraulic press and the hydraulic cylinder connected to the upper and lower back pressure rings, so that the semi-solid slurry obtains the follow-up back pressure provided by the upper and lower back pressure rings during the extrusion process, and when the mold is closed, the upper and lower back pressure rings give the sleeve parts back pressure and then eject them to obtain the semi-solid extruded sleeve parts, so as to achieve the purpose of obtaining parts with excellent mechanical properties and uniform and dense structure. This process flow is short, can achieve near-net forming, and has dense structure, excellent mechanical properties, and remarkable forming effect. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a back-pressure thixotropic extrusion forming method and device for a shaft sleeve part.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A back-pressure thixotropic extrusion forming method for a shaft sleeve part comprises the following steps:

[0009] (1) First, the semi-solid blank is remelted to a semi-solid temperature range and kept warm, and then placed in a mold cavity;

[0010] (2) When the upper slider of the hydraulic press moves downward with the upper die heat insulation plate 1, the upper die seat 2, the upper die fixing plate 3, the punch 4, the upper hydraulic cylinder 5 and the upper back pressure ring 6, the upper hydraulic cylinder connected to the upper back pressure ring is filled with oil, and the upper slider of the hydraulic press moves toward the die at a running speed of v1=(1.5-2.3)t1 until the upper back pressure ring contacts the semi-solid slurry; wherein t1 is the time taken for the upper back pressure ring to move from the top dead point of the hydraulic press toward the die until it contacts the semi-solid slurry;

[0011] (3) When the upper back pressure ring contacts the semi-solid slurry, the lower hydraulic cylinder connected to the lower back pressure ring starts to discharge oil from the full oil state, and the upper back pressure ring The running speed moves toward the die until the punch contacts the semi-solid slurry; where v 1max is the maximum speed of v1, t2 is the time from the upper back pressure ring contacting the semi-solid slurry to the punch contacting the semi-solid slurry;

[0012] (4) When the punch contacts the semi-solid slurry, the upper hydraulic cylinder starts to discharge oil, and the lower hydraulic cylinder maintains the oil discharge rate of step (3). At this time, the oil inlet of the lower hydraulic cylinder starts to fill with oil, and the upper back pressure ring is The running speed moves toward the die, where v 2max is the maximum speed of v2, t3 is the time from when the punch contacts the semi-solid slurry to when the lower back pressure ring contacts the lower limit post; when the lower back pressure ring begins to descend, the oil injection rate and oil discharge rate of the upper hydraulic cylinder are controlled to make the upper back pressure ring rise until the lower back pressure ring descends and contacts the lower limit post;

[0013] (5) When the lower back pressure ring is lowered and contacts the lower limit column, the upper die limit column moves to the dead point, the mold is closed, and the forming pressure is maintained at 252-350MPa for 9-26s. At this time, the upper hydraulic cylinder is in a contracted state, and then the upper slide of the hydraulic press is raised;

[0014] (6) Remove the flange, fill the lower hydraulic cylinder with oil, and push out the semi-solid sleeve parts.

[0015] As a preferred embodiment of the present invention, in step (1), the semi-solid temperature interval temperature is (T S +T L ) / 2; T S , T L They are respectively the solidus and liquidus temperatures of the semi-solid billet, the holding time is 4-30.5min, and the holding temperature is the semi-solid temperature range temperature.

[0016] As a preferred embodiment of the present invention, in step (2), the oil injection rate of the upper hydraulic cylinder is v 1上注油 ,

[0017] As a preferred embodiment of the present invention, in step (3), the rate at which the lower hydraulic cylinder discharges oil is v 2下排油 , v 2下排油 =(0.469~0.521)v2.

[0018] As a preferred embodiment of the present invention, in step (4), the rate of oil discharge of the upper hydraulic cylinder is v 3上排油 , v 3上排油 =(0.957~1.254)v2.

[0019] As a preferred embodiment of the present invention, in step (4), the rate of oil injection of the lower hydraulic cylinder is v 3下注油 , v 3下注油 =(0.365~0.456)v2.

[0020] As a preferred embodiment of the present invention, in step (4), when the lower back pressure ring begins to descend, the oil injection rate v of the upper hydraulic cylinder is 4上注油 and oil output rate v 4上排油 They are v 4上注油 =(0.213~0.398)v3,v 4上排油 =(0.478~0.612)v3.

