The traditional smelting mostly uses die-casting blanks and provides the rolled blanks in the form of “die-casting-starting/forging and blanking”. Except for a few high-alloy steels that are difficult to be deformed and have high compression ratio, continuous casting blanks are used. Its characteristics are as follows:
1 Using refining systems, many new control technologies have been introduced, such as arc heating, vacuum degassing, argon blowing, and reducing slag refining to strengthen the smelting technology and reduce the oxygen content and harmful impurities in the steel. For high performance bearing steels, high purity is required and must be used Ladle refining plus vacuum cycle degassing.
2 continuous casting equipment technology development: in the continuous casting process using tundish heating, electromagnetic stirring, crystallizer liquid level control, enhanced secondary cooling and liquid hole pressure technology, using immersion nozzle and protective slag protection casting technology; The use of large-section billet continuous casting technology and to solve the problem of central segregation of high-carbon steel, using advanced technology such as light reduction, large diameter roll strong compression and continuous forging and other large compression ratio rolling. According to relevant studies, continuous casting billets are superior to die casting billets in uniformity of inclusions.
In the past, the domestic steel tube enterprises used the “electric furnace→ingot casting→starting (forging) blanking→rolling (forging) round billet” production process in the tube smelting process in the past. Lack of out-of-furnace refining and the use of ingots, central blank segregation , Non-metallic (gas) inclusions slag, Ti and other trace metals can not be effectively controlled, the use of rolling billet energy consumption, high production costs. Since the development to the present, many electric furnace processes have been adopted, with the addition of furnace refining and vacuum degassing to produce bearing steel tubes.
Domestic steel pipe billet is currently more advanced steelmaking and continuous casting process
Furnaces → Ladle refining + Vacuum degassing → Ingot casting → Blooming (forging) blanking → Rolling (forging) round tube blanks → Continuous casting billet → Continuous rolling blank tube blank → Continuous casting round blank tube blank
However, some steel grades are also produced by using "hot blast furnace molten iron directly by top-blown oxy-alkaline converter + RH vacuum degassing + continuous casting" or "Vacuum induction melting (VIM), electroslag remelting (ESR)" production, such as high-temperature corrosion resistant aircraft grade bearing steel.