A method for regulating the microstructure and properties of high-speed steel materials for taps

Abstract

The invention discloses a method for regulating the microstructure and properties of high-speed steel materials for taps. The method is characterized in that plastic deformation is first carried out on the high-speed steel by cold rolling to form high-density dislocations in the high-speed steel, promoting the decomposition and spheroidization of carbides, and forming carbides with fine grain size, large quantity, near-spherical shape and uniform distribution as strengthening phases. After quenching and two tempering treatments, pulse magnetic field treatment is carried out to promote carbide precipitation, transformation of retained austenite, and increase the dislocation density, thereby realizing the regulation of the microstructure and properties of high-speed steel and toughening. The invention overcomes the problems existing in the existing regulation treatment technology, and realizes the regulation of the microstructure and properties of high-speed steel for taps based on the combination of force-thermal-magnetic, and can be used for manufacturing various high-performance metal cutting tools such as taps.

Description

Technical Field

[0001] The present invention relates to a method for regulating and controlling the microstructure and properties of a material, and particularly to a method for regulating and controlling the microstructure and properties of high-speed steel materials for taps, belonging to the technical fields of new materials, advanced manufacturing, and material forming technology. Background Art

[0002] High-speed steel (HSS) is a tool steel with high hardness, high wear resistance, and high heat resistance. Due to the presence of a relatively high amount of carbon and a large amount of alloying elements, it has high hardness, strength, hot hardness, and hardenability. High-speed steel is mainly used to manufacture complex thin-edge and impact-resistant metal cutting tools such as taps. The microstructure of high-speed steel is complex, the compositional uniformity is poor, the carbide composition and size vary greatly, and segregation is serious. To meet the requirements for the hardness and toughness of high-speed steel, it is very important to regulate and control the microstructure and properties of high-speed steel. Heat treatment is a commonly used method for regulating and controlling the microstructure and properties. CN113943901A discloses a heat-treated vanadium-containing high-boron high-speed steel and its heat treatment method. Under the condition of 1010-1060 °C, the vanadium-containing high-boron high-speed steel is quenched to obtain a quenched workpiece; then the quenched workpiece is tempered and air-cooled to room temperature to obtain the heat-treated vanadium-containing high-boron high-speed steel. The present invention improves the morphology of boron carbide by adding vanadium and heat treatment process, promotes matrix strengthening, and obtains a vanadium-containing high-boron high-speed steel with excellent strength and toughness. Applying the heat-treated vanadium-containing high-boron high-speed steel to actual production will be more suitable for harsh working conditions. CN105671251A discloses a heat treatment process for high-speed steel, with the material being W6Mo5Cr4V2. The heat treatment process includes the following steps: (1) loading the drill bit into a fixture and then performing two pre-heat treatments; (2) adopting step-by-step isothermal quenching. The heat treatment process of the high-speed steel in the present invention undergoes two pre-heat treatments, which slows down the oxidation and decarburization trends of the drill bit, and reduces the temperature difference, which is beneficial to reducing the deformation of the drill bit. Through step-by-step quenching, the temperature difference of the drill bit can be reduced, the thermal stress can be reduced, and the distortion tendency can be reduced. Isothermal quenching is beneficial to the transformation of retained austenite into lower bainite, reduces the brittleness of the drill bit, improves the toughness of the drill bit, and reduces the cracking tendency of the drill bit.

[0003] Although the existing heat treatment technologies of quenching and multiple tempering can improve the performance of high-speed steel for taps, with the complexity of the composition of high-speed steel, the microstructure and morphology of the carbides therein are also more complex. It still faces challenges to obtain a fine and uniform carbide distribution in high-speed steel. Currently, the performance requirements for high-speed steel for taps in engineering are continuously increasing, and there is an urgent need to form a new technology for regulating the microstructure of high-speed steel for taps to achieve high performance of high-speed steel for taps. Summary of the Invention

