Temperature is an important property to be monitored during cutting operations, such as in the milling of metals, because it affects the workpiece mechanical properties, the machining tool performance, and the process efficiency. For this reason, authors have used thermography to monitor thermal and spatial gradients, and to estimate temperature. The problem is that IR cameras native applications are mostly based on the diffuse-gray approximation, with emissivity set as a constant value. The diffuse-gray approach is a reasonable choice for opaque surfaces with emissivity approximately constant in respect to the wavelength, which is not the case in most of the time for metals under cutting operation. In this work we propose a more suitable methodology that uses radiative heat transfer directional-spectral relations to estimate cutting process temperatures during face milling of metals, using the full electrical response of commercial infrared cameras as an input. AISI H13 steel was used as the workpiece material. In the first part of the experiments, emissivity was estimated for eight different temperatures from 50 °C to 250 °C, using both directional-spectral and diffuse-gray approaches. Temperature was measured using a thermocouple type T, calibrated using a PT-100 reference from 50 °C to 250 °C. In the second part, we used the emissivity obtained in the first part to estimate the temperature for twelve different cutting conditions, again using both directional-spectral and diffuse-gray approaches. We compared the results of both methods, also with the direct application of emissivity provided in infrared cameras manuals. The temperature deviation between the different approaches were up to 41%, which demonstrates that the temperature estimation procedure affects the results substantially.

温度是切削操作（例如金属铣削）中要监控的重要属性，因为它会影响工件的机械性能，加工工具性能以及加工效率。由于这个原因，作者使用热成像技术来监视热梯度和空间梯度，并估算温度。问题在于，红外热像仪的本机应用主要基于漫射灰色近似，并且将发射率设置为恒定值。对于发射率相对于波长大致恒定的不透明表面，漫灰方法是一种合理的选择，而在大多数情况下，切割操作中的金属并非如此。在这项工作中，我们提出了一种更合适的方法，该方法使用辐射热传递方向-光谱关系来估计金属端面铣削过程中的切削过程温度，并使用商用红外热像仪的全电响应作为输入。AISI H13钢用作工件材料。在实验的第一部分中，使用方向光谱和漫灰色方法估算了从50°C到250°C八个温度的发射率。使用T型热电偶测量温度，并使用PT-100基准在50°C至250°C范围内进行校准。在第二部分中，我们使用在第一部分中获得的发射率来估计十二种不同切割条件的温度，同样使用方向光谱方法和漫灰方法。我们比较了两种方法的结果，还可以直接应用红外热像仪手册中提供的发射率。不同方法之间的温度偏差高达41％，这表明温度估算程序会严重影响结果。