Heat treatment process for forged powder metallurgy high-speed steel

Abstract

The invention relates to the technical field of powder metallurgy, in particular to a heat treatment process for forged powder metallurgy high-speed steel, which comprises the following steps: putting an HOP 10V material subjected to upsetting, die forging and correction in sequence into a vacuum furnace for annealing, and then sequentially carrying out quenching, first tempering, second tempering and third tempering on the annealed HOP 10V material, the HOP 10V material subjected to third tempering is subjected to surface treatment, and the process is completed; according to the method, the annealing system is optimized, so that the HOP10V material fully releases thermal stress brought by thermal processing in the cooling process, meanwhile, the lower the cooling speed is, the closer to the recrystallization equilibrium state is, the structure is more uniform and refined, and the overall performance of the material is also improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of powder metallurgy, in particular to a heat treatment process for powder metallurgy high-speed steel after forging. BACKGROUND

[0002] With the development and progress of science and technology, the pump structure of the fuel control system of an aero-engine is changed from a plunger pump to a centrifugal pump and a gear pump structure, and the oil pump gear, as a core part of the fuel accessory gear pump of the engine control system, is a key component for converting mechanical energy into kinetic energy and pressure energy of liquid, and is a key component for affecting the overall service life of the gear pump.

[0003] Through design analysis, experimental verification and foreign technology reference, the gear material is changed from the original alloy steel 2Cr3WMoV and 38CrMoAlA to super-hard high-temperature powder metallurgy material HOP10V. Through preliminary investigation, the HOP10V material is currently mainly used in key parts materials in the field of plastic machinery, such as screws of injection molding machines, building block screws and sleeves of extruders, and wear-resistant parts. The excellent material hardness and wear resistance of the material have great potential in the direction of aviation oil pump gears. Relying on the excellent wear resistance and good toughness of the material and a series of material advantages, the working life of the fuel pump can be greatly prolonged. The material has been applied in many fuel pump products.

[0004] The system of powder metallurgy high-vanadium steel currently follows the system of high-speed steel and other materials, but due to the characteristics of powder metallurgy, the heat treatment system of the steel manufactured by melting cannot fully meet the needs of the use of this material. Therefore, the present application decides to design a heat treatment process for powder metallurgy high-speed steel after forging to meet the material needs. SUMMARY

[0005] To solve the above problems, the present application provides a heat treatment process for powder metallurgy high-speed steel after forging.

[0006] A heat treatment process for powder metallurgy high-speed steel after forging, comprising the following steps:

[0007] The HOP 10V material after top forging, die forging and correction is placed in a vacuum furnace for annealing, the annealing method is: keeping at 865-875 DEG C for 2.5-3.5 h, then cooling to 750 DEG C at a speed of ≤7 DEG C / h, then cooling to 540 DEG C at a speed of ≤15 DEG C / h, then cooling to 75-85 DEG C by argon fan, and finally air cooling to room temperature after taking out of the furnace;

[0008] Then the annealed HOP 10V material is quenched, the quenching temperature is 1045-1055℃, the quenching time is 60-90min, oil cooling to room temperature; after quenching, the first tempering is carried out, the first tempering temperature is 595-605℃, the first tempering time is 120-150min, air cooling to room temperature; after the first tempering, the second tempering is carried out, the second tempering temperature is 635-645℃, the second tempering time is 120-150min, air cooling to room temperature; after the second tempering, the third tempering is carried out, the third tempering temperature is 640-650℃, the third tempering time is 120-150min, air cooling to room temperature;

[0009] Then the HOP 10V material after the third tempering is subjected to surface treatment, and the process is completed.

