The raw material for cold rolling is a hot rolled steel coil with a thickness of several millimeters obtained by hot rolling.
The heating temperature of ordinary steel before hot rolling is about 1200 °C, and the final rolling temperature (the temperature when leaving the last rolling mill) is 800-850 °C; but the heating temperature of oriented silicon steel before hot rolling should be increased to about 1400 °C, and the temperature of entering the rolling mill It is about 1200°C, the finishing temperature is controlled above 950°C, and then it is quickly cooled by water spray to below 550°C and coiled into coils.
The purpose of high temperature heating is to completely dissolve the MnS and AlN second phase particles in the billet, and to precipitate uniform and fine MnS particles during the hot rolling process, followed by rapid cooling to inhibit the precipitation of AlN. The difference and main difficulty in the production process of grain-oriented silicon steel and general steel is the control of MnS and AlN.
After the hot-rolled silicon steel coil as a semi-finished product is sent to the silicon steel plant, it is re-unrolled and welded into a continuous steel strip. The first step is normalization treatment, that is, heating to about 1100~900 ° C, so that precipitation during the coiling process after hot rolling The AlN is completely dissolved; then it is cooled to 550°C in a few seconds (the picture above shows the test of the aerosol cooling technology developed by MCC Southern Thermal Engineering Company, which relies on compressed air to atomize the cooling water into tiny droplets to realize silicon steel. high-speed and uniform cooling), and re-precipitate fine, uniform and stable AlN particles.
