steel-making

Definition of steelmaking: remove impurities in pig iron and scrap by oxidation and add an appropriate amount of alloy elements to make it a steel with high strength, toughness or other special properties. This process is called “steelmaking”.
For iron carbon alloys with carbon content ≤ 2.0%, the significance of 2.0% C in iron carbon phase diagram. High temperature: austenite, good hot working performance; Normal temperature: mainly pearlite.
Why steelmaking: pig iron cannot be widely used. High carbon content: no austenite at high temperature; Poor performance: hard and brittle, poor toughness, poor welding performance, unable to process; Many impurities: high content of S, P and inclusions.
Common elements in steel: five elements: C, Mn, s, P and Si (required). Other elements: V, Cr, Ni, Ti, Cu, etc. (according to steel grade). Existing reasons: ① process limitation: s and P cannot be completely removed; ② Raw material residue: Scrap residue Cu, Zn; ③ Improved properties: Mn improves the strength and Al refines the grain. Element content: ① national standard requirements: GB; ② Enterprise standard: determined by the enterprise; ③ Other national standards: swrch82b (Japan).
Main task of steelmaking: the main task of steelmaking is to refine molten iron and scrap steel into steel with required chemical composition, and make it have certain physicochemical and mechanical properties. The main task is summarized as “four removal, two removal and two adjustment”.
4. Decarbonization, desulfurization, dephosphorization and deoxidation;
Two removal: removing harmful gases and impurities;
Two adjustments: adjust the liquid steel temperature and alloy composition.


Post time: Apr-26-2022