中文摘要：

采用数值模拟方法在有限元软件SYSWELD中建立了焊接三维有限元模型，利用非线性材料热物性参数和双椭球移动热源作为热传递方程的边界条件，得到了在不同预热温度条件下能熔透母材的最低焊接线能量。采用材料为APIX65钢进行实验验证，表明模拟结果和实验结果基本吻合，为预热条件下采用合适的焊接工艺提供了科学的指导依据。

英文摘要：

A 3-D finite element model for the welding was established in SYSWELD software by numerical simulation. Nonlinear material thermal parameters and translate double ellipsoid heat source were used as boundary conditions in the heat transfer equation. The minimal welding line energy which can penetrate the base material under different preheat-temperatures can be obtained. Using API X65 steel material for experimental verification, it demonstrates that the simulation result is in agree with the experimental one. So this method can be a scientific guidance to provide a suitable welding process for the welding under preheat-temperature.