PURPOSE: To economically produce a steel for structural purposes in which the aspect ratio (the ratio of length/ breadth) of the colony of the aggregated structure having the same crystalline orientation in the structure of the surface layer part is specified and good in brittle fracture propagating properties with good productivity.
CONSTITUTION: A steel sheet excellent in brittle fracture properties and fatigue properties and in which, in the structure revealed by a temper color method over the range of ≥2% of the sheet thickness respectively on the surface and rear layer parts, the colony of the aggregated structure having the same crystalline orientation constituted by the similar color tone has ≤5μm average minor axis diameter as well as the intensity of the (100) plane of the aggregated structure parallel to the rolling face has ≥1.5 intensity ratio, and this is the method for producing the steel sheet. The steel sheet having, as arrest performance, ≤-70°C NDT properties and the temp. of ≤-70°C at which Kca properties are regulated to ≥600Kgf/mm1.5 can be obtd. in economical stability with good producivity.
TAKEZAWA HIROSHI
NOMIYAMA YUJI
YOSHIKAWA HIROSHI
| JPH032322A | 1991-01-08 | |||
| JPS61235534A | 1986-10-20 |