| 摘要 |
PURPOSE:To obtain a product having the high wear resistance on the inside surface of the part to be fitted to a shift lever with good workability in a shift fork made of a steel plate by using a low-carbon steel for steel plate stock, enriching locally the carbon content on the inside surface of the above-mentioned fitting part and hardening the inside surface. CONSTITUTION:The steel plate which consists of a steel having <=0.15wt% carbon content and having a required thickness is subjected to pressing in accordance with the conventional method to obtain a body having the part 4 to be fitted to the shift lever, etc. A carbon-enriching material consisting of a ferrous material having >=0.35wt% carbon content for the purpose of enriching carbon so that the carbon content of the hardened layer to be finally obtd. attains 0.25-0.45wt% is disposed on the inside surface of the part 4. High-density energy such as laser or plasma arc is irradiated onto the enriching material from above to heat locally and quickly the material, by which the enriching material and the surface layer part of the steel plate beneath said material are melted and alloyed. The molten layer is quickly cooled when the above-mentioned irradiation is stopped in succession thereto. The carbon is thereby enriched and the hardened layer 11 having >=350 Hv hardness is obtd.
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