A heat treatment method for cobalt-containing high-speed steel for cutting tools

Abstract

The invention discloses a heat treatment method for cobalt-containing high-speed steel for cutting tools, which is characterized in that high-density dislocations are first formed on the surface of the high-speed steel by bombarding with supersonic particles, and a new phase nucleation site provided by the high-density dislocations is used to promote M 2 The decomposition of C carbides achieves grain refinement and spheroidization, and after quenching and two temperings, the cobalt phase martensitic transformation and residual stress state are regulated by short-term and multiple liquid nitrogen-room temperature hot and cold cycles. The present invention overcomes the problems of traditional quenching-tempering treatment technology, realizes small-sized, large-quantity, high-sphericity carbides and high-performance cobalt-containing high-speed steel, and can be used for the manufacture of cutting tools such as taps, turning tools, milling cutters, broaches, drills, etc. in advanced machinery manufacturing.

Description

Technical Field

[0001] The invention relates to a heat treatment method, in particular to a heat treatment method for cobalt-containing high-speed steel for cutting tools, belonging to the technical field of new materials and material forming. Background Art

[0002] High-speed steel is a tool steel with high hardness, high wear resistance and high heat resistance, and is particularly suitable for manufacturing multi-edge tools such as taps and turning tools, milling cutters, broaches, drills and other tools with higher requirements for impact and vibration resistance. Heat treatment is a very critical process in the manufacture of high-speed steel tools, which greatly affects the performance of high-speed steel. CN107475488A discloses a high-speed steel heat treatment process method, including the following steps: Step 1: heating the high-speed steel to the quenching temperature of the material and keeping it warm for more than 10 seconds; Step 2: quickly transferring the part to a device with a temperature of T1 and keeping it warm for 2-30 minutes; Step 3: quickly transferring the part to a low-temperature liquid or low-temperature environment with a temperature of T2; Step 4: after the part reaches the temperature of T2, quickly transfer the part to a heating device with a temperature of T3 and keep it warm for more than 2 hours; Step 5: transfer the part to a low-temperature device with a temperature of T4 and keep it warm for more than 2 hours; Step 6: take the part out of the low-temperature device and restore it to room temperature in the air, and the process ends. This method can increase the martensite content and improve the quality of the strengthening phase. The hardness of the parts treated by this process method is 1HRC to 3HRC higher than that of the parts treated by the traditional process method, and the wear resistance is improved. CN102140568A discloses a high-speed steel heat treatment process used in the field of mold manufacturing. The existing technology of one 1250℃~1280℃ quenching plus three to four 550℃~570℃ tempering heat treatment process is changed to one 180℃~1230℃ quenching and two 300℃~400℃ tempering heat treatment processes. This process can make the high-speed steel obtain higher hardness and lower surface roughness; and the heat treatment time of the process of the present invention is 60% of the original, the quenching and tempering temperatures are reduced, the power consumption is reduced, and better economic processing accuracy is achieved. In addition, the high-speed steel treated by the process of the present invention can be used in mold products, and the working life and strength are significantly improved compared with the existing materials.

[0003] At present, high-speed steel is constantly developing, especially cobalt-containing high-speed steel, which can be used to manufacture various mechanical processing cutting tools such as taps, turning tools, milling cutters, broaches, drills, etc. In order to obtain excellent mechanical properties, its heat treatment technology is very critical. However, the current research on the heat treatment process of high-speed steel is mainly to optimize the process parameters of quenching and tempering, and to increase the conversion of martensite. However, the size, morphology, quantity, distribution, etc. of carbides in high-speed steel have an important influence on the performance of high-speed steel. The existing high-speed steel heat treatment process is still insufficient to regulate the high-speed steel structure (especially the characteristics of carbides). It is urgent to form a new heat treatment process for cobalt-containing high-speed steel for cutting tools to solve this problem. Summary of the invention

[0004] In view of the problem of poor mechanical properties caused by coarse grain size, uneven dispersion and small number of carbides after heat treatment of cobalt-containing high-speed steel for cutting tools using traditional quenching-tempering technology, the present invention proposes to form high-density dislocations on the surface of high-speed steel based on supersonic particle bombardment, utilize the new phase nucleation sites provided by the high-density dislocations to promote the decomposition of M2C carbides, achieve grain refinement and spheroidization, and regulate the cobalt phase martensitic transformation and residual stress state through short-term and multiple liquid nitrogen-room temperature hot and cold cycle treatments, ultimately achieving small size, large number, high sphericity carbides and high performance.

