爆発硬化した高マンガンオーステナイト鋳鋼の残留応力

抄録

For the improvement of wear-resistance of high manganese austenitic cast steel, explosion hardening treatment has been tried recently. From the previous study, it became clear that high tensile residual stress was generated in the hardened surface layer by explosion and microcracks were observed.
In this study, therefore, the distributions of biaxial residual stresses in the explosion hardened steel were examined and compared with those of the original and the shot peened steels.
The results obtained are as follows:
(1) In the longitudinal direction of the test specimen of explosion hardened steel, tensile residual stress was generated in the hardened layer from the surface to the depth of about 0.5mm, and the maximum value was about 80kgf/mm² at the depth of about 0.005mm. In the transverse direction, compressive stress appeared with the maximum value of about 27kgf/mm². On the other hand, in the shot peened steel both of these biaxial stresses were compressive.
(2) In the surface layer hardened by explosion, a good many microcracks perpendicularly intersecting to tensile residual stress were observed. The microcracks had a tendency to grow in the range of high tensile stress by 5% nital etching, and as the stress decreased the cracks disappeared by removing off thin layers successively by electrolytic polishing.
(3) It is supposed that the characteristics of residual stress in the explosion hardened steel mentioned above depend mainly on the configuration of test specimen, the setting method of an explosive and explosive heat.