加氢反应器用35CrMoA螺母开裂原因分析
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摘要
某石化公司加氢反应器检修更换法兰紧固件时,发现多个35CrMoA螺母备件存在外表面裂纹问题。采用化学成分分析、硬度测定、金相分析、扫描电镜(SEM)观察和能谱分析等手段,对加氢反应器用35CrMoA螺母开裂的原因进行了分析研究。结果表明:裂纹附近组织存在大量条块状和带状分布的夹杂物,这些夹杂物为Cr,Mn,Al,Si的氧化物,并以机械混合物的形式存在于钢中。由于夹杂物与钢的基体性能具有明显差异,在加工应力的作用下,夹杂物处萌生微裂纹并扩展,具有锻造裂纹的特征;在随后的调质过程中,裂纹继续扩展,具有淬火裂纹的特征;最终的裂纹面表现为韧窝断口。淬火裂纹的存在不符合SH/T 3404—2013标准和GB/T 5779.2—2000标准的规定。
The surface cracks were found on 35 CrMoA nut fittings during the maintenance of flange fit-tings of the reactor. The cracking causes of 35 CrMoA nut used in the hydrogenation reactor were analyzed bymeans of chemical composition analysis,hardness measurement,metallographic analysis,SEM observationand energy spectrum analysis,etc. The results showed that there were a lot of lumpy and banded inclusions inthe microstructure nearing the crack. These inclusions are the oxides of Cr,Mn,Al,Si,and they are presentin the steel in the form of mechanical mixtures. Due to the obvious difference between the properties of the in-clusions and the steel,under the action of processing stress,the microcracks in the inclusions were generatedand expanded,which had the characteristics of forging cracks. In the subsequent quenching and temperingprocesses,the cracks continued to expand,which showed the characteristics of quenching crack,and the finalcrack surface was the dimple fracture. The quenching crack did not meet the specifications of SH/T 3404—2013 standard and GB/T 5779. 2—2000 standard.
The surface cracks were found on 35 CrMoA nut fittings during the maintenance of flange fit-tings of the reactor. The cracking causes of 35 CrMoA nut used in the hydrogenation reactor were analyzed bymeans of chemical composition analysis,hardness measurement,metallographic analysis,SEM observationand energy spectrum analysis,etc. The results showed that there were a lot of lumpy and banded inclusions inthe microstructure nearing the crack. These inclusions are the oxides of Cr,Mn,Al,Si,and they are presentin the steel in the form of mechanical mixtures. Due to the obvious difference between the properties of the in-clusions and the steel,under the action of processing stress,the microcracks in the inclusions were generatedand expanded,which had the characteristics of forging cracks. In the subsequent quenching and temperingprocesses,the cracks continued to expand,which showed the characteristics of quenching crack,and the finalcrack surface was the dimple fracture. The quenching crack did not meet the specifications of SH/T 3404—2013 standard and GB/T 5779. 2—2000 standard.
引文
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[2]张本国,赵健,夏建生,等. 35CrMo钢螺栓在缩径加工时的断裂原因[J].机械工程材料,2017,41(6):96.
[3]杨琦,杨天钧. 35CrMo钢汽车螺栓的断裂失效分析[J].铸造技术,2017,38(12):2901.
[4]王德宝,张峰,浦红,等. 35CrMo高强度连接螺栓杯锥状断口失效分析[J].安徽冶金,2014(3):24.
[5]温爱玲,路文娟,王生武. 35CrMo螺栓断裂分析[J].理化检验-物理分册,2014,50(9):675.
[6]韩克甲,赵晓辉,李洪伟. 35CrMo钢高强螺栓断裂失效分析[J].理化检验-物理分册,2017,53(6):435.
[7]赵强,曹佳丽,丁景焕,等. 35CrMo钢螺栓断裂原因分析[J].上海金属,2017,39(6):73.
[8]陈瑗元,陆慧. 35CrMo钢螺栓断裂原因分析[J].理化检验-物理分册,2014,50(8):617.
[9]唐文忠. 35CrMo钢螺栓断裂原因分析[J].金属制品,2015,41(4):63.
[10]中华人民共和国国家质量监督检验检疫总局,中国国家标准化管理委员会.碳素钢和中低合金钢多元素含量的测定火花放电原子发射光谱法(常规法):GB/T 4336—2016[S].北京:中国标准出版社,2016.
[11]中华人民共和国国家质量监督检验检疫总局,中国国家标准化管理委员会.合金结构钢:GB/T 3077—2015[S].北京:中国标准出版社,2016.
[12]中华人民共和国国家质量监督检验检疫总局,中国国家标准化管理委员会.金属材料布氏硬度试验第1部分:试验方法:GB/T 231. 1—2009[S].北京:中国标准出版社,2009.
[13]中华人民共和国工业和信息化部.石油化工钢制管法兰用紧固件:SH/T 3404—2013[S].北京:中国石化出版社,2014.
[14]中华人民共和国国家质量监督检验检疫总局,中国国家标准化管理委员会.压力容器第2部分:试验方法:GB/T150. 2—2011[S].北京:中国标准出版社,2011.
[15]国家质量技术监督局.紧固件表面缺陷螺母:GB/T 5779.2—2000[S].北京:中国标准出版社,2001.