Method for preparing double-metal hot work tool mold by adopting hot isostatic pressing and application of double-metal hot work tool mold

Abstract

The invention belongs to the technical field of powder metallurgy, and particularly relates to a method for preparing a bimetal hot work tool die through hot isostatic pressing and application, and the method comprises the step that solid-powder combination of a die steel billet and GH4099 powder is achieved through the hot isostatic pressing technology. The maximum size of the steel ingot is designed according to the stress distribution and size in the using process of the die, a sawtooth structure is machined on the contact face of the steel ingot and GH4099 powder to increase the binding force of the steel ingot and the GH4099 powder, and the steel ingot can be manufactured under the condition that subsequent heat treatment is not needed through control over the multi-section hot isostatic pressing cooling speed. Tissue densification and tissue performance regulation and control are completed in one step through hot isostatic pressing. And shot blasting treatment is conducted on the surface of the target tool and mold to achieve the surface strengthening effect. By means of the method, the bimetal hot work tool die which is high in performance, low in cost and short in process can be prepared, and under the condition that the die is normally used, use of a low-cost steel material in a low-stress area and use of a high-temperature alloy material in a high-stress area are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder metallurgy, and particularly relates to a method for preparing a bimetallic hot working die by hot isostatic pressing and its application. Background Art

[0002] In modern industrial production, working dies have become a high-quality, efficient and low-consumption process equipment. As an important means of modern manufacturing, it plays an important role in the economic operation of our country and the development of various industrial sectors.

[0003] For common hot working die steel materials (5CrNiMo, 4Cr5MoSiV1, 3Cr2W8V), due to their poor high-temperature performance after long-term service, depressions, folds, wear, etc. will occur during the use of the working die, thus greatly reducing the service life of the working die.

[0004] The maximum service temperature of GH4099 alloy is 900 °C. When kept at 700 - 800 °C for a long time, no harmful precipitated phases will appear. Its organizational stability is strong at high temperatures, and it can still maintain good mechanical properties, so it can be used for hot working dies. However, GH4099 is often expensive, which makes the cost of manufacturing a hot working die made of superalloy rise steeply.

[0005] Therefore, there is an urgent need for a method to prepare a bimetallic hot working die with good high-temperature performance and low cost.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art, and propose a method for preparing a bimetallic hot working die by hot isostatic pressing and its application. This method prepares a high-quality and low-cost bimetallic hot working die through the control of the surface roughness and shape of the ingot, the control of the solid-powder bonding process of hot isostatic pressing of the ingot and the superalloy, and the surface strengthening of the working surface of the hot working die. The working area of this hot working die is made of GH4099 superalloy, and other areas are made of ingots, achieving the goal of using superalloy in the working area of the working die while using ingots in other areas to reduce costs.

[0008] In order to achieve the above purpose, the present invention adopts the following technical solutions: On the one hand, the present invention provides a method for preparing a bimetallic hot working die by hot isostatic pressing, which is characterized by including the following steps: Step 1: Prepare GH4099 powder by using an ultra-high-speed plasma rotating electrode, and pre-treat the GH4099 powder to obtain GH4099 powder in a specific particle size range; Step 2: Conduct numerical simulation according to the actual working conditions of the target tooling to be prepared, obtain the stress values of different regions of the target tooling during use, and determine the bottom ingot size of the target tooling based on the stress values; Step 3: Prepare a steel billet according to the ingot size obtained in Step 2 through the triple process of VIM+ESR+VAR (Vacuum Induction Melting+Electroslag Remelting+Vacuum Consumable Arc Melting), and then process the obtained steel billet to obtain an ingot; Wherein, one end of the ingot in contact with the GH4099 powder in a specific particle size range is a sawtooth structure; Step 4: Place the ingot obtained in Step 3 in a pre-prepared jacket, fixedly connect the ingot and the jacket, and then seal-weld the jacket; Step 5: Place the jacket containing the ingot on a vibration platform, then fill the jacket with the GH4099 powder pretreated in Step 1 through the jacket nozzle, and then perform vacuum degassing and seal-weld the jacket nozzle; Step 6: Perform hot isostatic pressing on the jacket sealed in Step 5 to obtain a tooling blank, and then successively perform machining and shot peening on the tooling blank to obtain the target tooling.