[0004] Aiming at the problems existing in the current methods for regulating the microstructure and properties of high-speed steel for taps, the present invention proposes a force-thermal-magnetic composite microstructure and property regulation technology. First, cold rolling is used to plastically deform the high-speed steel, forming high-density dislocations in the high-speed steel for taps as the nuclei for the formation of new phases, thereby promoting the decomposition and spheroidization of carbides in the high-speed steel, forming carbides with fine grain size, large quantity, near-spherical shape and uniform distribution as strengthening phases. After quenching and two tempering treatments, pulsed magnetic field treatment is carried out to promote the precipitation of carbides, the transformation of retained austenite, and increase the dislocation density, thereby realizing the regulation of the microstructure and properties and the strengthening and toughening of the high-speed steel for taps.

[0005] The method for regulating the microstructure and properties of the high-speed steel material for taps of the present invention is characterized by successively comprising the following steps:

[0006] (1) Plastic deformation of high-speed steel and formation of high-density dislocations: Heat the high-speed steel material for taps to 820 - 830 °C, hold for 1 - 1.5 h, and cool to 100 - 150 °C; then carry out multi-pass cold rolling plastic deformation on the high-speed steel, with the total rolling reduction being 10 - 20%, and the reduction thickness per pass being 0.1 - 1 mm; apply a tensile stress during rolling, control the front tensile stress to be 150 - 200 MPa, and the rear tensile stress to be 1.1 - 1.2 times that of the front tensile stress. The front and rear tensile stresses change the stress state in the rolling stress deformation zone from a triaxial compressive stress state to a biaxial compressive stress and uniaxial tensile stress state, and reduce the rolling force, so that no fracture occurs during the plastic deformation of the high-speed steel; after cold rolling plastic deformation, high-density dislocations are formed in the high-speed steel, and the dislocation density is 3×10 13 ~8×10 13 m -2 ;

[0007] (2) Carbide decomposition treatment: Put the high-speed steel after cold rolling plastic deformation into a heat treatment furnace, heat to 1000 - 1100 °C, hold for 3 - 5 h and then cool. The high-density dislocations in the high-speed steel act as the nuclei for the formation of new phases, which can promote the decomposition of M2C-type carbides into M6C and MC-type carbides. After decomposition, the number of carbide particles per square millimeter area in the high-speed steel is 4×10 5 ~9×10 5 ;

[0008] (3) Carbide spheroidization treatment: Put the high-speed steel after decomposition treatment into a heat treatment furnace, heat to 1150 °C, hold for 5 - 30 min and then cool, so that the carbides in the high-speed steel are spheroidized. After spheroidization treatment, the average aspect ratio of carbide particles is 1.6 - 1.8, and the average grain size of carbides is 3 - 5 μm;

[0009] (4) Quenching treatment of high-speed steel: Heat the high-speed steel after carbide spheroidization treatment to 1200 - 1250 °C, hold for 3 - 5 min, and then carry out oil quenching;

[0010] (5) Tempering treatment of high-speed steel: Heat the quenched high-speed steel to 560 - 580 °C, hold for 1 - 2 h, and then cool to complete one tempering treatment. The tempering treatment is repeated 2 times. After tempering, the hardness of the high-speed steel is 62 - 65 HRC, and the impact toughness is 20 - 35 J / cm 2 , compared with that after carbide decomposition treatment, the number of carbide particles per square millimeter area in the high-speed steel after tempering treatment increases by 1 - 3%;