[0010] Further, the steps of heading, die forging and correcting are as follows:

[0011] S1, heading:

[0012] The blank is heated to 1110-1130℃ as the initial forging temperature, and after heat preservation for 20-80min, the blank is subjected to heading: first, the blank is placed longitudinally for heading forming, then the blank is turned over again for heading forming, the striking energy of the two times of heading is 40-60%, the deformation amount of the two times of heading is 25-35%, the final forging temperature is 900-1000℃, and after the heading is completed, the blank is subjected to gray cooling and surface treatment;

[0013] S2, die forging:

[0014] The blank obtained in step S1 is heated to 1110-1130℃ as the initial forging temperature, and after heat preservation for 30-90min, the blank is subjected to die forging, the striking energy is 40-60%, the deformation amount is 25-35%, the final forging temperature is 900-1000℃, and after the die forging is completed, the blank is subjected to gray cooling, edge cutting and surface treatment;

[0015] S3, correction:

[0016] The blank obtained in step S2 is heated to 890-910℃, and after heat preservation for 8-20min, the blank is subjected to correction, the striking energy is 10-30%, the deformation amount is 0-1.5%, the final forging temperature is 850-910℃, and after the correction is completed, the blank is subjected to gray cooling and surface treatment.

[0017] Explanation: The above forging method can effectively reduce the consumption of raw materials and reduce the machining cost.

[0018] Further, in S1, the surface treatment method comprises: shot blasting-polishing-shot blasting.

[0019] Note: Remove oil stains, dirt and surface residual coating on the surface of the forging by shot blasting; polish the surface of the forging to remove cracks, folds and other defects. Pay attention to the smooth transition of the defect-removed area and the surrounding area.

[0020] Further, in S2, the surface treatment method comprises sand blasting-polishing-shot blasting.

[0021] Note: Remove oil stains, dirt and surface residual coating on the surface of the forging by shot blasting; polish the surface of the forging to remove cracks, folds and other defects. Pay attention to the smooth transition of the defect-removed area and the surrounding area.

[0022] Further, in S2, when trimming, the residual flash and over-trim amount of the HOP 10V material are ≤0.3mm.

[0023] Note: Ensure that the trimmed forging is free of defects such as crushing, stretching and over-trimming.

[0024] Further, in S3, the surface treatment method comprises sand blasting.

[0025] Note: Remove oil stains, dirt and surface residual coating on the surface of the forging by shot blasting; polish the surface of the forging to remove cracks, folds and other defects. Pay attention to the smooth transition of the defect-removed area and the surrounding area.

[0026] Further, the surface treatment method comprises sand blasting-polishing-shot blasting.

[0027] Note: Remove oil stains, dirt and surface residual coating on the surface of the forging by shot blasting; polish the surface of the forging to remove cracks, folds and other defects. Pay attention to the smooth transition of the defect-removed area and the surrounding area.

[0028] Further, in S4, after annealing and before quenching, the annealed HOP 10V material is subjected to surface strengthening treatment:

[0029] First, the annealed HOP 10V material is subjected to ultrasonic rolling, with a working static pressure of 300-320N, a rotation speed of 160-180r / min, a transverse feed rate of 0.2-0.4mm / min and 3-5 rolling times. Then, the ultrasonic-rolled HOP 10V material is subjected to a phased composite treatment, which comprises alternating shot blasting and deep cryogenic treatment, as follows:

[0030] The first stage: the shot diameter d1 is 0.3-0.5mm, the shot intensity I1 is 0.1-0.15MPa, and the shot time is 6-8min,

[0031] The second stage: the shot diameter d2 is 0.6-0.8mm, the shot intensity I2 is 0.2-0.25MPa, and the shot time is 10-12min,

[0032] The third stage: the shot diameter d3 is 0.8-1.0mm, the shot intensity I3 is 0.3-0.35MPa, and the shot time is 14-16min,

[0033] And the temperature T of the deep cooling treatment i =-80-(30×I i ), unit: ℃, the time t of the deep cooling treatment i =40+(15+d i ), unit: min, i is 1, 2, 3;

[0034] The surface strengthening treatment is completed.

