In the process of steelmaking, molten steel needs to be poured into molten steel tanks lined with refractory materials and then cast into ingots. Since the molten steel needs to stay in the tank for a period of time, part of the heat will be lost, so that condensation will easily occur on the surface of the molten steel, and residual steel may also form at the bottom of the tank. Therefore, a layer of carbon black can be covered on the surface of the molten steel. Due to the carbon content of carbon black High, slow combustion but high calorific value, less ash impurities, and low apparent density, so it will burn quickly and evenly on the surface of molten steel immediately after being added to the molten steel tank, which plays a good role in heat preservation, thereby eliminating condensation on the wide surface And the problem of residual steel at the bottom of the tank.
In the process of continuous casting, steel-making flux is added to isolate air, protect cooling devices and remove impurities in pig iron. The flux contains inorganic particles such as calcium silicate, carbon black, etc., and the amount of carbon black added is about 1% to 5%, which can play the effect of adjusting the melting speed.
In the casting process, carbon black can be used as a release agent, such as coating the carbon black dispersion on the surface of the model, which can make the casting smooth and easy to take out. When iron and copper are cast, the water dispersion mixed with carbon black and coke powder (100-300 mesh) is used to coat the iron or copper water channel to speed up the flow of molten iron or copper. In order to prevent the temperature of the outer layer of molten iron or copper from decreasing, carbon black and mica powder can be mixed and sprinkled, which has the effect of preventing oxidation and heat preservation.
During the casting process, the casting pattern is prone to cracking due to the intrusion of molten metal. To enhance chipping resistance, inorganic substances can be added to the molding sand. Carbonaceous materials such as asphalt powder, graphite powder, coal powder, etc. are often used as additives. The addition of furnace carbon black has the following advantages over the above materials: a small amount of addition can increase the strength of the mold, and it is easy to handle; the sand shakeout of the sand mold is reduced; no sulfur dioxide occurs. Toxic and odorous gases; can reduce the amount of water glass.
To sum up, in the process of steelmaking and casting, carbon black mainly has the following functions: make the surface of hot metal into reducing gas mist to prevent oxidation, act as heat insulation to reduce the cooling rate of metal, and reduce the speed of metal intrusion or penetration into the mold . Therefore, the performance requirements for carbon black are mainly: low sulfur content, good wettability and dispersibility. Generally, special carbon black for metallurgy can be used.