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How to control cooling water of hot rolled section steel
In the process of hot rolling, the heat and heat conduction of high temperature billet make the temperature of roll rise. In the opening area of hot rolled section steel, because of the large volume and high temperature of the forged billet, the surface temperature of the roll increases. When the temperature of the roll is high, the surface hardness will affect the roll wear resistance. When the surface of the roll is heated, the volume expansion will occur, but the temperature difference between the inside and outside of the roll will be formed due to the lower overall temperature of the roll, resulting in greater thermal stress. After the rolling material leaves the roll, the heat conduction stops, and the roll surface temperature drops accordingly. This state changes periodically, which is easy to generate hot cracks. Therefore, it is necessary to cool the roll scientifically to keep the roll surface temperature in a reasonable range. Yongxinsheng suggests the following measures to control roll cooling: the heat transfer efficiency of cooling water can be controlled by mixing 3% oil into cooling water. The water pressure of cooling water should be as low as possible under the premise of water flow density. The steady flow of cooling water to the roll surface can increase the contact time between the two, thus increasing the heat taken away by cooling water from the roll. If the cooling water splashes on the roller, the contact time of the two is shortened and the cooling is large. High water flow density in spray cooling area can obtain high heat dissipation rate. When the spray cooling area is arc-shaped, cool the parallel line. When the angle between the spray line of the nozzle and the axis of the roller is 30 °, good cooling can be produced. The diameter of the spray hole of the nozzle shall not be less than 3mm. It is better to use flat nozzle. In order to split the cooling water, the surface finish of the spray hole shall be maintained. It is better to keep the distance between roller surface and nozzle within 50-100mm. The temperature of cooling water should be as low as possible, and its degree should be as high as possible. Impurities in water affect the quality of products and rolls. In order to remove the burr on the surface of the roll pass caused by the wear of the scale, on the one hand, the pressure of the descaling machine can be used to remove the scale on the surface of the blank to a large extent; on the other hand, the high-pressure air pipe can be added in front of the rolling mill to blow the scale at the waist of the forging blank.