Processing technology of hard alloy mold

Abstract

The invention relates to a processing technology of a hard alloy die, and belongs to the technical field of hard alloy die processing, an upper die is divided into a die bridge male head part and an upper die shunting hole outer side part, the two parts are respectively subjected to fine processing, a groove for installing a contraction ring is processed at the excircle of the upper die, and the contraction ring is manufactured. The contraction ring is placed in the groove, then the two parts which are machined separately are embedded together according to the principle of thermal expansion and cold contraction to form a complete upper die, then a mounting groove of the pressure reducing cover is machined at a male head feeding port of the upper die, and the pressure reducing cover is manufactured and mounted; the size and the shape of the pressure reducing cover are matched with those of the mounting groove, the machined upper die and the machined lower die are assembled together, and the problems that in the prior art, in the extrusion process of a hard alloy die in an extrusion plant, large extrusion force can extrude towards the male head direction and the outer circle direction at the same time, so that the upper die is attacked by pressure in multiple aspects, strong shear force is generated, and the product quality is influenced are solved. And therefore, bridge cutoff or bridge cracking is caused.

Description

Technical Field

[0001] The invention belongs to the technical field of cemented carbide mould processing, and in particular relates to a processing technology of a cemented carbide mould. Background Art

[0002] The main component of the "7 series" aluminum alloy is zinc, such as 7075 alloy, which belongs to the aviation series. It is an aluminum-magnesium-zinc-copper alloy. It is a super-hard aluminum alloy with good wear resistance. It can also be hardened through heat treatment, approaching or exceeding the hardness of steel. Due to its high strength and wear resistance, it performs well under extreme conditions, so it is often used in high-tech fields such as aviation, aerospace, and military.

[0003] However, there are some problems in the extrusion process of the extrusion plant using 7 series carbide dies: 7 series aluminum alloy is a high-strength aluminum alloy with a high zinc content, which makes it have higher strength and hardness during the extrusion process. Due to these characteristics, 7 series aluminum alloy is more difficult to deform than other series of aluminum alloys during extrusion molding, so it requires several thousand tons or even greater extrusion force. When processing this carbide die, the larger extrusion force will extrude in the male head direction (i.e., the forward direction) and the outer circle direction at the same time, causing the upper die to be attacked by pressure from multiple directions, generating strong shear force, and the upper die bridge root is under the strongest pressure, but the expansion pressure strength is weak, resulting in broken bridges or cracked bridges. In this regard, a processing technology of carbide die is proposed. Summary of the invention

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a processing technology for a cemented carbide mold, which solves the problem in the prior art that during the extrusion process of the cemented carbide mold in the extrusion plant, a large extrusion force will simultaneously extrude in the direction of the male head and in the direction of the outer circle, causing the upper mold to be subjected to pressure attacks from multiple directions, generating strong shear force, thereby causing the bridge to break or crack.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A processing technology for a cemented carbide mold comprises the following steps:

[0007] S1: Initial processing: According to the design drawings, the mold is 3D modeled and the mold blank is rough-processed using a CNC machine tool to form the basic shape of the mold;

[0008] S2: Split processing: According to the characteristics of pressure, the upper mold is divided into two parts: the mold bridge connecting the male head part and the outer part of the upper mold diversion hole. These two parts are finely processed separately to ensure the accuracy of the size and shape of each part;

[0009] S3: Design of shrink ring: a groove for installing the shrink ring is machined on the outer circle of the upper die, and the shrink ring is manufactured and placed in the groove;

[0010] S4: Assembling and inlaying, inlaying the two parts processed separately together using the principle of thermal expansion and contraction to form a complete upper mold;

[0011] S5: Design of pressure relief cover: machining the installation groove of the pressure relief cover at the feed port of the upper die male head, manufacturing and installing the pressure relief cover;

[0012] S6: Process the lower die, process the overall shape of the lower die, and assemble the processed upper die and lower die together.