[0011] (6) Control of high-density dislocation introduction, carbide precipitation and retained austenite transformation in high-speed steel: Perform pulsed magnetic field treatment on the tempered high-speed steel. The intensity of the pulsed magnetic field is 1.5 - 2 T, and the treatment time is 3 - 5 min; The pulsed magnetic field treatment causes carbide precipitation, an increase in dislocation density and the transformation of retained austenite to martensite in the high-speed steel for tap, thereby realizing the regulation of tissue properties; Compared with that after carbide decomposition treatment, the number of carbide particles per square millimeter area in the high-speed steel after pulsed magnetic field treatment increases by 6 - 15%; Compared with that after tempering treatment, the dislocation density in the high-speed steel after pulsed magnetic field treatment increases from 0.5×10 13 ~ 1×10 13 m -2 to 1.1×10 13 ~ 1.5×10 13 m -2 , the volume percentage content of retained austenite in the high-speed steel decreases from 18 - 25% to 12 - 16%, the hardness increases by 1 - 2 HRC, and the impact toughness increases by 5 - 10 J / cm 2 ; After the treatment is completed, the average aspect ratio of carbide particles in the high-speed steel is 1.6 - 1.8, and the average grain size of carbides is 3 - 5 μm.

[0012] The method for regulating the tissue properties of the high-speed steel material for tap of the present invention is further characterized by successively including the following steps:

[0013] (1) When plastic deformation of high-speed steel and formation of high-density dislocations occur, the rolling speed during cold rolling is 0.2 - 0.5 m / s;

[0014] (2) In the carbide decomposition treatment, the heating rate is 4 - 8 °C / min, and after the holding ends, it is taken out of the furnace and air-cooled;

[0015] (3) In the carbide spheroidization treatment, the heating rate is 4 - 8 °C / min, and after the holding ends, it is taken out of the furnace and air-cooled;

[0016] (4) In the quenching treatment of high-speed steel, the heating rate is 4 - 8 °C / min;

[0017] When tempering high-speed steel, the heating rate is 4 - 8 °C / min, and after the holding is completed, it is taken out of the furnace and air-cooled;

[0018] (6)When controlling the introduction of high-density dislocations, carbide precipitation, and transformation of retained austenite in high-speed steel, the frequency of the pulsed magnetic field is 25 - 35 Hz.

[0019] The advantages of the present invention are as follows: (1) Adopting multi-pass cold rolling plastic deformation to introduce high-density dislocations into the high-speed steel for taps. The introduced high-density dislocations can serve as the nuclei for the formation of new phases, thereby promoting the decomposition of carbides in high-speed steel, reducing the segregation of carbides, increasing the number of carbide particles, reducing their particle size, and reducing the splitting and stress concentration effects of carbides on the matrix after spheroidizing treatment, so as to realize the regulation of carbides and improve the properties of high-speed steel. The action mechanism of traditional forging and other treatments is to break coarse carbides, and its effect is limited; the present invention is based on dislocation nucleation, with a more microscopic action and a greater refinement effect. (2) After quenching and tempering treatment, pulsed magnetic field treatment is carried out. Using the action of the magnetic field, carbide precipitation, an increase in dislocation density, and the transformation of retained austenite to martensite occur in the high-speed steel for taps. By using multiple mechanisms, the microstructure and properties are regulated, the properties are improved, and the strengthening and toughening of high-speed steel are realized. (3) Using plastic deformation treatment before quenching-tempering treatment and pulsed magnetic field treatment after that to realize the microstructure and property regulation of the high-speed steel for taps. The method of the present invention can reduce the number of tempering times to 2 times, reduce energy consumption, and reduce oxidation and carbide grain growth caused by multiple heating. Description of the Drawings

[0020] Figure 1 Schematic diagram of the microstructure and property regulation treatment method of the high-speed steel material for taps of the present invention. Detailed Embodiments

[0021] Example 1: The microstructure and property regulation treatment of the high-speed steel material for taps is carried out according to the following steps:

[0022] (1)Plastic deformation of high-speed steel and formation of high-density dislocations: Heat the high-speed steel material for W18 taps to 820 °C, hold for 1 h, and cool to 100 °C; then carry out 12 passes of cold rolling plastic deformation on the high-speed steel, with a total rolling reduction of 11%, a reduction thickness of 0.3 mm per pass, and a rolling speed of 0.2 m / s; apply a tensile stress during rolling, control the front tensile stress to be 150 MPa, and the rear tensile stress to be 1.1 times that of the front tensile stress, i.e., 165 MPa. The front and rear tensile stresses change the stress state in the rolling stress deformation zone from a triaxial compressive stress state to a biaxial compressive stress and uniaxial tensile stress state and reduce the rolling force, so that no fracture occurs during the plastic deformation of high-speed steel; after cold rolling plastic deformation, high-density dislocations are formed in the high-speed steel, and its dislocation density is 3.4×10 13 m -2 ;