[0035] Description: The ultrasonic rolling can reduce the surface roughness of the material, eliminate the surface defects after annealing, and provide a uniform substrate for subsequent composite treatment; the small-diameter shot and low-intensity shot in the first stage can further refine the surface layer grains on the basis of the plastic deformation layer formed by ultrasonic rolling, and the shot diameter and the surface roughness of ultrasonic rolling are matched to avoid damage to the flattened surface by excessive impact; the shot diameter and intensity increase in the second stage, which can expand the depth of the strengthening layer and form a continuous gradient with the deformation layer of ultrasonic rolling, avoiding the performance mutation of the strengthening layer and the substrate; the maximum shot diameter and intensity in the third stage can induce higher dislocation density in the surface layer, and promote the further dispersion distribution of carbides in the subsurface layer, increase the depth of the strengthening layer, and meet the demand of HOP 10V as a high-speed steel for deep strengthening; HOP 10V contains high vanadium (V) element, and the deep cooling temperature can promote the transformation of residual austenite to martensite, and avoid the brittleness of carbide precipitation caused by ultra-low temperature, at the same time, the temperature decreases with the increase of shot intensity, which can match the stress gradient introduced by shot peening, and realize layered stress release; the deep cooling time takes into account the gas escape in the pore of powder metallurgy steel and the kinetics demand of martensite transformation, and the longer treatment time can make the surface layer martensite uniformly distributed, reduce the micro-cracks caused by uneven transformation, and cooperate with the dislocation structure formed by shot peening to enhance the wear resistance.

[0036] Further, in the first stage, the shot for shot peening is a glass shot, and in the second and third stages, the shot for shot peening is a cast iron shot.

[0037] Explanation: The glass projectile has the characteristics of low impact and high uniformity, which is suitable for the first stage of fine strengthening, protects the surface quality after ultrasonic rolling and realizes uniform initial stress introduction; the cast iron projectile has the advantages of high hardness and high density, which is suitable for the second and third stages of high strength and deep strengthening, and efficiently improves the fatigue resistance and wear resistance of HOP 10V material.

[0038] Compared with the existing heat treatment method of powder metallurgy high-speed steel, the beneficial effects of the present application are:

[0039] (1) The optimization of the annealing system in the present application makes the HOP10V material fully release the thermal stress caused by hot working during the cooling process, and the lower the cooling speed, the closer to the recrystallization equilibrium state, the more uniform and refined the structure, and the overall performance of the material is also improved, so that the material is not prone to cracking and other conditions during subsequent processing, and after quenching and tempering, the impact toughness of the material is greater than or equal to 10J.

[0040] (2) After annealing, the material is subjected to cryogenic treatment, which can convert unstable and soft austenite into hard and brittle martensite, and provide a more stable and denser matrix for subsequent ultrasonic rolling and coating, reducing the instability and possible dimensional change caused by the decomposition of residual austenite during subsequent high-temperature treatment or service; ultrasonic rolling causes deep plastic deformation near the surface of the material, resulting in significant grain refinement in the deformation area, greatly improving the strength and hardness of the surface and near-surface, and effectively generating a high-amplitude and large-depth residual compressive stress field on the surface and subsurface of the material, which can offset or significantly reduce the tensile stress peak value generated by external load, greatly improving the fatigue life; finally, the magnetron sputtering coating forms a synergistic strengthening structure of "densified matrix surface layer with grain refinement + deep residual compressive stress field + coating layer", which has good strength and toughness.

[0041] (3) The present application firstly performs ultrasonic rolling on the returned materials, which can reduce the surface roughness of the materials, eliminate the surface defects after annealing, and provide a uniform base for subsequent composite processing; in the first stage, small diameter shot and low intensity shot peening can further refine the surface grains on the basis of the plastic deformation layer formed by ultrasonic rolling, and the shot diameter matches the surface roughness of ultrasonic rolling to avoid excessive impact and damage to the flattened surface; in the second stage, the shot diameter and intensity increase gradually, which can expand the depth of the strengthening layer and form a continuous gradient with the deformation layer of ultrasonic rolling to avoid sudden changes in the performance of the strengthening layer and the matrix; in the third stage, the maximum shot diameter and intensity can induce a higher dislocation density in the surface layer, and at the same time promote the further dispersion and distribution of subsurface carbides, thereby increasing the depth of the strengthening layer, meeting the deep strengthening requirements of HOP 10V as a high-speed steel; HOP 10V contains high vanadium (V) elements, and the deep cooling temperature can promote the transformation of retained austenite to martensite, and avoid the embrittlement of carbide precipitation caused by ultra-low temperature. At the same time, the temperature decreases with the increasing shot peening intensity, which can match the stress gradient introduced by shot peening and realize layered stress release; the deep cooling time takes into account the gas escape in the pores of powder metallurgy steel and the dynamic requirements of martensite transformation. The longer processing time can make the surface martensite evenly distributed, reduce the microcracks caused by uneven transformation, and synergistically enhance the wear resistance with the dislocation structure formed by shot peening. DETAILED DESCRIPTION