[0021] The present invention also claims protection for the back-pressure thixotropic extrusion forming die, including an upper die heat insulation plate 1, an upper die seat 2, an upper die fixing plate 3, an upper die limiting column, a punch 4, an upper hydraulic cylinder 5, an upper back pressure ring 6, a limiting bolt 7, a flange 8, a lower back pressure ring 9, a lower hydraulic cylinder 10, a concave die 11, a lower hydraulic cylinder fixing plate 12, a lower limiting column 13, a lower limiting column fixing component, a lower limiting column sliding column 17, a lower die seat 18, a lower die heat insulation plate 19 and a push rod 20;

[0022] The upper die heat insulation plate 1, the upper die seat 2, the upper die fixing plate 3 and the upper die limiting column are stacked and fixed from top to bottom; the upper end of the punch 4 is installed inside the upper die fixing plate 3, fixedly connected to the lower end surface of the upper die seat 2, and the lower end is placed in the cavity set inside the die 11; one end of the upper hydraulic cylinder 5 is fixedly connected to the upper die fixing plate 3, and the other end is fixedly connected to the upper back pressure ring 6, and the upper die limiting columns are located on both sides of the upper hydraulic cylinder 5;

[0023] The flange 8, the die 11, the lower die seat 18 and the lower die heat insulation plate 19 are stacked and fixed from top to bottom. The flange 8 is provided with a hole I facing the cavity provided inside the die 11 and a hole II facing the upper die limit column, so that the punch 4 can move up and down in the cavity, and the upper die limit column is limited in the hole II; the lower end of the limit bolt 7 is located inside the flange 8 and the die 11, and the two are fixedly connected;

[0024] The lower limit column fixing component is fixed to the upper surface of the lower die seat 18, the lower end of the lower limit column sliding column 17 is installed inside the lower die seat 18, fixed to the upper surface of the lower die heat insulation plate 19, and the upper end passes through the lower limit column fixing component and is located between the lower limit column fixing component and the lower hydraulic cylinder fixing plate 12, and does not contact the lower hydraulic cylinder fixing plate 12; the lower die seat 18 and the lower die heat insulation plate 19 are provided with a punching hole that is opposite to the punch, and the push rod 20 passes through the punching hole and is connected to the lower limit column fixing component; the lower hydraulic cylinder fixing plate 12 is located between the lower limit column fixing component and the lower hydraulic cylinder fixing plate 12. Above the lower limit column fixing component, it is fixed at the top of the concave cavity of the die 11, and a hole III is provided thereon which corresponds to the lower limit column 13. The upper end of the lower limit column 13 passes through the hole III, and the lower end is installed inside the lower limit column fixing plate 114, and is fixedly connected to the upper end surface of the lower limit column fixing plate pad 15; the lower end of the lower hydraulic cylinder 10 is fixed to the upper surface of the lower hydraulic cylinder fixing plate 12, and the upper end is fixedly connected to the lower back pressure ring 9 in the cavity of the die 11; the lower hydraulic cylinder 10 is located on both sides of the lower limit column 13.

[0025] As a preferred embodiment of the present invention, the lower limit column fixing component is composed of a lower limit column fixing plate Ⅰ14, a lower limit column fixing plate pad 15 and a lower limit column fixing plate Ⅱ16 which are stacked and fixed from top to bottom.

[0026] As a preferred embodiment of the present invention, the push rod 20 is connected to the lower limit column fixing plate II 16 through a punching hole, and the lower hydraulic cylinder fixing plate 12 is located above the lower limit column fixing plate I 14 .

[0027] As a preferred embodiment of the present invention, the inner wall of the upper back pressure ring 6 is clearance-matched with the outer wall of the punch 4 .

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention adopts a back-pressure thixotropic extrusion forming die, and controls the movement of the upper and lower back-pressure rings by adjusting the flow rate of the hydraulic cylinder inlet and outlet oil ports, and applies a follow-up back pressure to the semi-solid slurry during the deformation process, so as to obtain parts with uniform solid-liquid phase distribution and fine and dense grains.

[0030] (2) The present invention adopts a back-pressure thixotropic extrusion forming die and adds multiple limit devices, which can control the stroke more accurately, and the obtained parts are closer to near-net shape, which can shorten the processing flow and reduce production costs to a certain extent.

