Heat treatment processing method of high-speed steel for precise valve needle

Abstract

The invention discloses a high-speed steel heat treatment machining method for a precise valve needle, and relates to the field of high-speed steel heat treatment. High-speed steel continuous resistance furnace heat treatment processing; high-speed steel is straightened, straightened and cut off on line; and performing subzero treatment on the high-speed steel straight rod. According to the SKH51 high-speed steel treated through the method, internal carbide distribution is more uniform and fine, a quenched martensite structure and a part of retained austenite structure are fully tempered and converted into tempered martensite, and the content of a small amount of retained austenite is accurately controlled, so that the high hardness is guaranteed, and meanwhile, the service life of the SKH51 high-speed steel is prolonged. The toughness, the fatigue resistance and the dimensional stability of the material are greatly improved; the high-end precision valve needle processed by the high-speed steel has the advantages that the wear resistance is obviously enhanced, the fatigue resistance is outstanding, and the service life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of high-speed steel heat treatment, and more particularly to a method for heat treatment of high-speed steel for precision valve needles. Background Technology

[0002] Currently, the following two traditional processes are mainly used for heat treatment of SKH51 high-speed steel in the market: The first method involves using traditional closed quenching and tempering furnaces for heat treatment. This process has the following problems: (1) The furnace capacity is limited, the heat treatment cycle is long, and the overall operation is complicated. The material must first be hoisted into the quenching furnace or salt bath furnace for quenching, kept at a certain temperature for a certain time, then taken out and cooled, and then put into the tempering furnace for tempering. The production process is complicated and the output of a single furnace is low.

[0003] (2) The whole process has many uncertainties and is difficult to control precisely. Product quality is easily unstable due to equipment failure or fluctuations in process parameters. If the steel is not cooled to the required level and comes into contact with air during hoisting and transfer, surface decarburization is likely to occur, resulting in batch defects.

[0004] (3) Due to the limitations of the equipment structure, steel is prone to deformation and bending when heated and cooled in a vertical hoisting state. It is difficult to straighten it when it is subsequently processed into precision parts such as valve needles, which affects the finished product qualification rate.

[0005] The second method uses high-frequency induction heating, which uses the instantaneous high temperature generated by the induction coil to rapidly quench and temper SKH51 high-speed steel, achieving a surface hardness of 58-62 HRC. This process also has significant drawbacks: (1) The heating time of the induction coil is extremely short. Although it can make the material reach the required hardness, the metallographic structure transformation is insufficient and the tempering is inadequate, resulting in uneven internal structure of the material. It is impossible to obtain the required comprehensive mechanical properties, and the strength and toughness are both low.

[0006] (2) Induction coil heating itself is prone to uneven temperature distribution, which often leads to uneven material hardness and local hardness failure. Once the hardness is inconsistent, the entire batch of materials needs to be reprocessed, which affects production efficiency and cost.

[0007] Therefore, existing SKH51 high-speed steel products generally suffer from problems such as high brittleness, easy flattening and warping, insufficient toughness, and poor surface wear resistance during production. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a heat treatment processing method for high-speed steel used in precision valve needles. By optimizing the heat treatment process parameters and procedures, the surface toughness and overall hardness uniformity of SKH51 high-speed steel are significantly improved, and its internal metallographic structure and comprehensive properties are fundamentally optimized.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A method for heat-treating precision valve needles using high-speed steel includes the following steps: High-speed steel wire rod raw material drawing and annealing process; Continuous resistance furnace heat treatment of high-speed steel; Online stretching, straightening, and cutting of high-speed steel; Cryogenic treatment of high-speed steel straight bars.

[0010] The high-speed steel coil raw material drawing and annealing process includes: firstly, sandblasting the surface of the high-speed steel coil raw material using a wire shot blasting machine to remove oxide scale, floating rust, and other impurities from the raw material surface, preventing impurities from entering the drawing die during the subsequent drawing and sizing process and causing scratches on the surface of the high-speed steel; secondly, performing the first drawing and sizing of the sandblasted high-speed steel using a combined drawing machine; thirdly, annealing the high-speed steel using a pit-type annealing furnace, setting the annealing temperature to 840-860℃ and the holding time to 4-5 hours; and finally, performing a second drawing and sizing of the annealed high-speed steel using the combined drawing machine.