[0042] In order to further illustrate the approach and effects achieved by the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with experiments.

[0043] Example 1: A heat treatment process for powder metallurgy high-speed steel after forging, comprising the following steps:

[0044] The HOP 10V material, which has undergone top forging, die forging, and correction, was placed in a vacuum furnace for annealing. The annealing method was as follows: the material was kept at 870°C for 3 hours, then cooled to 750°C at a rate of 5°C / h, then cooled to 540°C at a rate of 10°C / h, and then cooled to 80°C using an argon fan. Finally, the material was taken out of the furnace and air-cooled to room temperature.

[0045] The annealed HOP 10V material is then quenched at a temperature of 1050°C for 75 minutes, and oil-cooled to room temperature. After quenching, the first tempering is performed at a temperature of 600°C for 135 minutes, and air-cooled to room temperature. After the first tempering, the second tempering is performed at a temperature of 640°C for 135 minutes, and air-cooled to room temperature. After the second tempering, the third tempering is performed at a temperature of 645°C for 135 minutes, and air-cooled to room temperature. Here, room temperature refers to 25°C.

[0046] After the third tempering, the HOP 10V material is subjected to surface treatment, the surface treatment method comprising: sand blasting-polishing-sand blasting, the polishing adopting steel shots with a time of 10 min, and the process is completed.

[0047] S1, top forging:

[0048] First, the HOP 10V blank with a diameter of φ40mm*125mm is rounded at both ends to R3, and then is roughly processed to have an end surface roughness of Ra3.2 at both ends. Then, the blank is heated to 1120℃ as a starting forging temperature, and is kept for 50 min. Then, the blank is subjected to top forging: the blank is longitudinally placed to be top forged, and then the blank is turned over to be top forged again. The striking energy of the two top forgings is 80 KJ, and the deformation amount of the two top forgings is 30%. The final forging temperature is 950℃, the deformation amount of the top forging is 30%, and after the top forging, the blank is subjected to ash cooling and surface treatment. The surface treatment method comprises: shot blasting-polishing-shot blasting, and the shot blasting and polishing adopt steel shots with a diameter of φ0.6mm and a time of 10 min.

[0049] S2, die forging:

[0050] The blank obtained in step S1 is heated to 1120℃ as a starting forging temperature, and is kept for 60 min. Then, the blank is subjected to die forging with a striking energy of 60 KJ and a deformation amount of 30%. The final forging temperature is 950℃. After the die forging, the blank is subjected to ash cooling, edge cutting and surface treatment. The residual flash and overcut amount of the blank after the edge cutting is 0.3mm. The surface treatment method comprises: sand blasting-polishing-shot blasting-shot blasting. The shot blasting and polishing both adopt steel shots with a diameter of φ0.6mm and a time of 10 min.

[0051] S3, correction:

[0052] The blank obtained in step S2 is heated to 900℃, and is kept for 14 min. Then, the blank is subjected to correction with a striking energy of 24 KJ and a deformation amount of 1%. The final forging temperature is 880℃. After the correction, the blank is subjected to ash cooling and surface treatment. The surface treatment method comprises: sand blasting.

[0053] In steps S1, S2 and S3, the transfer time of the blank obtained in each step to the next step is 10 s.

[0054] Example 2: The difference between this example and example 1 is that the blank is heated to 1120℃ as a starting forging temperature, and is kept for 20 min. Then, the blank is subjected to top forging with a final forging temperature of 900℃.