[0031] (3) The process flow of the present invention is short, the product has good mechanical properties, and near-net-shape forming can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of the back-pressure thixotropic extrusion forming die.

[0033] Figure 2 Schematic diagram of back-pressure thixotropic extrusion die closing.

[0034] Figure 3 Schematic diagram of the back-pressure thixotropic extrusion die opening.

[0035] Figure 4 It is a schematic diagram of the upper back pressure ring of the mold described in the present invention and the oil inlet and outlet ports of the connected upper hydraulic cylinder.

[0036] Figure 5 It is a schematic diagram of the lower back pressure ring of the mold described in the present invention and the oil inlet and outlet of the connected lower hydraulic cylinder.

[0037] In the figure, 1, upper die insulation plate, 2, upper die seat, 3, upper die fixing plate, 4, punch, 5, upper hydraulic cylinder, 6, upper back pressure ring, 7, limit bolt, 8, flange, 9, lower back pressure ring, 10, lower hydraulic cylinder, 11, die, 12, lower hydraulic cylinder fixing plate, 13, lower limit column, 14, lower limit column fixing plate I, 15, lower limit column fixing plate pad, 16, lower limit column fixing plate II, 17, lower limit column sliding column, 18, lower die seat, 19, lower die insulation plate, 20, ejector rod. DETAILED DESCRIPTION

[0038] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0039] Example 1

[0040] A back-pressure thixotropic extrusion forming die comprises an upper die heat insulation plate 1, an upper die seat 2, an upper die fixing plate 3, an upper die limiting column, a punch 4, an upper hydraulic cylinder 5, an upper back pressure ring 6, a limiting bolt 7, a flange 8, a lower back pressure ring 9, a lower hydraulic cylinder 10, a die 11, a lower hydraulic cylinder fixing plate 12, a lower limiting column 13, a lower limiting column fixing plate I 14, a lower limiting column fixing plate pad 15, a lower limiting column fixing plate II 16, a lower limiting column sliding column 17, a lower die seat 18, a lower die heat insulation plate 19 and a push rod 20.

[0041] The upper die heat insulation plate 1, the upper die base 2, the upper die fixing plate 3 and the upper die limiting column are stacked and fixed from top to bottom; the upper end of the punch 4 is installed inside the upper die fixing plate 3, fixedly connected to the lower end surface of the upper die base 2, and the lower end is placed in the cavity set inside the die 11; one end of the upper hydraulic cylinder 5 is fixedly connected to the upper die fixing plate 3, and the other end is fixedly connected to the upper back pressure ring 6, and the upper die limiting columns are located on both sides of the upper hydraulic cylinder 5.

[0042] The flange 8, the die 11, the lower die seat 18 and the lower die heat insulation plate 19 are stacked and fixed from top to bottom. The flange 8 is provided with a hole I facing the cavity provided inside the die 11 and a hole II facing the upper die limit column, so that the punch 4 can move up and down in the cavity, and the upper die limit column is limited in the hole II; the lower end of the limit bolt 7 is located inside the flange 8 and the die 11 to fix the two.

[0043] The limit bolt 7 is used to limit the movement position of the upper die and the upper back pressure ring. When the upper limit column shoulder contacts the die, the upper end surface of the limit bolt contacts the bottom of the punch fixing plate, and the fixing flange is connected to the die.

[0044] The lower limit column fixing plate Ⅰ14, the lower limit column fixing plate pad 15 and the lower limit column fixing plate Ⅱ16 are stacked and fixed from top to bottom to form a lower limit column fixing component, which is fixed on the upper surface of the lower die seat 18. The lower end of the lower limit column slide 17 is installed inside the lower die seat 18 and fixed on the upper surface of the lower die insulation plate 19. The upper end passes through the lower limit column fixing component and is located between the lower limit column fixing component and the lower hydraulic cylinder fixing plate 12, and does not contact the lower hydraulic cylinder fixing plate 12; the lower die seat 18 and the lower die insulation plate 19 are provided with punching holes that are opposite to the punch, and the push rod 20 passes through The punched hole is connected to the lower limit column fixing plate Ⅱ16; the lower hydraulic cylinder fixing plate 12 is located above the lower limit column fixing plate Ⅰ14, fixed at the top of the concave cavity of the die 11, and is provided with a hole Ⅲ which corresponds to the lower limit column 13. The upper end of the lower limit column 13 passes through the hole Ⅲ, and the lower end is installed inside the lower limit column fixing plate Ⅰ14, and is fixedly connected to the upper end surface of the lower limit column fixing plate pad 15; the lower end of the lower hydraulic cylinder 10 is fixed to the upper surface of the lower hydraulic cylinder fixing plate 12, and the upper end is fixedly connected to the lower back pressure ring 9 in the cavity of the die 11; the lower hydraulic cylinder 10 is located on both sides of the lower limit column 13.

