Japan - "three off" pretreatment, less slag smelting high-carbon steel technology, production of low-phosphorus low-oxygen steel;
Germany - converter low-carbon technology to ensure that the dephosphorization effect of the late converter, relies on tapping steel production of bearing steel.
Hot metal pretreatment: magnesium-based desulfurizer treatment, the molten iron into the furnace w[S] ≤ 0.005%, 100% slag removed after treatment;
Converter smelting: using high-pull carbon method, the endpoint carbon w[C] ≤ 0.40%, while controlling w[P] ≤ 0.010%. Aluminium-manganese titanium pyrolysis agent was added to the scrap steel - the end point of high-carbon control at the end of the supply was insufficient; the tapping temperature was 1700°C, the carbon content was 0.34%, and the phosphorus content was 0.007%;
During the tapping process, high Cr alloys, Si-Mn alloys and carbon powders are used for alloying and carbon addition in the package, and the slag blocking operation is performed. At the same time, bottom-blown argon stirring is used to remove the total oxygen in the molten steel.
Refining uses a low-basicity CaO-Al2O3 slag system with a desulfurization rate of 50%-70% and a reduction of Al-based inclusions. Consistent with the deoxidation products, the interfacial tension between the two is small, and they are easily combined into low-melting compounds. Strong absorption of Al2O3 inclusions, eliminating Class D inclusions containing CaO. At the same time the bottom blowing argon uniform composition, temperature;
Argon blowing weak stirring: According to the reference sample composition analysis, supplement high chromium, high manganese, carbon powder to adjust the composition to meet the internal control requirements, when the temperature is higher than the bag temperature 20-30 °C when the blowing argon weak stirring - inclusions further Floating.