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研究了不同冷速条件下氮对铌微合金化20Mn Si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。
The effect of nitrogen on the microstructure evolution of niobium microalloyed 20MnSi steel under different cooling rates was studied. The test steels were quickly cooled to Ac3 at 1 200 ° C and then cooled to room temperature at 200 and 100 ° C / h, respectively. The samples were observed by OM, SEM and TEM. The results show that the intensive precipitation of fine Nb (C, N) particles in the high-density dislocation zone in the original austenite grain leads to the formation of lean carbon zone, which in turn stimulates the nucleation and growth of acicular ferrite. The niobium microalloyed steel can effectively inhibit the formation of acicular ferrite, promote the formation of equiaxed ferrite and fine homogenization of pearlite pellets after nitrogen addition, while the degradation tendency of pearlite weakens or disappears.