[0023] (2) Carbide decomposition treatment: The high-speed steel after cold rolling plastic deformation is put into a heat treatment furnace, heated to 1000 °C at a heating rate of 4 °C / min, air-cooled after holding for 3 h. The high-density dislocations in the high-speed steel, serving as the nuclei for the formation of new phases, can promote the decomposition of M2C-type carbides into M6C and MC-type carbides. After decomposition, the number of carbide particles per square millimeter area in the high-speed steel is 4.7×10 5 ;

[0024] (3) Carbide spheroidization treatment: The high-speed steel after decomposition treatment is put into a heat treatment furnace, heated to 1150 °C at a heating rate of 4 °C / min, air-cooled after holding for 10 min to spheroidize the carbides in the high-speed steel. After the spheroidization treatment, the average aspect ratio of the carbide particles is 1.63, and the average grain size of the carbides is 3.2 μm;

[0025] (4) Quenching treatment of high-speed steel: The high-speed steel after carbide spheroidization treatment is heated to 1200 °C at a heating rate of 4 °C / min, and after holding for 3 min, oil quenching is carried out;

[0026] (5) Tempering treatment of high-speed steel: The high-speed steel after quenching treatment is heated to 560 °C at a heating rate of 4 °C / min, air-cooled after holding for 1 - 2 h to complete one tempering treatment. The tempering treatment is repeated 2 times. After tempering, the hardness of the high-speed steel is 62.3 HRC, and the impact toughness is 24 J / cm 2 , and the number of carbide particles per square millimeter area in the high-speed steel after tempering treatment is 4.8×10 5 ;

[0027] (6) Control of high-density dislocation introduction, carbide precipitation and retained austenite transformation in high-speed steel: The high-speed steel after tempering treatment is subjected to pulsed magnetic field treatment. The intensity of the pulsed magnetic field is 1.5 T, the frequency of the pulsed magnetic field is 25 Hz, and the treatment time is 3 min; The pulsed magnetic field treatment causes carbide precipitation, an increase in dislocation density and the transformation of retained austenite to martensite in the high-speed steel for tapping, thus realizing the regulation of tissue properties; After the pulsed magnetic field treatment, the number of carbide particles per square millimeter area in the high-speed steel is 5.1×10 5 , an 8.5% increase compared with that after carbide decomposition treatment; Compared with that after tempering treatment, the dislocation density in the high-speed steel after pulsed magnetic field treatment increases from 0.6×10 13 m -2 to 1.1×10 13 m -2 , the volume percentage content of retained austenite in the high-speed steel decreases from 21% to 14%, the hardness increases by 1.2 HRC, and the impact toughness increases by 6 J / cm 2; After the treatment, the average aspect ratio of carbide particles in the high-speed steel is 1.62, and the average grain size of the carbide is 3.1 μm.

[0028] Example 2: The microstructure and property control treatment of the high-speed steel material for taps is carried out according to the following steps:

[0029] (1) Plastic deformation of high-speed steel and formation of high-density dislocations: Heat the high-speed steel material for M2 taps to 830 °C, hold for 1.5 h, and then cool to 140 °C; then carry out 10 passes of cold rolling plastic deformation on the high-speed steel, with a total rolling reduction of 18%, the thickness reduction per pass is 0.6 mm, and the rolling speed is 0.4 m / s; a tensile stress is applied during rolling, and the front tensile stress is controlled to be 200 MPa, and the rear tensile stress is 1.2 times that of the front tensile stress, that is, 224 MPa. The front and rear tensile stresses change the stress state in the rolling stress deformation zone from a triaxial compressive stress state to a biaxial compressive stress and uniaxial tensile stress state and reduce the rolling force, so that no fracture occurs during the plastic deformation of the high-speed steel; after cold rolling plastic deformation, high-density dislocations are formed in the high-speed steel, and the dislocation density is 6.9×10 13 m -2 ;

