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采用Gleeble-3800热模拟试验机,研究铁素体区变形对含铌微合金高强度(HSLA)钢组织及显微硬度的影响。结果表明:相比于最终变形在Ar3附近(840℃)时获得近等轴状铁素体+退化珠光体组织,最终变形在铁素体区(550～650℃)时获得部分拉长的多边形铁素体+弥散分布的退化珠光体组织。此外,铁素体区最终变形析出的NbC与晶界析出的Fe3C析出相更加细小且弥散。与高温下最终变形相比,铁素体区最终变形获得的组织显微硬度增量达30 HV。通过强化机理分析表明,位错强化与析出相Fe3C和NbC的沉淀强化作用是铁素体区变形组织硬度提高的主要原因,退化珠光体和渗碳体的细化对硬度的提高也有一定量的贡献。
The effect of ferrite deformation on microstructure and microhardness of niobium microalloyed high strength (HSLA) steels was studied by Gleeble-3800 thermal simulator. The results show that the near-equiaxed ferrite + degenerate pearlite is obtained near Ar3 (840 ° C) compared with the final deformation, and the finally deformed polygons partially elongated at the ferrite region (550-650 ° C) Ferrite + Decentralized pearlite microstructure. In addition, the NbC precipitated in the final deformation of the ferrite zone is more finely dispersed than the Fe3C precipitates precipitated in the grain boundaries. Compared with the final deformation at high temperature, the microhardness of the microstructure obtained by the final deformation of the ferrite zone increases up to 30 HV. The strengthening mechanism analysis shows that the precipitation strengthening effect of dislocation strengthening and precipitation phases Fe3C and NbC is the main reason for the increase of the hardness of the deformed structure in the ferrite zone. The refinement of degenerated pearlite and cementite also has a certain amount of hardness improvement contribution.