There is blackening phenomenon in the pickling process of hot rolled steel strip, and the blackening attachment is the oxide pressed too deep into hot rolled raw material. The main causes of pickling blackness are pickling solution concentration, temperature, PH value of rinsing water and low temperature of hot air dryer. For this reason, the corresponding control measures should be taken in the pickling section are:

1. Improve the concentration and temperature of pickling solution

Increasing the temperature or concentration of hydrochloric acid can improve the pickling effect, but in hydrochloric acid solution, the effect of increasing the concentration is better than the effect of increasing the temperature. When the acid concentration increases from 2% to 2.5%, the pickling speed of hydrochloric acid increases by 10 times. Therefore, the concentration of hydrochloric acid in pickling tank should be increased.

By regularly dredging the graphite heater heating pickling solution, replacing the graphite heater failing to meet the heating requirements, controlling the temperature of each acid tank according to the requirements of the process rules, improving the surface quality of pickling.

2. Improve the PH value of rinsing water

Before each production inspection on pickling drying roller and cylinder, the existence of crack, degumming, wear serious drain roller replacement, immediately resume the function of squeeze roller cylinder, and according to the different positions and different material drain roll roll changing cycle, before change ahead of time, to improve the drying effect of squeeze roller, to reduce the amount of acid tank acid into the rinse tank, Increase the PH of the rinsing water.

3. Improve the hot air drying temperature and blowing effect

Heating steam pressure through the newspaper acuity 0.4 MPa, hot air dryer blowing temperature up to 120 ℃ above, and before the hot air drying device, equipped with a pair of blowing compressed air blowing device, will accumulate in the residual liquid on both sides of the steel strip to the outer side of the strip brushes, make steel strip edge is easy to dry, eliminates the pickling steel strip edge with the problem of water.