A mold and production method for producing a soil squeezer for agricultural machinery

Abstract

The present invention belongs to the field of manufacturing of soil squeezing knives for agricultural machinery, and specifically relates to a mold and a production method for the production of soil squeezing knives for agricultural machinery, wherein the mold comprises: a bottom plate, a cushion block, a lower module, an upper module, a guide column and a top plate, the bottom plate is fixedly connected to the cushion block and the lower module in sequence through long bolts, the lower module is fixedly connected to the lower end of the guide column, the upper module is slidably connected to the upper end of the guide column, the upper part of the upper module is fixedly connected with the top plate, the upper end of the top plate is connected to the output end of a hydraulic system, a tool blank is placed on a forming part between the lower module and the upper module, and a slope surface that is beneficial to blank forming is arranged between the forming parts of the lower module and the upper module; the device can perform die forging manufacturing on the soil squeezing knives for agricultural machinery, and the mold forming part achieves an effect of facilitating the flow of the blank through the slope surface, which is beneficial to achieving the purpose of improving the mechanical properties of the blade part.

Description

Technical Field

[0001] The invention relates to the field of production and manufacturing of soil squeezing knives for agricultural machinery, and in particular to a mould and a production method for the soil squeezing knives for agricultural machinery. Background Art

[0002] Agricultural machinery parts such as tillage blades, cutting blades (squeezing blades) and other parts not only have to contact with the soil, but the squeezing blade is a kind of cutting tool used in no-tillage machines. When in use, it often collides with sand and stones. Especially under harsh soil conditions, high-speed agricultural machinery parts are prone to breakage and failure during the collision. The core or bearing layer is required to have good toughness and the edge or surface has high wear resistance. Wear is the main factor causing the failure of agricultural machinery parts, and the failure form is mainly low-stress abrasive wear. Commonly used wear-resistant materials include medium-carbon low-alloy steel such as 65Mn, high-carbon steel such as T9, T12J, ductile iron and powder metallurgy materials. Further research and development of new wear-resistant materials with excellent performance, greatly improving the service life of easily worn parts, and strengthening the strength of the blade by improving the forging die of the tool are issues that need to be urgently addressed.

[0003] Therefore, in view of the above-mentioned existing problems, a mold and a production method for a soil squeezer for agricultural machinery are proposed. Summary of the invention

[0004] The present invention is aimed at the above-mentioned problems and specifically designs a mold and production method for agricultural machinery soil squeezing knives. The device can perform die forging on agricultural machinery soil squeezing knives. The slope of the mold forming part facilitates the flow of the blank, making the blade part denser, which is conducive to improving the performance of the blade part. The hardness and various properties of the tool are improved through metal ratio and heat treatment, thereby increasing the wear resistance and service life of the tool.

[0005] To achieve the above-mentioned purpose, the present invention provides a mold for producing agricultural machinery soil squeezing knives, comprising: a bottom plate, a cushion block, a lower module, an upper module, a guide column and a top plate, the bottom plate is fixedly connected to the cushion block and the lower module in sequence by long bolts, the lower module is fixedly connected to the lower end of the guide column, the upper module is slidably connected to the upper end of the guide column, the upper part of the upper module is fixedly connected to the top plate, the upper end of the top plate is connected to the output end of the hydraulic system, the tool blank is placed on the molding part between the lower module and the upper module, and a slope surface that is conducive to the molding of the blank is arranged between the molding parts of the lower module and the upper module.

[0006] In the above manner, the blank is placed between the upper and lower modules for forging. The forging parts of the upper and lower modules are both provided with slopes. When the slopes contact each other to extrude the blank, it is beneficial for the blank to flow, making the density of the blank blade part higher, thereby ensuring the comprehensive mechanical properties of the working part.

[0007] Furthermore, the molding part includes a lower mold core and an upper mold core, the lower mold core is slidably connected to the lower module, and the upper mold core is fixedly connected to the upper module. The upper and lower mold cores adopt a modular design and can be installed in conjunction with the upper and lower modules according to usage requirements.

