CN110408747B - Method for reducing residual stress and improving hardness of GT35 steel bonded hard alloy - Google Patents
Method for reducing residual stress and improving hardness of GT35 steel bonded hard alloy Download PDFInfo
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- CN110408747B CN110408747B CN201910803830.0A CN201910803830A CN110408747B CN 110408747 B CN110408747 B CN 110408747B CN 201910803830 A CN201910803830 A CN 201910803830A CN 110408747 B CN110408747 B CN 110408747B
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Abstract
The invention relates to a method for reducing the residual stress and improving the hardness of GT35 steel bonded hard alloy, belonging to the technical field of composite material processing. The method takes the GT35 steel bonded hard alloy in a forging state as a raw material, and directly carries out stress aging treatment on the raw material to obtain a product; and during stress aging treatment, the tensile stress loaded on the raw material is 200-400 MPa, the temperature is 50-300 ℃, and the time is more than 0.5 h. The reduction range of the surface residual stress of the product obtained by the method is 86-218 MPa, the improvement range of the hardness of the alloy is 157-260 MPa, the method simplifies the treatment process of the GT35 steel bond hard alloy, the product has excellent performance, and necessary conditions are provided for the GT35 steel bond hard alloy low-cost application.
Description
Technical Field
The invention relates to a method for reducing the residual stress and improving the hardness of GT35 steel bonded hard alloy, belonging to the technical field of composite material processing.
Background
The steel bonded hard alloy has excellent comprehensive properties such as high hardness, high strength, low density, low thermal expansion coefficient and the like, and is widely applied to the fields of tools and dies, strategic weapons, aerospace and the like. In the use process of the alloy, the alloy deformation can cause the reduction of the precision of the device, influence the quality of the product and reduce the service life of the precision device; the TiC reinforced steel bonded hard alloy with the mass fraction of 35% is mainly used for manufacturing core parts such as motor bearings and end covers in the field of aerospace, and the precision and reliability of inertia devices can be influenced by the tiny deformation of the parts. The dimensional stability of the steel bonded hard alloy is mainly influenced by microstructures and residual stress, and the microstructure transformation of residual austenite transformation, second phase precipitation and the like in the service process of the alloy can cause the change of the alloy volume, thereby influencing the dimensional stability of the alloy. The residual stresses generated during the preparation and heat treatment of the alloy can undergo stress relaxation during long term storage, which can also cause dimensional changes in the alloy. Therefore, the improvement of the dimensional stability of the steel bonded hard alloy can be regulated and controlled by improving the structural stability of the structure and reducing the residual stress of the alloy.
In the earlier research process, the inventor develops a process of quenching and then stress tempering the raw material by using GT35 steel bonded hard alloy as the raw material, and discloses CN 201711354239.9; when the patent is used for stress tempering, the butt joint is quenching treatment; but the inventor researches and discovers that: hard phase TiC particles in the forged steel bonded hard alloy are crushed and refined under the action of external force, complex carbide bridging phases are eliminated, defects in the alloy are welded in forging, the hard phase distribution is more uniform than that before forging, and the mechanical property of the alloy is obviously improved. Based on the above findings: the inventors propose a concept: if the forged steel bonded hard alloy can be directly utilized, the steel bonded hard alloy which can be directly used for preparing and using related devices such as tools and dies can be obtained after stress aging. Based on the assumption, the invention is obtained by developing experiments and optimizing.
Disclosure of Invention
In order to greatly reduce the residual stress in the alloy and simultaneously greatly improve the hardness of the alloy, the invention designs a method for reducing the residual stress of the GT35 steel bonded hard alloy and improving the hardness of the GT35 steel bonded hard alloy. The invention takes the GT35 steel bonded hard alloy in forging state as raw material. After the stress aging treatment is directly carried out on the alloy, metastable residual austenite in the alloy basically disappears, and the structure becomes more stable. The residual stress of the obtained product is small, and the hardness of the product is remarkably improved.
The invention relates to a method for reducing the residual stress of GT35 steel bond hard alloy and improving the hardness thereof;
taking the GT35 steel-bonded hard alloy in a forging state as a raw material, and directly carrying out stress aging treatment on the raw material to obtain a product; and during stress aging treatment, the tensile stress loaded on the raw material is 200-400 MPa, the temperature is 50-300 ℃, and the time is more than 0.5 h.
Preferably, the GT35 alloy after forging is loaded with 200-300 MPa of tensile stress and is kept at 100-300 ℃ for 8-36 h.
As a further preferred embodiment, the invention provides a method for reducing the residual stress and improving the hardness of the GT35 steel bonded hard alloy; the implementation scheme is as follows:
directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at the temperature of 100-; the residual stress of the surface of the sample piece is-52 to-135 MPa, and the hardness is 1000-1054 HV. The residual stress of the surface of the GT35 alloy in a forging state is-253 to-270 MPa, and the hardness is 810 to 846 HV.
As a further preferred aspect, the present invention provides a method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide; the implementation scheme is as follows:
directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 150 ℃, loading stress at 250-300 MPa, and loading for 8h to obtain a sample.
As a further preferred aspect, the present invention provides a method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide; the implementation scheme is as follows:
directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 100 ℃, loading stress at 300MPa, and loading for 12h to obtain a sample piece; the residual stress of the surface of the sample piece is-75 MPa, and the hardness is 1012 HV.
As a further preferred aspect, the present invention provides a method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide; the implementation scheme is as follows:
directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 200 ℃, loading stress at 300MPa, and loading for 8h to obtain a sample piece; the residual stress of the surface of the sample piece is-52 MPa, and the hardness is 1054 HV.
The reduction range of the surface residual stress of the product obtained by the method is 86-218 MPa, and the improvement range of the hardness of the alloy is 157-260 HV.