[0045] When the mold is closed, the thin end of the lower part of the upper limit column completely enters the hole II, the hole II is slightly larger than the thin end of the lower part of the upper limit column, and the part of the limiting bolt 17 that is higher than the flange plane is consistent with the length of the thick end of the upper part of the upper limit column.

[0046] The oil inlet arranged above the two upper hydraulic cylinders 5 is connected to the oil tank I through the oil pipe; the oil outlet arranged below the upper hydraulic cylinder 5 is connected to the oil tank II through the oil pipe. The upper end of the upper hydraulic cylinder 5 is connected to the upper mold fixing plate 3, and the lower end is embedded in the upper back pressure ring 6.

[0047] The oil outlet arranged above the lower hydraulic cylinder 10 is connected to the oil tank I through an oil pipeline, and the oil inlet arranged below the lower hydraulic cylinder 10 is connected to the oil tank II through an oil pipeline. The upper end of the lower hydraulic cylinder 10 is embedded in the lower back pressure ring 9, and the lower end is connected to the lower hydraulic cylinder fixing plate 12.

[0048] Example 2

[0049] The back-pressure thixotropic extrusion forming method of the sleeve part is carried out using the back-pressure thixotropic extrusion forming die of Example 1, the solidus temperature of the ZCuSn10P1 alloy is 876° C., and the liquidus temperature is 1024° C. The specific steps are as follows:

[0050] (1) First, the semi-solid billet is remelted to the semi-solid temperature range of 950 °C and kept isothermally for 15 min, and then placed in the mold cavity.

[0051] (2) When the upper slide of the hydraulic press moves downward, the two hydraulic cylinders connected to the upper back pressure ring 6 are filled with oil at a filling rate v 1上注油 for The upper back pressure ring 6 moves toward the die 11 at a running speed of v1=(1.5~2.3)t1 until the upper back pressure ring 6 contacts the semi-solid slurry, wherein t1 is the time taken for the upper back pressure ring to move from the top dead point of the hydraulic press toward the die until it contacts the semi-solid slurry.

[0052] (3) When the upper back pressure ring 6 contacts the semi-solid slurry, the lower hydraulic cylinder 10 connected to the lower back pressure ring 6 starts to discharge oil from the full oil state, and the oil discharge rate is v 2下排油 , v 2下排油 =(0.469~0.521)v2, upper back pressure ring 6 The running speed moves toward the die 11 until the punch 4 contacts the semi-solid slurry; wherein v 1max v1 is the maximum speed, and t2 is the time taken from the upper back pressure ring 6 contacting the semi-solid slurry to the punch 4 contacting the semi-solid slurry.

[0053] (4) When the punch 4 contacts the semi-solid slurry, the two upper hydraulic cylinders 5 connected to the upper back pressure ring 6 open the oil discharge valve. At this time, the oil inlet and outlet of the two upper hydraulic cylinders 5 connected to the upper back pressure ring 6 are both in an open state, and the oil discharge rate is v 3上排油 , v 3上排油 =(0.957~1.254)v2, the lower hydraulic cylinder maintains v 2下排油 The oil discharge rate is v. At this time, the oil inlet of the lower hydraulic cylinder begins to fill with oil, and the oil filling rate is v 3下注油 , v 3下注油 =(0.365~0.456)v2, upper back pressure ring 6 The running speed moves toward the die 11; wherein v 2maxis the maximum value of v2, t3 is the time from when the punch 4 contacts the semi-solid slurry to when the lower back pressure ring 9 contacts the lower limit column 13; when the lower back pressure ring 9 starts to descend at a slow rate, the oil injection rate v of the upper hydraulic cylinder 5 is controlled 4上注油 and oil output rate v 4上排油 , so that the upper back pressure ring 6 is in an upward state until the lower back pressure ring 9 is lowered to contact with the lower limit column 13, v 4上注油 =(0.213~0.398)v3,v 4上排油 =(0.478~0.612)v3.

