Vacuum carburization processing method, and method for manufacturing carburized component

Abstract

In the vacuum carburization processing method according to the present embodiment, when a flow of a carburizing gas, which has been calculated on the basis of a diffusion flux of carbon in a surface layer of a steel material, which is obtained in a diffusion simulation using a diffusion equation, is defined as a theoretical carburizing gas flow (FT), and when the time required for an actual carburizing gas flow to become equal to the theoretical carburizing gas flow after commencement of a carburizing step is defined as an intersection time te, the time from the commencement of the carburizingstep until the completion thereof is defined as a carburization time ta, and one-fifth of the carburization time is defined as a reference time ta/5, an early carburizing step (S1) from the commencement of the carburizing step to the intersection time te is performed wherein an actual carburizing gas flow (FR) is set to be equal to or greater than a theoretical carburizing gas flow (FT(te)) at the point where the reference time ta/5 has elapsed from the commencement of the carburizing step, and to be equal to or less than a theoretical carburizing gas flow (FT(20s)) at the point where twentyseconds have elapsed from the commencement of the carburizing step, and a late carburizing step (S2) from the intersection time te until the carburization time ta is performed wherein the actual carburizing gas flow (FR) is set to be within a range of 1.00 to 1.20 times of the theoretical carburizing gas flow (FT).

Description

technical field [0001] The present application relates to a vacuum carburizing treatment method and a method of manufacturing a carburized part. Background technique [0002] Steel parts for which high surface fatigue strength is required are manufactured by subjecting steel materials to surface hardening treatment. One of the surface hardening treatment methods is a vacuum carburizing treatment method. The vacuum carburizing treatment method includes a carburizing step and a diffusion step. In the carburizing step, a carburizing gas that is a hydrocarbon gas is introduced to increase the carbon concentration on the surface of the steel material heated to the carburizing temperature. The hydrocarbon gas is, for example, acetylene, propane, or the like. In the diffusion step, after the carburizing step, the introduction of the carburizing gas is stopped, and carbon is diffused in the depth direction of the surface layer of the steel material. By adjusting the time of the ...

AI Technical Summary

Problems solved by technology

At this time, the surface carbon concentration and carburizing depth distribution are uneven

Therefore, the surface layer of the carburized part cannot be maintained at a constant quality

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