[0005] The heat treatment method of the cobalt-containing high-speed steel for cutting tools of the present invention is characterized by comprising the following steps in sequence:

[0006] (1) Formation of surface deformation layer with high density of dislocations in cobalt-containing high-speed steel for cutting tools: First, the cobalt-containing high-speed steel was annealed. The high-speed steel material was heated to 820-830℃, kept at this temperature for 1-1.5h and cooled with the furnace. The surface was ground with a grinding amount of 0.2mm to remove the surface oxide layer. Then, a cemented carbide ball with a diameter of 0.5-1.0mm was used to bombard the surface of the high-speed steel with supersonic particles. The injection angle was 90°, the gas pressure was 1.5-2.5MPa, the air flow rate was 800-1000m / s, the injection distance was 60-70mm, and the injection time was 5-10min. After treatment, a surface deformation layer with high density of dislocations was formed on the surface of the high-speed steel. The thickness of the surface deformation layer was 50-100μm, and the dislocation density of the surface deformation layer was 3×10 13 ~9×10 13 m -2 ;

[0007] (2) Carbide state control treatment of cobalt-containing high-speed steel for cutting tools: The high-speed steel with a surface deformation layer of high-density dislocations is placed in a vacuum furnace and heated to 1000-1050°C for 2-3 hours. The M2C carbides in the high-speed steel are decomposed into M6C and MC carbides. The high-density dislocations in the surface deformation layer promote the decomposition of carbides, so the number of carbides in the surface layer is larger. Then, the carbides in the high-speed steel are heated to 1100-1150°C and kept for 30-60 minutes to spheroidize. After decomposition and spheroidization treatment, the carbide state control of the high-speed steel is achieved. The number density of carbides in the surface deformation layer of the high-speed steel is 1×10 6 ~1.5×10 6 mm -2 The average aspect ratio of carbide particles is 1.6~1.7, the average grain size of carbides is 3~4μm, and the number density of carbides inside high-speed steel is 5×10 5 ~8×10 5 mm -2 , the average aspect ratio of carbide particles is 1.9~2.1, and the average grain size of carbides is 6~8μm;

[0008] (3) Vacuum quenching and tempering of cobalt-containing high-speed steel for cutting tools: The high-speed steel that has undergone carbide state control treatment is placed in a vacuum heat treatment furnace, heated to 1200~1250℃, kept warm for 3~5min, and then oil quenched; after oil quenching, the high-speed steel is heated to 560~570℃, kept warm for 1~2h and cooled to complete one tempering treatment. The tempering treatment is repeated twice. The surface hardness of the treated high-speed steel is 64~66HRC, and the hardness of the high-speed steel inside is 61~63HRC; the impact toughness of the high-speed steel is 20~38J / cm 2 ; Compared with the carbide state control treatment, the number density of carbides in the surface layer of high-speed steel after tempering treatment increased by 3~6%, the average aspect ratio of carbide particles was 1.6~1.7, and the average carbide grain size was 3~4μm. The number density of carbides inside the high-speed steel increased by 1~3%, the average aspect ratio of carbide particles was 1.9~2.1, and the average carbide grain size was 6~8μm.

[0009] (4) Cobalt phase transformation strengthening and residual stress state regulation of cobalt-containing high-speed steel for cutting tools: The high-speed steel after vacuum quenching and tempering is placed in liquid nitrogen for cooling, kept for 5-10 minutes, then taken out and placed in air at room temperature for 5-10 minutes to complete a hot and cold cycle process. This liquid nitrogen-room temperature hot and cold cycle process is repeated 30-40 times, causing the cobalt phase in the high-speed steel to undergo a martensitic phase transformation and transform from a face-centered cubic structure to a close-packed hexagonal structure, and the residual tensile stress of the high-speed steel is transformed into a compressive stress, thereby achieving phase transformation strengthening and residual stress state regulation; compared with vacuum quenching and tempering treatment, the impact toughness of the high-speed steel after regulation is increased by 3-10 J / cm2 The proportion of cobalt in the close-packed hexagonal structure of the surface layer of high-speed steel increased from 3~5wt.% to 10~15wt.%, the volume percentage of retained austenite in the surface layer decreased from 16~20% to 10~15%, the hardness of the surface layer increased by 1~2HRC, the proportion of cobalt in the close-packed hexagonal structure increased from 1~2wt.% to 6~8wt.%, the volume percentage of retained austenite in the internal layer decreased from 21~30% to 15~20%, and the hardness of the internal layer increased by 0.5~1.5HRC; the number density of carbides in the surface layer and the internal layer, the average aspect ratio of carbide particles, and the average grain size of carbides remained unchanged.