The invention relates to a method for reducing the residual stress of a GT35 steel bonded hard alloy and improving the hardness of the hard alloy, which defines the size change rate of an obtained product after being placed for 30d at room temperature as A, and the size change rate of a product obtained from a forged GT35 alloy after being placed for 30d at room temperature as B; A/B is 0.5 to 0.8.
Advantages of
Compared with the prior art, the invention simplifies the process, and the hardness of the obtained product is improved to a degree superior to that of the prior art, and the stress reduction degree of the obtained product is greater than that of the prior art.
Through optimization, the surface residual stress of the product obtained by the invention is-52 to-167 MPa, and the hardness is 1003 to 1070 HV. After further optimization, the residual stress on the surface of the product obtained by the method can be reduced to-52 to-75 MPa; meanwhile, the hardness can be increased to 1054-1070 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.
In a particular embodiment of the invention, the GT35 alloy in the as-forged state has a residual stress of-253 MPa and a hardness of 810 HV.
Defining the size change rate of the obtained product after being placed for 30 days at room temperature as A, and the size change rate of the product obtained from the forged GT35 alloy after being placed for 30 days at room temperature as B;
example 1
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 100 ℃, the loading stress of 200MPa and the loading time of 24h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-162 MPa, and the hardness of the hard alloy is improved to 1012 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.5.
Example 2
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 200 ℃, the loading stress of 200MPa and the loading time of 24h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-142 MPa, and the hardness of the hard alloy is improved to 1070 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.55.
Example 3
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 150 ℃, the loading stress of 250MPa and the loading time of 8h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-134 MPa, and the hardness of the hard alloy is improved to 1034 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.62.
Example 4
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 200 ℃, the loading stress of 200MPa and the loading time of 12h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-167 MPa, and the hardness of the hard alloy is improved to 1018 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.53.
Example 5
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 150 ℃, the loading stress of 300MPa and the loading time of 8h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-57 MPa, and the hardness of the hard alloy is improved to 1003 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.68.
Example 6
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 100 ℃, the loading stress of 300MPa and the loading time of 12h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-75 MPa, and the hardness of the hard alloy is improved to 1012 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.71.
Example 7
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 200 ℃, the loading stress of 220MPa and the loading time of 24h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-108 MPa, and the hardness of the hard alloy is improved to 1035 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.64.
Example 8
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 100 ℃, the loading stress of 220MPa and the loading time of 24h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-135 MPa, and the hardness of the hard alloy is improved to 1048 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.78.
Example 9
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 300 ℃, the loading stress of 200MPa and the loading time of 8h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-121 MPa, and the hardness of the hard alloy is improved to 1040 HV. The dimensional change rate of the obtained product after being left for 30 days at room temperature is measured, and the A/B is calculated to be 0.73.
Example 10
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 200 ℃, the loading stress of 300MPa and the loading time of 8h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-52 MPa, and the hardness of the hard alloy is improved to 1054 HV. The dimensional change rate of the obtained product after being placed at room temperature for 30 days is measured, and A/B is calculated to be 0.58.
Comparative example 1
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 400 ℃, the loading stress of 200MPa and the loading time of 8h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-187 MPa, and the hardness of the hard alloy is improved to 921 HV.
Comparative example 2
And directly carrying out stress aging treatment on the GT35 alloy in a forging state at the heating temperature of 200 ℃, the loading stress of 100MPa and the loading time of 24h to obtain a sample piece. The residual stress of the alloy surface obtained after the treatment is-229 MPa, and the hardness of the hard alloy is improved to 1017 HV.
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 (7)
1. A method for reducing the residual stress and improving the hardness of GT35 steel bonded hard alloy; the method is characterized in that:
taking the GT35 steel-bonded hard alloy in a forging state as a raw material, and directly carrying out stress aging treatment on the raw material to obtain a product; during the stress aging treatment, the tensile stress loaded on the raw material is 220-300MPa, the temperature is 100-200 ℃, and the loading time is 6-24 h; the residual stress of the surface of the product is-52 to-135 MPa, and the hardness is 1000-minus 1054 HV; the reduction range of the surface residual stress of the obtained product is 86-218 MPa, and the improvement range of the hardness of the alloy is 157-260 HV.
2. A method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide according to claim 1; the method is characterized in that: directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 150 ℃, loading stress at 250-300 MPa, and loading for 8h to obtain a sample.
3. A method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide according to claim 1; the method is characterized in that: directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 100 ℃, loading stress at 300MPa, and loading for 12h to obtain a sample piece; the residual stress of the surface of the sample piece is-75 MPa, and the hardness is 1012 HV.
4. A method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide according to claim 1; the method is characterized in that: directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 200 ℃, loading stress at 220MPa, and loading for 24h to obtain a sample piece; the residual stress of the sample surface was-108 MPa, and the hardness was 1035 HV.
5. A method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide according to claim 1; the method is characterized in that: directly carrying out stress aging treatment on the GT35 alloy in a forging state, wherein the stress aging treatment comprises the following steps: heating at 200 ℃, loading stress at 300MPa, and loading for 8h to obtain a sample piece; the residual stress of the surface of the sample piece is-52 MPa, and the hardness is 1054 HV.
6. A method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide according to any one of claims 1 to 5; the method is characterized in that: the reduction range of the surface residual stress of the obtained product is 103-218MPa, and the increase range of the hardness of the alloy is 192-260 HV.
7. A method of reducing the residual stress and increasing the hardness of a GT35 steel bonded cemented carbide according to any one of claims 1 to 5; the method is characterized in that:
defining the size change rate of the obtained product after being placed for 30 days at room temperature as A, and the size change rate of the product obtained from the forged GT35 alloy after being placed for 30 days at room temperature as B; a/B = 0.5-0.8.
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