熔池温度是选区激光熔化金属成型过程的一个重要参数。为了实现熔池温度的闭环控制,基于比色测温与光电检测技术完成了熔池温度的在线检测。提出了一种复合结构的放大电路,它可成功检测到幅度小、变化快的熔池辐射信号。搭建嵌入式系统将熔池辐射数据上传至金属成型设备的工控机中,运用比色测温法解决了辐射光强检测受激光入射角等因素影响的问题,并求解得到了熔池温度。以90%Cu-10%Sn合金粉末作为成型材料进行实验,利用窄带滤光片测得在540~660 nm光谱范围内熔池辐射最强的波段位于580~590 nm;在40~200 W激光功率下,测算得到的熔池温度为700~1700 ℃。选区激光熔化金属成型熔池温度的在线检测,可为金属成型设备的控制系统提供熔池温度反馈,可作为升级该设备的一种参考。

The temperature of the molten pool is one of the most important parameters in the process of metal forming based on selective laser melting. To ensure the closed-loop control of molten pool temperature, this study implementes an online detection of molten pool temperature based on the colorimetric temperature measurement method and photoelectricity technology. It proposed a type of composite operational amplifier that successfully detected the molten pool radiation signal with small amplitude and fast change. An embedded system was built to upload the radiation data of the molten pool to the industrial computer of metal forming equipment. A method of colorimetric temperature measurement was employed to eliminate the effects of the laser incident angle and other agents on the detection of radiation intensity, and furthermore, to obtain the temperature of the molten pool. During the process of melting 90%Cu-10%Sn alloy powder, it is found that the band with the strongest radiation in the molten pool of the material is 580--590 nm within the spectral range of 540--660 nm. Under the laser power range of 40--200 W, the estimated molten pool temperature range is 700--1700 ℃. The online detection of molten pool temperature during metal forming based on selective laser melting provides feedback information of molten pool temperature for the control system of metal forming equipment. Furthermore, the proposed approach of online detection also can be considered as a reference to upgrade the equipment.