抄録
Soft steel machine parts were mirror-polished and annealed in a vacuum furnace at the temperature above recrystalization temperature.
There appeared on the surface, 11el white or black lines whose width was 0.3mm or thinner. The origin and reason of these lines were investigated through many experiments with many specimens. Several criticisms were done through experimental results of 8 microphotographs and 6 figures.
In conclusion we should say, firstly there happen the minute cracks ⊥ ar to the grinding direct ion on the surface of the specimen, by comparatively severe grinding operation which direction are ⊥ ar to the rolled direction and secondly if the surfaces of these ground and cracked specimens are mirror-polished, the cracks are covered up by the amorphous layer which should be affected later by thermal treatments in vacuum furnace.
Lastly the appeared white traces, thermal cracks and other related phenomena were all explained.
