Raw materials for electric furnace steelmaking

Steel materials

Electric furnace steel smelting has hot charging and cold charging. Hot charging mainly uses molten iron or molten steel for mixing. At present, electric furnace steel smelting directly uses hot charging very little. Cold charging mainly uses scrap steel, pig iron, scrap iron, soft steel, sponge iron and intermediate alloy materials and other metal materials.

Slag-making materials, oxidants, carbon-adding agents and carburizers

• Slag-making materials: In the process of electric furnace steelmaking, alkaline slag-making materials mainly include limestone, lime, fluorite and fire bricks. In special cases, a small amount of acidic slag-making materials such as silica or quartz sand are sometimes used. Alkaline electric furnace steelmaking has very strict requirements on the quality of slag-making materials. The use of high-quality slag-making materials will reduce gas and inclusions in steel, improve dephosphorization and desulfurization capabilities, shorten smelting time, and reduce power consumption and refractory consumption.
• Oxidant: In the process of smelting electric furnace steel, in order to stir the molten pool and remove harmful impurities such as gas and phosphorus in the steel, the oxidation effect of the oxidant is currently mostly used to complete the process. Commonly used oxidants include iron ore, iron oxide, oxygen, etc.
• Carbonizing agent: In order to make up for the lack of carbon content in scrap steel, in addition to using pig iron to add carbon, carbon materials such as natural graphite, electrode blocks, coke, etc. are often used to add carbon. These materials are collectively referred to as carbonizing agents. The use of carbon materials to add carbon to the charge is conducive to the formation of foam slag in the oxygen stage of electric furnace steelmaking. Commonly used carbonizing agents include: natural graphite, electrode blocks, and coke.
• Carburizer: In the process of smelting electric furnace steel, due to improper batching or charging and excessive decarburization, the carbon content in the steel sometimes does not meet the expected requirements. At this time, carbon must be added to the molten steel. Commonly used carburizers include: carburized pig iron, electrode powder, petroleum coke powder, charcoal powder, and coke powder.

Deoxidizers and alloy materials

Commonly used powdered deoxidizers include: ferrosilicon powder, calcium silicon powder, aluminum powder, intermediate alloy powder, calcium carbide powder, and silicon carbide powder.

Commonly used block deoxidizers and alloy materials include: calcium carbide blocks, ferrosilicon, ferromanganese, manganese silicon alloy, silicon calcium alloy, silicon zirconium alloy, silicon chromium alloy, ferrochrome, ferrotungsten, ferromolybdenum, ferrovanadium, ferrotitanium, ferroniobium, ferroboron, ferrophosphorus, nickel, cobalt, aluminum, copper, and rare earth alloys.

Refractory materials

Refractory materials generally refer to non-metallic materials with a refractoriness of more than 1580℃, which can withstand the physical and chemical effects of gases, dust, slag, liquid metals and other substances, and have a certain strength of masonry and knotting performance. Commonly used refractory materials in electric furnace steelmaking mainly include insulation materials, refractory products, furnace lining knotted refractory materials, refractory mud and refractory concrete. Click to jump to the detailed introduction of refractory materials.

Electrode

Electric furnace steelmaking uses lower voltage and larger current. Electrodes are needed to deliver strong current to the furnace. Electrodes are current conductors with very low resistance, which affect the productivity and cost of electric furnace steel. The electrodes used in electric furnace steelmaking are mainly:

1. Carbon electrode: It is made of low-ash carbon materials, such as low-ash anthracite, metallurgical coke, asphalt coke, petroleum coke, etc., in a certain proportion and particle size, and at a certain temperature, asphalt or coal tar binder is added to mix and press to form, and then placed in a roasting furnace for slow burning.
2. Graphite electrode: The carbon electrode is placed in a resistance furnace and subjected to desertification treatment at a high temperature of 2000-2500℃ to obtain a graphite electrode. During the desertification process, the power consumption per ton of electrode is very large, so it is expensive. The conductivity of graphite electrode is about 4 times higher than that of carbon electrode.
3. Anti-oxidation electrode: In order to prevent the surface oxidation of the electrode, a protective layer that resists high-temperature oxidation is sprayed on the surface of the electrode. Common processes include:
   1. Spraying aluminum on the electrode surface, then applying glaze on the aluminum layer, and repeatedly treating it with an electric arc;
   2. Spraying iron and aluminum or nickel and aluminum;
   3. Spraying a mixture of aluminum and silicon carbide or silicon and silicon carbide.
4. High-power-ultra-high-power electrodes: Since the use conditions of high-power-ultra-high-power graphite electrodes are more harsh and severe, they are required to have a higher rated current density and mechanical strength, higher conductivity, and lower thermal expansion coefficient and elastic modulus. Therefore, high-power-ultra-high-power graphite electrodes are made of petroleum needle coke as raw materials.

Binder

The following are commonly used binders in electric furnace steelmaking.

1. Brine: The main component is magnesium chloride (MgCl2). In electric furnace steelmaking, it can be used as a binder for ramming magnesia sand linings and blocking and padding furnace bodies. It is also used for refractory mud or magnesia mud slurry.
2. Water glass: also known as sodium silicate or sodium silicate. Because of its bonding ability, it is often used to prepare mud, coatings, refractory concrete, etc., and is also used for solid slag or heating agents configured during pouring.
3. Tar and asphalt: Tar is a by-product of coking, a black viscous liquid with great stickiness. In electric furnace steelmaking, it is mainly used as a binder for refractory materials and sometimes as a coating for ingot films. Asphalt is a product of tar fractionation, a black solid, and is mainly used as a binder for refractory materials in electric furnace steelmaking.

Other materials

1. Argon: Mainly used in jet metallurgy and stirring of molten steel to remove inclusions, etc.; in order to prevent secondary oxidation of molten steel, it is sometimes used as a protective agent during steel tapping and pouring.
2. Nitrogen: Mainly used for smelting high manganese steel, austenitic stainless steel and other steel grades.
3. Paraffin: Mainly used for protective pouring of steel.
4. Carbon tetrachloride: Mainly used for protective pouring of steel or coating of ingot films.
5. Benzene: It has strong dissolving ability and is often used to dilute tar.