[0013] As a further solution of the present invention, the size and shape of the pressure relief cover in S5 match the installation groove, and after the pressure relief cover is installed, it is necessary to ensure that the pressure during squeezing only acts on the cover.

[0014] As a further solution of the present invention, when the upper mold is divided into a mold bridge connecting the male head part and an outer part of the upper mold diversion hole in step S2, the thickness of the mold bridge connecting the male head part is increased by 10% to 15% than that of the outer part of the upper mold diversion hole, and the contact surfaces of the two parts adopt a stepped interlocking structure.

[0015] As a further solution of the present invention, the shrink ring in step S3 is made of elastic material.

[0016] As a further solution of the present invention, the shrink ring is made of 65Mn spring steel, the cross-section of the shrink ring body is a trapezoidal structure, the radial preload force of the shrink ring is controlled within the range of 50-80MPa, and the interference fit between the shrink ring and the groove body is 0.15-0.25mm.

[0017] As a further solution of the present invention, the thermal expansion and contraction embedding process in step S4 specifically includes: heating the outer part of the upper mold diversion hole to 300-350°C, and cooling the mold bridge connecting the male head part to -50--80°C, and performing rapid assembly after a heat preservation time of 30 to 45 minutes.

[0018] As a further solution of the present invention, the pressure relief cover in step S5 is made of tungsten-cobalt hard alloy, the working surface of the pressure relief cover is provided with a guide cone angle of 5°-15°, and the bottom of the installation groove is provided with a buffer gap of 0.2-0.5mm.

[0019] As a further solution of the present invention, the guide cone angle of the pressure reducing cover is specifically designed to be 8°±0.5°, and its working surface is treated with PVD coating with a coating thickness of 3-5 μm, and the coating material is a TiAlN composite coating.

[0020] As a further solution of the present invention, after the completion of steps S4 and S5, the assembly is subjected to isostatic pressing treatment, the treatment pressure is 200-250 MPa, the pressure holding time is 2-3 hours, and the treatment medium is silicon-based heat transfer oil.

[0021] As a further solution of the present invention, the lower die in step S6 processes a micro-texture array on the surface of the die cavity during the extrusion process in the extrusion plant, and the texture units are hemispherical pits with a diameter of 50-80 μm, and the area occupancy is controlled at 15% to 20%.

[0022] The beneficial effects of the present invention are:

[0023] By precisely matching the size of the pressure reducing cover with the installation slot, it is ensured that only the cover body bears the positive impact pressure after installation. The male head body is physically separated from the pressure source through structural isolation. At the same time, an elastic shrink ring is used to wrap the outer edge of the upper die to absorb circumferential pressure fluctuations through elastic deformation. The thermal expansion and contraction inlay process is also used to inlay the two parts of the upper die separately processed together using the principle of thermal expansion and contraction to form a complete upper die. This combined whole solves the problem in the prior art that during the extrusion process of the cemented carbide die in the extrusion plant, the larger extrusion force will squeeze in the direction of the male head and the outer circle at the same time, causing the upper die to be subjected to pressure attacks from multiple aspects and generating strong shear force, thereby causing the bridge to break or crack. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0025] Figure 1 It is a schematic diagram of the overall structure of the upper mold of the present invention;

[0026] Figure 2 It is a schematic diagram of the local structure of the upper mold of the present invention;

[0027] Figure 3 It is a schematic diagram of the installation of the shrink ring of the present invention.

[0028] Description of main component symbols:

[0029] In the figure: 1. Upper mold; 2. Male part; 3. Diverter hole; 4. Shrink ring. DETAILED DESCRIPTION

[0030] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0031] See also Figure 1 - Figure 3 This embodiment provides a processing technology for a cemented carbide mold, comprising the following steps:

[0032] S1: Initial processing: According to the design drawings, the mold is 3D modeled and the mold blank is rough-processed using a CNC machine tool to form the basic shape of the mold;

[0033] S2: Split processing: According to the characteristics of pressure, the upper mold is divided into two parts: the mold bridge connecting male head part and the outer part of the upper mold diverter hole. The two parts are finely processed separately using CNC machine tools or other fine processing tools to ensure the accuracy of the size and shape of each part. Split processing can reduce processing complexity, improve processing accuracy, and facilitate subsequent assembly. The size and shape of each part can be accurately controlled to ensure the performance and stability of the mold in actual use.