[0010] The heat treatment method of the cobalt-containing high-speed steel for cutting tools of the present invention is further characterized in that:

[0011] (1) During the formation of the surface deformation layer with high density dislocations in the cobalt-containing high-speed steel for cutting tools, the composition of the cemented carbide ball used during supersonic particle bombardment was WC-(15-20) wt.%Co;

[0012] (2) When the carbide state of the cutting tool is controlled by cobalt-containing high-speed steel, the vacuum degree is 1×10 -2 ~5×10 -2 Pa;

[0013] (3) When vacuum quenching and tempering of cobalt-containing high-speed steel for cutting tools, the vacuum degree is 1×10 -2 ~5×10 -2 Pa;

[0014] (4) When the cobalt phase transformation strengthening and residual stress state regulation of cobalt-containing high-speed steel for cutting tools are carried out, the temperature of liquid nitrogen is -196℃~-180℃.

[0015] The advantages of the present invention are as follows: (1) Before the conventional quenching-tempering treatment, the present invention forms a deformation layer with high-density dislocations on the surface of the cobalt-containing high-speed steel for cutting tools by supersonic particle bombardment, and uses dislocations as the core of nucleation to promote its decomposition and spheroidization. Compared with simple interface nucleation, a carbide state with small particle size, large number and high sphericity can be obtained, thereby improving the performance of the high-speed steel. (2) In the present invention, high-density dislocations are used to promote carbide decomposition and new phase nucleation to adjust the carbide state, which can reduce the temperature of the heat treatment temperature and avoid coarse grains. (3) When high-speed steel is used as a cutting tool, the surface hardness, wear resistance and internal toughness of the cobalt-containing high-speed steel after heat treatment of the present invention are required to be higher than the internal hardness, which can better meet the performance requirements of the cutting tool for the high-speed steel material. (4) The present invention promotes the cobalt phase transformation and residual austenite transformation in high-speed steel to improve mechanical properties through a short-term multiple liquid nitrogen-room temperature cooling and heating cycle method, and realizes the release of residual stress and the transformation from tensile stress to compressive stress, which are beneficial to the performance improvement of cobalt-containing high-speed steel for cutting tools. (5) The present invention can reduce the number of tempering times through a short-term multiple liquid nitrogen-room temperature cooling and heating cycle method. Compared with the traditional three-time tempering, it can alleviate the growth of grains and the decrease of hardness after multiple heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the heat treatment method of cobalt-containing high-speed steel for cutting tools of the present invention. DETAILED DESCRIPTION

[0017] Example 1: Heat treatment of cobalt-containing high-speed steel for cutting tools was carried out according to the following steps:

[0018] (1) Formation of surface deformation layer with high density of dislocations in cobalt-containing high-speed steel for cutting tools: First, the cobalt-containing high-speed steel W6Mo5Cr4V2Co5 was annealed. The high-speed steel material was heated to 820°C, kept at this temperature for 1 h and cooled with the furnace. The surface was ground with a grinding amount of 0.2 mm to remove the surface oxide layer. Then, the high-speed steel surface was subjected to supersonic particle bombardment using a cemented carbide ball with a diameter of 0.6 mm. The composition of the cemented carbide ball was WC-19wt.%Co. The injection angle was 90°, the gas pressure was 1.5 MPa, the gas flow rate was 850 m / s, the injection distance was 60 mm, and the injection time was 5 min. After treatment, a surface deformation layer with high density of dislocations was formed on the surface of the high-speed steel. The thickness of the surface deformation layer was 56 μm, and the dislocation density of the surface deformation layer was 4.1×10 13 m -2 ;

[0019] (2) Carbide state control treatment of cobalt-containing high-speed steel for cutting tools: The high-speed steel with a surface deformation layer with high density of dislocations was placed in a vacuum furnace with a vacuum degree of 2×10 -2Pa, heated to 1000℃, kept warm for 2h, the M2C carbides in the high-speed steel decomposed into M6C and MC carbides, the high-density dislocations in the surface deformation layer promoted the decomposition of carbides, so the number of carbides in the surface layer was larger; then heated to 1100℃ and kept warm for 30min to make the carbides in the high-speed steel spheroidized; after decomposition and spheroidization treatment, the carbide state of the high-speed steel was regulated, and the number density of carbides in the surface deformation layer of the high-speed steel was 1.1×10 6 mm -2 The aspect ratio of carbide particles is 1.6, the average grain size of carbides is 3.2 μm, and the number density of carbides inside the high-speed steel is 5.3×10 5 mm -2 , the aspect ratio of carbide particles is 1.9, and the average grain size of carbides is 6.4 μm;

