PRODUCTION OF HIGH CHROMIUM-CONTAINING RAW STEEL FOR ROLLING

PURPOSE:To prevent the development of inner flaw of a seamless steel pipe even in the case of manufacturing the seamless steel pipe with piercing rolling by continuously casting high chromium-containing raw steel for rolling as a cast bloom having the specific ratio of thickness and width. CONSTITUTION:By continuously casting the high chromiumcontaining raw steel for rolling containing 5% chromium as the cast bloom having 1.5-4.0 the ratio of thickness and width, porosity in the inner part is extremely little and concns. of P and Cr, etc., caused by center segregation can be restrained. Therefore, by using the cast bloom as the bloom for manufacturing the round billet and the square billet or directly using the cast billet, the high quality seamless steel pipe having no or extremely little inner flaw can be manufactured.