[0011] The combined drawing machine uses diamond molds to draw high-speed steel. During the drawing process, drawing oil is used for lubrication to ensure that the surface of the high-speed steel is smooth and free of defects after drawing.

[0012] The continuous resistance furnace heat treatment process for high-speed steel includes: S1. High-speed steel is quenched and heat-treated using a box-type resistance furnace: the high-speed steel is inserted into the furnace tube and conveyed forward with the furnace tube; the quenching temperature is set to 1130-1160℃ and the quenching time is 5-12 minutes. S2. The high-speed steel material after quenching and heat treatment is cooled by water along with the furnace tube. The water cooling is completed in the cooling water tank. The cooling water inside the cooling water tank is in an infinite circulation mode to ensure that the temperature of the cooling water is controlled below 30℃. S3. The high-speed steel that has reached room temperature is put into the first box-type tempering furnace along with the furnace tube for a first tempering heat treatment. The first tempering temperature is 580-620℃ and the tempering time is 40-60 minutes. S4. The high-speed steel material after the first tempering is cooled by water along with the furnace tube. The water cooling is completed in the cooling water tank. The cooling water inside the cooling water tank is in an infinite circulation mode to ensure that the temperature of the cooling water is controlled below 30℃. S5. The high-speed steel that has reached room temperature is put into the second box-type tempering furnace along with the furnace tube for secondary tempering heat treatment. The secondary tempering temperature is 580-620℃ and the tempering time is 30-40 minutes. S6. The high-speed steel after secondary tempering is cooled by water along with the furnace tube. The water cooling is completed in the cooling water tank, and the cooling water inside the cooling water tank is in an infinite circulation mode to control the temperature of the cooled steel at 280-320℃.

[0013] The box-type resistance furnace is 8 meters long, with a thermocouple installed every meter; the first box-type tempering furnace is 12 meters long, with a thermocouple installed every meter; the second box-type tempering furnace is 6 meters long, with a thermocouple installed every meter; the thermocouples are used to monitor the actual temperature inside the furnace.

[0014] The online stretching, straightening, and cutting process of high-speed steel includes: removing the furnace tube from the cooled high-speed steel and stretching and straightening it using a stretching and straightening device; and cutting the high-speed steel to length using a cutting device according to production requirements to obtain high-speed steel straight bars.

[0015] The cryogenic treatment steps for the high-speed steel straight bars include: bundling and fixing the high-speed steel straight bars after they have been cut to length, placing them in a cryogenic device, introducing liquid nitrogen into the device, and lowering the temperature to -185°C at a rate of 0.25-0.5°C per minute for 12 hours; then keeping them at that temperature for 24-36 hours, and then slowly raising them to room temperature at a rate of 0.25-0.5°C per minute.

[0016] The straightening device includes a motor, a reducer, a gearbox, a transmission gear, a coupling, a drive roller shaft, and rollers. The motor is connected to the reducer, which drives the reducer to slow down the rotation speed. The reducer is connected to the transmission gear in the gearbox, which drives the upper and lower couplings to rotate. The upper and lower couplings are respectively connected to the upper and lower drive roller shafts and drive the two drive roller shafts to rotate. The rollers include an upper roller and a lower roller. The upper and lower drive roller shafts are respectively fixedly connected to the upper and lower rollers. High-speed steel passes between the upper and lower rollers.

[0017] The straightening device also includes a handwheel, an adjusting wall plate, and a driven roller shaft. The adjusting wall plate is fixedly connected to both ends of the upper driving roller shaft and the upper driven roller shaft. The handwheel is connected to the adjusting wall plate, and rotating the handwheel can adjust the position of the adjusting wall plate up and down to straighten high-speed steel of different diameters. The driven roller shaft can provide uniform support to prevent the high-speed steel from deforming due to its own weight. The rollers of the driven roller shaft and the rollers of the driving roller shaft are paired to form a clamping area. By applying pressure to the high-speed steel, sufficient friction is generated to ensure that the high-speed steel can be reliably "grabbed" and pulled forward by the driving roller, preventing slippage. The forward pulling force of the driving roller shaft on the steel and the backward resistance of the driven roller shaft on the steel generate relative forces at both ends of the steel, thereby achieving the effect of straightening the heat-treated steel.

