Cause analysis and countermeasures for cracking of welded steel pipe in flattening test
ZHENG Shi-wei1, ZHU Li-guang2, CAO Sheng-li1,3, WU Xiao-yan1, ZHANG Qing-jun*1,3
1. Hebei High Quality Steel Continuous Casting Engineering Technology Research Center, College of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063009, China; 2. Hebei University of Science and Technology,Shijiazhuang 050018, China; 3. Analysis and Testing Research Center, North China University of Science and Technology, Tangshan 063210, China
Abstract：The flattening test is one of the methods to check the quality of steel tubes.The reasons for cracking in flattening test were analyzed to find out corresponding countermeasures and solve the cracking problems of welded steel pipe in flattening test. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and metallographic microscope (OM) were employed to analyze the reasons for cracking of welded steel pipe in flattening test in two aspects, i.e., metallographic examination and fracture analysis. The main conclusions could be obtained by metallographic analysis, and the final conclusions could be obtained by verifying the metallographic examination by fracture analysis. The results showed that the main reason for cracking of welded steel tube was the presence of a large number of silicate inclusions in the welded steel tube, which belonged to high temperature plastic inclusions and easily destroyed the transverse continuity of the matrix. It could cause stress concentration in flattening test, thus leading to the formation of cracks and the cracking of steel tubes. The secondary reason for the cracking of welded steel tube was the banded structure in sample and the distribution of meshy tertiary cementite at the grain boundary of ferrite. The plasticity of tertiary cementite was poor and the extension of cracks would be accelerated during flattening. By analyzing the reason for cracking, the production process of welded steel tube was optimized. The refining in ladle furnace (LF) as well as the rolling control and cooling control technology could reduce the inclusions in the steel tubes, thus improving the cracking of the welded steel tube in flattening. Therefore, the failure rate of steel tube was decreased and the quality of welded steel tube was improved.
刘星娟.焊接钢管压扁试验开裂原因分析[J].山东工业技术,2016(9):42.LIU Xing-juan.Crack analysis on welded steel tube during flattening test[J].Shandong Industrial Technology,2016(9):42.
[2]
王伟旬,关桂芬.焊接钢管压扁试验开裂原因分析[J].南方金属,2015(6):24-26,52.WANG Wei-xun,GUAN Gui-fen.Crack analysis on welded steel tube during flattening test[J].Southern Metals,2015(6):24-26,52.
[3]
刘新礼.非金属夹杂物对钢的机械与工艺性能的影响[J].甘肃冶金,1999(2):17-22.LIU Xin-li.Effects of nonmetallic inclusions on mechanical and technological properties of steel[J].Gansu Metallurgy,1999(2):17-22.
[4]
尤大勇.钢管压扁试验开裂的原因分析[J].金属热处理,2011,36(S1):405-407.YOU Da-yong.Crack analysis of steel tube during flattening test[J].Heat Treatment of Metals,2011,36(S1):405-407.
[5]
聂向晖,冯翔宇,谭依.Q235中板冷弯开裂原因探讨[J].理化检验:物理分册,2004,40(6):308-310,323.NIE Xiang-hui,FENG Xiang-yu,TAN Yi.Cracking analysis of Q235 plate cold bending[J].Physical Testing and Chemical Analysis Part A:Physical Testing,2004,40(6):308-310,323.
[6]
魏玉芝,魏鹏,张玉强.低碳热轧钢管中魏氏组织的形成及影响[J].钢管,2001,30(6):31-33.WEI Yu-zhi,WEI Peng,ZHANG Yu-qiang.Development and effect by widmannstatten structure in hot-rolled low carbon steel tube[J].Steel Pipe,2001,30(6):31-33.
[7]
魏秋华,刘福旺,武雪峰.渗碳体对低碳钢板冲压性能的影响[J].金属热处理,2010,35(12):134-135.WEI Qiu-hua,LIU Fu-wang,WU Xue-feng.Effect of cementite on stamping property of low carbon steel plate[J].Heat Treatment of Metals,2010, 35(12):134-135.
