X65管线厚板控冷残余应力的数值分析

Numerical analysis of residual stresses within X65 heavy pipeline plate during controlled cooling

为研究X65管线厚板控制冷却时板厚方向的残余应力,通过开发线性混合热膨胀模型、拓展Avrami相变动力学模型和应用Leblond模型建立了热力耦合有限元模型,用该模型研究了控冷工艺、相变效应对残余应力的影响.结果表明:当上表面层流冷却系数由1 mW/(mm2.K)分别增至2、3 mW/(mm2.K)而下表面维持1 mW/(mm2.K)不变时,上、下表面与心部两侧的平均温差由0℃分别增至9、10℃,上表面一侧的拉应力峰值锐减188 MPa,并使上表面和心部附近的拉、压应力峰向下表面方向大幅迁移,即上下表面的不对称控冷加剧了板厚方向温度和残余应力的不对称分布;实际控冷工艺下,相变效应通过产生拉、压应力峰值分别为779、-454 MPa的应力而显著影响板厚方向的残余应力.

To study residual stresses via thickness direction of X65 heavy pipeline plate during controlled cool ing process, a thermomechanical coupled finite element model, which consisted of the developed linear mixtur, thermal expansion model, the modified Avrami transformation dynamics model, and the Leblond model, was es tablished. The influence of controlled cooling technologies and phase transformation effect on residual stresse~ was studied by utilizing the above model. The result shows average temperature difference between top surfac, and inner increases from 0 ℃ to 9 ℃ ,however,10 ℃ for bottom surface. Peak value of tensile stress near th, top surface,meanwhile,sharply decreases 188 MPa,and tensile and compressive stress peak near the top sur face and inner shift to the bottom surface strongly, when laminar cooling coefficient of top surface increases from 1 mW/（mm2 · K）to 2,3 mW/（ mm2 · K） and that of bottom surface keeps 1 mW/（ mm2 ·K） un changed . That means the asymmetry of temperature and residual stresses via thickness direction of the plate ar, aggraated by the asymmetry controlled cooling between the top and bottom surfaces. The residual stresses via thickness direction of plate sigriificantly depend on the stress with the peak value,779 MPa and -454 MPa , resulted from phase transformation effect under the real controlled cooling case.