三旋内吊筒不锈钢焊缝高温服役断裂失效分析

针对催化裂化装置第三级旋风分离器吊筒焊缝断裂的现象,以吊筒不锈钢焊缝为研究对象,对焊缝断裂处的宏观形貌以及金相组织进行了分析,并采用有限元软件对破坏结构进行了热固耦合的数值分析,对结构的破坏原因进行了深入探讨。结果表明:第三级旋风分离器工作温度为700℃左右,奥氏体焊缝组织中析出脆性相,导致焊接接头脆化;内吊筒环焊缝热应力较大,;加之采用的是承载力较差的角接焊缝,易发生破坏。提出建议:采用更可靠的焊缝形式,设置结构过渡段;更换焊接工艺,控制接头脆化,采取不预热并快速冷却的方式。

Fracture failure analysis of stainless steel weld of internal hanging barrel in the 3-stage cyclone

The fracture of girth weld of internal hanging barrel in FCC 3-stage cyclone was found in operation.The fracture morphology analysis and metallographic structure analysis were made on the fractures of welds of the hanging barrel in combination with thermo-structural coupling analysis by ANSYS.The causes of failure were analyzed in detail.The results showed that the embrittlement occurred in weld joints of austenitic steel when the 3-stage cyclone was operating at a temperature of about 700 ℃.As the thermal stress of ring welds of hanging barrel wass higher and the angular contact welding was used for the barrel,the failure could easily occur.To solve these problems,the following recommendations were presented:application of more reliable welding process,design of a transition structure,changing of welding process,control of embrittlement of weld joint and application of fast cooling with no pre-heating.