| 摘要 |
PURPOSE:To increase the fatigue resistance of the processed steel sheet by controlling the constituents of the slag to the specified composition at finishing the deoxidation and by bringing the slag into contact with a steel bath thoroughly to decrease the Al2O3 ratio in the nonmetallic inclusions of the steel in the deoxidation of the stainless steel bath. CONSTITUTION:In the deoxidation refining of the bath of the austenitic stainless steel etc. for thin sheet spring material, the steel bath is fed to a vessel having a bottom blowing apparatus and an inert gas such as argon is blown from the bottom blowing tuyere to agitate the steel bath. CaO, SiO2 are added as a slag making agent both with the deoxidizing agent so as to generate the slag of 2- 100kg per 1ton molten steel, and the reaction is started at 1,600 deg.C and the treatment is finished at <=1,570 deg.C. The composition of the generated slag at this time is controlled to 35-55% CaO, 34-53% SiO2, 0.2-5% Mn and <=8% Al2O3. The nonmetallic inclusions contained in the steel become ductile with the low Al2O3 ratio, exist under thinly elongated state in the rolled sheet and the fatigue resistance of the steel sheet is not deteriorated. |
