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Case hardened steel and carburized parts obtained therefrom

A technology for hardening steel and components, applied in solid diffusion coating, coating, metal material coating process, etc., can solve technical difficulties and other problems, and achieve the effect of improving hardenability and excellent cold forgeability

Active Publication Date: 2018-11-16
DAIDO STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0011] That is, cold forgeability and hardenability are generally a trade-off relationship, and there are technical difficulties in satisfying both properties at the same time

Method used

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  • Case hardened steel and carburized parts obtained therefrom
  • Case hardened steel and carburized parts obtained therefrom
  • Case hardened steel and carburized parts obtained therefrom

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0187] Each steel material having the chemical composition shown in Table 1 was melted, kept under heating at 1,250°C for 4 hours, and then hot rolled at a temperature above 950°C, whereby the steel material was made into a cylindrical test piece and diameter A steel bar with a φ of 30 mm is used for the Jominy end hardenability test defined in JIS G 0561 (2011).

[0188] Each test piece for the Jominy end hardenability test was used and the Jominy end hardenability test was performed to obtain the DI value.

[0189] In addition, each steel bar having a diameter φ of 30 mm was used and various tests described below including a forging test were conducted.

[0190] Usually, since the part to be cold forged is subjected to softening heat treatment before forging, the steel bar is kept at 760°C for 4 hours, and then the temperature is reduced to 650°C at a rate of 15°C / h and air Cooling softening treatment, measuring the hardness after softening treatment (Rockwell hardness HRB)...

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Abstract

The present invention solves the problem of providing a case-hardened steel excellent in cold forgeability and hardenability and a carburized part obtained therefrom. The case-hardened steel satisfies the following relational formula (1): σMAX<12.8×DI+745 relational formula (1), where DI is the value determined by Jomini’s end hardenability test, and σMAX (MPa) is determined in the following manner The maximum resistance to deformation: Cut out a test piece with a size of 15 mm (diameter) × 22.5 mm from the material that has undergone spheroidizing annealing, and cool it at a compression ratio of 70% while keeping the end face of each test piece constrained. Press to deform it. The carburized part is obtained by carburizing and quenching case-hardened steel.

Description

technical field [0001] The present invention relates to a case-hardened steel having excellent cold forgeability and hardenability, and to a carburized part obtained using the same. Background technique [0002] As a method of forming steel into the shape of gears and other parts, hot forging, which forges steel at high temperatures, is widely used. [0003] However, in hot forging, it is necessary to heat the material to be forged under high temperature conditions, and it is necessary to heat the die. Therefore, since a large amount of thermal energy is consumed and the number of processing steps increases, there is a problem that required costs increase. [0004] The processing method has been changed from hot forging to cold forging. In cold forging, no heating is required and the number of processing steps is reduced. Therefore, it is possible to reduce the required cost. [0005] However, the deformation resistance of the material to be forged increases during cold ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00C22C38/60
CPCC22C38/00C22C38/60C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/50C23C8/22C23C8/80C22C38/48C22C38/54C21D1/06
Inventor 中山恭平森田敏之井上圭介
Owner DAIDO STEEL CO LTD
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