For medium- and high-carbon stainless steels, welding can induce sensitization in the heat affected zone (HAZ) adjacent to the weld, where chromium carbide \((\hbox {Cr}_{23}\hbox {C}_{6})\) precipitates out of the bulk metal and accumulates at the grain boundaries. This chromium depletion and precipitate accumulation at grain boundaries makes the alloy susceptible to intergranular corrosion, environmentally assisted cracking, and broader fracture. In this paper, we investigate the efficacy of using induction infrared thermography (IIRT) as a non-destructive method for detecting welding-induced sensitization, using the AISI 440C steel as an example. We start by presenting a laboratory experiment to demonstrate this approach, using a radio frequency function generator, an induction wand, and a FLIR SC8203 infrared camera. We use traditional metallography techniques and scanning electron microscopy (SEM) to identify the location of any sensitized regions and characterize the corresponding microstructure. The IIRT experimental results reveal a distinguishable heat signature, with higher temperature observed within the sensitized regions. Next, we present a computational study to simulate the IIRT experiment and investigate the underlying physics. We adopt a three-dimensional thermo-electro-magnetic model including Fourier’s law of heat conduction and Maxwell’s equations for predicting the electromagnetic field caused by a sinusoidal excitation current flowing through the induction coil. We solve the system of governing equations using the commercial solver COMSOL Multiphysics. To numerically investigate the possible causes of the disproportionate heating within the sensitized regions, we realistically vary the values of electrical resistivity and magnetic permeability therein. The simulated results indicate that the heat signature observed in the laboratory experiment may result from the increase of both electrical resistivity and magnetic permeability in the HAZ. The possible physical relationships between sensitization and the variation of these two properties are discussed.

对于中碳和高碳不锈钢，焊接会在与焊缝相邻的热影响区（HAZ）中引起敏化作用，其中碳化铬\（（\ hbox {Cr} _ {23} \ hbox {C} _ {6 }）\）从大块金属中析出并积累在晶界处。铬的耗竭和晶界处的沉淀积累使该合金容易受到晶间腐蚀，环境辅助的开裂和较宽的断裂。在本文中，我们以AISI 440C钢为例，研究了使用感应红外热成像（IIRT）作为检测焊接引起的致敏性的非破坏性方法的功效。我们首先使用射频功能发生器，感应棒和FLIR SC8203红外热像仪通过实验室实验来演示这种方法。我们使用传统的金相学技术和扫描电子显微镜（SEM）来识别任何敏感区域的位置并表征相应的显微组织。IIRT实验结果显示出明显的热特征，在敏化区域内观察到较高的温度。接下来，我们提出了一项计算研究，以模拟IIRT实验并研究基础物理学。我们采用包含热传导傅立叶定律和麦克斯韦方程组的三维热电磁模型来预测由流过感应线圈的正弦激励电流引起的电磁场。我们使用商业求解器COMSOL Multiphysics求解控制方程组。为了数值研究敏感区域内不均匀加热的可能原因，我们实际地改变了其中电阻率和磁导率的值。模拟结果表明，在实验室实验中观察到的热信号可能是由于热影响区中电阻率和磁导率的增加所致。讨论了敏化和这两种性质的变化之间可能的物理关系。