[0008] Furthermore, the forming part also includes a first slope surface and a second slope surface, the first slope surface is located on the top surface of the lower mold core, the second slope surface is located on the bottom surface of the upper mold core, the angle range between the first slope surface and the upper surface of the lower mold core is 10.8°-11°, the angle between the second slope surface and the lower surface of the upper mold core is equal to the angle between the first slope surface and the upper surface of the lower mold core, and the two slope surfaces are in contact with each other, and the bottom of the first slope surface is the blade part after the tool blank is formed.

[0009] Through the above method, the two slope surfaces are fitted and connected. When die forging is performed, the blank is placed between the two slope surfaces, and the blank flows along the slope surfaces. The blade part is at the bottom of the slope surface, where the density of the blank is the highest.

[0010] Furthermore, the lower module includes a lower mold cavity and a guide hole, the lower mold core is slidably connected in the lower mold cavity, the lower mold cavity is adapted to the shape of the lower mold core, the guide holes are opened on the lower module and located on both sides of the lower mold cavity, and the guide columns are placed in the guide holes.

[0011] Furthermore, the upper module includes a guide sleeve and an upper mold core notch, the upper mold core notch is opened on the lower surface of the upper module, the upper mold core is fixedly connected in the upper mold core notch, an installation hole is opened on the upper module, the guide sleeve is installed in the installation hole, and the guide column is slidably connected to the guide sleeve.

[0012] Furthermore, the lower mold core also includes a top block, the bottom surface of the bottom plate is provided with a through hole, the top block is a long plate structure, the top block is fixedly connected to the bottom of the lower mold core and the lower surface is flush with the bottom surface of the lower mold core, the through hole is located below the top block, and springs are fixedly connected at both ends of the top block, and the top end of the spring is in contact with the bottom of the lower module.

[0013] In the above manner, when forging is completed, the workpiece needs to be unloaded, and the push rod of the unloading mechanism pushes up the lower die core from the through hole in the middle of the bottom plate, thereby pushing the workpiece out.

[0014] Furthermore, the bottom plate further comprises a positioning block, which is fixedly connected to the lower surface of the bottom plate and protrudes from the lower surface of the bottom plate. The positioning block plays a role in assisting the positioning and installation of the mold.

[0015] The present invention also provides a method for producing an agricultural machinery soil squeezing knife, comprising the following steps:

[0016] Step 1: Select the blank with appropriate metal content according to the tool usage requirements, and reduce the inclusions and harmful gases in the raw materials through smelting; improve the purity of the material and effectively reduce the impurity rate and component segregation of the structure.

[0017] Step 2: Place the smelted blank on the lower die core, and drive the upper die core to forge the blank on the lower die core through the hydraulic press; accurately control the forging temperature of the blank and the entire forging time. This process not only meets the forging forming requirements, but also ensures that the heated forging blank completes the entire forging process within a temperature range with higher plasticity and lower deformation resistance, obtains a fine and uniform grain structure, and improves the mechanical properties of the forging.

[0018] Step 3: After forging is completed, the hydraulic system drives the upper die block to move upward, and the ejector rod of the ejector system below the die extends from the through hole to lift the lower die core, and the blank on the lower die core is taken out. The springs on both sides are pressed tightly against the bottom of the lower die block. After the discharge is completed, the ejector rod withdraws from the through hole, and under the action of the spring, the lower die core returns to its original position;

[0019] Step 4: Under the action of the first slope and the second slope, the metal flow direction of the soil extruder after forging is parallel to the direction of the force applied by the soil during operation, and the forged blank is subjected to vacuum heat treatment.

[0020] Furthermore, the content of the metal element in the blank in step 1 is:

[0021] C: 0.28%-0.3%, Si: 0.8%-1.5%; Mn: 0.28%-0.5%; P≤0.02%; S≤0.005%; Cr: 5.2%-5.7%; Mo: 1.6%-2.0%; V: 0.9%-1.5%; Ni≤0.3%.

[0022] Furthermore, the heat treatment in step 4 includes a quenching process and a tempering process. The quenching process adopts a segmented heating and heat preservation method. When the temperature drops to the set temperature after quenching, tempering is immediately performed, and the number of tempering times is set at 2-3 times.

