22SiMn2TiB超高强度钢焊接热影响区抗CI^-腐蚀性能

HAZ CORROSION OF 22SiMn2TiB ULTRA-STRENGTH STEEL WELDMENT IN 3.5%NaCl SOLUTION

采用Gleeble-1500热模拟试验机模拟了22SiMn2TiB超高强度钢焊接接头热影响区的组织,并利用SolaronSL1280B恒电位仪测定了热模拟HAZ各区在3.5％NaCl水溶液中的极化行为,建立了热模拟组织与其在3.5％NaCl水溶液中腐蚀行为的关系。结果表明:22SiMn2TiB超高强度钢显微组织转变受碳和硼的扩散、偏聚和碳化物的脱溶所控制,且依赖于最高加热温度θ_max和冷却时间t_8/5虽然热模拟组织发生了变化,但热模拟HAZ各区在3.5％NaCl水溶液中的极化曲线的形状和趋势大致相同,组织变化对自腐蚀电位有一定的影响,但影响幅度不大,自腐蚀电位与腐蚀电流之间无对应关系;腐蚀电流的大小由氧的极限扩散电流决定,在电偶腐蚀过程中,焊接熔合区作为阳极而溶解,需重点防护。

Weld heat affected zone (HAZ) microstructures of 22SiMn2TiB ultra-strength steel were thermally simulated by means of Gleeble-1500 machine. Polarization measurement of the quenched zone and tempered zone in 3.5%NaCl solution was conducted respectively with potention-stat/galvanostat Solaron SL1280B. The relation between the microstructure and the HAZ corrosion resistance in 3.5%NaCl solution was established. Carbon and boron diffusions, segregation and iron carbide or boride precipitation are dependent on simulated weld thermal cycle peak temperature θmax and continuous cooling time t8/5, and induce the microstructure transformation. The polarization curves and corrosion potentials of the simulated HAZ with different microstructures in 3.5%NaCl aqueous solution are slightly different; the limit diffusion current of dissolved oxygen in 3.5%NaCl solution decides corrosion current. Weld bond, which undergoes anodic dissolution in couple corroding, needs to be protected carefully.