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 effects of deformation in ferritic region on microstructure and micro-hardness of a Nb-containing HSLA steel were studied by a Gleeble-3800 thermal simulator. Results show that the microstructure of some elongated polygonal ferrite and dispersed degenerated pearlite was successfully obtained by processing B (PB) , for which the final deformation was performed in the ferritic region but that was quasi-equiaxed ferrite and large degenerated pearlite obtained by processing A (PA) , for which the final deformation was performed at near At3. A certain amount of Fe3 C and nano-sized NbC precipitates in the steel processed by PB were both finer than those in the steel obtained by PA. The hardness enhancement reaches 30 HV for the steel obtained by PB. The dislocation-strengthening and precipitation- hardening are the main mechanism for the hardness enhancement of the steel obtained by PB, and the refinement of degenerated pearlite and cementite also make some contribution to the hardness increase.
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