[0020] (3) Vacuum quenching and tempering of cobalt-containing high-speed steel for cutting tools: The high-speed steel that has undergone carbide state control treatment is placed in a vacuum heat treatment furnace with a vacuum degree of 3×10 -2 Pa, heated to 1200℃, kept warm for 3min, and then oil quenched; after oil quenching, the high-speed steel was heated to 560℃ again, kept warm for 1.5h and cooled to complete the first tempering treatment. The tempering treatment was repeated twice. The surface hardness of the treated high-speed steel was 64.2HRC, and the hardness inside the high-speed steel was 61.6HRC; the impact toughness of the high-speed steel was 23J / cm 2 Compared with the carbide state control treatment, the number density of carbides in the surface layer of high-speed steel after tempering treatment is 1.14×10 6 mm -2 The average aspect ratio of carbide particles is 1.6, the average grain size of carbides is 3.1 μm, and the number density of carbides inside high-speed steel is 5.4×10 5 mm -2 , the average aspect ratio of carbide particles is 1.9, and the average grain size of carbides is 6.3 μm;

[0021] (4) Cobalt phase transformation strengthening and residual stress state regulation of cobalt-containing high-speed steel for cutting tools: The high-speed steel after vacuum quenching and tempering was placed in liquid nitrogen at a temperature of -190°C for cooling, kept for 5 minutes, then taken out and placed in air at room temperature for 6 minutes to complete a hot and cold cycle. This liquid nitrogen-room temperature hot and cold cycle process was repeated 30 times, causing the cobalt phase in the high-speed steel to undergo a martensitic phase transformation and transform from a face-centered cubic structure to a close-packed hexagonal structure, and the residual tensile stress of the high-speed steel was transformed into a compressive stress, thereby achieving phase transformation strengthening and residual stress state regulation; compared with the high-speed steel after vacuum quenching and tempering, the impact toughness of the high-speed steel after regulation was increased by 4.7 J / cm 2The proportion of cobalt in the close-packed hexagonal structure in the surface layer of high-speed steel increased from 3.2wt.% to 13.5wt.%, the volume percentage of retained austenite in the surface layer decreased from 16.9% to 10.4%, the hardness of the surface layer increased by 1.3HRC, the proportion of cobalt in the close-packed hexagonal structure in the interior increased from 1.3wt.% to 6.1wt.%, the volume percentage of retained austenite in the interior decreased from 24.8% to 16.2%, and the hardness of the interior increased by 0.6HRC; the number density of carbides in the surface layer and the interior, the average aspect ratio of carbide particles, and the average grain size of carbides remained unchanged.

[0022] Example 2: Heat treatment of cobalt-containing high-speed steel for cutting tools was carried out according to the following steps:

[0023] (1) Formation of surface deformation layer with high density of dislocations in cobalt-containing high-speed steel for cutting tools: First, the cobalt-containing high-speed steel W2Mo9Cr4VCo8 was annealed. The high-speed steel material was heated to 825°C, kept at this temperature for 1.5 h and cooled with the furnace. The surface was ground with a grinding amount of 0.2 mm to remove the surface oxide layer. Then, the high-speed steel surface was subjected to supersonic particle bombardment using a cemented carbide ball with a diameter of 1.0 mm. The composition of the cemented carbide ball was WC-16wt.%Co. The injection angle was 90°, the gas pressure was 2 MPa, the gas flow rate was 900 m / s, the injection distance was 70 mm, and the injection time was 8 min. After treatment, a surface deformation layer with high density of dislocations was formed on the surface of the high-speed steel. The thickness of the surface deformation layer was 72 μm, and the dislocation density of the surface deformation layer was 6.4×10 13 m -2 ;