[0023] When the temperature of the product after quenching drops to the set temperature, tempering should be carried out immediately to avoid microcracks inside the product caused by quenching stress; the number of tempering is determined to be 2-3 times, because the structure after one tempering not only has a high content of residual austenite, but also generates structural stress when austenite transforms into martensite, so secondary or tertiary tempering is necessary. The determination of the tempering temperature has a great relationship with the final hardness, wear resistance and impact toughness of the product. The hardness of the quenched product will reach its peak when tempered at the set temperature. When actually determining the tempering temperature, adjust it according to the product hardness requirements.

[0024] In summary, the mold and production method for producing a soil squeezer for agricultural machinery of the present invention have the following advantages and beneficial technical effects:

[0025] 1. The slope on the mold core of the mold for producing the soil squeezing knife for agricultural machinery of the present invention is conducive to the flow of the blank during die forging, so that the density of the blank at the blade part is higher, the performance of the blade part is improved, the wear resistance of the finished soil squeezing knife is improved, and the service life of the tool is increased;

[0026] 2. The spring provided on the lower die core and the ejector block of the mold for producing the soil extruder of agricultural machinery of the present invention can conveniently eject the workpiece from the bottom after the die forging is completed, and automatically restore the lower die core to the original position through the spring and the contact connection with the lower die block, without affecting the next die forging step;

[0027] 3. The metal element content ratio of the tool blank in the production method of the agricultural machinery soil squeezing tool of the present invention improves the technical indicators such as the hardness, impact energy, wear resistance and service life of the tool;

[0028] 4. The production method of the soil squeezer for agricultural machinery of the present invention improves the mechanical properties of the product through heat treatment after forging, and at the same time avoids cracks inside the finished product, thereby improving the hardness of the product;

[0029] 5. The slope surface on the mold core of the mold for producing the soil squeezing knife of agricultural machinery of the present invention is conducive to the flow of the blade part of the blank during die forging, so that the density of the blank at the blade part is higher, and the force direction of the soil squeezing knife is parallel to the metal flow direction of the blade part of the soil squeezing knife, thereby improving the performance of the blade part, improving the wear resistance of the finished soil squeezing knife, and increasing the service life of the tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0031] Figure 1 It is a structural schematic diagram of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0032] Figure 2It is a structural schematic diagram of an upper mold core of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0033] Figure 3 It is a structural schematic diagram of a lower mold core of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0034] Figure 4 It is a bottom view of a lower mold core of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0035] Figure 5 It is a structural schematic diagram of a bottom plate of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0036] Figure 6 It is a structural schematic diagram of a lower module of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0037] Figure 7 It is a structural schematic diagram of an upper mold plate of a mold for producing a soil squeezer for agricultural machinery according to the present invention;

[0038] Figure 8 It is a top view of a top plate of a mold for producing a soil squeezing knife for agricultural machinery according to the present invention;

[0039] Fig. 9 The utility model is a structural schematic diagram of a cushion block of a mould for producing a soil squeezing knife of an agricultural machinery according to the present invention.

[0040] The reference numerals in the accompanying drawings are:

[0041] 1. Bottom plate; 11. Long bolt; 12. Positioning block; 13. Through hole;

[0042] 2. Cushion block; 3. Lower die block; 31. Inner cavity of lower die; 32. Guide hole; 33. Lower die core; 34. Top block; 35. Spring; 36. First slope surface;

[0043] 4. Upper die block; 41. Guide sleeve; 42. Upper die core notch; 43. Upper die core; 44. Second slope; 45. Block; 46. Card slot;

[0044] 5. Guide column; 6. Top plate. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the implementation of the present invention clearer, the technical solution in the embodiment of the present invention will be described in more detail below in conjunction with the drawings in the embodiment of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions; the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the embodiments described below with reference to the drawings and directional terms are exemplary and are intended to be used to explain the present invention, and cannot be understood as limitations on the present invention; based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The parts and equipment all adopt conventional models in the prior art, and the circuit connections adopt conventional connection methods in the prior art, which will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field. The embodiments of the present invention are described in detail below in conjunction with the drawings:

