激光加热辅助高速铣削高温合金关键技术

The characteristics of high temperature alloys lead to the poor cutting performance, low efficiency and high costs. The current process in the processing of high temperature alloys are often unable to achieve the desired efficiency and costs, particularly in the milling of high temperature alloys. Laser assisted machining technology used in the machining of difficult materials can be achieved to reduce cutting forces, reduced tool wear,and improve processing efficiency. The project is based on the high-speed milling technology and combined with the laser assisted machining which can be achieved to reduce cutting forces, reduced tool wear,and improve processing efficiency. Experimential and theoretical simulation was used to investigate the force-thermal coupling role and the mechanisms of softening effects of laser heating on cutting process were revealed. The methods of controlling cutting zone temperatures was obtained through the investigation on process of heat conduction in laser and cutting, and the genetic algorithm-based control method was used to maintain the stability of the cutting zone temperatures.Based on the analysis of tool wear mechanism in different tool materials, tool wear prediction model was established to optimize the tool geometry using finite element method. Finally, optimal process parameters were obtained by neural network and multi-objective optimization method in order to improve production efficiency and reduce processing costs.

高温合金的特点导致其切削性能较差，加工效率低、加工成本高。目前的工艺方法在加工高温合金材料，尤其在铣削高温合金时，加工效率与加工成本往往无法达到理想的结果。本项目在高速铣削高温合金技术的基础上，与可以降低切削力、减小刀具磨损、提高加工效率的激光加热辅助切削技术相结合：通过试验与理论仿真研究加工过程中的力-热耦合作用，揭示激光加热与切削热对材料的软化效应；通过对激光与切削的热传导过程研究，掌握切削区域温度的控制方法，利用基于遗传算法的控制方法保持切削区域温度稳定；在分析不同材料的刀具磨损机理基础上，采用有限元数值模拟结合试验结果，建立刀具磨损预测模型，对刀具几何参数进行优化；最终通过神经网络及多目标优化的方法得到最优的工艺参数，达到提高生产效率、降低加工成本的目的。

本项目通过建立激光加热温度场及激光加热辅助切削过程模型，分析了激光加热温度与切削过程温度相互的耦合影响。激光加热辅助铣削可以在较低切削速度时达到材料高速切削的状态，通过调整切削区域的温度，降低切削速度提高对刀具冲击的影响，提升了材料的可加工性能。通过温度场模型研究了工艺参数对切削区域温度的影响规律。为解决激光加热过程中温度不稳定的问题，将温度在线监测与功率控制结合建立了切削区域温度自控制系统。采用BP神经网络方法建立了切削区域温度与监测温度的映射模型，通过控制能量使监测温度及加工区域温度稳定，进而达到控制加工质量的目的。. 采用激光加热辅助铣削技术对铸造高温合金K24、变形高温合金GH4698与Inconel 718三种高温合金材料进行了加工实验研究。控制激光加热参数能够保证已加工表面组织性能不变情况下相比常规加工同样参数加工降低切削力30%，减小表面粗糙度66%并且能够提高刀具寿命20%。采用激光加热辅助后表面粗糙度明显降低，表面质量更为光滑。EDS分析表明激光加热辅助铣削与常规加工相比元素含量不变，加工后变质层的厚度稍有增加。采用遗传算法，以加工实验中得到的切削力、表面粗糙度及刀具寿命经验公式作为边界条件，以高加工效率与低加工成本为目标，建立了激光加热辅助铣削工艺多目标优化模型，最终得到最优的加工工艺参数。. 采用PVD、CVD涂层硬质合金、陶瓷及PCBN刀具进行了加工实验，揭示了不同刀具的磨损机理，得到了硬质合金刀具寿命的经验公式。CVD涂层由于耐高温性能好，激光加热辅助下刀具寿命比PVD涂层刀具寿命高。陶瓷及PCBN刀具采用激光加热辅助的方法能够降低刀具磨损，提升刀具寿命，但由于其抗冲击性能较差，刀具寿命小于硬质合金涂层刀具。. 采用激光加热辅助铣削技术进行了薄壁高温合金零件加工，通过温度场分析对激光参数进行了优化，控制了激光热应力诱导的变形。激光加热降低了切削力，减小了工件引起的变形，并且得到良好的表面粗糙度。另外为了解决激光加热辅助过程中激光光斑与铣刀相对位置固定，仅能加工直线轨迹的不足，改进了加工系统，增加了特殊的旋转轴，使激光加热点保持在加工轨迹前端，能够连续加工。以上两项研究探索了激光加热辅助铣削的应用技术，为其技术的推广应用提供理论基础与探索验证。