放電加工における応力分布に関する研究 (第3報)

単発放電, 繰返し放電および熱処理効果と応力分布の関係

抄録

In electric discharge machining, as the residual stress that generates on surface of workpiece is extremely harmful for the quality of products, it is strongly required to investigate the generated causes and its decrease with inquiring high reliability and accuracy of products. Previously, the residual stress was analyzed theoretically according to caluculation of heat conduction by the use of Monte Carlo method, and further the relationship between electric machining conditions such as energy supplying duration, peak discharge current and residual stress distributions were observed experimentally in the case of impulse discharge by the method of X-ray measuring. Consequently, it was found that the experimental values agreed well with the theoretical results. But, a many factors, that are affected to the numerical value and distribution etc. of residual stress, are considered except for those electrical machining conditions.
In this paper, considering the importance of these problem, the stress distribution that generates on surface of repetitional discharge machining was compared with the case of impulse discharge. And the residual stress on surface of the cold work die steel (SKD11, after heat treatment at annealing, quenching and tempering), which is used very frequently for die, was measured experimentally and observed. Subsequently, the metallographic observation of electric discharge machining surface was made by means of X-ray diffraction to discuss the connection with stress distribution.