[0054] (5) When the lower back pressure ring 11 is lowered to contact with the lower limit column 13, the upper mold limit column moves to the dead point, the mold is closed, and the forming pressure is maintained at 350 MPa for 9 seconds. At this time, the two upper hydraulic cylinders 5 connected to the upper back pressure ring 6 are in a contracted state, and then the upper slide of the hydraulic press is raised.

[0055] (6) Rotate the two limit bolts 7, remove the flange 8, and inject oil into the two lower hydraulic cylinders 10 connected to the lower back pressure ring 9 at a faster rate to eject the semi-solid sleeve parts.

[0056] The time and speed data required for this experiment are as follows:

[0057] t / s <![CDATA[t1=10]]> <![CDATA[t2=9]]> <![CDATA[t3=16]]> v / (mm / s) <![CDATA[v1=16]]> <![CDATA[v2=12.9]]> <![CDATA[v3=12.4]]>

[0058]

[0059] The shaft sleeve part prepared in this embodiment has a tensile strength of 510 MPa, an elongation of 15%, a dense structure, and no obvious defects.

[0060] Example 3

[0061] The back-pressure thixotropic extrusion forming method of the sleeve part is carried out using the back-pressure thixotropic extrusion forming die of Example 1, the solidus temperature of the 5083 aluminum alloy is 574° C., and the liquidus temperature is 638° C. The specific steps are as follows:

[0062] (1) First, the semi-solid billet was remelted to the semi-solid temperature range of 606 °C and kept isothermally for 20 min, and then placed in the mold cavity.

[0063] (2) When the upper slide of the hydraulic press moves downward, the two-liquid upper pressure cylinder 5 connected to the upper back pressure ring 6 is filled with oil at a filling rate v 1上注油 for The upper back pressure ring 6 moves toward the die 11 at a running speed of v1=(1.5~2.3)t1 until the upper back pressure ring contacts the semi-solid slurry; wherein t1 is the time taken for the upper back pressure ring to move from the top dead point of the hydraulic press toward the die until it contacts the semi-solid slurry.

[0064] (3) When the upper back pressure ring 6 contacts the semi-solid slurry, the lower hydraulic cylinder 10 connected to the lower back pressure ring 6 starts to discharge oil from the full oil state, and the oil discharge rate is v 2下排油 , v 2下排油 =(0.469~0.521)v2, hydraulic press upper slide The running speed moves toward the die 11 until the punch 4 contacts the semi-solid slurry; wherein v 1max v1 is the maximum speed, and t2 is the time from when the upper back pressure ring 6 contacts the semi-solid slurry to when the punch 4 contacts the semi-solid slurry.

[0065] (4) When the upper back pressure ring 6 drops to the limit position and the mold punch 4 contacts the semi-solid slurry, the two upper hydraulic cylinders 5 connected to the upper back pressure ring 6 open the oil discharge valve. At this time, the oil inlet and oil discharge ports of the two upper hydraulic cylinders 5 connected to the upper back pressure ring 6 are both in an open state, and the oil discharge rate is v3 upper oil discharge, v 3上排油 =(0.957~1.254)v2, the lower hydraulic cylinder maintains v 2下排油 The oil discharge rate is v. At this time, the oil inlet of the lower hydraulic cylinder begins to fill with oil, and the oil filling rate is v 3下注油 .v 3下注油 =(0.365~0.456)v2, upper slider The running speed moves toward the die 11, where v 2max is the maximum speed of v2, t3 is the time from when the punch 4 contacts the semi-solid slurry to when the lower back pressure ring 9 contacts the lower limit column 13; when the lower back pressure ring 9 starts to descend at a slow rate, the oil injection rate v of the upper hydraulic cylinder 5 is controlled. 4上注 and oil output rate v 4上排油 , v 4上注油 =(0.213~0.398)v3,v 4上排油 =(0.478~0.612)v3, so that the upper back pressure ring 6 is in an ascending state until the lower back pressure ring 11 is lowered to contact with the lower limit column 13.