[0055] Example 3: The difference between this example and example 1 is that the blank is heated to 1130℃ as a starting forging temperature, and is kept for 80 min. Then, the blank is subjected to top forging with a final forging temperature of 1000℃.

[0056] Example 4: This example differs from Example 1 in that the blank obtained in step S1 is heated to 1110°C, and after heating and keeping warm for 30 minutes, the blank is die forged, and the final forging temperature of the die forging is 900°C.

[0057] Example 5: This example differs from Example 1 in that the blank obtained in step S1 is heated to 1130°C, heated and kept warm for 90 minutes, and then die forged, with the final forging temperature of the die forging being 1000°C.

[0058] Example 6: This example differs from Example 1 in that the billet obtained in step S2 is heated to 890°C, kept warm for 8 minutes, and then the billet is calibrated to a final forging temperature of 850°C.

[0059] Example 7: This example differs from Example 1 in that the billet obtained in step S2 is heated to 910°C, kept warm for 20 minutes, and then the billet is calibrated to a final forging temperature of 910°C.

[0060] Example 8: The difference between this example and Example 1 is that the impact energy of the two upset forgings is 64KJ, the deformation of the two upset forgings is 25%, the impact energy of the die forging is 48KJ, the deformation is 35%, and the corrected impact energy is 12KJ, and the deformation is 0%.

[0061] Example 9: The difference between this example and Example 1 is that the impact energy of the two upset forgings is 96KJ, the deformation of the two upset forgings is 35%, the impact energy of the die forging is 72KJ, the deformation is 25%, and the corrected impact energy is 36KJ, and the deformation is 1.5%.

[0062] Example 10: The difference between this example and Example 1 is that the temperature is kept at 865°C for 2.5 hours. After the temperature is kept, it is first cooled to 755°C at a rate of 7°C / h, then cooled to 545°C at a rate of 15°C / h, and then cooled to 85°C by an argon fan. Finally, it is taken out of the furnace and air-cooled to room temperature.

[0063] Example 11: The difference between this example and Example 1 is that the temperature is kept at 875℃ for 3.5 hours. After the temperature is kept, it is first cooled to 745℃ at a rate of 7℃ / h, then cooled to 535℃ at a rate of 15℃ / h, and then cooled to 75℃ by an argon fan. Finally, it is taken out of the furnace and air-cooled to room temperature.

[0064] Example 12: This example differs from Example 1 in that the annealed HOP 10V material is quenched at a temperature of 1045° C. for 60 min, and then oil-cooled to room temperature.

[0065] Example 13: The difference between this example and Example 1 is that after annealing, the HOP 10V material is quenched, the quenching temperature is 1055℃, the quenching time is 90min, and oil cooling to room temperature.

[0066] Example 14: The difference between this example and Example 1 is that after quenching, the first tempering is carried out, the first tempering temperature is 595℃, the first tempering time is 120min, and air cooling to room temperature; after the first tempering, the second tempering is carried out, the second tempering temperature is 635℃, the second tempering time is 120min, and air cooling to room temperature; after the second tempering, the third tempering is carried out, the third tempering temperature is 640℃, the third tempering time is 120min, and air cooling to room temperature.

[0067] Example 15: The difference between this example and Example 1 is that after quenching, the first tempering is carried out, the first tempering temperature is 605℃, the first tempering time is 150min, and air cooling to room temperature; after the first tempering, the second tempering is carried out, the second tempering temperature is 645℃, the second tempering time is 150min, and air cooling to room temperature; after the second tempering, the third tempering is carried out, the third tempering temperature is 650℃, the third tempering time is 150min, and air cooling to room temperature.

