基于扫描振镜的激光淬火温度特性模拟与实验研究

Simulation and Experiment of Laser Quenching Temperature Characteristics Based on Galvanometer Scanning

目的与传统激光淬火(CLQ)进行对比研究,获得使用飞行光路的振镜扫描式激光淬火(GLQ)的温度变化特性和规律。方法使用两种淬火方式对45钢进行表面处理,将组织形貌和硬度分布进行比较,并结合数值模拟,研究两种激光淬火方式的温度变化特性和规律。结果在相同的总能量输入、扫描区域和扫描时间下,两种淬火方式硬化层横截面形貌呈现巨大差异:CLQ试样硬化层深度为753.66μm,宽度为3787.21μm,横截面形貌为"月牙形";GLQ试样硬化层深度为256.61μm,宽度为5808.77μm,形貌为"均匀性更好的近似月牙形"。截面硬度分布相似:均为中间主体区域高(GLQ试样硬度810~900HV,CLQ试样硬度790~830HV),两侧边缘区域低(均约为760HV)。模拟结果表明,CLQ试样特征点激光辐照时长共1.25 s,温度从508℃变为1063℃,奥氏体相变时间为1.17 s;GLQ试样特征点激光辐照时长共0.628 s,温度从500℃变成718℃,其波峰温度奥氏体相变时间为0.38 s,波谷温度均保持在马氏体转变温度以上。沿激光扫描方向,GLQ的温度变化率比CLQ大1个数量级;垂直激光扫描方向,GLQ温度变化率比CLQ大2个数量级。结论GLQ具有温度变化率更大、升降温多次循环、热处理相变时间更短、热积累更小等特点,有望在薄层大面积淬火上获得应用。

The work aims to study characteristics and mechanism of temperature variation in the process of the galvanometerbased laser quenching(GLQ)with laser on fly by comparing the conventional laser quenching(CLQ).The surface of 45 steel was treated by two quenching methods and the morphology and hardness distribution were compared.Combined with numerical simulation,the characteristics and mechanism of temperature variation by two quenching methods were studied.There was large difference in the cross-sectional morphology of the hardened layers by two quenching methods under the same total energy input,scanning area and scanning time.The thickness and width of the hardened layer of CLQ sample were 753.66μm and 3787.21μm respectively.The thickness and width of the hardened layer of the GLQ one were 256.61μm and 5808.77μm respectively.Meanwhile,the hardened area of GLQ sample presented"approximating crescent shape with better uniformity"looks,while the other one presented"crescent"looks.From the cross-section hardness,the hardness distribution of the two samples was similar,which was high in the middle body zone(hardness of sample treated by GLQ was 810~900 HV and that of CLQ sample was 790~830 HV)and low in the edge zones(about 760 HV).From the simulated results,it took 1.25 s for the temperature of CLQ sample to change from 508℃to 1063℃at the feature point during the laser irradiation process and the austenite transformation was 1.17 s,while it took 0.628 s for the temperature of the other to change from 500℃to 718℃at the same feature point and the time of peaks temperature above the austenite transformation was 0.38 s and the troughs temperature was kept above the martensite transformation temperature.Along the laser scanning direction,the temperature change rate of GLQ was one order of magnitude higher than that of CLQ,perpendicular to the laser scanning direction.The temperature change rate of GLQ was two orders of magnitude higher than that of CLQ.GLQ has the characteristics of greater temperature change rate,multiple cycles of heating and cooling process,shorter heat treatment time for phase transitions,as well as less heat accumulation.Therefore,it is expected to be used in thin-layer and large-area quenching.