CN109252026B - Heat treatment method of GT35 steel bonded hard alloy - Google Patents
Heat treatment method of GT35 steel bonded hard alloy Download PDFInfo
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- CN109252026B CN109252026B CN201811403244.9A CN201811403244A CN109252026B CN 109252026 B CN109252026 B CN 109252026B CN 201811403244 A CN201811403244 A CN 201811403244A CN 109252026 B CN109252026 B CN 109252026B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/78—Combined heat-treatments not provided for above
- C21D1/785—Thermocycling
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Abstract
The invention discloses a GT35 steel bond hard alloy heat treatment method. The GT35 steel bonded hard alloy is composed of CrMo low alloy steel as a binding phase and TiC particles with the mass fraction of 35% as a hard phase. And carrying out austenitizing treatment, quenching, isothermal tempering and cold-hot circulating comprehensive heat treatment on the forged alloy by adopting a heat treatment method to obtain the GT35 hard alloy with stable structure and small residual stress. Compared with the alloy obtained by the conventional treatment method, the GT35 steel bonded hard alloy applying the heat treatment method reduces the residual stress on the surface of the hard alloy, improves the hardness of the alloy, and has the size change less than 0.2 per mill after being placed at room temperature for half a year.
Description
Technical Field
The invention relates to a heat treatment process of GT35 steel bonded hard alloy, belonging to the technical field of composite material heat treatment processing.
Background
The GT35 steel bonded hard alloy has the characteristics of high hardness, good wear resistance, excellent machining performance and the like, and is widely applied to the fields of aerospace, automobile industry, tool and die and the like, and the GT35 steel bonded hard alloy consists of CrMo low alloy steel as a binding phase and TiC particles with the mass fraction of 35 percent as a hard phase. In the field of aerospace application, the GT35 material is used for manufacturing important components such as a shaft, a thrust plate and the like of a dynamic pressure gas bearing gyro motor in an inertial guidance system; small variations in the components can reduce the reliability of the device and even affect the operational stability of the entire inertial system. In the field of tool and die application, the deformation of die materials can also influence the quality of products to a certain extent, and the use precision and the service life of the die are reduced. The dimensional stability of the GT35 material is mainly affected by two aspects: firstly, the matrix phase is easy to have structural changes such as martensite phase transformation, residual austenite decomposition, carbide precipitation and the like in the preparation and service processes of the material. During these phase transitions, the dimensional stability of the material is affected from the point of view of microstructural stability due to the difference in volume of the phases; secondly, the material can generate macroscopic residual stress and microscopic stress in the preparation, processing and heat treatment processes, and stress relaxation and release behaviors can occur in the long-term storage or service process, so that the dimensional stability of the material is reduced. Thus, there are two main approaches to improve the dimensional stability of GT35 material: on one hand, the tissue structure stability of the material is further improved; and on the other hand, the residual stress of the material is reasonably regulated.
Therefore, the research on a heat treatment process and a method for improving the size stability of the GT35 steel bonded hard alloy comprehensively improves the structural property stability of the material, thereby improving the size stability of the material, and is a problem to be solved urgently in the practical application and popularization process of the GT35 material.
Disclosure of Invention
In order to better control the microstructure of the GT35 steel bond hard alloy and improve the dimensional stability of the GT35 steel bond hard alloy, the invention provides a heat treatment process of the GT35 steel bond hard alloy, the alloy treated by the heat treatment process of the invention has stable structure, small residual stress and small dimensional change after long-time placement. The specific technical scheme is as follows.
A heat treatment method of GT35 steel bonded hard alloy is characterized by comprising the following steps:
1) austenitizing the GT35 steel bonded hard alloy in a forging state;
2) quenching the GT35 steel bonded hard alloy treated in the step 1);
3) carrying out isothermal tempering treatment on the GT35 steel-bonded hard alloy treated in the step 2);
4) and carrying out cold-hot circulation treatment on the GT35 steel-bonded hard alloy treated in the step 3).
Further, the austenitizing treatment process comprises the following steps: and heating the GT35 steel-bonded hard alloy in a forging state to 800-1100 ℃, and preserving the heat for 20-100 min.
Further, the quenching treatment process comprises the following steps: and (3) carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the oil temperature is 20-40 ℃, the mass ratio of a quenching sample to a quenching medium is 1: 30-1: 35, and the quenching time is 5-10 min.
Further, the isothermal tempering treatment process comprises the following steps: and heating the quenched GT35 steel-bonded hard alloy to 150-300 ℃, preserving the heat for 0.5-12 h, and cooling in the air.
Further, the cold and hot circulation treatment process comprises the following steps: and cooling the tempered GT35 steel-bonded hard alloy to-40 to-196 ℃, preserving heat for 0.5 to 4 hours, then heating to 80 to 250 ℃, preserving heat for 0.5 to 6 hours, and carrying out cold-hot circulation treatment for 2 to 12 times.
