The function and application of casting powder
Since the beginning of the 60s 20th century, the first time using submerged nozzle and casting powder, casting powder technology has been highly developed. Different casting powder adapted to different slab section, steel and casting process was developed. The surface quality of the billet is greatly improved and the surface of the slab is gradually improved. The basic functions of mold powder are: to protect the mold meniscus molten steel from the secondary oxidation of air; has good spread performance and thermal insulation properties, to prevent the molten steel surface solidification or crust; can absorb the float to Meniscus non-metallic inclusions; control slag to the mold heat transfer speed and uniformity to reduce thermal stress; has a good function of lubricating slab, so that it can be successfully pulled out from the mold.
Viscosity is one of the most important properties of the casting powder, which is closely related to the continuous casting process parameters. It is generally agreed that the viscosity of the casting powder is inversely proportional to the speed of the casting, which keeps the slag between the mold wall and the slab A certain thickness. If the viscosity is too large, due to poor mobility, slag film is thin or not continuous, is not conducive to the diffusion and dissolution of inclusions; viscosity is too small will make the slag film is too thick and uneven, affecting the heat transfer to the mold. The viscosity of the mold powder can vary from 0.1 to 1.0 Pa ??? s.
The melting speed of the casting powder is the important index to determine the thickness of the slag layer, slag film thickness and slag consumption. The most important factor affecting the melting rate is the type and content of the carbonaceous material. With the increase of the content, the melting rate will be reduced The The appropriate melting rate should be able to make the mold within the molten steel surface to maintain 6 ~ 15mm thick slag layer, and can form a suitable thickness of the slag film. But there is no uniform standard for determining the melting rate.