[0046] like Figure 1 As shown, a mold for producing agricultural machinery soil squeezing knives includes: a base plate 1, a cushion block 2, a lower module 3, an upper module 4, a guide column 5 and a top plate 6. Bolt interfaces are provided on the cushion block 2 and the lower module 3. The base plate 1 is fixedly connected to the cushion block 2 and the lower module 3 in sequence through long bolts 11. The lower module 3 is fixedly connected to the lower end of the guide column 5. The upper module 4 is slidably connected to the upper end of the guide column 5. The upper part of the upper module 4 is fixedly connected to the top plate 6 by bolts. The upper end of the top plate 6 is connected to the output end of the hydraulic system. The tool blank is placed on the forming part between the lower module 3 and the upper module 4. A slope surface that is conducive to blank forming is set between the forming parts of the lower module 3 and the upper module 4. The base plate 1 also includes a positioning block 12. The positioning block 12 is fixedly connected to the lower surface of the base plate 1 by bolts and protrudes from the lower surface of the base plate 1, thereby assisting the positioning and installation of the mold.

[0047] The blank is placed between the upper and lower modules for forging. The forging parts of the upper and lower modules are provided with slopes. When the slopes contact each other to extrude the blank, it is beneficial for the blank to flow, making the density of the blank blade part higher, thereby ensuring the comprehensive mechanical properties of the working part.

[0048] like Figure 2 and Figure 3 As shown, the molding part includes a lower mold core 33 and an upper mold core 43. The lower mold core 33 is inserted into the middle of the upper mold module 4 and the lower mold core 33 is slidably connected to the lower mold module 3. The upper mold core 43 is fixedly connected to the upper mold module 4 by interference fit.

[0049] like Figure 2 and Figure 3As shown, the forming part also includes a first slope surface 36 and a second slope surface 44. The first slope surface 36 is located on the top surface of the lower mold core 33, and the second slope surface 44 is located on the bottom surface of the upper mold core 43. The angle formed by the first slope surface 36 and the upper surface of the lower mold core 33 is 10.8°. The angle formed by the second slope surface 44 and the lower surface of the upper mold core 43 is equal to the angle formed by the first slope surface 36 and the upper surface of the lower mold core 33, and the two slope surfaces fit each other. The slope surface is located in a partial area of ​​the end surface of the mold core, and the size of the area is changed according to the shape of the designed soil extrusion knife. The slope surface area is the working cutting part of the soil extrusion knife, and the bottom position of the slope is the blade part of the knife. The bottom of the slope of the first slope surface 36 is the blade part after the tool blank is formed.

[0050] like Figure 5 and Figure 6 As shown, the lower module 3 includes a lower mold cavity 31 and a guide hole 32. The lower mold core 33 is slidably connected in the lower mold cavity 31. The lower mold cavity 31 is adapted to the outer shape of the lower mold core 33. The guide holes 32 are opened on the lower module 3 and located on both sides of the lower mold cavity 31. The guide column 5 is fixedly connected in the guide hole 32 by bolt connection.

[0051] like Figure 7 and Figure 8 As shown, the upper module 4 includes a guide sleeve 41 and an upper mold core notch 42. The upper mold core notch 42 is provided on the lower surface of the upper module 4. The upper mold core 43 is fixedly connected in the upper mold core notch 42 by interference fit. A mounting hole is provided on the upper module 4. The guide sleeve 41 is installed in the mounting hole. The guide column 5 is slidably connected to the guide sleeve 41. A card slot 46 is provided on the edge of the upper mold core notch 42. A card block 45 adapted to the card slot 46 is integrally formed on the side of the upper mold core 43. When the upper mold core 43 is installed in the upper mold core notch 42, the card block 45 is installed in cooperation with the card slot 46, so that the upper mold core 43 is installed more firmly and plays a positioning role for the installation of the upper mold core 43.

