某热煨弯管开裂原因分析
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摘要
采用宏观分析、无损检测、化学成分分析、力学性能检测、金相分析和扫描电镜等试验,分析了弯管开裂原因,并对弯管开裂处材料分别进行了550℃、650℃的回火和900℃的正火热处理。结果表明:失效弯管起裂于外表面,并向内表面脆性扩展,开裂主要是由于弯管热煨工艺不当,产生硬而脆的马氏体组织,弯管抗脆性断裂能力严重不足所致;回火或正火热处理工艺后,弯管开裂处材料硬度明显下降,冲击韧性显著提高,性能得到改善,建议选用正火钢材用水冷却煨制的感应加热弯管,应在水冷后进行正火或回火热处理。
The cracking reason on induction heat bend pipe was analyzed through macroscopic analysis,non-destructive testing,chemical composition analysis, mechanical properties testing,metallographic analysis, scanning electron microscopy and other means,and the heat treatment on tempering at 550 ℃ or 650 ℃ and normalizing at 900 ℃ were carried out for the bend materials. The results show that the crack initiates from the outer surface and propagates brittlely to the inner surface, and the main reason for cracking is that the induction heat process of bend pipe is improper, which can result in the production of brittle martensite structure, and the brittle fracture resistance of bend pipe is seriously inadequate. After tempering or normalizing, the hardness obviously decreases, the impact toughness increases and the properties are improved. It is suggested that the induction heat bend pipe made of normalizing steel by water cooling should be re-tempered or re-normalized after water-cooling.
The cracking reason on induction heat bend pipe was analyzed through macroscopic analysis,non-destructive testing,chemical composition analysis, mechanical properties testing,metallographic analysis, scanning electron microscopy and other means,and the heat treatment on tempering at 550 ℃ or 650 ℃ and normalizing at 900 ℃ were carried out for the bend materials. The results show that the crack initiates from the outer surface and propagates brittlely to the inner surface, and the main reason for cracking is that the induction heat process of bend pipe is improper, which can result in the production of brittle martensite structure, and the brittle fracture resistance of bend pipe is seriously inadequate. After tempering or normalizing, the hardness obviously decreases, the impact toughness increases and the properties are improved. It is suggested that the induction heat bend pipe made of normalizing steel by water cooling should be re-tempered or re-normalized after water-cooling.
引文
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[3] 仝珂,谢学东,李亮,等.油气输送用弯管失效原因及典型案例分析[J].石油管材与仪器,2016,2(01):46-49.
[4] 马宗耀,田伟.16Mn钢油气集输管线弯管失效分析[J].金属热处理,2009(3),34(3):89-92.
[5] 潘鸿,吕文涛,钱英豪,等.L360钢级弯管开裂失效分析[J].热加工工艺,2016(4),45(8):253-255.
[6] 石油管材专业标准化技术委员会.油气输送用钢制感应加热弯管:SY/T 5257—2012[S].北京:石油工业出版社,2013.
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