What is the use of Ferromanganese in Steelmaking?

What is the use of Ferromanganese in Steelmaking?

Ferromanganese is used as a deoxidizer and alloy additive in steelmaking. It is a large amount of iron alloy. The manganese ore used to smelt ferromanganese generally requires 30-40% manganese in ferromanganese, the ratio of manganese to iron is greater than 7, and the ratio of phosphorus to manganese is less than 0.003.

Before smelting, the manganese carbonate ore is first roasted, and the refined ore is sintered into agglomerates. Ores with high iron and phosphorus content can only be used in combination, or manganese-rich slag with low iron and phosphorus can be obtained through selective reduction. Coke is used as a reducing agent during smelting, and lean coal or anthracite is also used in some factories. The auxiliary raw material is mainly lime, and silicon dioxide is generally added when smelting manganese-silicon alloy.

Steel castings should be used after heat treatment. Due to the presence of casting defects such as pores, cracks, shrinkage cavities and shrinkage cavities, coarse grains, uneven structure, and residual internal stress in steel castings in the as-cast state, the strength, especially the plasticity and toughness of steel castings are seriously affected. . decrease very much.

In order to refine grains, uniform structure, and eliminate internal stress, steel castings must be normalized or annealed. Normalized steel has higher mechanical properties and lower costs than annealed steel, so it is widely used. However, since normalizing produces greater internal stress than annealing, it is only suitable for steel castings with a carbon content of less than 0.35%. 

Due to the good plasticity of low-carbon steel castings, it is not easy to crack when cooling. In order to reduce internal stress, steel castings should be tempered at high temperatures after normalizing. Only annealing treatment can be performed for steel castings with carbon content ≥ 0.35%, complex structures, and cracks. Steel castings should not be quenched, otherwise, they will crack easily.

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Ferrochrome

Ferrochrome

Ferrochrome is divided into high-carbon ferrochrome according to carbon content, including charge-grade ferrochrome (C≤10%), medium-carbon ferrochrome (C≤4.0%), low-carbon ferrochrome (C≤0.5%), micro-carbon ferrochrome Ferrochrome Ferrochrome (C≦0.15%), etc. Commonly used are silicon chromium alloy, ferrochromium nitride, and so on. 

Ferrochromium is mainly used as an alloy additive in steelmaking and was added in the later stage of steelmaking in the past. To smelt low-carbon steel such as stainless steel, low-carbon, and micro-carbon ferrochrome must be used, so the production of refined ferrochrome was once developed on a large scale. 

Due to the improvement of the steelmaking process, when using the AOD method to produce stainless steel and other steel grades (see refining outside the furnace), carbon ferrochrome (mainly charge-grade ferrochrome) is used to charge the furnace, so it only needs to be added later. The composition of carbon ferrochrome is adjusted, so the focus of ferrochrome production is refining carbon ferrochrome.

With chromium ore prices strengthening again, bullish sentiment in the high-carbon ferrochromium market is gradually heating up. Today’s supplier quotations are generally raised by 100 yuan/50 basis tons. Southwest 8800-9100; Northwest 8700-8800; Northeast 8950-9000; East China 9000-9100; Central China 8900-9100; North China 8700-8900;

Affected by delays in shipping schedules, some factories in northern China have replenished spot chrome ore at ports to ensure production, thereby pushing up ore prices again. The tradable goods in the port are concentrated, and the miners are reluctant to sell them. Quotes are rising, and there is basically no room for bargaining. This week, the price of South African chrome ore increased by about 2 yuan/ton. It is expected that a new round of external quotations will also rise. , the cost of ferrochrome increases and the factory quotation can only be adjusted up according to the cost change.

Southern factories such as Hunan, Guizhou, and Sichuan have shut down a large area of production, and the supply of ferrochrome continues to show a downward trend. Due to the early closure of the downstream retail market a year ago, some steel mills had insufficient raw material inventory, the epidemic prevention policy was relaxed, and a series of macro measures were added. Stimulated by economic policies, the industry is optimistic about the demand and price of ferrochrome after the festival. Some dealers are optimistic about the market outlook and choose to inquire about replenishment, waiting for subsequent profits.

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The Role of Silicon Barium Calcium Inoculant

 

The Role of Silicon Barium Calcium Inoculant

(Summary description)Silicon Barium inoculant is mainly used in the production of gray cast iron and ductile iron. Nodular cast iron can significantly increase the number of graphite balls, and used in gray cast iron can reduce the tendency of white mouth. Refine grains and improve graphite morphology. In addition to obtaining higher mechanical properties, these inoculants also have a strong anti-decay ability. Generally, the inoculants contain Ba between 2% and 3%.

Various Inoculant Effects and Methods of Use

Foreign name: Inoculant

Si: 68-80%

AL: 0.5--1.5

Ba:2--6

Chinese Name: inoculant metallurgical refractory

What is Silicon Barium Calcium Inoculant?

