70Cr3NiMo钢轧辊探伤不合格原因分析及改善措施

Analysis on disqualification reason and improvement measures of steel 70Cr3NiMo roller by ultrasonic inspection

采用10500 kg锭型70Cr3NiMo钢锭锻造加工轧辊,检验发现锻件超声波探伤结果不符合标准要求,锻件心部位置存在密集和单点超标缺陷。为了找出探伤不合格原因,降低损失,采用化学成分分析、低倍检验、金相检验和扫描电镜分析等方法,对探伤缺陷位置进行了分析。分析结果表明,该轧辊探伤不合格原因是母材钢锭内部存在大量超级别Al2O3非金属夹杂物,这些夹杂物分割了钢材基体的连续性,造成探伤不合格。此外,通过分析Al2O3夹杂物的来源及其危害性,得到了对应的工艺改善方法。试验结果表明,改进后锻件探伤合格率为100%。

For the roller forged by steel ingot of 70 Cr3 NiMo(10500 kg),its quality do not meet the standard requirements by ultrasonic testing,and the defects of dense and single point exist in the center of forgings.In order to find out the cause of unqualified ultrasonic inspection and reduce the loss,the defect location was analyzed by chemical composition analysis,low power test,metallographic examination and scanning electron microscopy.The analysis results show that the reason of unqualified ultrasonic inspection for roller is that there are a lot of super grade Al2 O3 non-metallic inclusions in the base ingot,which break up the matrix continuity of steel.In addition,the source and harmfulness of non-metallic inclusions were analyzed,and the corresponding improvement measures are put forward.The experimental results show that the qualification rate of defect detection for the improved forgings is 100%.