[0009] Further, in Step 1, the pretreatment includes successively performing screening treatment-static electromagnetic separation for impurity removal-mixing treatment on the GH4099 powder to obtain GH4099 powder in the particle size range of 53~106μm.

[0010] Specifically, after screening, the powders of different particle sizes will have uneven distribution. Then pour the powder after screening and impurity removal into a mixer and rotate and mix it to obtain GH4099 powder in the particle size range of 53~106μm.

[0011] Further, in Step 2, use Deform software to simulate and calculate the stress values of different regions of the target tooling during use. When the maximum stress value in a certain region is less than the yield strength of the steel material at the use temperature, then use the steel material to prepare the ingot in this region, that is, obtain the ingot size.

[0012] Further, in Step 3, machine a sawtooth structure on the steel billet, and then perform finish machining on the entire surface of the steel billet to obtain an ingot; the surface roughness Ra of the ingot is <0.8μm.

[0013] Further, in Step 3, the sawtooth structure includes multiple inverted trapezoidal teeth. Specifically, the tooth width is 20~35mm, the tooth height is 30~50mm, and the tooth pitch is 15~20mm.

[0014] Further, in Step 5, powder loading is carried out under continuous vibration of the vibration platform, and the vibration frequency is set to 30~45Hz, and the amplitude is ±2mm.

[0015] Further, in step 5, the vacuum degassing temperature is 400 - 450 °C, and the vacuum degree is < 1.0×10 -4 Pa, followed by the encapsulation welding treatment.

[0016] Further, in step 6, the process of hot isostatic pressing treatment is as follows: heating at a heating rate of 0.05 - 0.1 °C / s to 1200 - 1250 °C, with a pressure of 180 - 200 MPa, holding the temperature and pressure for 3 - 4 h, then cooling at a cooling rate of 0.3 - 0.5 °C / s to 500 - 550 °C, with a pressure of 75 - 85 MPa, holding the temperature and pressure for 0.5 - 1 h, then heating at a heating rate of 0.05 - 0.1 °C / s to 750 - 800 °C, with a pressure of 120 - 130 MPa, holding the temperature and pressure for 16 - 20 h, then cooling at a cooling rate of 0.3 - 0.5 °C / s to 500 - 550 °C, with a pressure of 75 - 85 MPa, holding the temperature and pressure for 3 - 4 h, and finally cooling at a cooling rate of 0.3 - 0.5 °C / s to room temperature.

[0017] Further, in step 6, for the work - die blank after machining treatment, shot peening treatment is carried out on its working surface. Specifically, the shot peening treatment uses 304 stainless steel shot grains with a particle size of 0.15 - 0.2 mm, and the shot peening pressure is 0.5 - 0.75 MPa.

[0018] On the other hand, the present invention provides a work - die obtained by the method for preparing a bimetallic hot - working die using hot isostatic pressing as described above, which is applied in the forging field.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention provides a method for preparing a bimetallic hot - working die using hot isostatic pressing. This method designs the maximum size of the steel billet according to the stress distribution and magnitude during the use of the die, and then performs the solid - powder combination of dissimilar metals through the hot isostatic pressing method, completing the densification of the structure and the regulation of the tissue properties in one step, ensuring a well - combined and dense interface of dissimilar metals; in addition, this preparation method has the advantages of a short process and high efficiency; Specifically, a saw - tooth structure is machined on the surface of the steel ingot, and then the GH4099 powder is added to one end of the saw - tooth structure. The purpose of this design is to increase the contact area between the steel ingot and the GH4099 powder to enhance the bonding strength of the interface. In addition, the innovative design of the tooth is an inverted trapezoid structure, with its bottom narrower than the top, forming a "barbed - hook shape", which can prevent the disconnection of the interface from the structure; By controlling the cooling rate of hot isostatic pressing, it is possible to directly complete the densification of hot isostatic pressing and regulate the microstructure and properties with the same effect as heat treatment in a hot isostatic pressing equipment. Specifically, rapid cooling to 500 - 550 °C is carried out to achieve the effect of air cooling in heat treatment. Subsequently, the temperature is raised to 750 - 800 °C (i.e., the peak temperature of γ' precipitation in GH4099 alloy) to promote the full precipitation of γ' and improve the comprehensive mechanical properties of GH4099 alloy. Then, it is further rapidly cooled to 500 - 550 °C and held at 500 - 550 °C to eliminate the stress of the ingot and stabilize the microstructure.

