During the hot rolling process of the square rectangular tube, if it encounters the problem of scale, it will affect the surface quality, and it will also affect the subsequent cold rolling process. In order to solve this problem, we can take the following four measures:

(1) Lubricated rolling

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

(2) Fully remove phosphorus

  Adjust the height and assembly angle of the rectangular tube dephosphorization nozzle to maintain the best 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 water quality, regularly clean up debris and add new water.

(3) Rolling temperature

  When the temperature is high, the high-temperature slab will quickly generate a secondary oxide scale, and the oxide scale is in a molten state at high temperature and is difficult to remove. Especially the head and tail of the slab are more prone to oxidation due to the higher temperature of the radiant heat from the furnace wall. Therefore, in order to ensure effective dephosphorization of the square tube, on the one hand, the temperature of the finish rolling start at the head of the intermediate billet should be controlled as much as possible, and on the other hand, the parameters of the delay head and 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 meters. It can also reduce the online time of the intermediate billet and prevent the thickening of the oxide layer from causing difficulties. 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.

(4) Heating method

According to environmental changes and actual production conditions, the heating method has been adjusted, and it is best to divide summer heating and winter heating. 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.