It can promote graphitization, reduce the tendency of white mouth, improve the shape and distribution of graphite, increase the number of eutectic clusters, and refine the matrix structure. It can be used for a short period after incubation (

About 5-8 minutes) has a good effect. It is mainly suitable for general conditions of various situations or instant incubation in the later stage.

Main ingredients Metallurgical Refractories

Si: 68-80%, AL: 0.5-1.5 and trace amounts of Ca, Al, Mn, etc.

Instructions

1. Pour ladle inoculation: add the inoculant to the ladle, then flush the molten iron to melt it evenly, and then pour.

2. The added amount is about 0.2-0.4% of the weight of the molten iron.

Detailed Classification Metallurgical Refractories

(1) Ferrosilicon inoculant. Ferrosilicon inoculants are divided into three types: 45FeSi, 75FeSi, and 85FeSi.

The treatment effect of 45FeSi inoculant is poor, and the cost of 85FeSi is higher. 75FeSi is commonly used. The Ca and Al in 75FeSgreatly influence on the inoculation effect. Among them, Ca has the greatest influence, and it has a strong inking ability when it is greater than 0.5%. Generally, 75FeSi selects the following chemical composition range, Si: 74%～78%; Ca: 0.5%～1.0%; Al: 0.8%～1.5%.

(2) Silicon barium inoculant. Silicon Barium inoculant is mainly used in the production of gray cast iron and ductile iron. Used in nodular cast iron can significantly increase the number of graphite balls, and used in gray cast iron can reduce the tendency of white mouth. Refine grains and improve graphite morphology. In addition to obtaining higher mechanical properties, these inoculants also have a strong anti-decay ability. Generally, the inoculants contain Ba between 2% and 3%.

(3) Si-C inoculant. This type of inoculant is mainly an ink-forming inoculant. Its main advantages are low dosage and strong inking ability, but it is difficult to dissolve. For example, Si-C-Ca-Al has a good effect on preventing the whitening of thin-walled castings and is suitable for cupola hot metal use. Si-C-Al has a better softening effect and is used to improve cutting performance.

(4) Rare earth inoculants. Rare earth elements are an important component of high-efficiency and long-acting inoculants for cast iron. my country is extremely rich in rare earth resources. The research and application of this type of inoculant are of more practical significance. Generally speaking, this kind of inoculant has duality, and the rare earth residue in the inoculant cast iron has a certain range (RE is 0.3%～0.06%). When the carbon equivalent is low, the amount of rare earth added is small, and when the carbon equivalent is high, the amount of rare earth added is slightly larger. In addition, rare earth elements are also compounded with alloy elements such as Mn and Cu to improve the structure of cast iron and increase its mechanical strength.

(5) Silicon calcium inoculant. Silicon-calcium inoculant is a kind of ink inoculant used earlier, and low-calcium inoculant is often used now. It is more suitable for the production of low carbon equivalent cast iron, which can eliminate white mouths and increase strength.

(6) Stabilizing inoculants. The stabilized inoculant is a composite of inking elements and stabilizing elements. It can effectively promote graphitization while inhibiting the decomposition of cementite. It is more suitable for the production of higher carbon equivalent cast iron. Common rare earth stabilized inoculants, Nitrogen stabilized inoculants.

(7) Compound inoculant. The compound inoculant is a type of inoculant composed of the inking element and the element that hinders the growth of the eutectic cluster. It plays a role in nucleation and growth, so it has attracted more and more attention in the production of cast iron. Used with Bi-containing compound inoculant for ductile iron and CMSB compound inoculant for gray cast iron.

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Ferroalloy Production Cost Composition

Ferroalloy Production Cost Composition

Ferroalloys are mainly produced by electric furnaces, which require high power consumption and abundant and cheap power resources. France became the main producer of ferroalloys in the early stage, and Norway became the largest exporter of ferroalloys in the 1980s and 1990s, based on the rich local hydropower resources.

The production of ferroalloys is an energy-intensive process, and energy accounts for a large proportion of the cost structure of ferroalloys. 

As far as the main varieties of ferroalloys, manganese, chromium, and silicon are concerned, in addition to abundant China domestic resources and low prices of silica, about one-third of manganese ore needs to be imported due to factors such as low domestic grade, high mining cost, and reserves. 

The proportion of manganese alloy production cost is relatively large; China's chrome ore resources are extremely scarce, basically, all rely on imports, and chrome ore occupies a relatively large proportion of the cost structure of ferrochrome.

The production cost of ferromanganese alloy is mainly composed of manganese ore, electricity, and coke procurement costs, of which manganese ore costs account for about 60%, electricity costs account for about 20%-25%, and coke costs account for about 10%-15%. 

