Study On Real-time Measurement And Control Of The Hardened Band Width In Laser Surface Quenching

Laser surface quenching, an advanced surface treatment technology, has beenstudied and applicated widely because of its unique features. A lot of researches onhardening mechanism, process applications and temperature field simulation of lasersurface quenching have got relatively mature theories and production applications.Laser surface quenching is a complex process affected by multi-factors, there aresome questions about the hardening quality need to be solved.In this thesis, the measurement and control in the laser surface quenching processwas achieved through the semiconductor laser processing system, the CCD-linedetection system and the displacement real-time control system. The semiconductorlaser processing system was used to output laser to complied transformationhardening of the workpiece surface. The CCD-line detection system utilized CCDcamera to obtain heat radiation images, applied colorimetric measurement principle toobtain relative temperature values, displayed temperature field distribution throughdigital image processing, and then determined the hardening quality. Based on initialsetting parameters and temperature field distribution, the displacement real-timecontrol system applied the single neuron PID control method to adjust the laserscanning speed and improve the hardening quality. The design of measurement andcontrol system re-developed could display the distribution of temperature field andthe width of phase region at the same time，reduce the impact of part shapes, surfaceconditions and other uncertain factors, control the stability of the phase transitionregion width in laser surface quenching.A large amount of experimental study was carried out with the detection andcontrol system in the laser surface quenching. Compared with the lateral detection,the coaxial detection, which was less affected by the environment factors, wasselected as a method of the CCD detector. The effect of neutral filter was analyzed,then the appropriate neutral filter was selected in the different processing parameters.The hardened band width was changed according to the single neuron PID controlmethod which changes the scanning speed during the laser transformation hardeningtreatment. The measurement and control of the workpiece surface status, processparameters and continuous scanning situation were analyzed. It was found that themeasurement and control system improve the quality of the hardened layer. At last, the measurement and control of laser transformation hardening plays an importantrole in laser surface quenching process.