埋地管线钢在高pH值环境的膜致应力试验研究

Experimental Research on Additive Stress of Pipeline Steel in the Simulated High pH Soil Evironment

采用慢应变速率法测量了X70管线钢在模拟高pH值土壤介质应力腐蚀过程中的膜致应力。通过试验研究可知:X70管线钢在1N Na2CO3+1N NaHCO3溶液中存在大小约为31 MPa的膜致应力,该力在应力腐蚀破裂过程中一直存在,并与外应力相叠加,从而促进了位错的发射、增殖和运动。同时,运用灰色理论中的等间距数列预测建立了GM(1,1)模型,对膜致应力-时间的关系进行了数据分析。试验结果和灰色理论分析表明:膜致应力大约在4 h达到稳定,并在继续腐蚀过程中保持不变。

The additive stress of X70 pipeline steel during the course of stress corrosion cracking in the simulated high pH soil evironment is measured by applying the slow strain rate testing. The results show that the additive tensile stress existed in the 1N Na2CO3 ＋ 1N NaHCO3 solution is about 31 MPa, in the process of SCC （Stress Corrosion Cracking）. The stress can be overlapped with the external stress to promote the emission, multiplication and motion of dislocation. Meanwhile, through the grey forecasting of equidistant data sequent, GM（1,1） modeling is established, while the data analysis about the relationship between additive stress and time is made. The experimental results and grey theory analysis indicate that it takes 4 hours or so for the additive stress to reach its stabilization, and the stress can be nearly kept on the constant value in the continued process of SCC.