The appearance of scale in the hot rolling process of the square rectangular tube will affect its surface quality, and it will also have a great impact on the subsequent cold rolling process. In order to solve this problem, we can proceed from the following four aspects:

(1) Controlling the rolling temperature

  When the temperature is high, the high-temperature slab after dephosphorization will quickly generate a secondary oxide scale, and the oxide scale is in a molten state at high temperatures and is difficult to remove. The head and tail of the slab are especially prone to oxidation due to the higher temperature of the radiant heat from the furnace wall. Therefore, in order to ensure the effective dephosphorization of the square tube, on the one hand, the temperature of the finish rolling and starting rolling at the head of the intermediate billet should be controlled as much as possible, and on the other hand, the parameters of the descaling delay head and descaling delay tail should be reasonably controlled in operation. At the same time, control the tapping speed, prevent over-planned rolling, and reasonably control the number of rolling kilometers. It can also reduce the online time of the intermediate billet and prevent the thickening of the oxide layer from causing difficulties in descaling. At the same time, it can avoid the oxidation film peeling off of the work roll due to overload work, and the plowing phenomenon, which will cause the oxidation problem during the finishing rolling.

(2) Lubricated rolling

The rolls are lubricated during finishing rolling to improve the lubrication effect of the roll surface, which can effectively prevent the formation of scale and roll sticking, prevent damage to the roll surface, and improve the utilization rate of the roll and the surface quality of the square tube.

(3) Adjust the heating system

According to environmental changes and actual production conditions, the heating system has been adjusted, divided into a summer heating system and a winter heating temperature. In terms of square rectangular tube slabs, the temperature of the soaking section is considered according to the width of the slab, and some clear regulations can be made on the heating time according to the actual situation.

(4) Ensure normal descaling

Adjust the height and assembly angle of the rectangular tube descaling nozzle to maintain the best descaling effect. Check the condition of the nozzle to prevent excessive wear, clogging, and falling off. Check the nozzle seat for leakage and reduce the pipeline pressure, check the filter regularly, and replace it in time if any abnormality is found. Strengthen the maintenance of phosphorus removal water quality, regularly clean up debris, and replenish new water.