Why do bubbles appear on the surface of steel plate?

1. The temperature of extrusion barrel and ingot is too high;
2. The temperature and dimension of ingot exceed the allowable negative deviation;
3. If the ingot is too long, the filling is too fast, and the ingot temperature is uneven, it will cause non drum filling, so the exhaust in the cylinder is incomplete, or the operation is improper, and the exhaust process is not carried out;

4. The design of steel plate die hole is unreasonable, or the cutting debris is improper, the debris in the shunt hole and the diversion hole is partially taken out, and the gas in the space-time gap is squeezed into the surface. After hot rolling or forging, the steel plate is no longer subject to special heat treatment, and it is delivered directly after cooling, which is called hot rolling or hot forging state. The end temperature of hot rolling is generally 800 ~ 900 ℃, and then it is naturally cooled in air, so the hot rolling state is equivalent to normalizing treatment. The difference is that the end temperature of hot rolling is high or low, which is not strictly controlled by normalizing heating temperature, so the fluctuation of steel structure and properties is larger than that of normalizing. At present, many iron and steel enterprises adopt controlled rolling. Due to the strict control of finishing rolling temperature and forced cooling measures after finishing rolling, the grain of steel is refined and the delivered steel has high comprehensive mechanical properties.

5. Generally, after the steel plate surface is cleaned, it is unnecessary to apply oil, but for high-quality steel, alloy steel sheet, thin-walled pipe, alloy steel pipe, etc., after rust removal, the internal and external surfaces shall be coated with anti rust oil before storage;

6. In the warehouse, it is not allowed to stack together with corrosive materials such as acid, alkali, salt and cement. Different kinds of steel should be stacked separately to prevent confusion and contact corrosion;

7. For the steel plate with serious corrosion, it is not suitable for long-term storage after derusting, and it should be used as soon as possible.