热处理对连续油管焊缝沟槽腐蚀行为的影响

Effect of Heat Treatment on Grooving Corrosion Behaviors of Coiled Tubing Weld

采用控制电位的电化学极化方法,在w(NaCl)=3.5%溶液中对试样在-550 mV极化电位下极化144 h后,测定了不同热处理工艺下CT80钢级连续油管ERW焊缝沟槽腐蚀的敏感性。结果表明,这种高洁净度、低碳微合金化钢连续油管ERW焊缝在焊态、调质、回火三种状态下,焊缝沟槽腐蚀的敏感性均很小,敏感系数均小于1.3。其中,调质处理后焊缝沟腐蚀敏感系数只有1.03,与母材基本相同。三种状态下焊缝沟腐蚀敏感性强弱依次为:焊态>回火>调质。焊缝区夹杂物、组织和成分偏析以及残余应力等是引起焊缝沟槽腐蚀的主要因素。

After adopting electrochemistry polarization method to polarize samples 144 h at-550 mV polarized potential in 3.5%NaCl solution,the HFW weld grooving corrosion sensitivity of CT80 grade coiled tubing was detected.The results show that the sensitivity of this kind of high cleanliness and low carbon content micro-alloy coiled tubing HFW weld are all weak,under welding condition,quenching and tempering,tempering,its sensitivity coefficient is less than 1.3.Especially,the sensitivity coefficient of weld grooving corrosion is only 1.03 after quenching,which is closed to that of the base material.The grooving corrosion sensitivities of CT80 coiled tubing after three different heat treatment decrease in the sequence as welded conditiontemperingquenching and tempering.The weld inclusions,microstructure and composition segregation,and residual stress are the primary reasons for forming weld grooving corrosion.