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随着汽车行业的发展,汽车排气系统热端用铁素体不锈钢的使用温度越来越高,高温性能成为限制其发展的关键性能。研究铌含量对铁素体不锈钢组织与高温性能的影响可以指导钢种设计和工业化生产。选取了2种17%Cr超纯铁素体不锈钢进行高温时效试验,结果表明:铌的质量分数为0.2%时,铌没有明显的强化作用,950℃高温下晶粒迅速长大,高温强度迅速降低;铌的质量分数为0.4%时,在950℃高温下时效,材料中析出弥散第二相粒子Fe2Nb,阻止晶粒长大,提高强度,防止高温引起的材料软化。材料的高温强度是由固溶铌以及铌析出物的共同作用引起的,当固溶铌析出形成析出物时,固溶铌含量减少引起的强度降低以及析出引起强度升高的竞争导致了材料的强度变化。
With the development of automobile industry, ferritic stainless steel used in automobile exhaust system is getting higher and higher temperature, and high temperature performance has become the key performance limiting its development. Studying the effect of niobium content on the microstructure and high temperature properties of ferritic stainless steel can guide the design and industrial production of steel. Two kinds of 17% Cr ultrapure ferritic stainless steel were selected for high temperature aging test. The results show that when the mass fraction of niobium is 0.2%, there is no obvious strengthening effect of niobium. When the temperature is 950 ℃, the grains grow rapidly and the high temperature strength rapidly And when the mass fraction of niobium is 0.4%, aging at 950 ℃, the second phase particles Fe2Nb are precipitated and dispersed in the material to prevent grain growth, increase the strength and prevent softening of the material caused by high temperature. The high-temperature strength of the material is caused by the combined action of solid-solution niobium and niobium precipitates. When solid-solution niobium precipitates to form precipitates, the reduction in strength due to the reduction in solute niobium content and the resulting increase in precipitation lead to a Strength changes.