Material Stock and Flow Analysis of Stainless Steel Based on Mass Balances of Cr and Ni
This paper analyzed stainless steel stock and flow in Japan by using a dynamic modeling. Classifying different kind of alloys, stainless steel was subdivided into 13Cr, 18Cr, Ni–Cr, and Ni–Cr–Mo. Productions of heat-resistant steel, low-alloyed steels for machine structural use, cryogenic special steel, bearing steel, and spring steel were also taken into account as alloying steel including Cr and/or Ni in mass balances of Cr and Ni. In production processes, all raw materials for stainless steel were clarified by upholding mass balances of Cr, Ni and Fe. In-use stock of ferritics and austenitics at year 2005 were 4 Tg and 12 Tg, which could be converted to 3 Tg of Cr and 1 Tg of Ni. From the results of the model, collection rates as stainless steel scrap were estimated less than 35% for ferritics and more than 75% for austenitics. The collection rate of ferritics was estimated to be relatively small because some of ferritic scrap could be recovered as carbon steel scrap due to its magnetism. The dynamic model slso estimated that main source of ferritic scrap generation will be automobiles in the next decade. In order to promote recycling of ferritic scrap, recovery from automobiles would be important.