[0034] S3: Shrink ring design: a groove for installing the shrink ring is machined on the outer circle of the upper die, and a shrink ring is manufactured and placed in the groove; the shrink ring can enhance the tightness of the die and prevent the die from shifting or deforming due to pressure changes during use; the shrink ring is made of elastic material, and an elastic shrink ring is used to wrap the outer circle of the upper die to absorb circumferential pressure fluctuations through elastic deformation. The elastic ring can offset part of the circumferential tensile stress and prevent the outer circle of the die from bursting, thereby improving the dimensional stability of the die during continuous extrusion;

[0035] S4: Assembling and inlaying. The two parts processed separately are inlaid together using the principle of thermal expansion and contraction to form a complete upper mold. The two parts of the upper mold processed separately are inlaid together using the principle of thermal expansion and contraction. First, one part is heated to expand, and then the other part is contracted and inlaid. After cooling, the two parts fit tightly to form a complete upper mold. The thermal expansion and contraction assembly method can ensure that there is no gap between the two parts, thereby improving the sealing and stability of the mold.

[0036] S5: Since the positive pressure directly impacts the male head during the extrusion process, stress concentration occurs at the root of the male head, which can easily lead to fracture. In this regard, a pressure relief cover is designed, and a mounting groove for the pressure relief cover is machined at the feed port of the upper die male head, and the pressure relief cover is manufactured and installed; the size and shape of the pressure relief cover match the mounting groove, and after the pressure relief cover is installed, it is necessary to ensure that the pressure only acts on the cover during extrusion. By accurately matching the size of the pressure relief cover with the mounting groove, it is ensured that only the cover body bears the positive impact pressure after installation. Through structural isolation, the male head body is physically separated from the pressure source, and the pressure is limited to the replaceable pressure relief cover to avoid damage to the male head body. Reduce the impact load on the root of the mold bridge and extend the life of the mold. During the extrusion process, the pressure impacting the "diverter hole bridge" and the pressure impacting the "male head" have been separated in advance, so the shear force caused by pulling each other does not exist, and the broken or cracked bridge is also prevented;

[0037] S6: Process the lower die, process the overall shape of the lower die, and assemble the processed upper die and lower die together.

[0038] The main component of the "7 series" aluminum alloy is zinc, such as 7075 alloy, which belongs to the aviation series. It is an aluminum-magnesium-zinc-copper alloy. It is a super-hard aluminum alloy with good wear resistance. Due to its outstanding performance under extreme conditions, it is often used in high-tech fields such as aviation, aerospace, and military. However, there are some problems in the extrusion process of the 7 series carbide mold in the extrusion plant: the 7 series aluminum alloy is a high-strength aluminum alloy with a high zinc content, which makes it have higher strength and hardness during the extrusion process. Due to these characteristics, the 7 series aluminum alloy is more difficult to deform than other series of aluminum alloys during extrusion molding, so it requires several thousand tons or even greater extrusion force. When processing this carbide mold, the larger extrusion force will extrude in the direction of the male head and the outer circle at the same time, causing the upper mold to be attacked by pressure from multiple aspects, generating strong shear force, and the upper mold bridge root is under the strongest pressure, but the expansion pressure strength is weak, resulting in broken bridge or cracked bridge.