[0020] 2) For the method of preparing a bimetallic hot working die using hot isostatic pressing provided by the present invention, shot peening on the working surface of the processed bimetallic die blank can strengthen the surface of the die. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 is the process preparation flow chart of the bimetallic hot working die of the present invention; Figure 2 is the schematic diagram of the sawtooth structure of the contact surface between the ingot and the powder of the present invention; Figure 3 is the schematic diagram of the temperature - pressure curve during the hot isostatic pressing process of the present invention; Figure 4 is the schematic diagram of the stress nephogram at the corresponding temperature and the position of the ingot in Example 1; Figure 5 is the schematic diagram of the structure of the U - shaped die prepared in Example 1; Figure 6 is the schematic diagram of the stress nephogram at the corresponding temperature and the position of the ingot in Example 2; Figure 7 is the schematic diagram of the structure of the V - shaped die prepared in Example 2; Figure 8 is the schematic diagram of the stress nephogram at the corresponding temperature and the position of the ingot in Example 3; Figure 9 is the schematic diagram of the structure of the flat anvil die prepared in Example 3; Figure 10Microstructure diagram of the interface between GH4099 alloy and ingot for the mold of Example 1; Figure 11 Metallographic microstructure diagram of GH4099 alloy for the mold of Example 1; Figure 12 Scanning electron microscope image of the γ' precipitate phase of GH4099 alloy for the mold of Example 1; Figure 13 Metallographic microstructure of GH4099 alloy for the mold prepared by the prior art (hot isostatic pressing + heat treatment); Figure 14 Scanning electron microscope image of the γ' precipitate phase of GH4099 alloy for the mold prepared by the prior art (hot isostatic pressing + heat treatment); Figure 15 Microstructure diagram of the interface between GH4099 alloy and ingot for the mold of Example 2; Figure 16 Metallographic microstructure diagram of GH4099 alloy for the mold of Example 2; Figure 17 Scanning electron microscope image of the γ' precipitate phase of GH4099 alloy for the mold of Example 2; Figure 18 Microstructure diagram of the interface between GH4099 alloy and ingot for the mold of Example 3; Figure 19 Metallographic microstructure diagram of GH4099 alloy for the mold of Example 3; Figure 20 Scanning electron microscope image of the γ' precipitate phase of GH4099 alloy for the mold of Example 3. Detailed implementation manners

[0024] Here, the exemplary embodiments will be described in detail. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present invention. On the contrary, they are only examples consistent with some aspects of the present invention detailed in the appended claims.

[0025] On the one hand, please refer to Figure 1 , the present invention provides a method for preparing a bimetallic hot working die by hot isostatic pressing, including the following steps: Step 1: Prepare GH4099 powder by using an ultra-high speed plasma rotating electrode, and perform pretreatment on the GH4099 powder to obtain GH4099 powder in a specific particle size range; Among them, the pretreatment includes sequentially performing screening treatment - static electromagnetic separation and impurity removal treatment - mixing treatment on the GH4099 powder to obtain GH4099 powder in the particle size range of 53 - 106 μm.

[0026] Step 2: Design the cladding according to the structure and dimensions of the target tooling to be prepared. The cladding is formed by welding an upper cover, side plates, and a bottom plate through argon arc welding (i.e., obtaining the pre-prepared cladding); Step 3: Conduct numerical simulation based on the actual working conditions of the target tooling to be prepared, obtain the stress values in different regions during the use of the target tooling, and determine the size of the bottom ingot of the target tooling according to the stress values; Specifically, use Deform software to simulate and calculate the stress values in different regions during the use of the target tooling. When the maximum stress value in a certain region is less than the yield strength of the steel material at the service temperature, then the steel material is used to prepare the ingot in this region, that is, the size of this region is the ingot size.

[0027] For example, the yield strength of the steel material at the forging service temperature is 200 MPa. Then, during simulation, the regions with stress < 200 MPa use the steel material to prepare the ingot.

