分区预热对金属激光沉积成形温度场的影响

摘要

To reduce work-piece deformation and prevent cracking,a new idea of substrate partition preheating is pro-posed.Substrate forming area and near forming area were respectively preheated through partition preheating device, and the stress of work-piece was actively controlled and reduced base on thermal stretching effect.A numerical simu-lation model of 3D temperature field for single-pass and multi-layer laser deposition shaping process was established through the birth-and-death elements of ANSYS.Change rules of forming process temperature field and temperature gradient were studied,when substrate forming area and near forming area were respectively applied different preheating temperature and formed different preheating temperature difference between two areas (preheating temperature differ-ence are 100 ℃,200 ℃,300 ℃).Compared with the substrate whole preheating mode,the process temperature gra-dient is more stable under substrate partition preheating mode,and it is helpful to reduce the thermal stress.Analysis results will provide guidance for the design of partition preheating device and optimal selection of the preheating tem-perature.%为减小工件变形和防止工件开裂，提出了采用分区预热装置对基板成形区和近成形区进行分区预热，利用温差拉伸效应主动控制降低应力的新思路。利用ANSYS有限元中的“单元生死”技术，建立单道多层激光沉积成形过程三维温度场的数值模拟模型，深入研究了在基板成形区和近成形区施加不同预热温度以及两区形成不同预热温差（预热温差分别为100℃、200℃、300℃）状态下对成形过程温度场和温度梯度的影响规律，并指出相对于基板整体预热方式，基板分区预热方式下的成形过程温度梯度更趋于稳定，有利于降低热应力；上述分析结果可为分区预热装置设计、预热温度的选择优化提供指导依据。