应力对低合金钢焊接接头相电化学行为的影响

Effect of Stress on Electrochemical Behaviour of Various Thermal History Zones and Different Phase Structures on the Weldment for Low Alloy Steel

采用微区相电化学测试技术，测量和研究了１６Ｍｎ钢焊接接头上不同热经历区在硝酸盐溶液中的微区相电化学行为（包括自腐蚀电位、自腐蚀电流密度和极化曲线）以及外加载荷（应力）的影响．此外，还分别测量了各区中铁素体和珠光体的电化学行为，尤其是加载状态下的行为．结果表明，加载后各热经历区以及各区中铁素体和珠光体的自腐蚀电位均比未加载前负移，相应的自腐蚀电流密度增大，铁素体和珠光体之间电位差明显减小．加载后各热经历区中自腐蚀电位最负和次负的仍处在熔合线区和不完全正火区，从而成为焊接接头腐蚀电池中的率先腐蚀区．应力促进腐蚀并非是通过增大铁素体和珠光体之间的电位差，而是通过提高各微区相组织自身的电化学活性来实现的．

The electrochemical behaviour of various thermal history zones on the weldment for steel 16Mn and also of the ferrite,pearlite in various zones was measured by use of a self-developed measuring technique for investigating the electrochemicl behaviour of single and mixed phase structures in metal materials.Especially the effect of stress on this electrochemical behaviour was investigated.The results showed that by comparison with non-stress condition,the free corrosion potential of the various thermal history zones and of the ferrite,pearlite under stress condition was shifted in negative direction,correspondingly their free corrosion current density was increased,the free corrosion potential difference between ferrite and pearlite was decreased obviously. After applying stress the negativest and the second negativest free corrosion potentiats between vavious thermal history zones were still for the fusion line zone and the incomplete normallized zone,which thereby were become the preferrentially corroded locations on the weldment as a corrosion cell.The stress accelerated corrosion course that did act not through inceasing free corrsion potential difference between ferrite and pearlite,but through enhancing the electrochemical activity of the relevant micro zone and/or phase strueture.