Calibration of emissivity value of 18CrNiMo7-6 steel and study on cylindrical grinding temperature

To study the variation rule of workpiece temperature concerning machining parameters in the cylindrical transverse grinding process of gear steel, 18CrNiMo7-6 gear steel was selected as the workpiece material, and a CBN grinding wheel was used as the grinding tool. An infrared thermal imaging instrument was used to detect the temperature during the grinding process. A calibration scheme of thermal emissivity value, incorporating an additional air curtain device, was proposed. The high-speed airflow generated by the air curtain was used to slow down the entry of external air into the heating furnace, preventing the oxidation of samples during calibration, thus ensuring the accuracy of the emissivity value calibrated under high-temperature conditions. Based on the test results, the influence of workpiece speed ${v_{\text{w}}}$, workpiece grinding depth per revolution ${f_{\text{a}}}$, grinding wheel grain size ${d_{\text{g}}}$, grinding wheel diameter ${d_{\text{s}}}$ and grinding width $b$ on the temperature was analyzed. The workpiece grinding depth per revolution ${f_{\text{a}}}$ was identified as the most significant factor affecting the temperature change. The empirical formula between grinding temperature and aforementioned test parameters was obtained by fitting, with an error of 9.27%. The test measurement results of grinding temperature were compared with those derived from the theory of a moving heat source, Rayleigh distribution model and dry grinding heat distribution ratio model, resulting in a deviation of 8.51%.