[0039] In order to solve the above problems, in this embodiment, the upper mold is divided into two parts, namely, the mold bridge connecting the male head part and the outer part of the upper mold diverter hole according to the characteristics of the pressure, and the two parts are finely processed respectively to ensure the accuracy of the size and shape of each part, and a groove for installing the shrink ring is processed at the outer circle of the upper mold, and the shrink ring is manufactured, and the shrink ring is placed in the groove, and then the two separately processed parts are inlaid together using the principle of thermal expansion and contraction to form a complete upper mold, and then a mounting groove for the pressure relief cover is processed at the feed port of the male head of the upper mold, and the pressure relief cover is manufactured and installed; the size and shape of the pressure relief cover match the mounting groove, and after the pressure relief cover is installed, it is necessary to ensure that the pressure only acts on the cover during extrusion, and the overall shape of the lower mold is processed, and the processed upper and lower molds are assembled together, which solves the problem in the prior art that during the extrusion process of the cemented carbide mold in the extrusion plant, the large extrusion force will squeeze in the direction of the male head and the outer circle at the same time, causing the upper mold to be attacked by pressure from multiple aspects, generating strong shear force, thereby causing the bridge to break or crack.

[0040] Since the thickness of the mold bridge area in the current integral upper mold is insufficient, fatigue fracture is prone to occur under the action of shear force. In order to address this problem, in one embodiment, when the upper mold is divided into the mold bridge connecting the male head part and the outer part of the upper mold diverter hole in step S2, the thickness of the mold bridge connecting the male head part is increased by 10% to 15% than the outer part of the upper mold diverter hole, thereby enhancing the bending section modulus, and the contact surfaces of the two parts adopt a stepped interlocking structure to increase the contact area and shear resistance, thereby improving the shear strength of the mold bridge and avoiding tearing caused by multi-directional pressure. The stepped interlocking structure increases the bonding strength of the split components.

[0041] One thing that needs to be explained is that when an elastic ring is used as a shrink ring, since it needs to withstand a large force, the ordinary reinforcement ring is not elastic enough and the interference fit is prone to failure, resulting in the ring body falling off or stress concentration. In order to avoid this problem, in one embodiment, the shrink ring is made of 65Mn spring steel, the cross-section of the shrink ring body is trapezoidal, the radial preload force of the shrink ring is controlled within the range of 50-80MPa, the interference fit between the shrink ring and the groove body is 0.15-0.25mm, and the material is 65Mn spring steel with a yield strength of ≥785MPa. The elastic modulus is adapted to the cemented carbide substrate. The trapezoidal cross-section design makes the contact stress between the ring body and the groove wall evenly distributed, the interference amount of 0.15-0.25mm ensures that the preload force is controllable, and the radial preload force of 50-80MPa effectively compensates for the thermal expansion difference to avoid loosening of the ring body under high temperature conditions. The trapezoidal cross-section reduces the stress concentration factor to below 1.2 (the traditional rectangular cross-section is 1.8).

[0042] In actual use, the principle of thermal expansion and contraction is adopted during assembly and inlaying, that is, the two parts of the upper mold that are processed separately are inlaid together, one part is first heated to expand, and then the other part is shrunk and inlaid. After cooling, the two parts are tightly matched to form a complete upper mold. However, in this process, the external ambient temperature has a certain influence on the heating and cooling process of the component. High or low ambient temperature may affect the heating and cooling speed of the component, and then affect the formation of temperature difference, which may easily lead to insufficient temperature difference when the split component is inlaid. When the split component is inlaid, the insufficient temperature difference causes a micro gap on the bonding surface, which affects the structural strength. In order to cope with this problem, in one embodiment, the thermal expansion and contraction inlaying process in step S4 specifically includes: heating the outer part of the upper mold diversion hole to 300-350℃, and cooling the mold bridge connecting male head part to -50--80℃, and quickly assembling after a heat preservation time of 30-45 minutes, and heating the outer part to 300-350℃ (the linear expansion coefficient of cemented carbide is 5.2×10 -6 / ℃), the male part is deep cooled to -80℃ (shrinkage rate 0.12%), forming an assembly gap of 0.25-0.35mm. The temperature difference is restored after rapid assembly, achieving molecular-level bonding with an interference of 0.08-0.12mm, avoiding the problem of grain coarsening caused by high-temperature brazing, and improving the fatigue life of the mold;