[0018] The beneficial effects of this invention are: 1. This invention significantly improves the surface toughness and overall hardness uniformity of high-speed steel by optimizing heat treatment process parameters and procedures, and fundamentally optimizes its internal metallographic structure and comprehensive properties. High-end precision valve needles processed from this high-speed steel have the advantages of significantly enhanced wear resistance, outstanding fatigue resistance, and extended service life.

[0019] 2. This invention, through innovative heat treatment process design, effectively overcomes the inherent defects of traditional processes, such as insufficient microstructure transformation, uneven heating, and cumbersome procedures. SKH51 high-speed steel treated by this method exhibits a more uniform and finer distribution of carbides within its structure. The quenched martensite and some retained austenite are fully tempered and transformed into tempered martensite, with precise control over the content of a small amount of retained austenite. This significantly improves the material's toughness, fatigue strength, and dimensional stability while maintaining high hardness.

[0020] 3. This invention employs a water-cooling method, which aims to cool high-speed steel to a specified temperature within a limited cooling time while avoiding damage to its internal structure and surface quality due to drastic energy changes. Compared to natural cooling and air cooling, water cooling significantly shortens the cooling time while still falling into the category of slow cooling, thus ensuring the orderly and rational progress of the microstructure transformation process.

[0021] 4. In this invention, the high-speed steel is straightened when it is cooled to 280-320℃. If the temperature is too high, the high-speed steel is too soft and is prone to elliptical deformation after passing through the mechanical pressure rollers. If the temperature is too low, the material is too hard and is prone to incomplete straightening, resulting in defects such as S-bends or large bends.

[0022] 5. This invention employs a two-stage tempering process to ensure that the metallographic structure of high-speed steel can be fully transformed, which can significantly improve its toughness and bending resistance while maintaining the hardness of the steel.

[0023] 6. In the continuous resistance furnace heat treatment process of high-speed steel, the present invention sets the corresponding wire speed according to the different specifications of high-speed steel to ensure sufficient quenching and tempering time so that the high-speed steel can reach the predetermined hardness.

[0024] 7. The cryogenic treatment process employed in this invention can reduce the retained austenite content to below 2%, thereby eliminating the adverse effects of retained austenite. Cryogenic treatment also promotes the filling of internal voids by tempered martensite, making the metal surface denser; simultaneously, it increases the wear-resistant area, fines the grains, and ensures uniform precipitation of alloy components, increasing the depth of the quenched layer. Cryogenic treatment can precipitate carbide particles, increasing the strength and toughness of the metal material. Attached Figure Description

[0025] Figure 1This is a left view of the straightening and stretching device in this invention; Figure 2 This is a top view of the straightening and stretching device in this invention; Figure 3 This is a comparison table between the present invention and traditional heat treatment processes; The components are: 1. Motor; 2. Reducer; 3. Gearbox; 4. Transmission gear; 5. Coupling; 6. Drive roller shaft; 7. Roller; 8. Handwheel; 9. Adjusting wall plate; 10. Driven roller shaft. Detailed Implementation

[0026] The following is in conjunction with the appendix Figure 1 —2 The technical solutions of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0028] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used only for distinction and should not be construed as indicating or implying relative importance.

[0029] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Example 1 A method for heat-treating precision valve needles using high-speed steel includes the following steps: High-speed steel wire rod raw material drawing and annealing process; Continuous resistance furnace heat treatment of high-speed steel; Online stretching, straightening, and cutting of high-speed steel; Cryogenic treatment of high-speed steel straight bars.

[0031] The high-speed steel coil raw material drawing and annealing process includes: firstly, sandblasting the surface of the high-speed steel coil raw material using a wire shot blasting machine to remove oxide scale, rust, and other impurities from the raw material surface, preventing impurities from entering the drawing die during the subsequent drawing and sizing process and causing scratches on the surface of the high-speed steel, thus ensuring a smooth steel surface; secondly, performing the first drawing and sizing of the sandblasted high-speed steel using a combined drawing machine; thirdly, annealing the high-speed steel using a pit-type annealing furnace, setting the annealing temperature to 840-860℃ and the holding time to 4-5 hours, which can remove the internal stress of the drawn high-speed steel and reduce its hardness, preventing the steel from cracking due to excessive stress during subsequent heat treatment; and finally, performing a second drawing and sizing of the annealed high-speed steel using a combined drawing machine.

