考虑相变诱导塑性的埋弧堆焊过程数值模拟方法研究

Numerical Simulation of Submerged Arc Welding Process Considering Phase Transformation Induced Plasticity

目的通过数值计算预测埋弧堆焊修复失效轧辊工艺过程中相变塑性应力、组织相变对堆焊效果的影响。方法利用CALPHAD(Calculation of Phase Diagram)方法计算了堆焊材料温变物性参数,基于COMSOL多物理场耦合平台,对轧辊埋弧堆焊过程的瞬态温度场、马氏体相成分及相变诱导塑性(TRIP)应力演变过程进行了数值计算。结果轧辊堆焊过程的温度场分布、马氏体相变均对传热速率影响敏感。靠近基体一侧的焊缝,相比于堆焊层其传热更快,导致马氏体相变更加迅速,其相变塑性应力值呈更大的宽带分布。冷却过程中因马氏体相变使焊缝热影响区的应力值缓慢下降,焊件完全冷却后的残余应力最大值为376 MPa,马氏体相占比为94%。采用Zeiss-∑igma HD场发射扫描电镜观察了轧辊堆焊切片金相组织,验证了模型的准确性。结论该数值模拟方法能准确预测轧辊埋弧堆焊过程中塑性应力变化及组织演变规律,为减小和消除残余应力提供了有效途径与方法,且为预防轧辊堆焊层开裂等缺陷提供了一定的理论基础。

To predict the effect of phase transformation plastic stress and microstructure transformation on the hardfacing effect in the process of repairing the failed roll by submerged arc welding, this paper calculates the temperature dependent physical parameters of hardfacing material by CALPHAD(calculation of phase diagram), and numerically calculates the transient temperature field, martensite phase composition and transformation induced plasticity(TRIP) stress evolution process of roll submerged arc welding process based on COMSOL multi physical field coupling platform. The results show that the temperature field distribution and martensitic transformation are sensitive to the heat transfer rate. Compared with the hardfacing layer, the heat transfer of the weld near the substrate side is faster, resulting in faster martensitic transformation, and the transformation plastic stress value shows a larger broadband distribution. During the cooling process, the stress value of HAZ decreases slowly due to martensitic transformation. The maximum residual stress after cooling is 376 MPa, and the martensite phase accounts for 94%. The metallographic structure of roll hardfacing slice is observed by Zeiss-∑igma HD field emission scanning electron microscope, and the accuracy of the model is verified. It can be concluded that the numerical simulation method can accurately predict the plastic stress change and microstructure evolution law in the process of submerged arc welding, which provides an effective way and method to reduce and eliminate the residual stress, and offers a theoretical basis for preventing the defects of roll hardfacing layer.