Ferroalloy can be used as a deoxidizer in the field of steelmaking to play a significant role, commonly used ferroalloys are ferrosilicon, silicon manganese, aluminum iron, ferromanganese and so on.
So today let’s take a look at what role these ferroalloys play in steelmaking deoxidation, and why deoxidizers are used in steelmaking.
Speaking of this topic, we have to mention an element – oxygen, in the process of steelmaking, oxygen plays a two-faced role.
On the one hand, in the heating process of molten steel, oxygen is needed, and it is also necessary to use oxygen to produce chemical reactions with harmful substances such as carbon and sulfur in molten steel to improve the quality of steel. On the other hand, the oxygen molecules in the molten steel will affect the mechanical properties and strength of the steel, so the molten steel should be deoxidized.
What a bad effect oxygen itself has on steelmaking. The harmful effect of oxygen on cast steel is caused by the wide difference in solubility of oxygen in liquid and solid steel.
The main harmful effects of oxygen on steelmaking include:
1. oxygen is one of the reasons for the formation of steel casting pores
During the solidification process of liquid steel, because the solubility of oxygen decreases significantly with the decrease of temperature, the precipitated oxygen reacts with the carbon in the liquid steel, and the resulting CO bubbles become pores if they remain in the steel.
2. Oxygen promotes the formation of hot cracking of cast steel
When the oxygen content of liquid steel is too high, it will aggravate the hot cracking tendency of cast steel, because FeO and FeS meet to form a low melting point (940℃) eutectic (FeO·FeS), and are distributed in a thin film on the grain boundary, so it is easy to cause hot cracking.
3. oxygen is one of the main elements of the formation of non-metallic inclusions
Oxygen can oxidize with a variety of elements to form oxide inclusions, which, if retained in steel, will reduce the performance of cast steel.
Deoxidation requires the addition of some elements that combine with oxygen and are easily removed from the molten steel into the slag. According to the binding strength of various elements in the molten steel to oxygen, the order from weak to strong is as follows: chromium, manganese, carbon, silicon, vanadium, titanium, boron, aluminum, zirconium, calcium. Therefore, steel deoxidation is commonly used by silicon, manganese, aluminum, calcium composed of iron alloy.
Why does oxygen enter molten steel during steelmaking?
In the process of steelmaking, in order to remove harmful impurities such as carbon and sulfur in the molten iron, oxygen molecules need to be added to the molten iron by blowing oxygen or adding oxidants in the smelting process.
Deoxidizer commonly used in steelmaking
Generally speaking: the role of blowing oxygen is to oxidize with carbon, silicon, manganese, phosphorus, sulfur and other elements in hot metal to form gases or oxides with higher melting points, reduce these five impurities harmful to the composition of molten steel, and use the chemical heat released during its oxidation reaction to increase the temperature of hot metal.
Ferro silicon
Ferro silicon is made of coke, steel chips, quartz (or silica) as raw materials and is smelted by electric furnace. Silicon and oxygen are easy to combine into silicon dioxide, so iron silicon is often used in steelmaking deoxidizer, at the same time due to SiO2 generation release a lot of heat, at the same time deoxidation, can increase the temperature of molten steel, reduce the energy consumption of bottom steelmaking. As an alloying element additive, ferrosilicon is widely used in low-alloy structural steel, bonding steel, spring steel, bearing steel, heat-resistant steel and electrical silicon steel, and is commonly used to manufacture monocrystalline silicon or prepare non-ferrous metal alloys.
Ferrosilicon is an essential deoxidizer in steelmaking industry. In steelmaking, ferrosilicon is used to precipitate deoxidizers and diffuse deoxygenation. Ferrosilicon is also used as an alloying agent in steelmaking. Adding a certain amount of silicon to steel can significantly improve the strength, hardness and elasticity of steel, improve the permeability of steel, and reduce the hysteresis loss of transformer steel. The general steel contains 0.15%-0.35% silicon, the structural steel contains 0.40%-1.75% silicon, the tool steel contains 0.30%-1.80% silicon, the spring steel contains 0.40%-2.80% silicon, the stainless acid-resistant steel contains 3.40%-4.00% silicon, and the heat-resistant steel contains 1.00% ~ 3.00% silicon. Silicon steel contains 2% to 3% silicon or higher.
Why is ferrosilicon silicon manganese indispensable deoxidizer in steelmaking?
Due to the strong affinity between silicon and oxygen, after adding ferrosilicon to steelmaking, the following deoxidation reaction occurs:
2FeO+Si=2Fe+SiO₂
Silicon dioxide is the product of deoxidation, it is lighter than molten steel, floating on the surface of steel into the slag, thereby removing the oxygen in the steel, can significantly improve the strength, hardness and elasticity of steel, improve the permeability of steel, reduce the hysteresis loss of transformer steel.
Silicon manganese alloy
Manganese silicon alloy is a kind of iron alloy composed of manganese, silicon, iron, etc., is the main alloy agent in steelmaking. Manganese in solid solution in steel plays a strengthening role, can improve the strength of ferrite, can improve the mechanical properties of steel, enhance the strength of steel, ductility, toughness and wear resistance. Silicon exists in solid form in steel, which can increase the strength, fatigue limit, corrosion and wear resistance of steel. Therefore, manganese silicon alloy is an indispensable alloying agent in steelmaking.
Ferro-aluminium
Pure aluminum has always been the main deoxidizer in the steelmaking industry, in the production of high ductility, high stamping of the sedative steel, especially for the production of cold tied sheet of low carbon sedative steel, are using pure aluminum deoxidizing process, and can not use ferrosilicon and ferromanganese as deoxidizer, because silicon and manganese and other elements in the smelting of such steel, are strictly controlled elements; Moreover, this type of steel requires more aluminum to refine the grain. However, because the specific gravity of aluminum is much less than the specific gravity of molten steel, the liquid steel is floating on the surface of the liquid steel when it is deoxidized, easy oxidation, and large burning loss, which reduces the utilization rate of aluminum, increases the consumption of aluminum, increases the production cost, and reduces the economic benefits. In order to solve the above problems, the steel research department has developed a new deoxidizer – aluminum-iron deoxidizer.
Ferromanganese
Ferromanganese is a commonly used deoxidizer, “no manganese is not steel”, manganese is an essential element in the steel industry, almost all steel contains a certain amount of manganese. Manganese can refine the grain of steel, improve the hardenability of steel, enhance the resistance to atmospheric corrosion, and improve the calcinability and rolling ability of steel.
The above is a brief introduction of us as a ferroalloy manufacturer, if you want to know more about ferroalloy knowledge, or want to get a quote, please contact us.