[0028] Step 4: Prepare the steel billet according to the ingot size obtained in Step 3 through the traditional VIM+ESR+VAR triple process, and then process the obtained steel billet to obtain the ingot; Among them, one end of the ingot in contact with the GH4099 powder in the 53~106 μm particle size range is a serrated structure; specifically, machine the serrated structure on the steel billet, and then perform finish machining on the entire surface of the steel billet through a grinding machine to obtain the ingot, and the surface roughness Ra of the ingot < 0.8 μm.

[0029] More specifically, the serrated structure includes multiple inverted trapezoidal teeth. Specifically, the tooth width is 20~35 mm, the tooth height is 30~50 mm, and the tooth pitch is 15~20 mm, as Figure 2 shown.

[0030] Step 5: Place the ingot obtained in Step 4 on the bottom plate of the cladding designed in Step 2, fix the two through argon arc welding, and then weld the side plates and the upper cover through argon arc welding to achieve the sealing welding of the cladding (the upper cover is provided with a cladding nozzle for adding powder, which is common knowledge in the industry); Step 6: Place the cladding containing the ingot on the vibration platform, and then fill the GH4099 powder pretreated in Step 1 into the cladding through the cladding nozzle, and then perform vacuum degassing and sealing welding treatment on the cladding nozzle; Among them, powder loading is carried out under continuous vibration of the vibration platform, the vibration frequency is set to 30~45 Hz, and the amplitude is ±2 mm; the vacuum degassing temperature is 400~450 °C, and the vacuum degree < 1.0×10 -4 Pa before performing the cladding sealing welding treatment.

[0031] Step 7: Perform hot isostatic pressing on the jacket after the sealing welding in Step 6 to obtain a blank of the tool and die, and then successively perform machining and shot peening on the blank of the tool and die to obtain the target tool and die; Among them, the process of hot isostatic pressing is specifically as follows: Heat up at a heating rate of 0.05 - 0.1 °C / s to 1200 - 1250 °C, with a pressure of 180 - 200 MPa, hold the temperature and pressure for 3 - 4 h, then cool down at a cooling rate of 0.3 - 0.5 °C / s to 500 - 550 °C, with a pressure of 75 - 85 MPa, hold the temperature and pressure for 0.5 - 1 h, then heat up again at a heating rate of 0.05 - 0.1 °C / s to 750 - 800 °C, with a pressure of 120 - 130 MPa, hold the temperature and pressure for 16 - 20 h, then cool down at a cooling rate of 0.3 - 0.5 °C / s to 500 - 550 °C, with a pressure of 75 - 85 MPa, hold the temperature and pressure for 3 - 4 h, and finally cool down to room temperature at a cooling rate of 0.3 - 0.5 °C / s, as Figure 3 shown.

[0032] After hot isostatic pressing, machine to remove the excess material, and perform shot peening strengthening on the working surface.

[0033] Specifically, for the shot peening treatment, 304 stainless steel shot grains with a particle size of 0.15 - 0.2 mm are selected, and the shot peening pressure is 0.5 - 0.75 MPa.

[0034] It should be noted that the order of the above Steps 1, 2, and 3 is not limited and they can also be carried out synchronously.

[0035] On the other hand, the present invention provides a tool and die prepared by the method for preparing a bimetallic hot working tool and die by hot isostatic pressing as described above, which is applied in the forging field. Such as dies for open die forging, die forging, and isothermal forging, etc.

[0036] The method of the present invention is to prepare a die for forging. In order to further verify the efficacy of the present invention, the inventor conducted the following specific tests:

[0037] Example 1 In this example, a U-shaped tool and die for 8000-ton titanium alloy open die forging is prepared, and its detailed preparation process is as follows: Step 1: Use an ultra-high-speed plasma rotating electrode to prepare GH4099 powder, and successively perform screening treatment - static electromagnetic separation for impurity removal treatment - mixing treatment on the GH4099 powder to obtain GH4099 powder in the particle size range of 53 - 106 μm; Step 2: Design the jacket according to the structure and dimensions of the U-shaped tool and die to be prepared, and use argon arc welding to weld the jacket components; Step 3: Conduct numerical simulation according to the actual working conditions of the U-shaped tooling to be prepared (temperature, press pressure, pressing rate, and pressing amount during the production process), obtain the stress values of different regions of the U-shaped tooling during use, and determine the size of the bottom ingot of the U-shaped tooling based on the stress values; Specifically, use Deform software to simulate and calculate the stress values of different regions of the U-shaped tooling during use. When the maximum stress value in a certain region is less than the yield strength of the steel material at the service temperature, the steel material is used to prepare the ingot in this region, that is, the size of this region is the ingot size, as Figure 4 shown.

