汽轮机EH油系统用奥氏体不锈钢弯管开裂的原因分析
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摘要
对某电厂汽轮机EH油开裂弯管进行了宏观检查、磁记忆检测、硬度试验、金相检验等分析。结果显示:材质为TP304H不锈钢的EH油弯管内壁存在原始制造的轧伤缺陷、弯管圆度超标、维氏硬度超标、带状夹杂物超标和应力集中等产品质量问题。分析认为,带状非金属夹杂物破坏了基体组织连续性,降低弯管内表面成型质量;圆度和硬度超标导致弯管存在应力集中现象,在中性面内表面严重轧伤处应力集中最为明显,形成裂纹源导致了弯管开裂。建议加强不锈钢管原材料质量检验工作,制定合理的冷弯工艺,冷弯后采取固溶处理或去应力退火等处理措施。
The macro inspection, magnetic memory test, hardness test and metallographic test of EH oil cracking bend tube of steam turbine in a power plant were carried out. The results show that, the inner wall of TP304 H stainless steel EH oil bend tube has the original manufacture rolling defects, the roundness of the bend tube exceeds the standard, the Vickers hardness exceeds the standard, the banded inclusion exceeds the standard and it has stress concentration and so on. It is considered that, the banded non-metallic inclusions destroy the continuity of matrix structure and reduce the forming quality of the inner surface of the bend tube. The roundness and hardness exceeding the standard, which leads to the phenomenon of stress concentration in the bend tube, and the crack source is formed at the serious rolling injury on the inner surface of the neutral surface with most obvious stress concentration, which leads to the cracking of the bend tube. It is suggested that, the quality inspection of stainless steel pipe raw materials should be strengthened, reasonable cold bending process should be worked out, and the treatment measures such as solid solution treatment or de-stress annealing should be taken after cold bending.
The macro inspection, magnetic memory test, hardness test and metallographic test of EH oil cracking bend tube of steam turbine in a power plant were carried out. The results show that, the inner wall of TP304 H stainless steel EH oil bend tube has the original manufacture rolling defects, the roundness of the bend tube exceeds the standard, the Vickers hardness exceeds the standard, the banded inclusion exceeds the standard and it has stress concentration and so on. It is considered that, the banded non-metallic inclusions destroy the continuity of matrix structure and reduce the forming quality of the inner surface of the bend tube. The roundness and hardness exceeding the standard, which leads to the phenomenon of stress concentration in the bend tube, and the crack source is formed at the serious rolling injury on the inner surface of the neutral surface with most obvious stress concentration, which leads to the cracking of the bend tube. It is suggested that, the quality inspection of stainless steel pipe raw materials should be strengthened, reasonable cold bending process should be worked out, and the treatment measures such as solid solution treatment or de-stress annealing should be taken after cold bending.
引文
[1]胡钢,许淳淳,袁俊钢．奥氏体304不锈钢形变诱发马氏体相变与磁记忆效应[J]．无损检测,2008,30(4):216-219.
[2]冷建成,王犇,王学增．基于磁记忆技术的铁磁性材料早期损伤诊断方法研究[D]哈尔滨：哈尔滨工业大学,2012:11-24.
[3]邢海燕基于双正交法的焊缝早期隐性损伤临界状态磁记忆特征[J]．机械工程学报,2015,51(16):71-76.
[4]中国电力企业联合会．电站弯管：DL/T 515-2018[S]．北京：中国电力出版社,2018.
[5]Hausild P, Davydov, Drahokoupil J, et al.Characterization of strain-induced martensitic transformation in a metastable austenitic stainless steel[J].Materials&Design,2010,31(4):1821-1827.
[6]韩飞．304奥氏体不锈钢冷加工硬化及退火软化的研究[D].长沙：中南大学,2004:33-40.
[7]李雅娴,应变强化奥氏体不锈钢低温容器材料成型和工艺研究[D]．杭州：浙江大学,2010:13-21.
[8]吴斌,陈兴润,王建．304不锈钢热轧板中非金属夹杂物的研究[J]．钢铁研究,2015,43(1):16-19.
[9]滕涛,陈银莉,赵爱民．304不锈钢冷轧薄板表面线缺陷的形貌[J]．钢铁钒钛,2007,28(3):28-32.
[2]冷建成,王犇,王学增．基于磁记忆技术的铁磁性材料早期损伤诊断方法研究[D]哈尔滨：哈尔滨工业大学,2012:11-24.
[3]邢海燕基于双正交法的焊缝早期隐性损伤临界状态磁记忆特征[J]．机械工程学报,2015,51(16):71-76.
[4]中国电力企业联合会．电站弯管：DL/T 515-2018[S]．北京：中国电力出版社,2018.
[5]Hausild P, Davydov, Drahokoupil J, et al.Characterization of strain-induced martensitic transformation in a metastable austenitic stainless steel[J].Materials&Design,2010,31(4):1821-1827.
[6]韩飞．304奥氏体不锈钢冷加工硬化及退火软化的研究[D].长沙：中南大学,2004:33-40.
[7]李雅娴,应变强化奥氏体不锈钢低温容器材料成型和工艺研究[D]．杭州：浙江大学,2010:13-21.
[8]吴斌,陈兴润,王建．304不锈钢热轧板中非金属夹杂物的研究[J]．钢铁研究,2015,43(1):16-19.
[9]滕涛,陈银莉,赵爱民．304不锈钢冷轧薄板表面线缺陷的形貌[J]．钢铁钒钛,2007,28(3):28-32.
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