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Cr-Mn-N奥氏体耐热钢在时效过程中有变脆的倾向,可能成为高溫长期使用的障碍.本文研究了下列三方面变脆的影响因素:(1)碳和氮含量的增加,促进时效变脆,硼防止时效变脆的作用随C+N含量的增加而減弱.在时间-溫度-等冲击值曲线上出现双C形式,它们与碳氮化物的析出和χ相生成有关.(2)碳、硼及钼等元素在晶界有偏聚现象.碳、钼等元素的偏聚促进沿晶界碳化物析出,加速钢的变脆.硼则有延缓晶界碳化物析出的作用,抑制时效脆性.(3)在长期时效过程中,碳氮化物及中间相的析出引起基体合金元素的贫化,从而降低γ相的稳定性,在形变过程中发生ε及马氏体相变,也会引起钢的变脆.
Cr-Mn-N austenitic heat-resistant steel tends to be brittle during the aging process, which may become a long-term obstacle to high temperature.This paper studies the following three factors that affect the brittleness: (1) The increase of carbon and nitrogen content , The effect of embrittlement on the embrittlement of brittle aging and the embrittlement of boron to prevent embrittlement diminishes with the increase of C + N. The double C form appears on the time-temperature-impact curve, which are related to the precipitation of carbonitride and the χ-phase formation . (2) The segregation of carbon, boron, molybdenum and other elements in the grain boundaries. The segregation of elements such as carbon and molybdenum promotes the precipitation of carbides along the grain boundaries and accelerates the brittleness of the steel. Boron, on the other hand, delays grain boundary carbide precipitation (3) In the long-term aging process, the precipitation of carbonitride and mesophase lead to the depletion of the matrix alloying elements, thus reducing the stability of γ phase, ε and martensite occur in the deformation process Phase change can also cause the steel to become brittle.