用扫描电镜观察与能谱分析方法研究了X70管线钢板超声波探伤不合格的原因。试验分析表明:超声波探伤缺陷是由数量较多、尺寸为100 μm以上的气孔与缩松经轧制变形压合而形成的;气孔是由原X70管线钢坯连铸时下水口保护浇铸的氩气所引起,缩松是由连铸拉速过大所致。关闭下水口保护浇铸的氩气,并降低拉速可使X70管线钢板超声波探伤合格率达到100%。

With SEM and Energy Spectrum to study the unqualified reason by ultrasonic testing of X70 pipeline steel plate. The experiment confirms that the unqualified district was formed by large amount of and size more than 100 μm gas cavity and shrinkage porosity which were pressed and combined in rolling process;the gas cavity was caused by argon gas for protection which was at collector nozzle during the continuous casting. Shrinkage porosity was caused by higher drawing speed for continuous casting . The experiments conclusion was that with closing the argon for protection at collector nozzle and lowering down the speed can make qualified rate to reach 100% during ultrasonic testing of X70 pipeline steel plate.