氮对含铌20MnSi钢组织演变的影响

 研究了不同冷速条件下氮对铌微合金化20MnSi钢组织演变的影响。试验钢经1 200 ℃全固溶处理后快冷至Ac3，]然后分别以200、100 ℃/h速度冷却至室温。对试样进行了OM、SEM和TEM观察。结果表明：钢中细小Nb(C，N)粒子在原奥氏体晶内高密度位错区的密集析出导致贫碳区的形成，进而激发针状铁素体的形核长大。铌微合金钢增氮后能有效抑制钢中针状铁素体的生成，促进等轴铁素体的生成和珠光体球团的细小均匀化，同时珠光体退化倾向减弱或消失。

Effect of nitrogen on the microstructure evolution in 20MnSi steel bearing with niobium

Investigations were carried out to evaluate the influence of nitrogen on the microstructure evolution in 20MnSi steel bearing with niobium. Two steels with different nitrogen contents solution treated at 1 200 ℃ were rapidly cooled to theirAc3]and then cooled to the room temperature at the cooling rates of 200 and 100 ℃/h， respectively. Observations were conducted by optical microscopy(OM)，scanning electron microscopy(SEM）and transmission electron microscopy(TEM). The results demonstrate that the acicular ferrite nucleated and grew at the carbon-poor areas which were caused by the Nb(C， N) precipitation at the high density dislocation region within the prior austenite grain. The enhancement of nitrogen was beneficial to inhibit the formation of the acicular ferrite and promote the formation of equaxied ferrite. Also， the fraction of degenerated pearlite was decreased and the pearlite nodules were in a fine and uniform distribution.