抄録
The life cycle of steel begins in the mining of iron-ore from the earth. Steels are produced in steel works and used in various products. Some of the steels are recycled at the end-of-life of the products and used as a resource for the production of steel products in electric furnace, while the other steels are used just one time in products and go into landfill. As the recycle ratios of steel from used products increase, the average number of times of use and residence time of Iron element that comes into society as iron are and goes out from the society as landfill will increase. So these values indicate "sustainability of material use" in a society. In this work, a methodology was developed for analyzing the average number of times of use and residence time of Iron element in a society by applying Markov chain model. It was calculated that the average number of times of use and residence time of Iron element in a society based on the material flow of steels in Japan in 2000 are 2.67 and 62.9 years, respectively. Both of these values are significantly dependent on the recycle ratio of steels from civil & building facilities and automobiles. It was indicated that the average number of times of use and residence time of Iron element in a society would increase up to 3.17 and 75.8 if the recycle ratio of steels from civil and building facilities increase from 50 to 60%.
