中国汽车、船舶和家电中钢铁的存量与流量

存量是指社会经济系统中正在被使用的产品（或物质）的数量（或重量）。人类不断增长的物质需求推动了存量的消耗和更新,最终导致了物质在社会经济系统中的流动。本文利用存量驱动的动态物质流模型分析了1949—2050年中国汽车、船舶和家电行业终端产品中钢铁的存量、理论报废量和理论需求量的变化趋势。研究结果表明：汽车、船舶和家电中的钢铁理论需求量在2020—2030年之间达到峰值后呈现降低的趋势。三个行业终端产品中钢铁的理论报废量将在2040年之后逐渐超越理论需求量,并在2050年分别达到8300万t/年（汽车）、2700万t/年（船舶）和441万t/年（家电）。研究结果可为我国典型行业钢铁的可持续生产与利用提供政策启示,为有效推动循环经济的开展提供数据基础。

Stocks and flows of steel in automobiles,vessels and household appliances in China

Material flow analysis (MFA) characterizes and quantifies flows of materials into, out of, and through a socio-economic system of interest, balancing all flows by stocks. Stocks are the amount of concerned manufactured products and materials in active use. Flows refer to the inflow (demand) and outflow (scrap) of products or materials between different processes. Stocks are the driving force for the flows and circulation of substances in the socio-economic system. In this paper, we analyzed steel stocks and flows in automobiles, vessels, and household appliances in the past (1949-2018) and future (2019-2050) by using the dynamic stock-driven model. The results showed that: (1) Steel demand in three industries will be saturated or decreased after reaching its peak; (2) Steel scrap of the three industries will exceed demand after 2040, (3) There will be a large amount of steel scrap produced in automobiles (83 million tons/year), vessels (27 million tons/year), and household appliances (4 million tons/year) by 2050. The results of this paper are intended to provide policy implications for sustainable production and utilization of steel.