[0024] (2) Carbide state control treatment of cobalt-containing high-speed steel for cutting tools: The high-speed steel with a surface deformation layer with high density of dislocations was placed in a vacuum furnace with a vacuum degree of 5×10 -2 Pa, heated to 1050℃, kept warm for 2.5h, the M2C carbides in the high-speed steel decomposed into M6C and MC carbides, the high density dislocations in the surface deformation layer promoted the decomposition of carbides, so the number of carbides in the surface layer was larger; then heated to 1150℃ and kept warm for 40min to make the carbides in the high-speed steel spheroidized; after decomposition and spheroidization treatment, the carbide state of the high-speed steel was regulated, and the number density of carbides in the surface deformation layer of the high-speed steel was 1.4×10 6 mm -2 , the aspect ratio of carbide particles is 1.7, the average grain size of carbides is 3.4 μm, and the number density of carbides inside the high-speed steel is 6.6×10 5 mm -2 , the aspect ratio of carbide particles is 2.0, and the average grain size of carbides is 6.7 μm;

[0025] (3) Vacuum quenching and tempering of cobalt-containing high-speed steel for cutting tools: The high-speed steel that has undergone carbide state control treatment is placed in a vacuum heat treatment furnace with a vacuum degree of 5×10 -2 Pa, heated to 1250℃, kept warm for 4 min, and then oil quenched; after oil quenching, the high-speed steel was heated to 570℃ again, kept warm for 1h and cooled to complete the first tempering treatment. The tempering treatment was repeated twice. The surface hardness of the treated high-speed steel was 65.7HRC, and the hardness of the high-speed steel inside was 62.2HRC; the impact toughness of the high-speed steel was 34J / cm 2 Compared with the carbide state control treatment, the number density of carbides in the surface layer of high-speed steel after tempering treatment is 1.45×10 6 mm -2 The average aspect ratio of carbide particles is 1.7, the average grain size of carbides is 3.3 μm, and the number density of carbides inside high-speed steel is 6.7×10 5 mm -2 , the average aspect ratio of carbide particles is 1.9, and the average grain size of carbides is 6.6 μm;

[0026] (4) Cobalt phase transformation strengthening and residual stress state regulation of cobalt-containing high-speed steel for cutting tools: The high-speed steel after vacuum quenching and tempering was placed in liquid nitrogen at a temperature of -180°C for cooling, kept for 10 minutes, then taken out and placed in air at room temperature for 8 minutes to complete a hot and cold cycle. This liquid nitrogen-room temperature hot and cold cycle process was repeated 35 times, causing the cobalt phase in the high-speed steel to undergo a martensitic phase transformation and transform from a face-centered cubic structure to a close-packed hexagonal structure, and the residual tensile stress of the high-speed steel was transformed into a compressive stress, thereby achieving phase transformation strengthening and residual stress state regulation; compared with the high-speed steel after vacuum quenching and tempering, the impact toughness of the high-speed steel after regulation was increased by 5.8 J / cm 2 The proportion of cobalt in the close-packed hexagonal structure in the surface layer of high-speed steel increased from 4.1wt.% to 14.3wt.%, the volume percentage of retained austenite in the surface layer decreased from 19.2% to 12.5%, the hardness of the surface layer increased by 1.7HRC, the proportion of cobalt in the close-packed hexagonal structure in the interior increased from 1.8wt.% to 7.4wt.%, the volume percentage of retained austenite in the interior decreased from 27.9% to 16.7%, and the hardness of the interior increased by 1HRC; the number density of carbides in the surface layer and the interior, the average aspect ratio of carbide particles, and the average grain size of carbides remained unchanged.