[0030] (2) Carbide decomposition treatment: Put the high-speed steel after cold rolling plastic deformation into a heat treatment furnace, heat it to 1100 °C at a heating rate of 8 °C / min, hold for 5 h and then air-cool. The high-density dislocations in the high-speed steel, as the nuclei for the formation of new phases, can promote the decomposition of M2C-type carbides into M6C and MC-type carbides. After decomposition, the number of carbide particles per square millimeter area in the high-speed steel is 7.7×10 5 ;

[0031] (3) Carbide spheroidization treatment: Put the high-speed steel after decomposition treatment into a heat treatment furnace, heat it to 1150 °C at a heating rate of 7 °C / min, hold for 20 min and then air-cool to spheroidize the carbides in the high-speed steel. After spheroidization treatment, the average aspect ratio of carbide particles is 1.78, and the average grain size of the carbide is 4.5 μm;

[0032] (4) Quenching treatment of high-speed steel: Heat the high-speed steel after carbide spheroidization treatment to 1250 °C at a heating rate of 8 °C / min, hold for 5 min, and then perform oil quenching;

[0033] (5) Tempering treatment of high-speed steel: Heat the high-speed steel after quenching treatment to 570 °C at a heating rate of 8 °C / min, hold for 1.5 h and then air-cool to complete one tempering treatment. The tempering treatment is repeated 2 times. The hardness of the high-speed steel after tempering is 63.5 HRC, and the impact toughness is 29 J / cm 2 , and the number of carbide particles per square millimeter area in the high-speed steel after tempering treatment is 7.8×10 5 ;

[0034] (6) Introduction, carbide precipitation, and residual austenite transformation control in high-speed steel: The high-speed steel after tempering treatment is subjected to pulsed magnetic field treatment. The intensity of the pulsed magnetic field is 2T, the frequency of the pulsed magnetic field is 30Hz, and the treatment time is 5min. The pulsed magnetic field treatment causes carbide precipitation, an increase in dislocation density, and the transformation of residual austenite to martensite in the high-speed steel for tapping, thereby realizing the regulation of tissue properties. After the pulsed magnetic field treatment, the number of carbide particles per square millimeter area in the high-speed steel is 8.5×10 5 , an increase of 10.3% compared with that after carbide decomposition treatment; compared with that after tempering treatment, the dislocation density in the high-speed steel after pulsed magnetic field treatment increases from 0.8×10 13 m -2 to 1.4×10 13 m -2 . The volume percentage content of residual austenite in the high-speed steel decreases from 23% to 15%, the hardness increases by 1.5HRC, and the impact toughness increases by 7J / cm 2 ; after the treatment, the average aspect ratio of carbide particles in the high-speed steel is 1.77, and the average grain size of carbide is 4.4μm.

