Research On Silicon Steel Pickling Line Automatic Cleaning Process Of Silicon Mud

Wtih the soaring price increasing of raw material and the intense market competition, the traditional developmental strategy of iron and steel industry in the world had faced the new challenge day by day. As a kind of soft magnetic material, the silcon steel was a important alloy for the electron power system, electronic and military industry.The manufacture technique and the product quality of the silicon steel plates was an important sign of special steel production and science technoly level of a country. Steel-pickling guaranteed the quality of the steel and iron products.It was considered as the objective of steel-pickling to remove the residual oxide scale of the steel. The existence of the oxide scale would be harmful to the follow-up process, therefore steel-pickling was a effective method to remove the residual oxide scale completely.According to the problems of the pickling line of the silcon steel, it was analyzed and summarized for the forming mechanism of the iron scale and the principle of pickling in this paper, a thorough study was done with the oxides of the silicon steel and the chemical constituents and forming mechanism of the silicon sludge in the way of chemical analysis and x-ray diffraction. It was determined that the main components of the silicon sludge is amorphous silica, and the forming mechanism of the silicon sludge was also determined. It was found that the forming mechanism is related to the concentration of pickling agent and the silicide nearby the equipment surface.The research and analysis which was based on the repeated experiments showed that the hydrofluoric acid was the best material to clean the amorphous silica(SiO₂), and concentrated sodium hydroxide solutions took the second place. The hydrofluoric acid would make the surface of the silicon sludge into the form of porous loose structure.That would decrease the binding force of the matrix and the silicon sludge. Compared to the sodium hydroxide solutions,the hydrofluoric acid was more suitable for the cleaning in the flowing state. With the increasing of the temperature, the cleaning effect would be significantly increased. When the concentration of hydrofluoric acid was 2wt%, the flow was larger than 1.13m/s,while the temperature was 90℃, the best cleaning effect happened. The optimum cleaning time was 4⁶ hours.The research and analysis of the test results of different acids, solutions of alkali and complexing agent showed that when the velocity of the flowing hydrofluoric acid was1.13 m/s, the rate of cleaning out met the requirements. With the existence of complexing agent,the improvement for the cleaning effect was not obvious.Based on the large amount investigations with the equipments of acid circulation system, a series of modification and optimization of the equipments of steel-pickling were done, the difficulty of demolition and assemblage of the carbon heater can be avoid. The unplanned downtime and breakdown of the pickling line of the silcon steel caused by the silicon sludge was eliminated and a great economic benefits had been made.