[0068] Example 16: The difference between this example and Example 1 is that after annealing and before quenching, the annealed HOP 10V material is subjected to surface strengthening treatment:

[0069] First, the annealed HOP 10V material is subjected to ultrasonic rolling, the working static pressure of ultrasonic rolling is 310N, the rotation speed is 170r / min, the transverse feed amount is 0.3mm / min, and the rolling number is 4 times, and then the HOP 10V material subjected to ultrasonic rolling is subjected to a staged composite treatment, the composite treatment includes alternating shot peening treatment and cryogenic treatment, the steps are as follows:

[0070] First stage: the shot diameter d1 is 0.4mm, the shot peening intensity I1 is 0.12MPa, and the shot peening time is 7min,

[0071] Second stage: the shot diameter d2 is 0.7mm, the shot peening intensity I2 is 0.23MPa, and the shot peening time is 11min,

[0072] Third stage: the shot diameter d3 is 0.9mm, the shot peening intensity I3 is 0.32MPa, and the shot peening time is 15min,

[0073] And the temperature T of cryogenic treatment i = -80-(30×I i), unit is ℃, time of deep freezing treatment t i =40+(15+d i ), the unit is min, i is 1, 2, 3; then T1 = -92 ° C, t1 = 7.4 min, T2 = -86.9 ° C, t2 = 11.7 min, T3 = -89.6 ° C, t3 = 15.9 min. It can be understood that the calculation formula of temperature and time is only the numerical value of the calculated result, and its unit has nothing to do with the unit of the parameters involved in the calculation formula;

[0074] In the first stage, the shot peening projectiles are glass shot peening projectiles, and in the second and third stages, the shot peening projectiles are cast iron shot peening projectiles, and the surface strengthening treatment is completed.

[0075] Example 17: The difference between this example and Example 16 is that the working static pressure of ultrasonic rolling is 300N, the rotation speed is 160r / min, the lateral feed rate is 0.2mm / min, and the rolling times is 3 times.

[0076] Example 18: The difference between this example and Example 16 is that the working static pressure of ultrasonic rolling is 320N, the rotation speed is 180r / min, the lateral feed rate is 0.4mm / min, and the number of rolling times is 5 times.

[0077] Example 19: This example differs from Example 16 in that, in the first stage: the shot diameter d1 is 0.3 mm, the shot peening intensity I1 is 0.1 MPa, and the shot peening time is 6 min.

[0078] Example 20: This example differs from Example 16 in that, in the first stage, the shot diameter d1 is 0.5 mm, the shot peening intensity I1 is 0.15 MPa, and the shot peening time is 8 min.

[0079] Example 21: The difference between this example and Example 16 is that, in the second stage: the shot diameter d2 is 0.6 mm, the shot peening intensity I2 is 0.2 MPa, and the shot peening time is 10 min.

[0080] Example 22: This example differs from Example 16 in that, in the second stage, the shot diameter d2 is 0.8 mm, the shot peening intensity I2 is 0.25 MPa, and the shot peening time is 12 min.

[0081] Example 23: This example differs from Example 16 in that, in the third stage: the shot diameter d3 is 0.8 mm, the shot peening intensity I3 is 0.3 MPa, and the shot peening time is 14 min.

[0082] Example 24: The difference between this example and Example 16 is that in the third stage: the diameter d3 of the shot is 1.0 mm, the shot intensity I3 is 0.35 MPa, and the shot time is 16 min.

[0083] Experimental Example: The description of this experimental example is based on the description in Example 1, and is intended to illustrate the actual application effect of the present application.

[0084] Investigation 1: Investigation of the effect of the heat treatment system on the performance of HOP 10V material.

[0085] Examples 1-4 are four parallel samples under the same conditions, and the heat treatment process after forging is as follows: after the end of S3 correction, the HOP 10V material is placed in a vacuum furnace for annealing, the annealing method is: annealing at 870℃ for 3h, cooling to 500℃ at a rate of 15℃ / h, then vacuum furnace cooling to 300℃, cooling to 80℃ by argon fan, and air cooling to room temperature (25℃) after furnace cooling; the annealed HOP 10V material is quenched, the quenching temperature is 1070℃, the quenching time is 75 min, and the oil is cooled to room temperature (25℃); then tempered, the first tempering temperature is 550℃, the first tempering time is 135 min, and air cooling to room temperature (25℃); the second tempering temperature is 650℃, the first tempering time is 135 min, and air cooling to room temperature (25℃); the third tempering temperature is 650℃, the third tempering time is 135 min, and air cooling to room temperature (25℃); the performance results are shown in Table 1:

