JPH0466658A - Method for plasma carburizing and plasma carburizing apparatus - Google Patents

Abstract

PURPOSE:To stably form a thin carburized layer at high speed by using high frequency induction heating as the heating for the object to be carburized. CONSTITUTION:In a plasma carburizing method, the object to be carburized is heated by using high-frequency induction heating. By the high frequency, the object to be carburized is rapidly heated, and the heating is stopped at the moment when the temp. of only the surface rises to >= the A3 transformation point. When the high frequency is impressed and stopped, plasma is left to generate for a time in which the material to be carburized is in high temperature so that the solid soln. depth of C and the concn. can stably be controlled. At the time of increasing the frequency and shortening the impressing time, only the shallowest part on the surface layer of the object to be carburized can be carburized. Furthermore, because the heating is one for only the surface by high frequency, after the carburization, it is naturally hardened, so that oil hardening generally executed can be obviated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a heating method in plasma carburizing.

[Conventional technology]

Conventional heating methods for plasma carburizing use resistance heaters or infrared heaters to sufficiently heat the carburized material to a uniform temperature state. This is because the shape of the object to be carburized is often complex (if the whole part is not heated uniformly, solid solution and diffusion of C will be uneven during plasma carburizing, resulting in defects such as distortion, cracking, and failure to meet carburizing depth standards) However, although this method carburizes uniformly, the depth of carburization becomes more than 0.5 mm, which results in thin carburized objects (for example, 0.2 m thick).
It was impossible to form a shallow carburized layer (for example, 0.05 tan) in the steel. In other words, for example, when carburizing low carbon steel, the material to be carburized is held at a temperature just above the transformation point and carburized by generating plasma for a short time. Because the carburizing depth does not change, the individual carburizing depths vary greatly.

[Problem to be solved by the invention]

As described above, the conventional technology has a problem in that it is not possible to stably form a shallow carburized layer of 0.5 mm or less.

The present invention is intended to solve this problem, and its purpose is to obtain a thin carburized layer at high speed and stably.

[Means to solve the problem]

The plasma carburizing method is characterized by using high-frequency induction heating to heat the object to be carburized.

〔Example〕

In the examples of the present invention, 1% St@ was used for the carburized material. This material is difficult to carburize using normal gas carburizing methods, but it can be carburized using plasma carburizing. The thickness of the carburized material is 0.2 rye
s, and the target carburizing depth is 0.05+m+. This carburized material was placed in a plasma carburizing device and evacuated, and then propane gas and Ar were introduced.

Gas pressure was 0.5 pa. Next, a potential is applied to generate plasma and attract C ions to the carburized material.

At this time, the carburized material is at a low temperature, so most of the C is dissolved in solid solution.
Does not spread. Next, the carburized material is rapidly heated by high frequency.
Stop heating the moment only the surface reaches the A3 transformation point or higher.

Fluctuations occur in the plasma during heating, but as soon as heating is stopped, it immediately returns to its original state, that is, the surface of the carburized object is A, and at the moment when it is heated above the transformation point, C is solidly dissolved only on the surface. C
The solid solution depth and concentration of can be determined by applying high frequency, rather than controlling by the short plasma generation time as in the prior art. For example, frequency, application time, etc. Since the plasma continues to be generated while the carburized material is at a high temperature while the high frequency is applied and stopped, the depth and concentration of C solid solution can be stably controlled. If the frequency is increased and the application time is shortened (1 to 2 sec), only a very shallow part of the surface layer of the object to be carburized can be carburized. Fluctuations in the plasma during heating do not contribute to solid solution of C. This is thought to be because the solid solution of C is mainly carried out after the high frequency application because the high frequency is only applied for a short period of time.

With the above method and device, 1%Ski is 0.05±0,0
The carburizing depth could be controlled with an accuracy of 0.05 to 0.05.

〔Effect of the invention〕

As described above, by using high-frequency induction heating to heat the object to be carburized in the plasma carburizing method, it is possible to stably form carburization as shallow as 0.5 mm or less. Furthermore, since only the surface is heated by high frequency, quenching occurs naturally after carburizing, which also has the effect of omitting the commonly used oil quenching.

that's all Applicant: Seiko Epson Corporation

Claims (2)

[Claims] (1) A plasma carburizing method characterized in that high-frequency induction heating is used to heat the object to be carburized. (2) A plasma carburizing apparatus characterized in that high-frequency induction heating is used to heat the object to be carburized.