Claims

1. A method for controlling the microstructure and properties of high-speed steel materials for taps, characterized in that The following steps are included in sequence: (1)Plastic deformation of high-speed steel and formation of high-density dislocations: Heat the high-speed steel material of the tap to 820 - 830 °C, hold for 1 - 1.5 h, and then cool to 100 - 150 °C; then perform multi-pass cold rolling plastic deformation on the high-speed steel, with a total rolling reduction of 10 - 20%, and the reduction thickness per pass is 0.1 - 1 mm; apply a tensile stress during rolling, control the front tensile stress to be 150 - 200 MPa, and the rear tensile stress is 1.1 - 1.2 times that of the front tensile stress. The front and rear tensile stresses change the stress state in the rolling stress deformation zone from a triaxial compressive stress state to a biaxial compressive stress and uniaxial tensile stress state and reduce the rolling force, so that no fracture occurs during the plastic deformation of the high-speed steel; after cold rolling plastic deformation, high-density dislocations are formed in the high-speed steel, and the dislocation density is 3×10 13 ~8×10 13 m -2 ; (2)Carbide decomposition treatment: The high-speed steel after cold rolling plastic deformation is put into a heat treatment furnace, heated to 1000 - 1100 °C, cooled after holding for 3 - 5 h. The high-density dislocations in the high-speed steel, serving as the nuclei for the formation of new phases, can promote the decomposition of M2C-type carbides into M6C and MC-type carbides. After decomposition, the number of carbide particles per square millimeter area in the high-speed steel is 4×10 5 ~9×10 5 ; (3) Carbide spheroidization treatment: The high-speed steel after decomposition treatment is placed in a heat treatment furnace, heated to 1150°C, kept at this temperature for 5 to 30 minutes, and then cooled to spheroidize the carbides in the high-speed steel. After spheroidization treatment, the average aspect ratio of the carbide particles is 1.6 to 1.8, and the average grain size of the carbides is 3 to 5 μm. (4) High-speed steel quenching treatment: The high-speed steel after carbide spheroidization treatment is heated to 1200~1250℃, kept at this temperature for 3~5min, and then oil quenched; (5)High-speed steel tempering treatment: Heat the quenched high-speed steel to 560 - 580 °C, hold for 1 - 2 h, and then cool to complete one tempering treatment. The tempering treatment is repeated 2 times. After tempering, the hardness of the high-speed steel is 62 - 65 HRC, and the impact toughness is 20 - 35 J / cm 2 , compared with that after carbide decomposition treatment, the number of carbide particles per square millimeter area in the high-speed steel after tempering treatment increases by 1 - 3%; (6)Introduction, carbide precipitation, and transformation control of retained austenite in high-speed steel: After tempering treatment of high-speed steel, pulsed magnetic field treatment is carried out. The intensity of the pulsed magnetic field is 1.5 - 2 T, and the treatment time is 3 - 5 min. Pulsed magnetic field treatment causes carbide precipitation, an increase in dislocation density, and the transformation of retained austenite to martensite in high-speed steel for taps, thereby realizing the regulation of tissue properties. Compared with after carbide decomposition treatment, the number of carbide particles per square millimeter area in high-speed steel after pulsed magnetic field treatment increases by 6 - 15%. Compared with after tempering treatment, the dislocation density in high-speed steel after pulsed magnetic field treatment increases from 0.5×10 13 ~1×10 13 m -2 to 1.1×10 13 ~1.5×10 13 m -2 , the volume percentage of retained austenite in high-speed steel decreases from 18 - 25% to 12 - 16%, the hardness increases by 1 - 2 HRC, and the impact toughness increases by 5 - 10 J / cm 2 ; After the treatment, the average aspect ratio of carbide particles in high-speed steel is 1.6 - 1.8, and the average grain size of carbides is 3 - 5 μm.

2. The method for controlling the microstructure and properties of high-speed steel materials for taps according to claim 1 is further characterized by comprising the following steps in sequence: (1) When high-speed steel undergoes plastic deformation and high-density dislocations are formed, the rolling speed during cold rolling is 0.2~0.5m / s; (2) During the carbide decomposition treatment, the heating rate is 4-8°C / min, and after the heat preservation is completed, the furnace is taken out of the furnace and air-cooled; (3) During the carbide spheroidization treatment, the heating rate is 4-8°C / min, and after the heat preservation is completed, the carbide is taken out of the furnace and air-cooled; (4) During the quenching treatment of high-speed steel, the heating rate is 4~8℃ / min; (5) During the tempering treatment of high-speed steel, the heating rate is 4~8℃ / min, and the steel is air-cooled after the heat preservation. (6) When high-density dislocation introduction, carbide precipitation and residual austenite transformation control are carried out in high-speed steel, the frequency of the pulsed magnetic field is 25~35Hz.

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