X80管线钢焊接热影响区的韧性分析

Analysis of toughness in HAZ for X80 pipeline steel welding

X80管线钢在焊接过程中,热影响区由于受到焊接过程热的作用,其组织和性能会发生较大的变化。韧性是天然气长输管线的重要性能,采用热模拟技术、现代工程测试手段和显微分析方法,分析了不同热输入参数下X80管线钢焊接热影响区粗晶区(CGHAZ)韧性(夏比冲击功和CTOD)的差异及其原因。在一定范围内,较高焊接热输入下CGHAZ的韧性比较低热输入下CGHAZ的韧性明显高,超过一定范围,随着热输入的增加韧性激剧下降。造成不同热输入下韧性差异的根本原因是由CGHAZ显微组织的差异引起的。较低的热输入下CGHAZ中产生了一定量的低碳马氏体,从而导致韧性较差。

The microstructure and properties of X80 steel will be changed greatly because of heat cycle in welding process.Toughness is a very important property of long distance natural gas transmission pipeline.The toughness characteristic(Charpy-V impact and crack opening displacement,i.e.CTOD)and reason of X80 Coarse Grained Heat Affect Zone(CGHAZ) with different welding heat inputs was analyzed by weld thermal simulation technique,modern test and microstructure analyses methods.The results indicted that the toughness of CGHAZ of higher heat input is better than that of lower heat input in some extend,and the toughness violently decrease as increasing of heat input beyond the extend.The essential reason of these results is the different microstructures of CGHAZ for different heat input.The low carbon martensite constituent found for lower heat input makes CGHAZ toughness be bad.