[0032] The combined drawing machine uses diamond dies to draw high-speed steel. During the drawing process, drawing oil is used for lubrication to ensure that the surface of the high-speed steel is smooth and defect-free after drawing, and to ensure that the diameter tolerance of the steel is +0.02 / 0 and the ellipticity is <0.01mm.

[0033] The continuous resistance furnace heat treatment process for the high-speed steel is as follows: S1. The drawn high-speed steel coils are placed on a transfer tray. The drive motor under the transfer tray rotates slowly, providing forward conveying power to thread the high-speed steel into the furnace tube, which then moves forward with the furnace tube. A box-type resistance furnace is used for quenching heat treatment of the high-speed steel. The high-speed steel, along with the furnace tube, is conveyed through the box-type resistance furnace to a traction device in front of the furnace outlet. The traction device continues to move the high-speed steel and furnace tube forward. The appropriate conveying speed is set according to the different specifications of the steel to ensure that each specification of high-speed steel receives sufficient quenching time. The box-type resistance furnace is set to a quenching temperature of 1150℃. The quenching time for φ2.3 high-speed steel is 5 minutes, and the quenching time for φ12.3 high-speed steel is 12 minutes. The hardness of the quenched high-speed steel reaches 65HRC.

[0034] S2. The high-speed steel material after quenching and heat treatment is cooled by water along with the furnace tube; the water cooling is completed in the cooling water tank, which is made of 304 stainless steel and bent into shape. The tank is equipped with an inlet and an outlet, connected to the corresponding pipelines, and designed as an internal infinite circulation mode of cooling water to ensure that the temperature of the cooling water is controlled below 30℃. After this cooling process is completed, the temperature of the steel material has dropped to room temperature.

[0035] S3. The high-speed steel material that has reached room temperature is put into the first box-type tempering furnace along with the furnace tube for a first tempering heat treatment. The first tempering temperature is 600℃. The tempering time for φ2.3 high-speed steel material is 40 minutes, and the tempering time for φ12.3 high-speed steel material is 60 minutes. The hardness of the high-speed steel material after tempering reaches 58-62HRC. S4. The high-speed steel after the first tempering is cooled by water along with the furnace tube. The water cooling is completed in the cooling water tank. The cooling water inside the cooling water tank is in an infinite circulation mode to ensure that the temperature of the cooling water is controlled below 30℃. After this cooling process is completed, the temperature of the steel has dropped to room temperature. S5. The high-speed steel material that has reached room temperature is introduced into the second-stage box-type tempering furnace along with the furnace tube for secondary tempering heat treatment. The secondary tempering temperature is 580℃ and the tempering time is 40 minutes. This ensures that the metallographic structure of the high-speed steel material is further fully transformed, and that the high-speed steel material has stronger toughness and bending resistance without reducing its hardness.

[0036] S6. The high-speed steel after the second tempering is cooled by water along with the furnace tube. The water cooling is completed in the cooling water tank, and the cooling water inside the cooling water tank is in an infinite circulation mode. The temperature of the steel after this cooling process is about 300℃.

[0037] The box-type resistance furnace is 8 meters long, with a thermocouple installed every meter; the first box-type tempering furnace is 12 meters long, with a thermocouple installed every meter; the second box-type tempering furnace is 6 meters long, with a thermocouple installed every meter. The thermocouples are used to monitor the actual temperature inside the furnace, and they transmit the actual temperature inside the furnace to the temperature display on the distribution cabinet for real-time monitoring of the furnace temperature.