[0066] (5) When the lower back pressure ring 9 is lowered to contact the lower limit column 13, the upper mold limit column moves to the dead point, the mold is closed, and the forming pressure is maintained at 252MPa for 26s. At this time, the two upper hydraulic cylinders 5 connected to the upper back pressure ring 6 are in a contracted state, and then the upper slide of the hydraulic press is raised;

[0067] (6) Rotate the two limit bolts 7, remove the flange 8, and inject oil into the two lower hydraulic cylinders 10 connected to the lower back pressure ring 9 at a faster rate to eject the semi-solid sleeve parts.

[0068] The time and speed data required for this experiment are as follows:

[0069] t / s <![CDATA[t1=10]]> <![CDATA[t2=9]]> <![CDATA[t3=16]]> v / (mm / s) <![CDATA[v1=16]]> <![CDATA[v2=12.9]]> <![CDATA[v3=12.4]]>

[0070]

[0071] The shaft sleeve part prepared in this embodiment has a tensile strength of 460 MPa, an elongation of 20%, a dense structure, and no obvious defects.

[0072] Comparative Example 1

[0073] The thixotropic reverse extrusion forming method of the sleeve parts is carried out using a thixotropic reverse extrusion forming die (i.e., without upper and lower back pressure rings and the connected hydraulic cylinder). The solidus temperature of the ZCuSn10P1 alloy is 876°C and the liquidus temperature is 1024°C. The specific steps are as follows:

[0074] (1) First, the semi-solid billet is remelted to the semi-solid temperature range of 950 °C and kept isothermally for 15 min, and then placed in the mold cavity.

[0075] (2) The slide block on the hydraulic press moves toward the die 11 at a running speed of v1 = (1.5 ~ 2.3) t1.

[0076] (3) The mold is closed and the forming pressure is maintained at 350 MPa for 9 seconds. Then the upper slide of the hydraulic press is raised to eject the sleeve part.

[0077] The shaft sleeve part prepared in this comparative example has a tensile strength of 380 MPa, an elongation of 6%, a dense structure, and no obvious defects.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A back-pressure thixotropic extrusion forming method for a sleeve part, characterized in that: The following steps are involved: (1) First, the semi-solid blank is remelted to a semi-solid temperature range and kept warm, and then placed in a mold cavity; (2) When the upper slider of the hydraulic press drives the upper back pressure ring to move downward, the upper hydraulic cylinder connected to the upper back pressure ring is filled with oil, and the upper back pressure ring moves toward the die at a running speed of v1=(1.5-2.3)t1 until the upper back pressure ring contacts the semi-solid slurry; wherein t1 is the time taken for the upper back pressure ring to move from the top dead point of the hydraulic press toward the die until it contacts the semi-solid slurry; (3) When the upper back pressure ring contacts the semi-solid slurry, the lower hydraulic cylinder connected to the lower back pressure ring starts to discharge oil from the full oil state, and the upper back pressure ring The running speed moves toward the die until the punch contacts the semi-solid slurry; where v 1max is the maximum speed of v1, t2 is the time from the upper back pressure ring contacting the semi-solid slurry to the punch contacting the semi-solid slurry; (4) When the punch contacts the semi-solid slurry, the upper hydraulic cylinder starts to discharge oil, and the lower hydraulic cylinder maintains the oil discharge rate of step (3). At this time, the oil inlet of the lower hydraulic cylinder starts to fill with oil, and the upper back pressure ring is The upper back pressure ring moves toward the die at a running speed of , where v2max is the maximum speed of v2, and t3 is the time from when the punch contacts the semi-solid slurry to when the lower back pressure ring contacts the lower limit post; when the lower back pressure ring starts to descend, the oil injection rate and oil discharge rate of the upper hydraulic cylinder are controlled to make the upper back pressure ring descend until the lower back pressure ring is lowered to contact the lower limit post; (5) When the lower back pressure ring is lowered to contact the lower limit column, the upper mold limit column moves to the dead point, the mold is closed, and the forming pressure is maintained at 252-350MPa for 9-26s. At this time, the upper hydraulic cylinder is in a contracted state, and then the upper slide of the hydraulic press is raised; (6) Remove the flange, fill the lower hydraulic cylinder with oil, and push out the semi-solid sleeve parts.

2. The back-pressure thixotropic extrusion forming method of a sleeve part according to claim 1, characterized in that: In the step (1), the semi-solid temperature interval temperature is (T S +T L ) / 2; T S 、T L They are respectively the solidus and liquidus temperatures of the semi-solid billet, and the holding time is 4-30.5min.

