二次精鍊技術の開発，発展の歴史と将来展望

摘要

我が国の製鉄業が発展するにつれ，鋼材の大型化，高合金化，高品質化，およびこれらの量産化が要望されてきた。Fig.1 に示すように1950年代後半より，転炉•電気炉の一次精鍊プロセスにより粗鋼が量産され，それらを受けて二次精練プロセスは，その機能の一部を代替し，あるいは新たな機能を付加することにより，一次精練の能率を向上させるとともに，溶鋼を安定して鎊造工程に供給し，さらには従来製造ができなかつた高品質鋼材の製造を可能とし1970年代以降に急速に進展した。%As steel industry of our country developed, upsizing of steel materials and the mass production of various steel grades such as the high alloyed steel and the nigh quality steel have been requested. Crude steel was mass-produced from the late 1950 s by the primary refining process of the BOF and the electric arc furnace. After the initial period, the secondary refining technology replaced a part of the primary refining process function, improved the efficiency of the primary refining process by adding the new function and supplied the molten steel to the casting process stably. Furthermore, the secondary refining process enabled the production of the high quality steel materials and progressed rapidly in the after 70 s. In our country, nearly 100% of the BOF steel and the electric arc furnace steel are treated by the secondary refining process now. Vacuum degassing is performed for approximately 80% of BOF steel.A variety of secondary refining processings are carried out in the electric furnace for the production of special steels, and the LF processing ratio reaches 95% in the electric arc furnace for common steel production. Secondary refining process comes to take charge of a reduction refining function. In tms paper, the development of the secondary refining process and technology, and its history are looked back, and the future prospects are reviewed.