Further, the GT35 steel bonded hard alloy treated by the step 4) is placed at room temperature for half a year, and the size change of the product is less than 0.2 per thousand.
Further, the hardness of the GT35 steel bonded hard alloy treated by the step 4) is 970-1050 HV.
The heat treatment method of the invention is based on the alloy in a forging state, and the GT35 steel bond hard alloy can obviously reduce the structural defects of pores, microcracks and the like after being sintered after being forged, the hard phase particles are more uniformly distributed, and the density, hardness and strength of the alloy are obviously improved. The forged alloy is subjected to heat treatment, so that the strength of the alloy is improved, and the dimensional stability of the alloy is enhanced.
The austenitizing treatment can fully dissolve carbide in a binding phase of the GT35 steel bonded hard alloy into a matrix, promote uniform diffusion of alloy elements and make full tissue preparation for quenching; the oil quenching treatment can greatly reduce the structural stress of the quenched workpiece and reduce the deformation and cracking tendency of the workpiece; meanwhile, the viscosity of the quenching medium is reduced by improving the oil temperature, the fluidity of the quenching medium is improved, and the cooling capacity of the oil quenching treatment in a high-temperature section is improved; the isothermal tempering treatment can reduce or eliminate quenching stress and improve the comprehensive mechanical property of the alloy on the premise of ensuring the high hardness of the steel matrix.
The cold-hot circulation treatment is circulation stabilization treatment, is an effective way for improving the performance stability of the alloy structure after tempering, is the extension and the extension of the traditional heat treatment process, and can obviously improve the toughness of the workpiece on the premise of not reducing the strength and the hardness of the workpiece. The advantage of the improved stability of the alloy structure performance after the cold and hot circulation treatment is as follows: after the cold and hot circulation, the metastable residual austenite amount in the alloy is obviously reduced, and the dimensional stability of the workpiece can be improved; because the retained austenite generates martensite phase transformation, the microhardness of the alloy can be further improved; the increase of martensite content and the precipitation of fine carbides can improve the wear resistance of the alloy.
Compared with the conventional treatment method, the GT35 steel-bonded hard alloy obtained by the heat treatment method has the advantages that the residual stress on the surface of the alloy is reduced from-250 to-200 MPa to-120 to-50 MPa, the hardness of the alloy is improved from 900 to 940 HV to 970 to 1050HV, and the dimensional change of the alloy after being placed at room temperature for half a year is less than 0.2 per mill (the use precision is 10)-7m's test equipment determines the change in length of the sample); wherein the hardness of the GT35 steel-bonded hard alloy in a forging state is 420-440 HV.
Detailed Description
In order to further enhance the understanding of the present invention, the following detailed description of the present invention is provided in connection with examples, and it should be noted that the scope of the present invention is not limited by the following examples.
Example 1
Heating the GT35 steel bond hard alloy in a forging state to 800 ℃ for 100 min of austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 10 engine oil, the oil temperature is 25 ℃, the mass ratio of a quenching sample to the quenching medium is 1:30, and the quenching time is 5 min; heating the quenched hard alloy to 150 ℃, and keeping the temperature for 12h for tempering; and cooling the tempered hard alloy to-40 ℃, preserving heat for 4 h, then heating to 80 ℃, preserving heat for 6h, and repeating the steps for 12 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-113 MPa, the hardness of the hard alloy is improved to 981 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 2
Heating the GT35 steel bond hard alloy in a forging state to 850 ℃ for 80 min of austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 20 engine oil, the oil temperature is 25 ℃, the mass ratio of a quenching sample to the quenching medium is 1:30, and the quenching time is 8 min; heating the quenched hard alloy to 150 ℃, and keeping the temperature for 8 hours for tempering treatment; and cooling the tempered hard alloy to-80 ℃, preserving heat for 4 h, then heating to 120 ℃, preserving heat for 5h, and repeating the steps for 10 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-109 MPa, the hardness of the hard alloy is improved to 975 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 3
Heating the GT35 steel bond hard alloy in a forging state to 900 ℃ for 60 min for austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 30 engine oil, the oil temperature is 25 ℃, the mass ratio of a quenching sample to the quenching medium is 1:30, and the quenching time is 10 min; heating the quenched hard alloy to 200 ℃, and keeping the temperature for 4 hours for tempering treatment; and cooling the tempered hard alloy to-100 ℃, preserving heat for 3 h, then heating to 150 ℃, preserving heat for 4 h, and repeating the steps for 8 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-93 MPa, the hardness of the hard alloy is improved to 992 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 4
