热轧态Cr、Ni微合金化高强度耐候钢组织与耐蚀性能

Microstructure and Corrosion Resistance of Hot Rolled Cr/Ni Micro-alloying High Strength Weathering Steel

采用电化学测试、浸泡实验及SEM、XRD等方法研究了热轧态Cr、Ni微合金化高强度耐候钢组织及耐蚀性能。结果表明:热轧态高强度耐候钢试样组织均由珠光体和铁素体组成,Cr在两相中均匀分布,Ni在铁素体相中含量更多。Cr、Ni含量较高的Q700H耐候钢在3.5%(质量分数)NaCl溶液中具有较低的年腐蚀速率。浸泡60 d后,两种钢自腐蚀电流密度增加,但Q700H钢具有较高的电荷转移电阻和较小的自腐蚀电流密度。浸泡150 d后,Q700H钢表面的点蚀坑较Q500H钢表面的更细小。Cr、Ni含量的增加促进了锈层中致密α-FeOOH的生成;Cr、Ni在锈层中发生富集,Cr集中在内锈层,Ni富集于基体和锈层界面处,且随Cr、Ni含量增加,富集越明显。

The microstructure and corrosion resistance of hot rolled Cr/Ni micro-alloyed high strength weathering steels Q500 H and Q700 H were studied by means of electrochemical test, immersion test, SEM, EDS and XRD. Results showed that the two hot rolled high strength weathering steels present the same microstructure composed of pearlite and ferrite, while Cr was distributed evenly in the above mentioned two phases, and Ni was more rich in ferrite phase. The Q700 H weathering steel with higher Cr-and Ni-content showed lower annual corrosion rate. After immersion in 3.5%（mass fraction） Na Cl solution for 60 d, the corrosion current density of the two steels increased, but Q700 H weathering steel has higher charge transfer resistance and smaller corrosion current density. The corrosion pits on the surface of Q700 H steel was smaller after 150 d immersion. The increase of Cr-and Ni-content promoted the for mation ofα-Fe OOH,which was dense and stable.Cr was concentrated in the inner rust layer,Ni was enriched at the interface between the substrate and the rust layer,the higher the content of Cr and Ni was,the much obvious enrichment they had.