Why do bubbles appear on the surface of weathering board?

1. The temperature of the extrusion cylinder and the extruded ingot is too high.

2. The temperature and size of the steel ingot exceed the allowable negative deviation range.

3. The ingot is too long, the filling is too fast, and the temperature of the ingot is uneven, resulting in non-drum filling, incomplete exhaust of the cylinder, or improper operation and poor exhaust.

4. The die hole design of the weathering board is improper, or the amount of residual data is too much during cutting, and the residual data in the shunt hole and the shunt hole are partially removed. During the extrusion process, the gas in the air gap flows into the surface. After the weathering board is hot rolled or forged, it does not undergo special heat treatment, but is directly shipped after cooling. This state is called hot rolling or hot forging.

Under normal circumstances, the end temperature of hot rolling is 800~900℃, and then it is naturally cooled in the air, so the hot rolling state is normalized. The difference is that the final temperature of hot rolling is higher or lower than the normalizing temperature. Unlike normalizing, the heating temperature is not strictly controlled, so the structure and properties of steel fluctuate more than during normalizing. At present, many steel companies adopt the controlled rolling process. In the finishing rolling process, strict temperature control and forced cooling measures are adopted to refine the grains, thereby improving the comprehensive mechanical properties of the steel.

5. Generally speaking, the surface of weather-resistant steel plate does not need to be oiled after cleaning. However, the internal and external surface quality of Q345NH high-quality steel, alloy sheet, thin-walled pipe, and alloy steel pipe is better. Anti-rust agent should be applied first after storage.