[0038] The online straightening and cutting process for high-speed steel involves removing the furnace tubes from the cooled high-speed steel and straightening it using a straightening device. According to production requirements, the high-speed steel is then cut to length using a cutting device to obtain straight high-speed steel bars. The high-speed steel needs to be straightened within the optimal straightening time period, which is when the steel cools to 300℃. This is also the optimal straightening temperature range. If the temperature is too high, the steel is too soft and easily deforms after passing through the mechanical rollers, resulting in an elliptical product. If the temperature is too low, straightening may be incomplete, leading to S-bends or large bends. The cutting device (patent CN202120155030.5 of our company) is set to a fixed length. When the high-speed steel material reaches the sensor position, the device receives a cutting signal. The cylinder controls the fixed clamping block to clamp the high-speed steel material, the electric spindle controls the saw to rotate, and the stepper motor controls the entire cutting system to move downward to complete the cutting. During the cutting, the entire cutting device also moves forward with the high-speed steel material to ensure that the cut high-speed steel material is in a straight state. After cutting, it resets to the initial state.

[0039] The cryogenic treatment steps for the high-speed steel straight bars are as follows: The cut high-speed steel straight bars are bundled into 50kg bundles and secured tightly from top to bottom with wire to prevent deformation during the process. They are then placed in a cryogenic nitriding furnace, through which liquid nitrogen is introduced, lowering the temperature to -185°C at a rate of 0.3°C per minute for 12 hours. The temperature is then held at this temperature for 30 hours, followed by a slow increase to room temperature at a rate of 0.3°C per minute. Generally, the temperature is raised to room temperature during the heating phase. However, if the components manufactured from the high-speed steel straight bars have special applications, such as operating at higher temperatures, the temperature can be further increased to 160°C.

[0040] The purpose of the slow cooling stage is to completely eliminate residual stress. During quenching and tempering, residual stress is generated within the metal matrix. The volume expansion during the transformation of retained austenite into tempered martensite also increases residual stress. Only slow cooling can offset this increase and completely eliminate residual stress. Residual stress within the matrix is ​​generally not considered important, but it is precisely this residual stress that causes defects such as chipping in cutlery products. Rapid cooling will actually increase residual stress.

[0041] The purpose of the holding stage is to transform as much of the retained austenite in the matrix as possible into tempered martensite and to generate as many carbide particles as possible. Because the transformation of retained austenite into tempered martensite is a slow process, the length of the holding time will affect the amount of retained austenite transformation. At the same time, the lifespan after cryogenic treatment is mainly determined by the length of the holding time. Under normal circumstances, performance is improved after 2 to 4 hours of holding. However, for high-quality products, a holding time of more than 24 hours is required. The increase in lifespan is directly related to the length of the holding time.

[0042] The straightening and straightening device includes a motor 1, a reducer 2, a gearbox 3, a transmission gear 4, a coupling 5, a drive roller shaft 6, and rollers 7. The motor 1 is connected to the reducer 2, and the motor 1 drives the reducer 2 to slow down the speed. The reducer 2 is connected to the transmission gear 4 in the gearbox 3. The gear transmission 4 drives the upper and lower couplings 5 ​​to rotate. The upper and lower couplings 5 ​​are respectively connected to the upper and lower drive roller shafts 6 and drive the two drive roller shafts 6 to rotate. The rollers 7 include an upper roller and a lower roller. The upper and lower drive roller shafts 6 are respectively fixedly connected to the upper roller and the lower roller of the roller 7. High-speed steel passes through the groove between the upper roller and the lower roller of the roller 7.

[0043] The straightening device also includes a handwheel 8, an adjusting wall plate 9, and a driven roller shaft 10. The adjusting wall plate 9 is fixedly connected to both ends of the upper driving roller shaft 6 and the upper driven roller shaft 10. The handwheel 8 is connected to the adjusting wall plate 9. Rotating the handwheel 8 can adjust the position of the adjusting wall plate 9 up and down for straightening high-speed steel of different diameters. The driven roller shaft 10 can provide uniform support to prevent the high-speed steel from deforming due to its own weight. The rollers 7 of the driven roller shaft 10 and the rollers 7 of the driving roller shaft 6 are paired to form a clamping area. By applying pressure to the high-speed steel, sufficient friction is generated to ensure that the high-speed steel can be reliably "grabbed" and pulled forward by the driving roller, preventing slippage. The forward pulling force of the driving roller shaft on the steel and the backward resistance of the driven roller shaft on the steel generate relative forces at both ends of the steel, thereby achieving the effect of straightening the heat-treated steel.

