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Heat treatment method for improving the bearing capacity of thin wall steel pieces

A technology of bearing capacity and thin-walled parts, which is applied in the field of heat treatment, can solve the problems of limited thickness of ferrite diffusion layer, high brittleness of compound layer, and limitation of nitriding process, etc., and achieves small workpiece distortion, reduced workpiece distortion, and high overall structure The effect of intensity

Inactive Publication Date: 2005-06-01
SHANGHAI JIAO TONG UNIV
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Problems solved by technology

However, due to the high brittleness of the compound layer, the thickness of the ferrite diffusion layer is limited, and the strength is not high, thus limiting the application of the nitriding process in improving the structural strength.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0013] The hardness of industrial pure iron thin-walled parts with a thickness of 1mm is about 100HV. According to the conversion relationship between microhardness and strength, the tensile strength of the material is about 375MPa. Nitriding in an atmosphere with a temperature of 640°C and an ammonia decomposition rate of 86-88% for 6 hours, and after 12 hours of constant temperature in a nitrate bath at 225°C, the maximum hardness of the austenite decomposition layer can reach 1100HV, and the average hardness is 700HV. The thickness of one side is about 50μm, and the overall average hardness of the workpiece is about 182HV. According to the conversion relationship between microhardness and strength, the overall tensile strength of the material is about 609MPa, which is 234MPa higher than that before treatment.

Embodiment 2

[0015] Ultra-low carbon steel thin-walled parts with a thickness of 0.5mm and a hardness of about 100HV are nitrided in an atmosphere with a temperature of 640°C and an ammonia decomposition rate of 86-88% for 4 hours, then quenched in an oil tank at 120°C, and then Put it in an air furnace at 300°C for 1 hour, the maximum hardness of the austenite decomposition layer can reach 800HV, the thickness of one side is about 28μm, the average hardness is about 600HV, and the average hardness of tempered martensite is about 500HV. The side thickness is about 13μm, the average hardness of nitrogen-containing ferrite is about 200HV, the thickness of one side is about 15μm, and the others are ferrite, so the overall average hardness of the treated pure iron thin-walled parts is about 181HV. The conversion relationship between microhardness and strength shows that the overall tensile strength of the material is about 609MPa, which is 234MPa higher than that before treatment.

Embodiment 3

[0017] Industrial pure iron thin-wall parts with a thickness of 2.5mm are nitriding in an atmosphere with a temperature of 640°C and an ammonia decomposition rate of 86-88% for 6 hours, and then the temperature is increased to 700°C, and the ammonia decomposition rate is 90-92% Continue nitriding in the atmosphere for 6 hours, and after cooling to room temperature quickly, after aging at 180°C for 70 hours, the maximum hardness of the original austenite decomposition layer can reach 1100HV, the average hardness is about 700HV, and the thickness of one side is about 80μm; The hardness of the tempered martensite remains at about 500HV, the thickness of one side is about 30μm, the average hardness of the nitrogen-containing ferrite layer is about 180HV, and the thickness of one side is about 200μm, so the overall average hardness of the material after aging treatment It is about 157HV. According to the conversion relationship between microhardness and strength, the overall tensile...

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Abstract

The heat treatment method of raising bearing capacity of thin-wall steel part includes first heating the cold deformation formed workpiece to the temperature range of Fe-N system austenite arean and nitriding to form nitrogen containing austenite layer, and then cooling the workpiece fast to below 300 deg.c to inhibit the euterctoid conversion of the nitrogen containing austenite and to decompose the austenite layer into dispersed two-phase structure or to convert into martensite. The said method makes the nitrogen containing austenite layer reinforced and the raises the overall structural strength of the thin-wall steel part greatly. The said method of raising the bearing capacity features no special requirement in the chemical components of the material and is suitable for ultralow carbon steel, low carbon steel, low alloy steel, etc.

Description

technical field [0001] The invention relates to a heat treatment method used in the field of chemical heat treatment of iron and steel, in particular to a heat treatment method for improving the bearing capacity of thin-walled steel parts. Background technique [0002] Most of the thin-walled steel parts are manufactured by cold deformation. In order to ensure the deformation capacity of the material, the strength of the material is required not to be too high, thus limiting the bearing capacity of the thin-walled steel parts. In the existing technology, in order to improve the structural strength of thin-walled steel parts, the method of adding alloy elements or the method of forming martensite by quenching after forming is generally used. Although the strength of thin-walled parts can be improved by adding alloying elements, the cold deformation ability is deteriorated and the cost is increased. Although the method of quenching after cold deformation can improve the stren...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23F17/00
Inventor 胡明娟李晓玲潘健生刘占仓蒋志俊
Owner SHANGHAI JIAO TONG UNIV
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