Ti-Nb微合金钢及焊接热影响区中的第二相粒子

Secondary Phase Particles in Ti-Nb Microalloyed Steel and Coarse-Grained Heat Affected Zone

利用萃取复型和焊接热模拟技术 ,对 0 14C 1 34Mn 0 0 17Ti 0 0 2 3Nb微合金钢及模拟焊接粗晶热影响区中第二相粒子的形态、数量及物相进行了研究。结果表明 ,母材中第二相粒子形状不规则 ,Nb的相对含量 (Nb (Nb +Ti) )在 2 5 %～ 82 %之间的粒子平均直径为 14 2nm ,尺寸较大的粒子 (～ 5 0nm)含Ti较高 ,呈方形 ,尺寸较小的粒子中Nb含量较高 ,呈球形。焊接热循环后 ,第二相粒子数量显著减小 ,平均尺寸增大 ,呈方形。 80 0℃至 5 0 0℃冷却时间t8 5从 16s增加至 6 0s时 ,粒子中Nb的相对含量为 2 0 %～ 5 0 % ,粒子平均尺寸由 31 4nm增大至 37 2nm ,粒子数量由 1 95 μm2 减少至 1 2 0 μm2 。但t8 5从 6 0s增至 12 0s时 ,因冷速慢 ,析出温度低 ,粒子平均尺寸减小至 2 6 3nm ,粒子数量增加至 3 5 6 μm2 。

The morphology, quantity and size distribution of secondary phase particles in 0.14C-1.34Mn-0.017Ti-0.023Nb microalloyed steel has been investigated by using carbon extraction replica technology and weld thermal simulation of coarse-grained heat affected zone (CGHAZ). Experiment results showed that shape of secondary phase in the steel was irregular, of which average diameter was 14.2 nm and Nb relative content- Nb/(Nb+Ti) was 25%～82%, the larger particles (～50 nm) were square with high Ti content and the smaller particles were spherical with high Nb content. After welding thermal cycle, the secondary particles were square of which average diameter increased and amount obviously decreased; as t 8/5- cooling time from 800 ℃ to 500 ℃ increased from 16 s to 60 s the Nb relative content in particle decreased to 20%～50%, while average diameter of particles increased to 37.2 nm from 31.4 nm with particles number decreasing to 1.20/μm 2 from 1.95/μm 2; however as t 8/5 increased further from 60 s to 120 s, due to slow cooling rate and low precipitating temperature the average diameter of particles decreased again to 26.3 nm with particles number increasing to 3.56/μm 2 and spherical particles with higher Nb content were re-observed.