[0044] The straightening and tensioning device can be set up in parallel with 4 rows, which reduces the floor space required. At the same time, it can handle the straightening, tensioning and conveying of 4 groups of high-speed steel, thus improving work efficiency.

[0045] The working process of the straightening device is as follows: The upper and lower rollers of roller 7 form the straightening component. Motor 1 provides rotational kinetic energy to roller 7. When the high-speed steel material passes through the groove between the upper and lower rollers, it is driven forward by roller 7. This process not only straightens the high-speed steel material but also serves as the power source for the entire production line, continuously dragging the high-speed steel material forward. The vertical position of the wall plate 9 is adjusted by rotating the handwheel 8, thereby achieving the purpose of clamping the material and stably conveying it forward. In addition, roller 7 can be replaced according to different specifications of high-speed steel material, and the traction force can be changed by adjusting the speed of motor 1.

[0046] This invention significantly improves the surface toughness and overall hardness uniformity of high-speed steel by optimizing heat treatment process parameters and procedures, and fundamentally optimizes its internal metallographic structure and comprehensive properties. High-end precision valve needles processed from this high-speed steel exhibit significantly enhanced wear resistance, excellent red hardness, outstanding fatigue resistance, and extended service life.

[0047] This invention, through innovative heat treatment process design, effectively overcomes the inherent defects of traditional processes, such as insufficient microstructure transformation, uneven heating, and cumbersome procedures. SKH51 high-speed steel treated by this method exhibits a more uniform and finer distribution of carbides within its structure. The quenched martensite and some retained austenite are fully tempered, transforming into tempered martensite. The content of a small amount of retained austenite is precisely controlled, thereby significantly improving the material's toughness, fatigue strength, and dimensional stability while maintaining high hardness.

[0048] This invention employs a water-cooling method, which aims to cool high-speed steel to a specified temperature within a limited cooling time while avoiding damage to its internal structure and surface quality due to drastic energy changes. Compared to natural cooling and air cooling, water cooling significantly shortens the cooling time while still falling into the category of slow cooling, thus ensuring that the microstructure transformation process proceeds in an orderly and rational manner.

[0049] This invention employs a two-stage tempering process to ensure that the metallographic structure of high-speed steel can be fully transformed, thereby significantly improving its toughness and bending resistance while maintaining the hardness of the steel.

[0050] In the continuous resistance furnace heat treatment process of high-speed steel, the present invention sets the corresponding wire speed according to the different specifications of high-speed steel to ensure sufficient quenching and tempering time so that the high-speed steel can reach the predetermined hardness.

[0051] The cryogenic treatment process used in this invention can reduce the content of retained austenite to below 2%, thereby eliminating the adverse effects of retained austenite.

[0052] The high-speed steel used in this embodiment is SKH51 high-speed steel.

[0053] like Figure 3 As shown in the comparison table between the present invention and traditional heat treatment processes, the present invention has significant improvements and advantages in terms of straightness, yield, service life, output, and metallographic structure.

[0054] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims. Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for heat-treating precision valve needles using high-speed steel, characterized in that, Includes the following steps: High-speed steel wire rod raw material drawing and annealing process; Continuous resistance furnace heat treatment of high-speed steel; Online stretching, straightening, and cutting of high-speed steel; Cryogenic treatment of high-speed steel straight bars.

2. The method for heat treatment of high-speed steel for precision valve needles according to claim 1, characterized in that, The high-speed steel coil raw material drawing and annealing process includes: firstly, sandblasting the surface of the high-speed steel coil raw material using a wire shot blasting machine; secondly, drawing and sizing the sandblasted high-speed steel using a combined drawing machine; thirdly, annealing the high-speed steel using a pit-type annealing furnace, setting the annealing temperature to 840-860℃ and the holding time to 4-5 hours; and fourthly, drawing and sizing the annealed high-speed steel using a combined drawing machine.

3. The method for heat treatment of high-speed steel for precision valve needles according to claim 2, characterized in that, The combined drawing machine uses diamond molds to draw high-speed steel. During the drawing process, drawing oil is used for lubrication to ensure that the surface of the high-speed steel is smooth and free of defects after drawing.