[0052] like Figure 3 , Figure 4 and Figure 5 As shown, the lower mold core 33 also includes a top block 34, a through hole 13 is opened in the middle of the bottom surface of the bottom plate 1, the top block 34 is a long plate structure, the top block 34 is fixedly connected to the bottom of the lower mold core 33 by bolts and the lower surface is flush with the bottom surface of the lower mold core 33, the through hole 13 is located below the top block 34, the two ends of the top block 34 extend out of the two sides of the lower mold core 33, and the two ends of the top block 34 are fixedly connected with springs 35, and the top end of the spring 35 is in contact with the bottom of the lower module 3.

[0053] The production method of a soil squeezing knife for agricultural machinery of the present invention is as follows:

[0054] Step 1: Select the blank with appropriate metal content according to the tool usage requirements, and reduce the inclusions and harmful gases in the raw materials through smelting; improve the purity of the material and effectively reduce the impurity rate and component segregation of the structure.

[0055] Step 2: Place the smelted blank on the lower die core 33, and drive the upper die core 43 to forge the blank on the lower die core 33 through the hydraulic press; accurately control the forging temperature of the blank and the entire forging time. This process not only meets the forging forming requirements, but also ensures that the heated forging blank completes the entire forging process within a temperature range with higher plasticity and lower deformation resistance, obtains a fine and uniform grain structure, and improves the mechanical properties of the forging.

[0056] Step 3: After forging is completed, the hydraulic system drives the upper die block 4 to move upward, and the ejector rod of the ejector system below the die extends from the through hole 13 to lift the lower die core 33, and the blank on the lower die core 33 is taken out. The springs 35 on both sides are pressed tightly against the bottom of the lower die block 3. After the discharge is completed, the ejector rod withdraws from the through hole 13, and under the action of the spring 35, the lower die core 33 returns to its original position;

[0057] Step 4: Under the action of the first slope 36 and the second slope 44, the metal flow direction of the soil extruder after forging is parallel to the direction of the force applied by the soil during operation, and the forged blank is subjected to vacuum heat treatment.

[0058] The content of metal elements in the blank in step 1 is:

[0059] C: 0.28%, Si: 0.8%; Mn: 0.28%; P: 0.02%; S: 0.005%; Cr: 5.2%; Mo: 1.6%; V: 0.9%; Ni: 0.3%.

[0060] The heat treatment in step 4 includes a quenching process and a tempering process. The quenching process adopts a segmented heating and heat preservation method. When the temperature after quenching drops to the set temperature, tempering is immediately performed, and the number of tempering times is set at 2-3 times; when the temperature of the product after quenching drops to the set temperature, tempering should be performed immediately to avoid quenching stress causing micro cracks inside the product; the number of tempering times is determined to be 3 times, because not only the content of residual austenite in the structure after one tempering is high, but also structural stress will be generated when austenite is transformed into martensite, so secondary or tertiary tempering must be performed. The determination of the tempering temperature has a great relationship with the final hardness, wear resistance and impact toughness of the product. The hardness of the quenched product will reach a peak when it is tempered at the set temperature. When the tempering temperature is actually determined, it is adjusted according to the product hardness requirements.

[0061] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mold for producing a soil squeezer for agricultural machinery, characterized in that: include: A bottom plate (1), a cushion block (2), a lower module (3), an upper module (4), a guide column (5) and a top plate (6), wherein the bottom plate (1) is fixedly connected to the cushion block (2) and the lower module (3) in sequence by means of long bolts (11), the lower module (3) is fixedly connected to the lower end of the guide column (5), the upper module (4) is slidably connected to the upper end of the guide column (5), the upper part of the upper module (4) is fixedly connected to the top plate (6), the upper end of the top plate (6) is connected to the output end of a hydraulic system, a tool blank is placed on a forming portion between the lower module (3) and the upper module (4), and a slope surface conducive to blank forming is provided between the forming portions of the lower module (3) and the upper module (4); The molding part comprises a lower mold core (33) and an upper mold core (43), wherein the lower mold core (33) is slidably connected to the lower mold block (3), and the upper mold core (43) is fixedly connected to the upper mold block (4); The forming part further comprises a first slope surface (36) and a second slope surface (44), wherein the first slope surface (36) is located on the top surface of the lower mold core (33), and the second slope surface (44) is located on the top surface of the upper mold core (43), and the angle formed by the first slope surface (36) and the upper surface of the lower mold core (33) is in the range of 10.8°-11°, and the angle formed by the second slope surface (44) and the lower surface of the upper mold core (43) is equal to the angle formed by the first slope surface (36) and the upper surface of the lower mold core (33), and the two slope surfaces are in contact with each other, and the bottom of the first slope surface (36) is the blade portion of the tool blank after forming; The lower mold core (33) further comprises a top block (34), the bottom surface of the bottom plate (1) is provided with a through hole (13), the top block (34) is a long plate structure, the top block (34) is fixedly connected to the bottom of the lower mold core (33) and the lower surface is flush with the bottom surface of the lower mold core (33), the through hole (13) is located below the top block (34), and springs (35) are fixedly connected at both ends of the top block (34), and the top end of the spring (35) is in contact with the bottom of the lower mold block (3).

