SUB-ZERO TREATMENT METHOD OF STEEL SHEET FOR SUB-ZERO TREATMENT AND BINDING TOOL FOR SUB-ZERO TREATMENT

摘要

PROBLEM TO BE SOLVED: To obtain sub-zero treated steel sheets having a high flattening degree by applying sub-zero treatment so that binding force is controlled in accordance with the shape before heat treatment of the materials to be heat-treated, and a uniform temperature distribution can be obtained even by cooling for a short time.;SOLUTION: Metallic surface plates 2 are arranged at the upper and lower sides of the steel sheets 1 to be treated, and metallic square pipes 3 for uniform cooling are arranged at the outside of the metallic surface plates 2, and in a state where facial pressure controlled to ≥100 kg/m² with a coil spring 8 is applied to the space between the upper and lower metallic square pipes 3 for cooling, cooling is performed at a cooling rate of ≤10°C/h, thus the steel sheets 1 to be treated are subjected to sub-zero treatment. The steel sheets 1 to be treated are flatly straightened before the cooling by the application of the controlled facial pressure from the surface plates, the steel sheets 1 to be treated are uniformly cooled with a cooling medium filled into the metallic square pipes 3 for uniform cooling, and the whole is simultaneously transformed into martensite, thus the flat sub-zero-treated steel sheets can be obtained without the strain remaining.;COPYRIGHT: (C)2006,JPO&NCIPI