[0043] In addition, the impact of the metal flow at the feed port during mold production may also cause pressure fluctuations, resulting in micro-wear between the pressure relief cover and the groove body. In this regard, in one embodiment, the pressure relief cover of step S5 is made of tungsten-cobalt cemented carbide, and the working surface of the pressure relief cover is provided with a guide cone angle of 5°-15° to reduce the impact kinetic energy, and a buffer gap of 0.2-0.5mm is provided at the bottom of the mounting groove. The 0.2-0.5mm buffer gap allows the pressure relief cover to move slightly, absorb instantaneous impact, and improve the uniformity of the metal flow.

[0044] In order to avoid metal deflection caused by cone angle deviation, which leads to increased wear on the surface of the pressure reducing cover, in one embodiment, the guide cone angle of the pressure reducing cover is specifically designed to be 8°±0.5°, and the cone angle tolerance is controlled at ±0.5°. Through fluid simulation, 8° is determined to be the optimal balance point. The working surface is treated with PVD coating, and the coating thickness is 3-5μm. The coating material is TiAlN composite coating. The TiAlN coating (hardness HV3200) reduces the friction coefficient to below 0.15. The coating improves wear resistance, and the precise guide angle improves material utilization.

[0045] Furthermore, since the residual stress introduced by the split inlay and the pressure relief cover assembly reduces the overall bearing capacity of the mold, in order to address this problem, in one embodiment, after steps S4 and S5 are completed, the assembly is subjected to isostatic pressing treatment with a treatment pressure of 200-250MPa. The 200-250MPa isostatic pressing treatment forces silicon-based thermal oil to penetrate into micro-gaps and evenly transmit pressure. The pressure is maintained for 2-3 hours. The treatment medium is silicon-based thermal oil. By maintaining the pressure for 2-3 hours, part of the assembly stress is eliminated. The silicone oil medium avoids the problem of cemented carbide oxidation caused by traditional water pressure.

[0046] Since high-zinc aluminum alloys (such as 7075) have strong adhesion, demolding is difficult and the mold cavity wears quickly. In this regard, in one embodiment, the lower mold of step S6 processes a micro-texture array on the surface of the mold cavity during the extrusion process in the extrusion plant. The texture units are hemispherical pits with a diameter of 50-80μm. The hemispherical pits with a diameter of 50-80μm form a micro-oil storage structure, and the area occupancy is controlled at 15% to 20%. By reducing the friction coefficient and the demolding force, the continuous production of the mold is ultimately improved, and the pits can be repaired by secondary processing.

[0047] The working principle and use process of the present invention:

[0048] According to the characteristics of pressure, the upper mold is divided into two parts: the mold bridge connecting male head part and the outer part of the upper mold diverter hole. The two parts are finely processed separately to ensure the accuracy of the size and shape of each part. A groove for installing the shrink ring is processed on the outer circle of the upper mold, and the shrink ring is manufactured. The shrink ring is placed in the groove, and then the two separately processed parts are inlaid together using the principle of thermal expansion and contraction to form a complete upper mold. Next, a mounting groove for the pressure relief cover is processed at the feed port of the upper mold male head, and the pressure relief cover is manufactured and installed; the size and shape of the pressure relief cover match the mounting groove, and after the pressure relief cover is installed, it is necessary to ensure that the pressure only acts on the cover during extrusion, and the overall shape of the lower mold is processed, and the processed upper and lower molds are assembled. Together, the size of the pressure reducing cover is precisely matched with the installation groove to ensure that only the cover body bears the positive impact pressure after installation. The male head body is physically separated from the pressure source through structural isolation. At the same time, the outer edge of the upper mold is wrapped with an elastic shrink ring to absorb circumferential pressure fluctuations through elastic deformation. The thermal expansion and contraction inlay process is also used to inlay the two parts of the upper mold separately processed together using the principle of thermal expansion and contraction to form a complete upper mold. The combined whole solves the problem of the existing technology that during the extrusion process of the cemented carbide mold in the extrusion plant, the larger extrusion force will squeeze in the direction of the male head and the outer circle at the same time, causing the upper mold to be attacked by pressure from multiple aspects and generate strong shear force, thereby causing the bridge to break or crack.

