低碳钢焊接接头氢渗透与氢损伤行为分析

对退火态低碳钢焊接接头进行了电解充氢,得到了接头不同位置产生氢损伤的微观组织,用电化学方法测量了焊后接头不同位置的氢渗透曲线,计算了接头不同位置的扩散系数、稳态平均氢浓度和扩散氢含量,解释了低碳钢焊接接头的不同位置充氢产生氢气泡、氢鼓泡及氢致裂纹数目差异的机理.结果表明,母材处表征扩散系数远小于焊缝处,平均氢浓度远大于焊缝处,导致母材处的氢渗透与损伤行为较明显,表面溢出氢气泡和近表面产生的氢鼓泡数目远多于焊缝处,然而焊缝处由于塑韧性较母材差,焊接残余应力较大,产生较多氢致裂纹,多位于氢浓度较大的近表面,内部由于拘束较大而产生少数细长裂纹.

Hydrogen permeation and hydrogen damage behavior of low carbon steel welded joint

The microscopic photos in different locations of annealed low carbon steel welded joint were obtained after the welded joint was cathodic electrolyte hydrogen-charged to produce hydrogen damage. The diffusion coefficient, average hydrogen concentration and diffusion hydrogen content in deferent locations of welded joint were calculated and the hydrogen permeation curves were measured with electrochemical method, in order to explain the reason why different locations of the welded joint had different numbers of hydrogen bubbles, hydrogen blistering and hydrogen induced cracking after hydrogen charging. It is shown that the diffusion coefficient of base metal was far less than that of weld beam, the average hydrogen concentration of base metal was far larger than that of weld beam, leading to that hydrogen permeation and hydrogen damage behavior of base metal was more obvious. The hydrogen bubbles from surface spillover and hydrogen blistering produced near the surface of base metal were far more than those of weld beam. However, the plasticity and toughness of weld beam was lower than those of base metal, and the residual tensile stress in weld beam was higher than that in base metal, thus more hydrogen induced cracks formed in weld beam mostly near the surface because of the higher hydrogen concentration, and a few elongated cracks generated inside weld beam due to larger restraint.