In addition, when many enterprises produce manganese ferroalloys, in addition to using domestic low-phosphorus, low-iron, low-sulfur, and low-silicon manganese ores, in order to improve the grade of raw materials, increase the recovery rate of manganese, reduce power consumption and production The cost needs to be smelted after purchasing part of the imported ore and mixing the domestic ore. 

Therefore, fluctuations in the price of manganese ore, electricity, and coke have a greater impact on the production of ferromanganese alloys.

Similar to ferromanganese alloy, chrome ore also accounts for a large proportion of the production cost of ferrochrome. China's chrome ore resources are very few. 

In 2013, chrome ore consumption was nearly 14 million tons, and China’s supply was only about 2 million tons. 

The rest was settled by imports. The cost of chromium ore accounts for about 60% of the production cost of ferrochrome in China, the cost of electricity accounts for about 25%-30%, and the cost of coke accounts for about 10%-15%.

Due to the low price of silica, the proportion of energy consumption in the production of ferrosilicon is the largest. Production of one ton of ferrosilicon raw materials and power consumption are 1780-1850 kg of silica, 890-930 kg of coke, 220-230 kg of steel shavings, 45-55 kg of electrode paste, and 8400-9000 kWh/t of electricity. In the cost of ferrosilicon, electricity accounts for about 70%.

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Consumption of Graphite Electrodes in Electric Arc Furnaces

Consumption of Graphite Electrodes in Electric Arc Furnaces

The consumption of graphite electrodes in electric arc furnace steelmaking runs through the entire smelting process, and its consumption is affected by many factors. Here we only analyze the operation of the smelting process.

1. Poor steel scrap quality or improper proportioning results in a poor slagging effect and prolongs the smelting time; The extension of smelting time is the direct factor leading to the increase of power consumption and electrode consumption and loss.

2. The electric furnace power supply equipment does not match the electrode specifications. The electric arc furnace power transmission is a high-current and low-voltage operation. Overload and overtime operation will cause the greatest loss and consumption of graphite electrodes.

3. In the oxidation period, the chemical energy is forced to be increased and the smelting intensity is increased. During the smelting, the amount of oxygen blowing is forced to be increased to achieve rapid melting and increase the furnace temperature. In high-temperature flame. When the electrode is in this kind of furnace environment, most of them have the serious phenomena of layering and surface oxidation.

4. The technicality of the configuration and operation of the electric furnace. The selection of power transmission curve and gear during operation, the control of arc starting and arc stabilization voltage and current, the coordinated use of the long, medium, and short arcs, the configuration and application of water cooling systems, etc., all affect the service life and consumption of electrodes played a key role.

5. The quality of graphite electrodes now the smelting and process of electric arc furnaces have more and more strict requirements on the anti-oxidation performance and thermal shock resistance of graphite electrodes, and the high consumption caused by quality fluctuation has attracted great attention from direct users. Therefore, the balance and stability of graphite electrode quality are the most important factors that determine the size of consumption.

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The Importance of Refining Steel Castings Outside the Furnace

The Importance of Refining Steel Castings Outside the Furnace

The control of non-metallic inclusions puts forward the requirement of "clean steel".

In the general steelmaking method, in order to remove the gas and inclusions in the molten steel, the molten steel formed by the decarburization reaction is used to boil, so the molten steel needs to be strongly oxidized.

In the next step, in order to remove a large amount of residual oxygen in the molten steel, it is necessary to deoxidize the molten steel, so a large number of inclusions are produced again, which is a contradiction that is difficult to solve in the general steelmaking method.

1. The refining method outside the furnace is adopted, and the refining process is realized by the action of vacuum and inert gas bubbles, thereby exempting the process requirement of using a deoxidizer for deoxidation.

This fundamentally reformed the steelmaking process, and the purity of the molten steel was greatly improved.

Therefore, the mechanical properties of steel, especially the toughness, are greatly improved.

2. Reduce the smelting loss of alloying elements. In the steelmaking process combining electric arc furnaces and out-of-furnace refining, alloying elements are generally added to the process of out-of-furnace refining.

Under the action of vacuum or inert gas, the melting loss of alloying elements is very slight, so the absorption rate of alloying elements is extremely high, and it is also convenient to accurately control the chemical composition of the steel.

3. Open up a way for smelting ultra-low carbon steel Under normal steelmaking conditions, it is difficult to reduce the carbon content of the steel to a very low level. This is due to the presence of carbon-oxygen balance in molten steel. If the carbon content of the steel is to be very low, the oxygen content in the steel must be high. For this reason, the burden of deoxidation in the reduction period will be increased, and the quality of steel will deteriorate.

Adopting out-of-furnace refining technology, relying on the effect of vacuum and inert gas, can reduce carbon content without increasing oxygen. Therefore, the smelting problems of low-carbon (w(C) <0.06%) and ultra-low-carbon (w(C) <0.03%) steels are fundamentally solved.

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