[0049] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A processing technology for a cemented carbide mold, characterized in that: The following steps are involved: S1: Initial processing: According to the design drawings, the mold is 3D modeled and the mold blank is rough-processed using a CNC machine tool to form the basic shape of the mold; S2: Split processing: According to the characteristics of pressure, the upper mold is divided into two parts: the mold bridge connecting the male head part and the outer part of the upper mold diversion hole. These two parts are finely processed separately to ensure the accuracy of the size and shape of each part; S3: Design of shrink ring: a groove for installing the shrink ring is machined on the outer circle of the upper die, and the shrink ring is manufactured and placed in the groove; S4: Assembling and inlaying, inlaying the two parts processed separately together using the principle of thermal expansion and contraction to form a complete upper mold; S5: Design of pressure relief cover: machining the installation groove of the pressure relief cover at the feed port of the upper die male head, manufacturing and installing the pressure relief cover; S6: Process the lower die, process the overall shape of the lower die, and assemble the processed upper die and lower die together.

2. The processing technology of a cemented carbide mold according to claim 1 is characterized in that: The size and shape of the pressure relief cover in S5 match the installation groove, and after the pressure relief cover is installed, it is necessary to ensure that the pressure during squeezing only acts on the cover.

3. The processing technology of a cemented carbide mold according to claim 1 is characterized in that: When the upper mold is divided into the mold bridge connecting male head part and the outer part of the upper mold diverter hole in the step S2, the thickness of the mold bridge connecting male head part is 10% to 15% greater than that of the outer part of the upper mold diverter hole, and the contact surfaces of the two parts adopt a stepped interlocking structure.

4. The processing technology of a cemented carbide mold according to claim 1 is characterized in that: The shrink ring in step S3 is made of elastic material.

5. The processing technology of a cemented carbide mold according to claim 4 is characterized in that: The shrink ring is made of 65Mn spring steel, the cross section of the shrink ring body is a trapezoidal structure, the radial preload force of the shrink ring is controlled within the range of 50-80MPa, and the interference fit between the shrink ring and the groove body is 0.15-0.25mm.

6. The processing technology of a cemented carbide mold according to claim 1, characterized in that: The thermal expansion and contraction embedding process in step S4 specifically includes: heating the outer part of the upper mold diversion hole to 300-350° C., and cooling the mold bridge and male head part to -50--80° C., and performing rapid assembly after a heat preservation time of 30-45 minutes.

7. The processing technology of a cemented carbide mold according to claim 1, characterized in that: The decompression cover in step S5 is made of tungsten-cobalt hard alloy, the working surface of the decompression cover is provided with a guide cone angle of 5°-15°, and the bottom of the installation groove is provided with a buffer gap of 0.2-0.5mm.

8. The processing technology of a cemented carbide mold according to claim 7, characterized in that: The decompression cover has a flow guide cone angle specifically designed to be 8°±0.5°, and its working surface is treated with PVD coating, the coating thickness is 3-5 μm, and the coating material is a TiAlN composite coating.

9. The processing technology of a cemented carbide mold according to claim 1, characterized in that: After the steps S4 and S5 are completed, the assembly is subjected to isostatic pressing treatment, the treatment pressure is 200-250 MPa, the pressure holding time is 2-3 hours, and the treatment medium is silicon-based heat transfer oil.

10. The processing technology of a cemented carbide mold according to claim 1, characterized in that: In the step S6, the lower die is processed into a micro-texture array on the surface of the die cavity during the extrusion process in the extrusion plant. The texture units are hemispherical pits with a diameter of 50-80 μm, and the area occupancy rate is controlled at 15% to 20%.

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