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为了减轻空气污染和缓解全球变暖,各个国家均出台了尾气排放标准,且限制标准越来越严格。在此背景下,多种技术已被应用以满足相关要求,如提高燃油燃烧率、催化效率,降低排气管热容量等。而这一系列措施均会导致汽车尾气的最高温度上升。近些年,汽车排气系统零件主要用铁素体不锈钢制作,因为铁素体不锈钢的热膨胀系数小,耐循环氧化和耐高温疲劳性能均优于奥氏体不锈钢。介绍了日新制钢新研发的汽车排气系统用耐热不锈钢,以及该钢种的研发现状和发展趋势。Nb、Mo、Cu在700℃时的固溶强化和析出强化对提高铁素体不锈钢的高温强度非常有效,而添加Nb、Mo、W主要是在900℃时起到固溶强化作用。Cr,Si和Mn可降低铁素体不锈钢(含14%Cr)在大气中950℃保温200h的氧化程度。特别是添加0.8%及以上的Mn可有效提高氧化皮的附着力。事实证明,日新制钢开发的NSSHR-1(14Cr-1Mn-0.9Si-Nb)和NSSHR-2(10Cr-0.9Si-Nb-Ti)铁素体不锈钢与441和439不锈钢相比,具有更高的耐热性和成形性。
In order to reduce air pollution and mitigate global warming, various countries have issued emission standards, and more stringent restrictions. In this context, a variety of technologies have been used to meet the relevant requirements, such as increasing the fuel burn rate, catalytic efficiency, reducing exhaust pipe heat capacity and the like. And this series of measures will result in the maximum temperature of the vehicle exhaust rise. In recent years, automotive exhaust system components are mainly made of ferritic stainless steel, because ferritic stainless steel has a smaller coefficient of thermal expansion, better cyclic oxidation resistance and high temperature fatigue resistance than austenitic stainless steel. Introduced Nisshin Steel newly developed automobile exhaust system with heat-resistant stainless steel, and the steel research and development status and trends. The solid solution strengthening and precipitation strengthening of Nb, Mo and Cu at 700 ℃ are very effective for increasing the high temperature strength of ferritic stainless steel. The addition of Nb, Mo and W mainly plays the role of solid solution strengthening at 900 ℃. Cr, Si and Mn can reduce the degree of oxidation of ferritic stainless steel (containing 14% Cr) in the atmosphere at 950 ℃ for 200h. In particular, adding 0.8% or more of Mn can effectively improve the adhesion of the scale. NSSHR-1 (14Cr-1Mn-0.9Si-Nb) and NSSHR-2 (10Cr-0.9Si-Nb-Ti) ferritic stainless steels developed by Nisshinbo Steel have proved to be higher in strength than 441 and 439 stainless steels Heat resistance and formability.