[0086] L1, L2, L3, L4 are four parallel samples under the same conditions as Example 1,

[0087] Table 1 Performance comparison of Control Examples 1-4 and L1-L4 (Example 1)

[0088]

[0089]

[0090] From the results in Table 1, after optimizing the heat treatment system, the tensile strength and yield strength of the present application are reduced compared to Control Examples 1-4, but the elongation, reduction of area, and impact toughness are all improved; therefore, the heat treatment method of the present application is beneficial to enhancing the comprehensive performance of the material, especially the impact toughness.

[0091] Investigation 2: Investigation of the effect of the heat treatment parameters of the present application on the performance of HOP 10V material.

[0092] Table 2 Impact toughness of HOP 10V material in Examples 10-15

[0093] Group Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Impact toughness / J 11.6 12.1 11.5 12 11.4 11.9

[0094] From the results of Table 2, it can be seen that too low annealing parameters, too low quenching parameters, and too low or too high tempering parameters can all reduce impact toughness; but the impact toughness of Example 11 is higher than that of Example 1, but the increase is starting to flatten, so from the perspective of economy, the parameters of Example 1 are relatively more optimal.

[0095] Investigation 3: Explore the influence of the forging parameters of the present application on the performance of HOP 10V material.

[0096] Table 3: Impact toughness of HOP 10V material in Example 2-Example 9

[0097]

[0098] From the results of Table 3, it can be seen that too small or too large upsetting parameters, too small or too large die forging parameters, and too small or too large correction parameters can all reduce the impact toughness of HOP 10V material, so from the comprehensive perspective, the parameters of Example 1 are relatively more optimal.

[0099] Investigation 4: Explore the influence of surface strengthening treatment on the performance of HOP 10V material.

[0100] Table 4: Impact toughness of HOP 10V material in Example 16-Example 24 and Control Example 5-Control Example 6

[0101]

[0102]

[0103] Control Example 5 differs from Example 16 in that the temperature and time of cryogenic treatment are kept constant in each stage;

[0104] Control Example 6 differs from Example 16 in that ultrasonic rolling is not performed;

[0105] From the results of Table 4, it can be seen that after surface strengthening treatment, a synergistic strengthening structure of "fine-grained dense matrix surface layer + deep residual stress field + plating layer" is formed, which has good strength and toughness, and the impact toughness is significantly improved compared with Example 1;

[0106] Comparative Example 5 lacks the phase change of cryogenic treatment, the degree of transformation of the residual austenite in the matrix to martensite is reduced, and the hardness and wear resistance are limited to improve; Comparative Example 6 lacks ultrasonic rolling, the rough surface is easy to become a stress concentration source, the deformation basis of the substrate for subsequent composite processing is poor, and the degree of grain refinement is reduced; Therefore, the impact toughness of the HOP 10V material of Comparative Example 5-Comparative Example 6 is lower than that of Example 16-Example 24;

[0107] From Comparative Examples 16-24, it can be seen that too small or too large ultrasonic rolling parameters, too small or too large first-stage composite processing parameters, too small or too large second-stage composite processing parameters, and too small or too large third-stage composite processing parameters all reduce the impact toughness of the HOP 10V material, so from a comprehensive perspective, the parameter effect of Example 16 is relatively more optimal.

Claims

1. A heat treatment process for powder metallurgy high-speed steel after forging, characterized in that: The following steps are involved: The HOP 10V material that has been subjected to top forging, die forging, and correction is placed in a vacuum furnace for annealing. The annealing method is as follows: keep the temperature at 865-875°C for 2.5-3.5 hours, cool it to 745-755°C at a rate of ≤7°C / h, then cool it to 535-545°C at a rate of ≤15°C / h, then cool it to 75-85°C using an argon fan, and finally take it out of the furnace and air-cool it to room temperature. The annealed HOP 10V material is then quenched at a temperature of 1045-1055°C for 60-90 minutes, and oil-cooled to room temperature. After quenching, the first tempering is performed at a temperature of 595-605°C for 120-150 minutes, and air-cooled to room temperature. After the first tempering, the second tempering is performed at a temperature of 635-645°C for 120-150 minutes, and air-cooled to room temperature. After the second tempering, the third tempering is performed at a temperature of 640-650°C for 120-150 minutes, and air-cooled to room temperature. The HOP 10V material after the third tempering is then surface treated, and the process is completed.

