本文研究了12MnMoVNbTi低合金钢在饱和H_3S溶液中的极化和应力腐蚀行为,并与电解充氢条件下的应力破裂行为进行了对比。证明钢中Mo、Nb含量的变化与热处理条件的不同对其一般腐蚀行为影响很小,但能显著改变其抗应力腐蚀性能,12MnMoVNbTi钢在H_2S介质中的应力腐蚀破裂行为与它们在充氢条件下的应力破裂行为非常类似,显示其应力腐蚀破裂的实质是氢脆。充氢条件下应力弛豫和恒载荷拉伸试验结果表明,氢有引起钢的软化和硬化的双重作用。由于氢的进入所产生的软化作用使钢在屈服强度以下发生塑性变形,但随后的硬化过程又使变形速度逐步减慢。这种由氢的作用引起的在较低应力下发生的塑性变形过程并不直接导致断裂,但塑性变形行为和氢应力破裂行为之间的关系表明,这种变形过程中的位错运动能够帮助氢的移动和向塑变区及裂纹尖端集中,促进氢脆断裂。
The polarization and stress corrosion cracking behavior of 12 MnMoVNbTi steels in H_2S saturated solution was studied and comparison with hydrogen stress cracking behavior was made. The results show that the variation of Mo, Nb contents and difference in microstructure of steels have no important effect on corrosion rate but influence their stress corrosion cracking behavior considerably. The similarity between stress cracking behavior of these steels in H_2S solution and in hydrogen charging condition implies that the nature of sulfide stress cracking of steels is hydrogen embrittlement. The experimental results of stress relaxation and constant load tests in hydrogen charging condition prove that hydrogen has dual action of softening and hardening steel.It is found that the entrance of hydrogen induces plastic deformation of 12MnMoVNbTi steels below their yield stress level. The plastic deformation rate slows down with time and will not lead to fracture. From the relationship between hydrogen stress cracking and plastic deformation behavior, it is suggested that the dislocation movement in this deformation process would help the trasport of hydrogen to plastic zone and crack tip and promote hydrogen embrittlement.
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