4. The method for heat treatment of high-speed steel for precision valve needles according to claim 1, characterized in that, The continuous resistance furnace heat treatment process for high-speed steel includes: S1. High-speed steel is quenched and heat-treated using a box-type resistance furnace: the high-speed steel is inserted into the furnace tube and conveyed forward with the furnace tube; the quenching temperature is set to 1130-1160℃ and the quenching time is 5-12 minutes. S2. The high-speed steel material after quenching and heat treatment is cooled by water along with the furnace tube, and the temperature of the cooling water is controlled below 30℃. S3. The high-speed steel that has reached room temperature is put into the first box-type tempering furnace along with the furnace tube for a first tempering heat treatment. The first tempering temperature is 580-620℃ and the tempering time is 40-60 minutes. S4. After the high-speed steel is tempered once, it is cooled by water along with the furnace tube. The temperature of the cooling water is controlled below 30°C. S5. The high-speed steel that has reached room temperature is put into the second box-type tempering furnace along with the furnace tube for secondary tempering heat treatment. The secondary tempering temperature is 580-620℃ and the tempering time is 30-40 minutes. S6. After secondary tempering, the high-speed steel is cooled by water along with the furnace tube, and the temperature of the cooled steel is controlled at 280-320℃.

5. The method for heat treatment of high-speed steel for precision valve needles according to claim 4, characterized in that, The box-type resistance furnace is 8 meters long, with a thermocouple installed every meter; the first box-type tempering furnace is 12 meters long, with a thermocouple installed every meter; the second box-type tempering furnace is 6 meters long, with a thermocouple installed every meter; the thermocouples are used to monitor the actual temperature inside the furnace.

6. The method for heat treatment of high-speed steel for precision valve needles according to claim 1, characterized in that, The online stretching, straightening, and cutting process for high-speed steel includes: stretching and straightening the cooled high-speed steel using a stretching and straightening device; and cutting the high-speed steel to length using a cutting device according to production requirements.

7. The method for heat treatment of high-speed steel for precision valve needles according to claim 1, characterized in that, The cryogenic treatment steps for the high-speed steel straight bars include: bundling and fixing the high-speed steel straight bars after they have been cut to length, placing them in a cryogenic device, introducing liquid nitrogen into the device, and lowering the temperature to -185°C at a rate of 0.25-0.5°C per minute for 12 hours; then keeping them at that temperature for 24-36 hours, and then slowly raising them to room temperature at a rate of 0.25-0.5°C per minute.

8. The method for heat treatment of high-speed steel for precision valve needles according to claim 6, characterized in that, The straightening device includes a motor (1), a reducer (2), a gearbox (3), a transmission gear (4), a coupling (5), a drive roller shaft (6), and a roller (7). The motor (1) is connected to the reducer (2), and the motor (1) drives the reducer (2) to slow down the speed. The reducer (2) is connected to the transmission gear (4) in the gearbox (3), and the transmission gear (4) drives the upper and lower couplings (5) to rotate. The upper and lower couplings (5) are respectively connected to the upper and lower drive roller shafts (6) and drive the two drive roller shafts (6) to rotate. The roller (7) includes an upper roller and a lower roller. The upper and lower drive roller shafts (6) are respectively fixedly connected to the upper roller and the lower roller of the roller (7). High-speed steel passes between the upper roller and the lower roller of the roller (7).

9. A method for heat-treating precision valve needles using high-speed steel according to claim 8, characterized in that, The straightening device also includes a handwheel (8), an adjusting wall plate (9), and a driven roller shaft (10). The adjusting wall plate (9) is fixedly connected to both ends of the upper driving roller shaft (6) and the upper driven roller shaft (10). The handwheel (8) is connected to the adjusting wall plate (9). Rotating the handwheel (8) can adjust the position of the adjusting wall plate (9) up and down. It can be used to straighten high-speed steel of different diameters. The driven roller shaft (10) can provide uniform support to prevent the high-speed steel from deforming due to its own weight. The rollers of the driven roller shaft (10) are paired with the rollers of the driving roller shaft (6) to form a clamping area.

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