1) Composition and thickness distribution of scale on strip steel surface.
The composition and thickness distribution of scale on the surface of strip steel affect the temperature of each part during coiling along hot-rolled strip steel, resulting in different cooling rates of strip steel, that is, different temperatures and cooling rates at the head, middle and tail along the length direction of strip steel and at the edge and middle along the width direction, resulting in different scales structure and thickness at each part of the same strip steel, resulting in insufficient local pickling during cold rolling.
2) Stretching and straightening machine technology
The cold rolling tension leveler is not working properly or the elongation coefficient of the tension leveler is not enough, so that the iron sheet is not completely broken and peeled off, which affects the pickling effect.
3) Shape quality of strip steel plate
The shape difference of strip steel plate, such as sickle bend, wave shape, etc. In particular, the wave shape of hot rolled incoming materials is more common, which is easy to cause local pickling.
4) pickling process
Improper pickling process, such as too low pickling concentration and temperature, too fast pickling speed, insufficient pickling time, too high ferrous concentration, failure to replenish acid in time, too high tension of strip steel in pickling tank, low sag of strip steel during pickling, etc.