加热炉对流段焊缝开裂原因分析  

Cause Analysis of Weld Cracking in Convection Section of Reheating Furnace

作　　者：冉平 RAN Ping(CNOOC Ningbo Daxie Petrochemical Co.Ltd.,Ningbo 315812,China)

机构地区：[1]中海石油宁波大榭石化有限公司,浙江宁波315812

出　　处：《工业加热》2023年第9期74-76,共3页Industrial Heating

摘　　要：某公司装置主汽提塔底重沸炉(F-6201)于2014年建成投用,在2017至2020年度运行周期中,顶部对流段经常有热浪溢出,初步判断为蒸汽泄漏。停工期间打开弯头箱发现,有4道焊缝存在目视可见裂纹,经过射线检测发现另外4道焊缝存在裂纹。通过合金分析确认炉管的化学成分满足标准要求;通过金相分析发现存在裂纹的焊缝热影响区主要为马氏体组织并且晶粒粗大,焊缝裂纹处金相组织更是发生了相变;通过对所有对流段炉管的焊缝进行硬度检测发现,绝大部分焊缝及热影响区硬度值超标。结合金相分析及硬度检测结果,判定焊缝开裂的原因为焊接时线能量过大,且焊接完成后的消应力热处理未到位,导致焊缝硬度高,应力大。最终通过重新消应力热处理降低焊缝硬度,降低焊缝开裂风险。The main stripper bottom reboiler furnace(F-6201)of a certain company was built and put into operation in 2014.During the operation period from 2017 to 2020,there were often heat waves overflowing from the top convection section,which was preliminarily determined to be steam leakage.During the shutdown period,it was found that 4 welds had visible cracks when opening the elbow box.After radiographic testing,it was found that another 4 welds had cracks.Confirm through alloy analysis that the chemical composition of the furnace tube meets the standard requirements;Through metallographic analysis,it was found that the heat affected zone of the weld seam with cracks is mainly composed of martensite structure and coarse grains,and the metallographic structure at the crack site of the weld seam undergoes phase transformation;Through hardness testing on all the welds of the convection section furnace tubes,it was found that the majority of the welds and heat affected zone had hardness values exceeding the standard.Based on metallographic analysis and hardness testing results,it is determined that the cause of weld cracking is excessive linear energy during welding,and the stress relief heat treatment after welding is not in place,resulting in high weld hardness and high stress.Ultimately,the hardness of the weld seam is reduced by re stress relieving heat treatment,thereby reducing the risk of weld cracking.

关 键 词：裂纹 加热炉 炉管 硬度 金相分析 

分 类 号：TG156.23[金属学及工艺—热处理]