18CrNiMo7-6钢发射率值标定及外圆磨削温度研究

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

为研究齿轮钢外圆横向磨削过程中工件温度受加工参数变化的影响,以18CrNiMo7-6齿轮钢作为工件材料,CBN砂轮作为磨具进行试验,使用红外热像仪对磨削过程温度进行检测。提出一种增设气幕装置的热辐射发射率值标定方案,通过气幕生成的高速气流减缓外界空气进入加热炉,防止标定过程中试样被氧化,保证高温条件下标定得到的发射率值的准确度;依据检测结果,分析工件转速v_(w)、工件每转的磨削深度f_(a)、砂轮磨粒粒度d_(g)、砂轮直径d_(s)和磨削宽度b对温度的影响。结果表明:f_(a)对温度变化影响最显著。通过拟合得到磨削温度与试验参数间的经验公式,其误差为9.27%。将磨削温度的试验测量结果与运用移动热源理论、瑞利分布模型和干式磨削热分配比模型进行理论推导的结果作对比,偏差为8.51%。

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_(w),workpiece grinding depth per revolution f_(a),grinding wheel grain size d_(g),grinding wheel diameter d_(s) and grinding width on the temperature was analyzed.The workpiece grinding depth per revolution f_(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%.