CERTAIN BASIC SUBJECTS ON CLEAN STEEL
关于洁净钢的若干基本问题

Clean steel is a general designation of certain types of steel with higher cleanness upgraded gradually by steel factories with promotion of process and equipment step by step according to the customer demands on product quality. The requirements for cleanness of typical steel and the possible lowest level of impurity in commercial steel since last half century were introduced. The total oxygen content in steel is extremely important for its cleanness. Relevant theories of changes and decreases of total oxygen content during refining and solidification processes used by major steel factories at home and abroad were enumerated. Decreasing the inclusion amount and controlling its shape are also key tasks for clean steel production. The influences of deoxidization products, re--oxidation of deoxidizer as well as top slag composition and refractory materials on the cleanness were mentioned separately, inclusion control in stainless steel series 430 and optimum stirring intensity in refining process were introduced, the theory foundation of inclusion transformation in aluminum--killed steel treated by calcium was briefly outlined, the metallurgical principles of ultra--low phosphorus steel and ultra--low sulphur steel productions were emphasized, ultra--low sulphur and sulphide shape control which are required by anti--HIC of linepipe steel was introduced, the possible ways of removing other impurities from steel were also discussed.