正火对420MPa建筑用钢性能与Nb、V析出量的影响

Influence of Normalization on the Properties and Nb、V Precipitations of Grade 420 MPa Steel Plate for Construction

研究了建筑结构用钢Q420GJC热轧及正火后的组织、性能及Nb、V析出物变化。采用电解法对热轧和正火后钢板进行Nb、V的析出物定量分析,在透射电子显微镜下进行析出物观察,结果表明,钢板正火后强度下降明显;热轧钢板厚度方向不同部位V的析出量差别不大,约为加入数量的30%,正火不能有效提高低氮钢中V的析出量,热轧态钢板中Nb的析出量从厚钢板表层到心部递增,空冷后钢板中Nb的析出量大于控冷后Nb的析出量;正火后Nb的析出量稍高于热轧。

The microstructure and mechanical properties and Nb, V precipitations of Q420 GJ steel platefor construction was investigated after hot rolling and normalizing. Quantitative analysis of Nb, V precipi-tates had been performed by electrolytic method for hot rolled and normalized steel plates, the precipitateswere observed under transmission electron microscope. Tensile tests indicated that strengths of the steelplate after normalizing remarkable decreased. TEM observation showed there was no visible difference invanadium precipitation through thickness direction of the plate after hot rolling, and about 30% of totaladded vanadium precipated. Normalizing process could not effectively improve vanadium precipitation inlow nitrogen steels. Niobium precipitation increased from the surface to the centre of the as- hot rolledplate, the amount of precipitated niobium after air cooling is larger than that after controlled cooling. Theamount of precipitated niobium after normalizing was somewhat higher than that of as-hot rolling.