Abstract
Development in sheet steels has progressed with a strong relation with automotive industry in Japan. To meet with the requirements from automotive industry, various types of sheet steels including high and ultra-high strength steel sheets have been developed. Progresses in three types of steel series will be discussed by checking the historical facts and technologies and their contributions. Introductions of interstitial free (IF) steel and continuous annealing system are the important events in mild steel developments for panels. Extensive work on finding the optimum mixtures of hard and soft phases to improve elongation of steels contributed to improve the crashworthiness of autobodies. Continuous annealing system also played an important role in producing these advanced high strength steels. Precipitation is used in characteristic ways which is to scavenge solute carbon and nitrogen and to prevent coarse cementite particle precipitation. It is also worth to point out that the strong collaborative activities particularly characteristic in Japan between steel manufacturers and auto companies have affected on the progress in advanced sheet steels.