Heating the GT35 steel bond hard alloy in a forging state to 950 ℃ for 50 min of austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 20 engine oil, the oil temperature is 30 ℃, the mass ratio of a quenching sample to the quenching medium is 1:35, and the quenching time is 5 min; heating the quenched hard alloy to 300 ℃, and keeping the temperature for 2 hours for tempering treatment; and cooling the tempered hard alloy to-196 ℃, preserving heat for 2h, then heating to 200 ℃, preserving heat for 3 h, and repeating the steps for 6 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-79 MPa, the hardness of the hard alloy is improved to 1005 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 5
Heating the GT35 steel bond hard alloy in a forging state to 950 ℃ for 50 min of austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 10 engine oil, the oil temperature is 30 ℃, the mass ratio of a quenching sample to the quenching medium is 1:35, and the quenching time is 10 min; heating the quenched hard alloy to 300 ℃, and keeping the temperature for 1 h for tempering; and cooling the tempered hard alloy to-196 ℃, preserving heat for 2h, then heating to 250 ℃, preserving heat for 3 h, and repeating the steps for 10 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-70 MPa, the hardness of the hard alloy is improved to 998 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 6
Heating the GT35 steel bond hard alloy in a forging state to 1000 ℃ for 30 min for austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 20 engine oil, the oil temperature is 40 ℃, the mass ratio of a quenching sample to the quenching medium is 1:35, and the quenching time is 8 min; heating the quenched hard alloy to 250 ℃, and keeping the temperature for 2 hours for tempering treatment; and cooling the tempered hard alloy to-196 ℃, preserving heat for 2h, then heating to 150 ℃, preserving heat for 4 h, and repeating the steps for 8 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-68 MPa, the hardness of the hard alloy is improved to 1017 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 7
Heating the GT35 steel bond hard alloy in a forging state to 1000 ℃ for 50 min of austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 10 engine oil, the oil temperature is 40 ℃, the mass ratio of a quenching sample to the quenching medium is 1:35, and the quenching time is 5 min; heating the quenched hard alloy to 200 ℃, and keeping the temperature for 4 hours for tempering treatment; and cooling the tempered hard alloy to-196 ℃, preserving heat for 4 h, then heating to 250 ℃, preserving heat for 6h, and repeating the steps for 10 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-62 MPa, the hardness of the hard alloy is improved to 1024 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
Example 8
Heating the GT35 steel bond hard alloy in a forging state to 1100 ℃ for 20 min of austenitizing treatment; carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the quenching medium is No. 10 engine oil, the oil temperature is 40 ℃, the mass ratio of a quenching sample to the quenching medium is 1:35, and the quenching time is 5 min; heating the quenched hard alloy to 150 ℃, and keeping the temperature for 12h for tempering; and cooling the tempered hard alloy to-196 ℃, preserving heat for 4 h, then heating to 200 ℃, preserving heat for 6h, and repeating the steps for 12 times to obtain a sample. The residual stress of the surface of the existing hard alloy obtained by the treatment of the embodiment is-59 MPa, the hardness of the hard alloy is improved to 1027 HV, and the dimensional change after the hard alloy is placed at room temperature for half a year is less than 0.2 per thousand.
The embodiments and features of the embodiments of the present invention may be combined with each other. The present invention is not limited to the above-described embodiments, which are only illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (6)
1. A heat treatment method of GT35 steel bonded hard alloy is characterized by comprising the following steps:
1) austenitizing the GT35 steel bonded hard alloy in a forging state;
2) quenching the GT35 steel bonded hard alloy treated in the step 1);
3) carrying out isothermal tempering treatment on the GT35 steel-bonded hard alloy treated in the step 2);
4) carrying out cold-hot circulation treatment on the GT35 steel-bonded hard alloy treated in the step 3);
the cold and hot circulation treatment process comprises the following steps: and cooling the tempered GT35 steel-bonded hard alloy to-40 to-196 ℃, preserving heat for 0.5 to 4 hours, then heating to 80 to 150 ℃, preserving heat for 0.5 to 6 hours, and carrying out cold-hot circulation treatment for 2 to 12 times.
2. The heat treatment method of GT35 steel bonded hard alloy according to claim 1, wherein the austenitizing process is: and heating the GT35 steel-bonded hard alloy in a forging state to 800-1100 ℃, and preserving the heat for 20-100 min.
3. The heat treatment method of GT35 steel bonded hard alloy according to claim 1, wherein the quenching process comprises: and (3) carrying out oil quenching treatment on the GT35 steel bonded hard alloy subjected to austenitizing treatment, wherein the oil temperature is 20-40 ℃, the mass ratio of a quenching sample to a quenching medium is 1: 30-1: 35, and the quenching time is 5-10 min.
4. The heat treatment method of GT35 steel bonded hard alloy according to claim 1, wherein the isothermal tempering process comprises: and heating the quenched GT35 steel-bonded hard alloy to 150-300 ℃, preserving the heat for 0.5-12 h, and cooling in the air.
5. The method for heat treating a GT35 steel bonded hard alloy as claimed in claim 1, wherein the GT35 steel bonded hard alloy treated in the step 4) is left at room temperature for half a year, and the dimensional change of the product is less than 0.2 ‰.
6. The heat treatment method of GT35 steel bonded hard alloy according to claim 1, wherein the hardness of GT35 steel bonded hard alloy treated by the step 4) is 970-1050 HV.
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