加工硬化和退火软化效应对316不锈钢厚壁管-管对接接头残余应力计算精度的影响  

Influence of Strain Hardening and Annealing Effect on the Prediction of Welding Residual Stresses in a Thick-Wall 316 Stainless Steel Butt-Welded Pipe Joint

作　　者：李索[1] 陈维奇 胡龙 邓德安[1] LI Suo;CHEN Weiqi;HU Long;DENG Dean(College of Materials Science and Engineering,Chongqing University,Chongqing 400045,China)

机构地区：[1]重庆大学材料科学与工程学院,重庆400045

出　　处：《金属学报》2021年第12期1653-1666,共14页Acta Metallurgica Sinica

基　　金：中央高校基本科研业务费项目No.2018CDYJSY0055;国家自然科学基金项目No.51875063。

摘　　要：采用数值模拟和实验相结合的方法研究了加工硬化和退火软化效应对316不锈钢厚壁管-管对接接头残余应力计算精度的影响。基于通用有限元软件Abaqus开发了新的动态退火模型,研究了应变硬化模型(各向同性硬化模型和Chaboche混合硬化模型)和退火模型(阶跃退火模型和动态退火模型)对Satoh数值实验中应力和累积塑性应变在多重热循环条件下的形成过程与机理的影响。同时,采用2D轴对称模型计算了管-管对接接头的温度场和焊接残余应力分布,并分别与焊接热循环实验数据和由切片法、固有应变法和深孔法测量得到的残余应力结果进行对比与验证。结果表明,退火软化效应对累积塑性应变和焊接残余应力的形成过程有显著影响,不考虑退火软化效应的残余应力模拟结果与实验值相比明显偏高。新开发的动态退火模型的计算结果与实验数据吻合良好,具有较高的计算精度。当考虑退火软化效应时,采用各向同性硬化模型可以获得较精确且偏保守的计算结果,而采用Chaboche混合硬化模型的焊接残余应力计算精度更高。对于316不锈钢而言,当采用阶跃退火模型时,建议将退火温度设定为900~1000℃。Stress corrosion cracking(SCC) is a major problem in the welded components of austenitic stainless steel in nuclear power plants.High tensile residual stress is an important factor resulting in the SCC of materials.Austenitic stainless steel has a strong tendency for work hardening owing to its fcc crystal structure and low stacking-fault energy.High plastic strain can accumulate during a multipass welding process.On the other hand,accumulated strain hardening can be reduced or even eliminated during the welding thermal cycles owing to dynamic recovery,recrystallization,and grain growth below the melting point,which is called the annealing effect.Influence of strain hardening and annealing effect needs to be investigated to predict the welding-induced residual stresses accurately in austenitic stainless steel joints.In this study,a new time-temperature-dependent annealing model was proposed based on the Johnson-Mehl-Avrami equation.Numerical Satoh tests were performed to clarify the influence of strain-hardening models(i.e.,the isotropic strain-hardening model and Chaboche mixed isotropickinematic strain-hardening model) and annealing models(i.e.,the single-stage annealing model and new time-temperature-dependent annealing model) on the formation of residual stresses and the accumulated plastic strain during multiple thermal cycles.Thermoelastic-plastic finite element(FE) analyses were carried out to predict the welding residual stresses and accumulated plastic strain in a thick-wall 316 stainless steel butt-welded pipe joint with 85 welding passes.The residual stresses of the welded joint were measured by the sectioning method,inherent strain method,and deep-hole drilling method.The simulations of welding residual stresses were compared with the measurements.Annealing effect significantly influences the formation of accumulated plastic strain and welding residual stresses,neglecting which will result in a significant overestimation of FE results.The proposed annealing model showed an excellent match to the exper

关 键 词：奥氏体不锈钢 退火软化效应 加工硬化 焊接残余应力 有限元模拟 

分 类 号：TG404[金属学及工艺—焊接]