2. The heat treatment process after forging of powder metallurgy high-speed steel according to claim 1, characterized in that: The steps of top forging, die forging and correction are as follows: S1. Upsetting: The blank is heated to 1110-1130℃ as the initial forging temperature, kept at this temperature for 20-80min, and then subjected to top forging: the blank is placed longitudinally for top forging, and then the blank is turned over and top forged again. The impact energy of the two top forgings is 64-96KJ, the deformation of the two top forgings is 25-35%, and the final forging temperature is 900-1000℃. After the top forging is completed, gray cooling and surface treatment are performed; S2. Die forging: The blank obtained in step S1 is heated to 1110-1130° C. as the initial forging temperature, kept at this temperature for 30-90 minutes, and then die-forged with an impact energy of 48-72 kJ, a deformation of 25-35%, and a final forging temperature of 900-1000° C. After die forging, the blank is subjected to gray cooling, trimming, and surface treatment; S3. Calibration: The blank obtained in step S2 is heated to 890-910°C and kept warm for 8-20 minutes, then calibrated with an impact energy of 12-36 kJ, a deformation of 0-1.5%, and a final forging temperature of 850-910°C. After calibration, the blank is quenched and surface treated.

3. The heat treatment process after forging of powder metallurgy high-speed steel according to claim 2, characterized in that: In S1, the surface treatment method includes: shot blasting - polishing - shot blasting.

4. The heat treatment process after forging of powder metallurgy high-speed steel according to claim 2, characterized in that: In S2, the surface treatment method includes: sand blasting - grinding - shot blasting - sand blasting.

5. The heat treatment process after forging of powder metallurgy high-speed steel according to claim 2, characterized in that: In S2, during the trimming, the residual burrs and overcut amount of the HOP 10V material are maintained to be ≤0.3 mm.

6. The heat treatment process after forging of powder metallurgy high-speed steel according to claim 2, characterized in that: In S3, the surface treatment method includes: sand blasting.

7. The heat treatment process for powder metallurgy high-speed steel after forging according to claim 1, characterized in that: The surface treatment method includes: sand blasting-grinding-sand blasting.

8. The heat treatment process for powder metallurgy high-speed steel after forging according to claim 1, characterized in that: After annealing and before quenching, the annealed HOP 10V material is subjected to surface strengthening treatment: First, the annealed HOP 10V material is ultrasonically rolled. The working static pressure of the ultrasonic rolling is 300-320N, the rotation speed is 160-180r / min, the cross feed rate is 0.2-0.4mm / min, and the number of rolling times is 3-5. Then, the HOP 10V material after ultrasonic rolling is subjected to a staged composite treatment. The staged composite treatment includes alternating shot peening and cryogenic treatment. The steps are as follows: The first stage: the shot diameter d1 is 0.3-0.5 mm, the shot peening intensity I1 is 0.1-0.15 MPa, and the shot peening time is 6-8 min. The second stage: the projectile diameter d2 is 0.6-0.8 mm, the shot peening intensity I2 is 0.2-0.25 MPa, and the shot peening time is 10-12 minutes. The third stage: the shot diameter d3 is 0.8-1.0 mm, the shot peening intensity I3 is 0.3-0.35 MPa, and the shot peening time is 14-16 min. The cryogenic treatment temperature T i =-80-(30×I i ), unit is ℃, time of deep freezing treatment t i =40+(15+d i ), the unit is min, i is 1, 2, 3; Surface strengthening treatment completed.

9. The heat treatment process for powder metallurgy high-speed steel after forging according to claim 8, characterized in that: In the first stage, the shot peening shots are glass shot, and in the second and third stages, the shot peening shots are cast iron shot.

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