Cu-P-Cr钢及其焊接接头的周期腐蚀性能

Corrosion performance of welded joint and base steel of Cu-P-Cr weathering steel by cyclic immersion in Na HSO_3 solution

通过中试轧制、电渣压力焊制备了Cu-P-Cr钢及其焊接接头,利用光学显微镜研究了电渣压力焊接接头的组织晶粒度,利用干湿交替实验机、SEM、EPMA、XRD研究了Cu-P-Cr钢及其焊接接头在1.0×10-2mol/L的Na HSO3溶液中的耐腐蚀性能、锈层元素分布及组成,分析了母材与焊接接头的耐腐蚀机理及其影响因素。研究结果表明:焊接接头与母材的腐蚀速率相比碳钢分别为64.6%与61.5%。焊接接头锈层中Cu、Cr元素的大量富集、α-Fe OOH相的转变是腐蚀性能优异的主要原因,而焊缝及熔合区形态各异的铁素体+珠光体+魏氏组织和晶粒尺寸不均等导致了锈层中Cu、Cr富集程度低于母材、腐蚀性能稍弱于母材。

Welded joint of a low carbon Cu-P-Cr weathering steel was prepared by electric slag pressure welding. Microstructure and grain size of the welding joint were analyzed by optical microscope. Corrosion behavior of the welded joint and a plain carbon steel Q235 was examined by means of cyclic immersion corrosion test in 1%( mass fraction) Na HSO3 solution. Corrosion rust layers were analyzed by SEM,EPMA and XRD. The results show that weld joint exhibits lower corrosion rate than base steel. The cyclic immersion corrosion rates of the welded joint and base steel are 64. 6% and 61. 5% of that of Q235 carbon steel,respectively. The enrichment of Cu and Cr elements and the transformation of α-Fe OOH in corrosion rust layers are responsible for the excellent corrosion property of the welding joint steel. The lower corrosion property of the welding joint than the base steel is ascribed to its uneven microstructure of ferrite,pearlite and widmanstatten structure with ununiform grain size of leading to the lower degree of Cu and Cr enrichment.