超快速冷却条件下Ti微合金钢中纳米碳化物及其强化作用

Nano-carbide precipitates in Ti microalloyed steel under ultra fast cooling condition and their strengthening effect

具有较高强度的Ti微合金钢已广泛应用于国民经济及国防工业的各个领域.针对超快速冷却条件下(轧制冷却速度高达64℃/s)的Ti微合金钢,采用无损电解提取技术获得Ti微合金钢中的纳米碳化物.在此基础上,运用化学相分析、X射线小角散射及透射电镜综合分析纳米碳化物的物理化学特征,并考察其强化作用.结果表明:Ti微合金钢中存在大量纳米尺寸的FexC、TiC析出物,其平均粒度分别为76.06 nm和133.95 nm;同时,超快速冷却条件强化了FexC的析出行为,使得其析出强化增量达到243.8 MPa,而TiC的析出强化增量仅为63.1 MPa;然而,钢中每增加0.01%(质量分数)的TiC析出物(<40 nm)却可大幅贡献强化增量77.1 MPa,远高于Fe_xC析出物(<40 nm)的强化贡献量.因此,强化TiC的析出行为在提高钢屈服强度方面具有重要潜力.

Ti microalloyed steel is a high strength steel and has been widely used in national economy and defense industry. The nano-carbide precipitates in the Ti microalloyed steel produced by the ultra fast cooling process with a rolling cooling rate up to 64 ℃/s were obtained by nondestructive electrolysis extraction technology, and investigated through chemical phase analysis, X-ray small angle scattering and transmission electron microscopy. In addition, its effect on steel strengthening was also discussed. The results show that a large number of nano--sized FexC and TiC precipitates exist in the Ti microalloyed steel and their average particle size are 76.06 nm and 133.95 nm, respectively. The FexC precipitation behavior is strengthened by the ultra fast cooling process. Thus, the yield strength induced by FexC precipitate reaches 243.8 MPa, while that of TiC precipitate is only 63.1 MPa. However, the increasing mass fraction of TiC precipitate （〈40 nm） by 0.01% can obviously improve the yield strength by 77.1 MPa, which is far higher than that of FexC precipitate （〈40 nm）. Therefore, strengthening the precipitation behavior of TiC plays an important role in improving steel yield strength.