[0038] Step 4: Pour 5CrNiMo according to the ingot size simulated in Step 3 through the traditional VIM+ESR+VAR triple process to obtain a 5CrNiMo steel billet, and then process the obtained 5CrNiMo steel billet to obtain a 5CrNiMo steel ingot; Among them, one end of the 5CrNiMo steel ingot in contact with the GH4099 powder in the 53-106μm particle size range is a serrated structure; specifically, machine the serrated structure on the 5CrNiMo steel billet, and then perform finish machining on the entire surface of the 5CrNiMo steel billet through a grinding machine to obtain a 5CrNiMo steel ingot, and the surface roughness Ra of the 5CrNiMo steel ingot is 0.8μm.

[0039] More specifically, the serrated structure includes multiple inverted trapezoidal teeth. Specifically, the tooth width is 20mm, the tooth height is 35mm, and the tooth pitch is 15mm.

[0040] Step 5: Place the 5CrNiMo steel ingot prepared in Step 4 in a jacket, fix the 5CrNiMo steel ingot and the jacket by argon arc welding, and then weld the jacket cover. All the processing procedures here are the same as the above method; Step 6: Place the jacket containing the 5CrNiMo steel ingot on a vibration platform, then fill the GH4099 powder pretreated in Step 1 into the jacket through the jacket nozzle, and then perform vacuum degassing and seal welding treatment on the jacket nozzle; Among them, powder filling is carried out under continuous vibration of the vibration platform, the vibration frequency is set to 30-45Hz, and the amplitude is ±2mm; the vacuum degassing temperature is 450°C, and the vacuum degree is 1.0×10 -4 Pa, and then seal welding treatment of the jacket is carried out.

[0041] Step 7: Perform hot isostatic pressing treatment on the jacket after seal welding in Step 6 to obtain a tooling blank, and then perform machining and shot peening treatment on the tooling blank in sequence to obtain a U-shaped tooling, as Figure 5 shown; Among them, the process of hot isostatic pressing is specifically as follows: heating up to 1200°C at a heating rate of 0.05°C / s, with a pressure of 190 MPa, holding the temperature and pressure for 4 h, then cooling down to 550°C at a cooling rate of 0.5°C / s, with a pressure of 75 MPa, holding the temperature and pressure for 0.5 h, then heating up to 800°C at a heating rate of 0.05°C / s, with a pressure of 120 MPa, holding the temperature and pressure for 16 h, then cooling down to 500°C at a cooling rate of 0.3°C / s, with a pressure of 75 MPa, holding the temperature and pressure for 4 h, and finally cooling down to room temperature at a cooling rate of 0.5°C / s.

[0042] After hot isostatic pressing, the surplus is removed by machining, and shot peening strengthening is carried out on the working surface.

[0043] Specifically, 304 stainless steel shot with a particle size of 0.15 - 0.2 mm is selected for shot peening, and the shot peening pressure is 0.5 MPa.

[0044] Figure 10 It is the microstructure diagram of the interface between GH4099 alloy and steel ingot of the U-shaped tool and die. It can be seen from the microstructure that a dense tissue interface between GH4099 alloy and steel ingot can be obtained through the present invention.

[0045] In order to prove the technical effect of the present invention, Example 1 of the present invention is compared with the prior art (hot isostatic pressing + heat treatment), as Figures 11 to 14 , in addition, with reference to high-temperature tensile test in accordance with GB / T228.2 - 2015; room-temperature tensile test in accordance with GB / T228.1 - 2021; impact performance test in accordance with: GB / T229 - 2020, the performance test results of the die are compared, as shown in Table 1 and Table 2.

[0046] Table 1 Mechanical property data of GH4099 alloy of U-shaped tool and die

[0047] Table 2 Mechanical property data of GH4099 alloy of U-shaped tool and die prepared by the prior art

[0048] It can be seen from Table 1 and Table 2 that the size of the precipitation phase in the microstructure of the prior art is close to that of the present invention, and the mechanical properties are basically the same.

[0049] It can be known from the comparison that the present invention achieves the same effect of tissue regulation as heat treatment by controlling the cooling rate of hot isostatic pressing, and no subsequent heat treatment process is required.

