基于电阻原理的涂层刀具刀-屑接触热阻及非均质传热机理研究

High-grade NC machine tools is the “crown” in modern industrial civilization, the cutting tools is the diamond on the crown, and the light shining of diamond is derived from the cutting tools coating. The coatings on the carbide cutting tools can improve the tools’ wear resistance and heat resistance, thus can reduce the friction between tools and workpiece. However, the friction between cutting tool coating and workpiece material can generate a lot of frictional heat. The frictional heat can cause the rise of cutting tool temperature which is the fundamental reason for the failure of coated tools such as bond, oxidation and heat crack. Therefore, reduce the tool temperature during the machining can greatly improve coated tools wear resistance and extend the tools service lives. Consequently, the machining of H13 steel using TiN and TiAlN PVD coated carbide tools will be selected as research object in this study. In accordance with the tool-chip contact characteristics, the tool-chip friction coefficient will be obtained. Based on the principle of parallel resistors, the theoretical model of tool-chip thermal contact resistance will be present in the condition of non-uniform load and non-uniform heat flux. In accordance with heat transfer characteristics of the coating materials, the principle of series resistors is employed to establish the non-homogeneous heat transfer model in tool-chip interface when using coated cutting tools. The generation mechanism of tool-chip thermal contact resistance in the condition of non-uniform contact and the mechanism of heat transfer in the conditions of non-uniform contact and non-uniform heat transfer medium will be revealed. The heat transfer problem in the conditions of non-uniform contact and non-uniform structure during the coated tools cutting will be solved. The calculation method of cutting thermal resistance will be present based on the principle of resistor. The effect of tool-chip thermal contact resistance and coating resistance on the cutting heat transfer will be proved. This study can provide the theoretical basis for the prediction and control of the coated cutting tools temperature so as to further improve tools service lives.

高档数控机床是现代工业文明的“皇冠”，切削刀具是皇冠上的钻石，而刀具涂层给了钻石闪耀的光芒。在硬质合金刀具基体上进行涂层可以提高刀具表面的耐磨性和耐热性、降低摩擦系数，从而减少刀具磨损。然而，涂层刀具失效的最根本原因在于刀具与工件材料摩擦产生大量切削热而引起的刀具高温。因此降低涂层刀具切削温度则可以大大延长刀具寿命。本项目以TiN、TiAlN 两种PVD涂层硬质合金刀具切削H13模具钢为研究对象，基于PVD涂层刀具刀-屑实际摩擦接触特性，构建刀-屑接触热阻模型；结合PVD涂层的传热特性，建立刀-屑接触面传热模型；揭示非均匀接触条件下的刀-屑接触热阻产生机理和非均匀接触、非均匀传热介质条件下的刀-屑接触面传热机理；解决非均匀接触和非均匀结构的涂层刀具传热难题。提出基于电阻原理的切削热阻计算方法，探明刀-屑接触热阻和涂层热阻对切削热传导的作用规律，为涂层刀具切削温度的预测和控制提供理论基础。

目前制造业实际应用中有80%~85%的刀具是涂层刀具，采用先进的刀具涂层可以减少刀具与工件的摩擦，降低切削热分配到刀具中的比例，从而延长刀具寿命。然而在切削过程中刀-屑接触面的切削热分配及传导机理尚未明确，刀具涂层对切削热传导的影响机制尚不清晰。因此，对于涂层刀具温度的精确预测和主动控制尚存在许多难题，刀具寿命的进一步提高遇到了瓶颈。本项目以涂层硬质合金刀具切削淬硬H13模具钢为研究对象，开展了切削过程中涂层刀具刀-屑接触面热阻、传热机理及涂层刀具的切削性能研究。. 通过对涂层刀具的显微结构和力学性能分析为刀-屑接触热阻、切削热传导及涂层刀具切削性能研究提供材料性质参数。研究了非均布载荷、非均匀热流密度条件下的切削第二变形区刀-屑接触状态，并基于电阻原理构建了刀-屑粘结区和滑动区的接触热阻模型。通过切削试验对刀-屑接触区形貌进行了观察并测量了刀-屑接触长度，定性探讨了刀-屑接触热阻的演变规律。搭建了接触热阻的试验平台，进行了刀-屑接触的模拟试验，研究了接触温度和接触面积对接触热阻的影响规律。通过有限元仿真计算了刀-屑间不同接触热导时的刀具体内温度分布，探讨了刀具涂层对切削热传导的阻碍作用。利用移动热源法建立了在剪切热源和刀-屑摩擦热源协同作用下前刀面温度模型，获取了刀-屑接触面切削热分配系数，研究了切削参数、涂层材料和涂层厚度对前刀面温度和刀-屑接触面热分配系数的影响并进行了试验验证，并对刀具体内温度的进行了对比试验研究。进行了涂层刀具非均质传热的仿真研究，分析了涂层材料、涂层厚度及涂层-基体实际接触面积对非均质传热的影响。进行了涂层刀具切削加工淬硬H13钢的切削性能试验，探讨了涂层材料和切削参数对切削力、切削温度、表面粗糙度的影响规律，并对涂层刀具磨损形貌进行了显微观察和分析，揭示了涂层刀具的磨损机理。为涂层刀具切削温度的预测和主动调控提供重要的理论基础，对于进一步提高刀具寿命、降低制造业生产成本具有重要的研究意义。