Carbon raiser means a substance containing carbon added in the smelting of steel and iron for making up the carbon content lost. In molten iron, factors such as the smelting time, holding time, and longer overheating time lead to the carbon content decreases. As a result, the carbon content will not reach the theoretical value expected for refining. That is why a carbon raiser is added, and why it is also called a carbon additive. The high-quality carbon raiser is an indispensable auxiliary additive to produce high-quality steel and iron foundries. ZHENXIN also supplies silicon nitride，ferrochrome nitride, silicon briquette, etc., ferroalloys for steelmaking and other applications.
Specification of carbon raiser
|Model Item||C (min)(%)||S (max)(%)||Ash (max)(%)||Volatile Matter (max)(%)||Moisture (max)(%)|
Size: 1-3mm 3-5mm 5-8mm Packing:25kg bag or one-ton jumbo bag packing as customer requirement.
Application of carbon raiser
Mainly used in steelmaking in an electric furnace, it can increase the carbon content in steelmaking and ductile iron foundries, greatly increase the amount of scrap steel, reduce the amount of pig iron or eliminate the need for pig iron. It replaces traditional recarburizers and effectively reduces steelmaking costs. It is also used in metallurgy, glass production, casting, smelting of graphite crucible, aluminum, titanium, and other industries.
In the feeding method of electric furnace smelting, the carbon raiser should be put in with the scrap steel and other charges, and small doses can be added to the surface of the molten iron. However, it is necessary to avoid large batches of materials in the molten iron to prevent excessive oxidation and the occurrence of insignificant recarburization effects and insufficient carbon content of the castings. The amount of carbon raiser added is determined according to the ratio of other raw materials and the carbon content. For different types of cast iron, choose different types of recarburizers according to your needs. The carbon raiser selects pure carbon-containing graphitized substances to reduce excessive impurities in the pig iron, and the appropriate selection of the carbon raiser can reduce the production cost of castings.
Types of carbon additive
Carbon additive includes calcined petroleum coke, graphite petroleum coke, calcined anthracite coal, electrical calcined anthracite, and natural graphite. We mainly introduce the most commonly used carbon additives.
CAC: Calcined anthracite coal
The raw material of the anthracite recarburizer is anthracite, which went through dry distillation at 1300°C to reduce volatile matter and increase the solid carbon content.
CPC: Calcined petroleum coke
Calcined petroleum coke is the most suitable carbon raiser for steel making. The raw material is raw coke, which contains high impurities and cannot be used as a carbon additive. The carbon additive is obtained after high-temperature calcination of petroleum coke. After the petroleum coke is calcined at a high temperature of 1200-1400℃, most of the moisture and volatiles, and other impurities are removed. The carbon content is as high as 98.5%. The carbon additive is irregularly shaped carbon particles with metallic luster and more transparent carbon particle pores. The high quality of calcined petroleum coke is mainly dependent on the low content of sulfur which finally affects the quality of steel.
GPC: Graphite petroleum Coke
The raw material of graphite carbon additive is also green coke, but the calcination temperature ratio is 3000. The degree of carbon fixation is high, and the content of S, N, and P is much lower than that of coal. Graphite carbon additive is mainly used for ductile iron with the characteristic of quick absorption, high carbon, and low sulfur.
Advantages of carbon additive
The impact of carbon additives on precision casting products mainly has three aspects.
- To obtain high-strength gray cast iron castings under the condition of high carbon content, the smelting process adopts the process of adding all scrap steel with carbon additive, which makes the molten iron purer and produces high-performance casting materials.
- Iron Liquid recarburization technology, especially in electric furnace smelting, can increase graphite nuclei and reduce the oxidation of liquid iron at the same time.
- Adding carbon is the best measure to prevent or reduce shrinkage tendency. Due to the effect of graphitization expansion during the solidification of molten iron, good graphitization will reduce the shrinkage tendency of molten iron.
The function of carbon additive
As one of the main sources of graphite elements in molten iron, carbon additive is not only to supplement the right amount of carbon. Other effects are often overlooked. Adding a recarburizer is not simply “increasing C”, but an important measure to increase the graphitization ability of its cast-iron products to achieve better matrix structure and mechanical properties. Not all recarburizers can achieve this effect. The production of qualified recarburizers must undergo a strict selection of materials, and then undergo high-temperature graphitization. The process not only reduces impurities such as sulfur, gases (nitrogen, hydrogen, oxygen), ash, volatiles, and moisture but also improves their purity and graphitization. Carbon atoms can change from the original disordered arrangement to an orderly arrangement, and most of the carbon atoms can become a good driving force for graphitization. The carbon atoms can be quickly melted in the molten iron, and are adsorbed on the nucleation core, and grows into graphite under the action of a strong driving force when the molten iron is solidified. If the selected recarburizer has not undergone high-temperature graphitization treatment, the graphitization driving ability of carbon atoms will be greatly reduced, and the graphitization ability will be weakened. Even if the same carbon content can be achieved, the quality of the product is completely different. Therefore, petroleum coke products that have undergone high-temperature graphitization treatment and graphite electrode fragments manufactured at high temperatures are currently suitable carbon additives for the production of high-quality cast iron products. It not only meets the requirements of carbon increasing but also provides a good source of power for the production of cast iron products.