[0050] Specifically, the existing technical solution is to perform heat treatment after conventional hot isostatic pressing. The hot isostatic pressing regime is as follows: heating up to 1200°C at a heating rate of 0.05°C / s, with a pressure of 150 MPa, holding the pressure for 4 hours, and cooling in the furnace. The heat treatment regime is solution treatment at 1100°C / 4h / AC + aging treatment at 700 - 800°C / 20h / AC.

[0051] Example 2 In this example, a V-shaped tool and die for free forging of 12,000 tons of superalloy is prepared, and its detailed preparation process is as follows: Step 1: Prepare GH4099 powder using an ultra-high-speed plasma rotating electrode, and successively perform screening treatment - static electromagnetic separation for impurity removal - mixing treatment on the GH4099 powder to obtain GH4099 powder in the particle size range of 53 - 106 μm. Step 2: Design the jacket according to the structure and size of the V-shaped tool and die to be prepared, and weld the jacket components using argon arc welding. Step 3: Perform numerical simulation according to the actual working conditions (temperature, press pressure, reduction rate, and reduction amount during the production process) of the V-shaped tool and die to be prepared, obtain the stress values in different regions during the use of the V-shaped tool and die, and determine the bottom ingot size of the V-shaped tool and die according to the stress values. Specifically, use Deform software to simulate and calculate the stress values in different regions during the use of the V-shaped tool and die. When the maximum stress value in a certain region is less than the yield strength of the steel material at the service temperature, the ingot in this region is prepared using the steel material, that is, the size of this region is the ingot size, as Figure 6 shown.

[0052] Step 4: Pour 4Cr5MoSiV1 according to the ingot size simulated in Step 3 through the traditional VIM + ESR + VAR triple process to obtain a 4Cr5MoSiV1 steel billet, and then process the obtained 4Cr5MoSiV1 steel billet to obtain a 4Cr5MoSiV1 steel ingot. Among them, one end of the 4Cr5MoSiV1 steel ingot in contact with the GH4099 powder in the 53 - 106 μm particle size range is a serrated structure; specifically, machine the serrated structure on the 4Cr5MoSiV1 steel billet, and then perform finish machining on the entire surface of the 4Cr5MoSiV1 steel billet using a grinding machine to obtain a 4Cr5MoSiV1 steel ingot, and the surface roughness Ra of the 4Cr5MoSiV1 steel ingot is 0.63 μm.

[0053] More specifically, the serrated structure includes multiple inverted trapezoidal teeth. Specifically, the tooth width is 35 mm, the tooth height is 50 mm, and the tooth pitch is 15 mm.

[0054] Step 5: Place the 4Cr5MoSiV1 steel ingot obtained in Step 4 in a pre-prepared jacket, seal-weld the 4Cr5MoSiV1 steel ingot and the jacket by argon arc welding, and then weld the upper cover of the jacket. All the processing procedures here are the same as the above method; Step 6: Place the jacket containing the 4Cr5MoSiV1 steel ingot on a vibrating platform, then fill the jacket with the GH4099 powder pretreated in Step 1, and then perform vacuum degassing and jacket seal-welding treatment; Among them, powder filling is carried out under continuous vibration of the vibrating platform, the vibration frequency is set to 30 - 45 Hz, and the amplitude is ±2 mm; the vacuum degassing temperature is 450 °C, and the vacuum degree is 5.0×10 -5 Pa, and then jacket seal-welding treatment is carried out.

[0055] Step 7: Perform hot isostatic pressing treatment on the jacket after seal-welding in Step 6 to obtain a workpiece die blank, and then perform machining and shot peening treatment on the workpiece die blank in sequence to obtain a V-shaped workpiece die, as Figure 7 shown, and the microstructure diagram is as Figures 15 to 17 ; Among them, the process of hot isostatic pressing treatment is specifically as follows: heat up to 1250 °C at a heating rate of 0.05 °C / s, with a pressure of 200 MPa, keep the temperature and pressure for 4 h, then cool down to 520 °C at a cooling rate of 0.5 °C / s, with a pressure of 85 MPa, keep the temperature and pressure for 0.5 h, then heat up to 750 °C at a heating rate of 0.05 °C / s, with a pressure of 130 MPa, keep the temperature and pressure for 20 h, then cool down to 500 °C at a cooling rate of 0.4 °C / s, with a pressure of 85 MPa, keep the temperature and pressure for 4 h, and finally cool down to room temperature at a cooling rate of 0.5 °C / s.