3. The back-pressure thixotropic extrusion forming method of a sleeve part according to claim 1, characterized in that: In step (2), the oil filling rate of the upper hydraulic cylinder is v1 upper oil filling, 4. The back-pressure thixotropic extrusion forming method of a sleeve part according to claim 1, characterized in that: In step (3), the rate at which the lower hydraulic cylinder discharges oil is v 2下排油 , v 2下排油 =(0.469~0.521)v2.

5. The back-pressure thixotropic extrusion forming method of a sleeve part according to claim 1, characterized in that: In step (4), the rate at which the upper hydraulic cylinder discharges oil is v 3上排油 , v 3上排油 =(0.957~1.254)v2.

6. The back-pressure thixotropic extrusion forming method of a sleeve part according to claim 1, characterized in that: In step (4), the rate of oil injection of the lower hydraulic cylinder is v 3下注油 , v 3下注油 =(0.365~0.456)v2.

7. The back-pressure thixotropic extrusion forming method of a sleeve part according to claim 1, characterized in that: In step (4), when the lower back pressure ring begins to descend, the oil injection rate v of the upper hydraulic cylinder is 4上注油 and oil output rate v 4上排油 They are v 4上注油 =(0.213~0.398)v3,v 4上排油 =(0.478~0.612)v3.

8. A back-pressure thixotropic extrusion forming die, characterized in that: It includes an upper die heat insulation plate, an upper die seat, an upper die fixing plate, an upper die limit column, a punch, an upper hydraulic cylinder, an upper back pressure ring, a limit bolt, a flange, a lower back pressure ring, a lower hydraulic cylinder, a die, a lower hydraulic cylinder fixing plate, a lower limit column, a lower limit column fixing component, a lower limit column sliding column, a lower die seat, a lower die heat insulation plate and a push rod; The upper die heat insulation plate, the upper die seat, the upper die fixing plate and the upper die limiting column are fixed from top to bottom; the upper end of the punch is installed inside the upper die fixing plate and fixedly connected to the lower end surface of the upper die seat, and the lower end of the punch is placed in the cavity set inside the die; one end of the upper hydraulic cylinder is fixedly connected to the upper die fixing plate, and the other end is fixedly connected to the upper back pressure ring; the upper die limiting columns are located on both sides of the upper hydraulic cylinder; The flange, the die, the lower die seat and the lower die heat insulation plate are stacked and fixed from top to bottom. The flange is provided with a hole I facing the cavity provided inside the die and a hole II facing the upper die limit column, so that the punch can move up and down in the cavity and the upper die limit column is limited in the hole II. The lower end of the limit bolt is located inside the flange and the die to securely connect the two; The lower limit column fixing component is fixed on the upper surface of the lower die base, the lower end of the lower limit column sliding column is installed inside the lower die base and fixed on the upper surface of the lower die insulation plate, the upper end passes through the lower limit column fixing component, is located between the lower limit column fixing component and the lower hydraulic cylinder fixing plate, and has no contact with the lower hydraulic cylinder fixing plate; the lower die base and the lower die insulation plate are provided with punching holes opposite to the punch, and the push rod passes through the punching holes and is connected with the lower limit column fixing component; the lower hydraulic cylinder fixing plate is located above the lower limit column fixing component, fixed to the top end of the concave cavity of the die, and is provided with a hole III corresponding to the lower limit column, the upper end of the lower limit column passes through hole III, and the lower end is fixed in the lower limit column fixing component; the lower end of the lower hydraulic cylinder is fixed on the upper surface of the lower hydraulic cylinder fixing plate, and the upper end is fixedly connected to the lower back pressure ring in the die cavity; the lower hydraulic cylinder is located on both sides of the lower limit column.

9. The back-pressure thixotropic extrusion forming die according to claim 8, characterized in that: The lower limit column fixing component is composed of a lower limit column fixing plate I, a lower limit column fixing plate pad and a lower limit column fixing plate II which are stacked and fixed from top to bottom; the lower end of the lower limit column is installed inside the lower limit column fixing plate I and is fixedly connected to the upper end surface of the lower limit column fixing plate pad.

10. The back-pressure thixotropic extrusion forming die according to claim 9, characterized in that: The push rod passes through the punching hole and is connected with the lower limit column fixing plate II, and the lower hydraulic cylinder fixing plate is located above the lower limit column fixing plate I.

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