What is High Carbon Silicon?

What is High Carbon Silicon?

High carbon silicon alloy is an alloy composed of silicon and carbon, also known as high-carbon silicon. It is ferrosilicon with high carbon content.
High-carbon silicon alloy is a new alloy used in converters. It can completely replace the carburizer and deoxidizer. Silicon-aluminum iron is added to the bottom of the ladle or along with the steel flow. Due to the high specific gravity of high-carbon silicon alloy, it can be added to the molten steel in the form of blocks. It plays a deoxidizing role, greatly improving the carbon recovery rate (the carbon recovery rate can reach more than 98%).
High-carbon silicon alloy can improve the quality of molten steel, improve product quality, improve product new properties, reduce the amount of alloy added, reduce steelmaking costs, increase economic benefits, greatly improve environmental conditions, and at the same time reduce workers’ labor intensity.

featured image of high carbon silicon

High CarboHigh Carbon Silicon

Si60C10, Si65C15, Si68C18

Oxygen exists in the molten steel in the molecular form of its compound with iron, ferrous oxide (FeO). If more FeO is dissolved in the molten steel, pores will be generated during the solidification process of the steel. In addition, since the solubility of ferrous oxide in molten steel is large but the solubility in solid steel is extremely small, when the molten steel contains a large amount of ferrous oxide, ferrous oxide will precipitate due to saturation during the solidification process of the steel. At the grain boundaries of steel, the strength and plasticity of steel are reduced, seriously damaging the mechanical properties of steel. In order to avoid damage caused by oxygen during the steelmaking process, it is necessary to remove the remaining ferrous oxide as much as possible during the steelmaking process, that is, deoxidize the steelmaking process. Deoxidation treatment is usually completed by adding a deoxidizer to the molten steel. In the traditional steelmaking process, pure aluminum is used as a deoxidizer for steelmaking. Although aluminum is a strong deoxidizer, due to its low density, it easily floats up into the scum after being put into the molten steel, and is difficult to enter the interior of the molten steel. This seriously affects its utilization and increases the consumption of aluminum. This increases the production cost. In addition, aluminum also has the problems of low melting point and high specific heat.

Based on existing problems, ferro aluminum barium and ferro aluminum strontium composite deoxidizers have been proposed, but barium and strontium are expensive; the aluminum-manganese-iron composite deoxidizer provided in Chinese Patent Bulletin 92107299.6 can only be used in steel types containing manganese. , its use area is very narrow.

The purpose of the high-carbon silicon alloy is to overcome the above-mentioned shortcomings of the existing technology and provide a master alloy deoxidizer for steelmaking with strong deoxidizing performance, low production cost, and wide applicability.
High-carbon silicon alloy includes the following components, which are melted and formulated by weight: silicon 50 to 68%, carbon 15 to 20%, phosphorus ≤ 0.05%, sulfur ≤ 0.05%.

The preparation method of high carbon silicon alloy, that is, the processing steps are as follows: dispensing steel materials – smelting – slag removal – ingot casting – testing – adjusting ingredients – remelting – adding aluminum ingots – stirring – slag removal – incubation – pouring into blocks.
When the composition of the steel material is relatively certain, the remelting process does not need to be used. The preparation method is to prepare the steel material – smelting – adding aluminum ingots – stirring – slag removal – incubation – pouring into blocks.

The steel material used in the production method of high carbon silicon alloy can be scrap steel with an appropriate amount of ferrosilicon added. The scrap steel should be shot blasted and rust removed before smelting.

The positive effects of high-carbon silicon alloy are: 1. Since the silicon content in high-carbon silicon alloy is more than 50%, it has a strong deoxidation effect, and the deoxidizer does not contain manganese and other elements, so it has wide applicability; 2. High The proportion of carbon-silicon alloy is relatively large. When put into molten steel, it easily enters the interior of the molten steel and combines with oxygen, so that the molten steel can be fully deoxidized and the deoxidizer utilization rate is high. 3. Compared with pure aluminum, the production cost is greatly reduced, and the use of scrap steel can further Reduce costs; 4. The carbon content is high, the deoxidizer has strong fluidity during casting and molding, and the filling performance is good; 5. The remelting process in the preparation process can be used to adjust the composition of the high-carbon silicon alloy to ensure its chemical The ingredients must be determined reliably to avoid mixing harmful elements and other inclusions. 6. Use an inoculant to incubate the food before it is released from the oven to make it difficult to pulverize.

Example 1 Equipment: 160KW thyristor medium frequency induction furnace, melting capacity 150kg.
Preparation process: a. 88kg of scrap steel and 1kg of 75SiFe are prepared. The scrap steel is shot blasted and derusted. b. The scrap steel is put into the furnace and melted. When the temperature is >1570°C, ferrosilicon is put in. c. After slag removal, the molten steel comes out of the furnace and is poured into steel ingots. , d. Test the steel ingot and adjust its composition to C 0.40%, Si 1.20%, P 0.05%, S 0.04%, Fe balance, e. Put the steel ingot into the furnace for remelting, and carry out the feeding and removal of the composition adjustment Material, f. Wait until the molten steel rises to >1600°C. After slagging and slag removal, 71kg of blue carbon is added. g. After stirring, degassing, deoxidation and incubation are carried out, and pouring is carried out quickly. The pouring temperature is 1250~1280°C.

High-carbon silicon alloy deoxidizer was obtained through post-furnace testing.

High Carbon Ferrosilicon Uses

High-carbon ferrosilicon is a new type of alloy used in converters. It can replace ferrosilicon, silicon carbide, and carburizers, reduce the amount of deoxidizer, and is used in the deoxidation alloying process of converter smelting. The effect is stable, and the chemical composition, mechanical properties and The quality of internal control is better than that of traditional processes. As a new type of strong composite deoxidizer, it can also be used for tempering general steel, alloy steel and special steel. In addition, as a temperature-raising agent, it can replace the more expensive traditional temperature-raising agent required in converter and open-hearth steelmaking.

High Carbon Silicon Advantages

High carbon ferrosilicon is a commonly used deoxidizer with the following advantages:

No hydrogen source is produced during the deoxidation process, ensuring safety and reliability; carbon and silicon are important elements that determine the function of steel. High-carbon ferrosilicon can not only react with oxygen in molten steel to achieve a deoxidation effect, leaving unoxidized carbon and Silicon can also be dissolved in molten steel to increase silicon and carburization, achieving the effect of killing two birds with one stone. In order to obtain steel with qualified chemical composition and ensure the quality of steel, steelmaking must be deoxidized. The chemical affinity between silicon and oxygen is very large, so ferrosilicon is a strong deoxidizer for steelmaking and is used for precipitation and diffusion deoxidation. Adding a certain amount of silicon to steel can significantly improve the strength, hardness and elasticity of the steel.

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