[0056] After hot isostatic pressing treatment, machine to remove the surplus, and perform shot peening strengthening on the working surface.

[0057] Specifically, the shot peening uses 304 stainless steel shot grains with a particle size of 0.15 - 0.2 mm, and the shot peening pressure is 0.7 MPa.

[0058] Example 3 This example prepares a flat anvil workpiece die for 12,000-ton superalloy free forging, and its detailed preparation process is as follows: Step 1: Prepare GH4099 powder using an ultra-high-speed plasma rotating electrode, and perform screening treatment - static electromagnetic separation for impurity removal - mixing treatment on the GH4099 powder in sequence to obtain GH4099 powder in the particle size range of 53 - 106 μm; Step 2: Design the jacket according to the structure and dimensions of the flat anvil workpiece die to be prepared, and weld the jacket components by argon arc welding; Step 3: Conduct numerical simulation based on the actual working conditions of the flat anvil tooling to be prepared (temperature, press pressure, reduction rate, and reduction amount during the production process), obtain the stress values of different regions of the flat anvil tooling during use, and determine the bottom ingot size of the flat anvil tooling according to the stress values; Specifically, use Deform software to simulate and calculate the stress values of different regions of the flat anvil tooling during use. When the maximum stress value in a certain region is less than the yield strength of the steel material at the service temperature, the steel ingot in this region is prepared using the steel material, that is, the size of this region is the ingot size, as Figure 8 shown.

[0059] Step 4: Pour 5CrMnMo according to the ingot size simulated in Step 3 through the traditional VIM+ESR+VAR triple process to obtain a 5CrMnMo steel billet, and then process the obtained 5CrMnMo steel billet to obtain a 5CrMnMo steel ingot; Among them, one end of the 5CrMnMo steel ingot in contact with the GH4099 powder in the 53~106μm particle size range is a serrated structure; specifically, machine the serrated structure on the 5CrMnMo steel billet, and then perform finish machining on the entire surface of the 5CrMnMo steel billet through a grinding machine to obtain a 5CrMnMo steel ingot, and the surface roughness Ra of the 5CrMnMo steel ingot is 0.63μm.

[0060] More specifically, the serrated structure includes multiple inverted trapezoidal teeth. Specifically, the tooth width is 30mm, the tooth height is 30mm, and the tooth pitch is 20mm.

[0061] Step 5: Place the 5CrMnMo steel ingot obtained in Step 4 in a pre-prepared jacket, fix the 5CrMnMo steel ingot and the jacket by argon arc welding, and then weld the jacket cover. All the processing procedures here are the same as the above method; Step 6: Place the jacket containing the 5CrMnMo steel ingot on a vibration platform, and then fill the GH4099 powder pretreated in Step 1 into the jacket through the jacket nozzle, and then perform vacuum degassing and seal welding treatment on the jacket nozzle; Among them, powder filling is carried out under continuous vibration of the vibration platform, the vibration frequency is set to 30~45Hz, and the amplitude is ±2mm; the vacuum degassing temperature is 420°C, and the vacuum degree is 7.5×10 -5 Pa, and then seal welding treatment of the jacket is carried out.

[0062] Step 7: Perform hot isostatic pressing treatment on the jacket after seal welding in Step 6 to obtain a tooling blank, and then perform machining and shot peening treatment on the tooling blank in sequence to obtain a flat anvil tooling, as Figure 9 shown, and the microstructure diagram is as Figures 18 to 20 ; Among them, the process of hot isostatic pressing is specifically as follows: heating up to 1230°C at a heating rate of 0.1°C / s, with a pressure of 180 MPa, holding the temperature and pressure for 4 h, then cooling down to 500°C at a cooling rate of 0.4°C / s, with a pressure of 80 MPa, holding the temperature and pressure for 1.0 h, then heating up to 800°C at a heating rate of 0.1°C / s, with a pressure of 125 MPa, holding the temperature and pressure for 18 h, then cooling down to 550°C at a cooling rate of 0.3°C / s, with a pressure of 80 MPa, holding the temperature and pressure for 3 h, and finally cooling down to room temperature at a cooling rate of 0.3°C / s.

