Vacuum carburizing treatment method and manufacturing method of carburized parts

Abstract

In the vacuum carburizing treatment method according to this embodiment, the flow rate of carburizing gas calculated from the diffusion flux of carbon in the surface layer of the steel material obtained from the diffusion simulation using the diffusion equation is defined as the theoretical carburizing gas flow rate (FT) , the moment when the actual carburizing gas flow rate is equal to the theoretical carburizing gas flow rate after the carburizing process starts is defined as the intersection time te, and the time from the beginning to the end of the carburizing process is defined as the carburizing time ta, and the carburizing process is defined as The time of 1 / 5 of the time is defined as the reference time ta / 5. At this time, in the early carburizing process (S1) from the start of the carburizing process to the intersection time te, the actual carburizing gas flow rate (FR) It is: the theoretical carburizing gas flow rate (FT(te)) above the reference time ta / 5 from the start of the carburizing process, and the theoretical carburizing gas flow rate (FT(20s) at 20 seconds from the start of the carburizing process )) or less; in the late carburizing process (S2) from the intersection time te to the carburizing time ta, the actual carburizing gas flow rate (FR) is 1.00 to 1.20 times the theoretical carburizing gas flow rate (FT) within range.

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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