2. The mold for producing a soil squeezer for agricultural machinery according to claim 1, characterized in that: The lower die block (3) comprises a lower die inner cavity (31) and a guide hole (32); the lower die core (33) is slidably connected in the lower die inner cavity (31); the lower die inner cavity (31) is adapted to the outer shape of the lower die core (33); the guide hole (32) is formed on the lower die block (3) and is located on both sides of the lower die inner cavity (31); and the guide column (5) is placed in the guide hole (32).

3. The mold for producing a soil squeezer for agricultural machinery according to claim 1, characterized in that: The upper module (4) comprises a guide sleeve (41) and an upper mold core notch (42); the upper mold core notch (42) is provided on the lower surface of the upper module (4); the upper mold core (43) is fixedly connected to the upper mold core notch (42); a mounting hole is provided on the upper module (4); the guide sleeve (41) is installed in the mounting hole; and the guide column (5) is slidably connected to the guide sleeve (41).

4. The mold for producing a soil squeezer for agricultural machinery according to claim 1, characterized in that: The base plate (1) further comprises a positioning block (12), wherein the positioning block (12) is fixedly connected to the lower surface of the base plate (1) and protrudes from the lower surface of the base plate (1).

5. A method for producing a soil squeezer for agricultural machinery, characterized in that: Using the mold for producing a soil extruder for agricultural machinery as claimed in claim 1 for die forging comprises the following steps: Step 1: Select the blank with appropriate metal content according to the tool usage requirements, and reduce the inclusions and harmful gases in the raw materials by smelting; Step 2: placing the smelted blank on the lower die core (33), and driving the upper die core (43) through a hydraulic press to forge the blank on the lower die core (33); Step 3: After the forging is completed, the hydraulic system drives the upper die block (4) to move upward, and the ejector rod of the ejector system below the die extends from the through hole (13) to lift the lower die core (33), and the blank on the lower die core (33) is brought out. The springs (35) on both sides are pressed tightly against the bottom of the lower die block (3). After the discharge is completed, the ejector rod withdraws from the through hole (13), and under the action of the spring (35), the lower die core (33) returns to its original position; Step 4: Under the action of the first slope surface (36) and the second slope surface (44), the metal flow direction of the soil extruder after forging is parallel to the force direction after contacting the soil during operation, and the forged blank is subjected to vacuum heat treatment.

6. The method for producing a soil squeezer for agricultural machinery according to claim 5, characterized in that: The content of metal elements in the blank in step 1 is: C: 0.28%-0.3%, Si: 0.8%-1.5%; Mn: 0.28%-0.5%; P≤0.02%; S≤0.005%; Cr: 5.2%-5.7%; Mo: 1.6%-2.0%; V: 0.9%-1.5%; Ni≤0.3%.

7. The method for producing a soil squeezer for agricultural machinery according to claim 5, characterized in that: The heat treatment in step 4 includes a quenching process and a tempering process. The quenching process adopts a segmented heating and heat preservation method. When the temperature drops to the set temperature after quenching, tempering is immediately performed, and the number of tempering times is set at 2-3 times.

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