[0063] After hot isostatic pressing, the surplus is removed by machining, and shot peening strengthening is carried out on the working surface.

[0064] Specifically, 304 stainless steel shot with a particle size of 0.15 - 0.2 mm is selected for shot peening, and the shot peening pressure is 0.7 MPa.

[0065] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0066] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A method for preparing a bimetallic hot working die by hot isostatic pressing, characterized in that, It includes the following steps: Step 1: Prepare GH4099 powder using an ultra-high speed plasma rotating electrode and preprocess the GH4099 powder to obtain GH4099 powder in a specific particle size range; Step 2: Conduct numerical simulation according to the actual working conditions of the target tooling to be prepared, obtain the stress values in different regions during the use of the target tooling, and determine the bottom ingot size of the target tooling based on the stress values; Step 3: Prepare a steel billet according to the ingot size obtained in Step 2 through the VIM+ESR+VAR triple process, and then process the obtained steel billet to obtain an ingot; Wherein, one end of the ingot in contact with the GH4099 powder in the specific particle size range is a serrated structure; Step 5: Place the ingot prepared in Step 3 in a pre-prepared sleeve, fixedly connect the ingot and the sleeve, and then seal-weld the sleeve; Step 6: Place the sleeve containing the ingot on a vibrating platform, then fill the pre-treated GH4099 powder in Step 1 into the sleeve through the sleeve nozzle, and then conduct vacuum degassing and seal-weld the sleeve nozzle; Step 7: Conduct hot isostatic pressing on the sleeve sealed in Step 5 to obtain a tooling blank, and then successively conduct machining and shot peening on the tooling blank to obtain the target tooling.

2. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, characterized in that, In Step 1, the preprocessing includes successively screening the GH4099 powder - static electromagnetic separation for impurity removal - mixing treatment to obtain GH4099 powder in the particle size range of 53~106μm.

3. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, wherein In Step 2, use Deform software to simulate and calculate the stress values in different regions during the use of the target tooling. When the maximum stress value in a certain region is less than the yield strength of the steel material at the use temperature, then the steel material is used to prepare the ingot in this region, that is, the ingot size is obtained.

4. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, characterized in that In Step 3, machine the serrated structure on the steel billet, and then conduct finish machining on the entire surface of the steel billet to obtain an ingot; the surface roughness Ra of the ingot < 0.8μm.

5. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1 or 4, characterized in that, In Step 3, the serrated structure includes multiple inverted trapezoidal teeth. Specifically, the tooth width is 20~35mm, the tooth height is 30~50mm, and the tooth pitch is 15~20mm.

6. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, characterized in that, In Step 5, powder loading is carried out under continuous vibration of the vibrating platform, and the vibration frequency is set to 30~45Hz, and the amplitude is ±2mm.

7. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, wherein In Step 5, the vacuum degassing temperature is 400~450 °C, and after the vacuum degree is < 1.0×10 -4 Pa, the cladding welding treatment is carried out.

8. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, characterized in that, In Step 6, the process of hot isostatic pressing is specifically as follows: heat up at a heating rate of 0.05~0.1℃ / s to 1200~1250℃, with a pressure of 180~200MPa, hold for 3~4h, then cool down at a cooling rate of 0.3~0.5℃ / s to 500~550℃, with a pressure of 75~85MPa, hold for 0.5~1h, then heat up at a heating rate of 0.05~0.1℃ / s to 750~800℃, with a pressure of 120~130MPa, hold for 16~20h, then cool down at a cooling rate of 0.3~0.5℃ / s to 500~550℃, with a pressure of 75~85MPa, hold for 3~4h, and finally cool down to room temperature at a cooling rate of 0.3~0.5℃ / s.

9. The method for preparing a bimetallic hot working die by hot isostatic pressing according to claim 1, characterized in that, In step 6, the tool and die blank after machining is subjected to shot peening on its working surface. Specifically, 304 stainless steel shot with a particle size of 0.15 - 0.2 mm is selected for shot peening, and the shot peening pressure is 0.5 - 0.75 MPa.

10. A tool and die produced by the method for preparing a bimetallic hot working tool and die by hot isostatic pressing as claimed in any one of claims 1 - 9, which is applied in the forging field.

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