X80管线钢焊接热影响区组织和氢渗透行为研究

为了进一步研究X80管线钢热影响区组织对氢渗透行为的影响，利用焊接热模拟技术模拟了X80管线钢在不同峰值温度下生成的焊接热影响区，研究了800~1 350 ℃的峰值温度对焊接热影响区的组织、显微硬度和氢渗透行为的影响。焊接热影响区组织分析结果显示，当峰值温度为800 ℃时，组织主要为铁素体和贝氏体，晶粒大小分布不均匀，M-A组元呈岛状；峰值温度为900 ℃时，组织主要为细小的铁素体和粒状贝氏体，晶粒分布均匀，M-A组元呈岛状和粒状；峰值温度为1 150~1 350 ℃时，组织均以粒状贝氏体为主，M-A组元主要分布在原奥氏体晶界处。焊接热影响区硬度试验和氢渗透试验结果显示，显微硬度随着峰值温度的升高，呈先升高后降低趋势，并且发生了明显的软化；随着峰值温度的升高，组织的氢扩散通量和氢表现扩散系数逐渐增大，吸附氢浓度逐渐减小。研究表明，在焊接热影响区组织中，部分相变区的氢脆敏感性最高，容易造成氢聚集，进而引起氢脆等现象。

Study on Microstructure and Hydrogen Permeation Behavior of Welding Heat Affected Zone of X80 Pipeline Steel

In order to further study the effect of microstructure of heat affected zone of X80 pipeline steel on hydrogen permeation behavior, the welding heat affected zone of X80 pipeline steel at different peak temperatures was simulated by welding thermal simulation technology. The effects of peak temperature of 800~1 350 ℃ on microstructure, microhardness and hydrogen permeation behavior of welding heat affected zone were studied. The results of microstructure analysis of HAZ show that when the peak temperature is 800 ℃, the microstructure is mainly ferrite and bainite, the grain size distribution is uneven, and the M-A component is island shaped. When the peak temperature is 900 ℃, the microstructure is mainly fine ferrite and granular bainite, the grain distribution is uniform, and the M-A component is island shaped and granular. When the peak temperature is 1 150~1 350 ℃, the microstructure is mainly granular bainite, and the M-A components are mainly distributed at the grain boundary of the original austenite. The results of hardness test and hydrogen permeation test of welding heat affected zone show that the microhardness decreases after increasing with the increase of peak temperature, and obvious softening occurs. With the increase of peak temperature, the hydrogen diffusion flux and hydrogen apparent diffusion coefficient of the tissue gradually increased, and the adsorbed hydrogen concentration gradually decreased. The results show that in the microstructure of welding heat affected zone, some phase transformation zones have the highest sensitivity to hydrogen embrittlement, which is easy to cause hydrogen accumulation and hydrogen embrittlement.