爆発硬化した高マンガンオーステナイト鋳鋼テーパ付き長尺ブロックの残留応力

概要

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Explosion hardened austenitic manganese cast steel has been tried for railroad frogs and crossings recently. In the present study, by using a lomg size tapered block which had the shape and dimensions similar to those of the nose-rail of crossing and was explosively hardened at the faces of its head, the residual stress, handness distribution and microcracks in the hardened layer were examined. The summary of the results is as follows: (1) A high tensile residual stress existed in the hardened surface layer, and the stress value decreased gradually from about 2000 MPa near the detonating point about 275 MPa at the end of hardened layer. At the side of the head the stress distributed comparatively uniformly. The high tensil stress at the handened surface decreased rapidly in the inner layer near the detonating point, and the change of stress was small at the end of explosion. Hardness at the surface of hardened layer decreased gradually from the location near the detonating point toward the end of explosion, but on the contrary it increased gradually in the inner layer. Those variation of residual stress and hardness depended on the dimension of cross sedtion and the setting method of explosive. (2) The microracks produced at the handed surface may promoto wear in the practical use, but may not cause failure of the rail.
1985-09-15