Claims

1. A heat treatment method for cobalt-containing high-speed steel for cutting tools, characterized in that The following steps are included in sequence: (1) Formation of a surface deformation layer with high-density dislocations in cobalt-containing high-speed steel for cutting tools: First, the cobalt-containing high-speed steel is annealed by heating the high-speed steel material to 820-830°C, keeping it at this temperature for 1-1.5 h, and then cooling it with the furnace; The surface was ground with a grinding amount of 0.2 mm to remove the surface oxide layer. Then, a carbide ball with a diameter of 0.5-1.0 mm was used to bombard the surface of the high-speed steel with supersonic particles. The spray angle was 90°, the gas pressure was 1.5-2.5 MPa, the air flow rate was 800-1000 m / s, the spray distance was 60-70 mm, and the spray time was 5-10 min. After treatment, a surface deformation layer with high-density dislocation was formed on the surface of the high-speed steel. The thickness of the surface deformation layer was 50-100 μm, and the dislocation density of the surface deformation layer was 3×10 13 ~9×10 13 m -2 ; (2) Carbide state control treatment of cobalt-containing high-speed steel for cutting tools: The high-speed steel with a surface deformation layer with high dislocation density is placed in a vacuum furnace and heated to 1000-1050°C for 2-3 h. The M2C carbides in the high-speed steel are decomposed into M6C and MC carbides. The high-density dislocations in the surface deformation layer promote the decomposition of carbides, so the number of carbides in the surface layer is larger. Then, the carbides in the high-speed steel are heated to 1100-1150°C and kept for 30-60 min to spheroidize. After decomposition and spheroidization treatment, the carbide state control of the high-speed steel is achieved. The number density of carbides in the surface deformation layer of the high-speed steel is 1×10 6 ~1.5×10 6 mm -2 The average aspect ratio of carbide particles is 1.6~1.7, the average grain size of carbides is 3~4μm, and the number density of carbides inside high-speed steel is 5×10 5 ~8×10 5 mm -2 , the average aspect ratio of carbide particles is 1.9~2.1, and the average grain size of carbides is 6~8μm; (3) Vacuum quenching and tempering of cobalt-containing high-speed steel for cutting tools: The high-speed steel that has undergone carbide state control treatment is placed in a vacuum heat treatment furnace, heated to 1200~1250℃, kept warm for 3~5min, and then oil quenched; after oil quenching, the high-speed steel is heated to 560~570℃, kept warm for 1~2h and cooled to complete one tempering treatment. The tempering treatment is repeated twice. The surface hardness of the treated high-speed steel is 64~66HRC, and the hardness of the high-speed steel inside is 61~63HRC; the impact toughness of the high-speed steel is 20~38J / cm 2 ; Compared with the carbide state control treatment, the number density of carbides in the surface layer of high-speed steel after tempering treatment increased by 3~6%, the average aspect ratio of carbide particles was 1.6~1.7, and the average carbide grain size was 3~4μm. The number density of carbides inside the high-speed steel increased by 1~3%, the average aspect ratio of carbide particles was 1.9~2.1, and the average carbide grain size was 6~8μm. (4) Cobalt phase transformation strengthening and residual stress state regulation of cobalt-containing high-speed steel for cutting tools: The high-speed steel after vacuum quenching and tempering is placed in liquid nitrogen for cooling, kept for 5-10 minutes, then taken out and placed in air at room temperature for 5-10 minutes to complete a hot and cold cycle process. This liquid nitrogen-room temperature hot and cold cycle process is repeated 30-40 times, causing the cobalt phase in the high-speed steel to undergo a martensitic phase transformation and transform from a face-centered cubic structure to a close-packed hexagonal structure, and the residual tensile stress of the high-speed steel is transformed into a compressive stress, thereby achieving phase transformation strengthening and residual stress state regulation; compared with vacuum quenching and tempering treatment, the impact toughness of the high-speed steel after regulation is increased by 3-10 J / cm 2 The proportion of cobalt in the close-packed hexagonal structure of the surface layer of high-speed steel increased from 3~5wt.% to 10~15wt.%, the volume percentage of retained austenite in the surface layer decreased from 16~20% to 10~15%, the hardness of the surface layer increased by 1~2HRC, the proportion of cobalt in the close-packed hexagonal structure increased from 1~2wt.% to 6~8wt.%, the volume percentage of retained austenite in the internal layer decreased from 21~30% to 15~20%, and the hardness of the internal layer increased by 0.5~1.5HRC; the number density of carbides in the surface layer and the internal layer, the average aspect ratio of carbide particles, and the average grain size of carbides remained unchanged.

2. The heat treatment method of cobalt-containing high-speed steel for cutting tools according to claim 1, further characterized by: (1) During the formation of the surface deformation layer with high density dislocations in the cobalt-containing high-speed steel for cutting tools, the composition of the cemented carbide ball used during supersonic particle bombardment was WC-(15-20) wt.%Co; (2) When the carbide state of the cutting tool is controlled by cobalt-containing high-speed steel, the vacuum degree is 1×10 -2 ~5×10 -2 Pa; (3) When vacuum quenching and tempering of cobalt-containing high-speed steel for cutting tools, the vacuum degree is 1×10 -2 ~5×10 -2 Pa; (4) When the cobalt phase transformation strengthening and residual stress state regulation of cobalt-containing high-speed steel for cutting tools are carried out, the temperature of liquid nitrogen is -196℃~-180℃.

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