Research On On-line Determination Of Microstructures In Ultra-Low Carbon Steel Sheets

Online microstructure detection technique is a prerequisite for achieving steel sheet microstructure and mechanical properties online closed-loop control,it is an urgently needed technology for modern steel sheet manufacturer to ensure the production line reliability and stability. In this paper, we focus on determination of grain size and texture in ultra-low carbon steel sheets, the average grain size and texture of hot-rolled steel sheets were detected by the non-contact, remote sensing, applied to some of the high temperature and other harsh environments laser ultrasonic technique; the texture of cold-rolled steel sheets were detected by the short detection time, high precision, high requirements on the sample surface two-dimensional X-ray area detector. The schemes of online testing industrial applications were proposed aiming to precision of product quality and quality control in real time.The main works and results are as follows:(1) Improved the calculation method for average grain size prediction by laser ultrasonic attenuation. The energy attenuation method was proposed through the laser ultrasonic echo signal analysis and processing. when there is a large the average grain size difference between the detection sample and standard sample, the calculated error decreased from43.2%to17.8%using the improved calculation method. This method can effectively improve the accuracy of the average grain size prediction. The application scheme of online average grain size measurement in hot-rolled steel sheets industrial line was also proposed.(2) Gives a formula to calculate the fourth-order texture coefficients which can description of the mechanical properties of deep drawing materials.The angular dependence of the surface acoustic wave velocities and variations on the surface of the main texture components in ultra-low carbon steel was analyzed. The texture caused angular dependence of the surface acoustic wave velocities and variations of ultra-low carbon interstitial free steel were measured by laser ultrasonic technique. The fourth-order texture coefficient accurately calculated by the given relationship between the angular dependence of the surface acoustic wave velocity variations and the fourth-order texture coefficient. where, the C411calculation error is less than7%, and the calculation errors of C412and C413are less than20%. This model could be used in online texture measurement in hot-rolled steel sheets industrial line.(3) According to the principle of two-dimensional X-ray diffraction geometry and rapid texture detection theory, the online texture measurement setup using two-dimensional X-ray area detector technology was built in the laboratory and the texture of the moving steel sheets were detected. When the strip speed up to0.65m/s, the Strong texture information can still be recorded, the speed of the moving steel sheets has little impact on the strong texture data accuracy collected by two-dimensional X-ray area detector. Lay the foundation for online texture determination by two-dimensional X-ray area detector technology.