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2021年6月23日星期三

The Proportion of Raw Materials for Smelting High-carbon Ferrochromium

High-carbon Ferrochromium Smelting Furnace

The Proportion of Raw Materials for Smelting High-carbon Ferrochromium

The production methods of high carbon ferrochrome include the electric furnace method, shaft furnace (blast furnace) method, plasma method, and smelting reduction method.

The raw materials for smelting high-carbon ferrochrome are chrome ore, coke, and silica.

The Proportion of Raw materials for Smelting High-carbon Ferrochromium

In chrome ore, Cr2O3≥40%, Cr2O3/∑FeO≥2.5, S<0.05%, P<0.07%, the content of MgO and Al2O3 should not be too high, and the particle size should be 10～70mm. For refractory ore, the particle size should be appropriately smaller.

Coke requires no less than 84% fixed carbon, less than 15% ash, S<0.6%, and particle size 3-20mm.

Silica is required to contain SiO2≥97%, Al2O3≤1.0%, good thermal stability, no soil, and particle size 20～80mm.

The principle of chromium ore matching: In the actual production of high-carbon ferrochromium, it is often necessary to select the appropriate mineral collocation and matching ratio.

The Main Principles of Chromium Ore Matching are:

1) Appropriate Ratio of Chromium to Iron ( Cr2o3/∑FeO).

Generally speaking, smelting alloys with chromium content greater than 50% require that the ratio of Cr2o3/ΣFeO into the furnace is greater than 2.0; while smelting alloys with chromium content greater than 60% requires this ratio to be greater than 2.6.

2) Appropriate MgO/Al2o3 Ratio.

It not only affects the conductivity and reduction properties of the slag but also affects the carbon-containing disk of the alloy.

In actual production, MgO/Al2o3 is used. Chrome ore with a low ratio needs to be equipped with sufficient coke to increase the thickness of the coke layer. On the one hand, it is to ensure that the bottom of the furnace is not easily damaged, and on the other hand, it is also to increase the unreduced core. The residence time in the coke layer. Reduce chromium in the slag.

3) Appropriate Size Matching.

When the fine ore is used alone, it is easy to cause the fine ore to sinter, make the air permeability of the material surface worse, and seriously damage the smelting atmosphere; the use of large chromium ore is easy to increase the thickness of the refining layer, resulting in the low carbon content of the alloy.

4) Appropriate Melting Performance.

The simple use of fusible chromium ore will cause slag to form prematurely, which will make the melting speed faster than the reduction speed, and will easily cause the phenomenon of high chromium in the slag; the simple use of refractory chromium ore will thicken the refining layer, and a large number of unreduced ore cores and alloys will appear. Low carbon content and other phenomena have brought great difficulties to normal smelting.

A reasonable mix of chromium ore to make the slag have a reasonable melting point is very important for improving economic indicators.

Free send inquiry to stella@hanrm.com if any needs.

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2021年6月16日星期三

New Technology of Electric Furnace Steelmaking

In steel production, the cost is the decisive factor, and it must be reduced to promote the development of electric furnace steel. Optimize the production process, strengthen the fine management and operation, start with optimizing the burden design, reducing the consumption of steel materials, adding alloy concentrates and reductant to achieve direct alloying and recycling of scrap steel slag, so as to pursue the lowest process cost and guarantee system cost.

In terms of optimizing the burden design, according to the steel grade requirements and market price changes, the ratio of scrap, molten iron, pig iron in each furnace, as well as the ratio of different types of scrap steel, is finely matched to achieve the optimal burden design. Consumption of steel materials is the largest item in the cost of electric furnaces, and reducing steel consumption is the key to reducing costs. Through strengthening management and fine operation, it has played an important role in reducing the cost of electric furnace steel.

Direct reduced iron is used as a substitute for steel scrap to supplement the deficiencies of steel scrap. With the advancement of industrial technology, users' requirements for steel quality and varieties have increased, and the proportion of electric furnace steel has increased, resulting in an increasingly tight supply of scrap steel, especially the raw materials required for the production of high-quality steel and pure steel; Controlling the content of non-ferrous metal inclusions and harmful elements in scrap steel is the basis for improving the quality of steel.

Direct reduced iron does not contain these impurity elements and few harmful elements. When used in electric furnace production, it can dilute harmful elements and significantly improve the quality of steel; adding direct reduced iron in electric furnace smelting can form carbon boiling and formation during the melting period. The foamed slag promotes the melting of the charge, reduces the nitrogen and hydrogen content in the steel, protects the furnace lining, and shortens the refining period and smelting time; the direct reduced iron has a uniform and stable composition, moderate lumps, and can be continuously fed.

Adding alloy concentrates and direct reduction alloying are very beneficial to reduce the cost of alloy materials. However, due to various factors such as concentrate grade, recovery rate, harmful elements, slag amount, etc., the current use of alloy concentrates in electric furnaces is still not mature. As technology advances, this technology will have a profound impact on cost reduction.

Reasonable recycling of scrap steel slag can effectively use the metal and heat energy in it. Hani Tech Company uses a variety of methods to recover the iron-containing materials in the steel slag, and at the same time returns the refined slag to the primary smelting furnace during production, making full use of the high basicity slag material and heat energy in the refined slag. Electric furnace dephosphorization plan.

Reducing production costs is a systematic work, including management and technical aspects, but with the refinement of management and technological progress, I believe that there is still room for reduction in the cost of electric furnace steel.

Through repeated research and comparison of various direct reduction technologies at home and abroad, the world's leading new type of direct reduction electric furnace steelmaking short-process equipment has been developed. The specific feature of this equipment is that it uses powdered ore and coal to be mixed in proportion to make pellets. After drying, it is placed in equipment with the functions of continuous feeding, continuous preheating, continuous melting, and continuous smelting. It is heated to 1250～1350℃ with pulverized coal (or gas) to achieve rapid reduction and production of metalized pellets, which are discharged Afterwards, it is directly hot-charged and continuously added to the electric furnace for smelting to produce high-quality molten iron. This method has high efficiency and low unit investment, which has become a leap in iron and steel metallurgy technology.

Free send inquiry to stella@hanrm.com if any needs.

Whatsapp/Wechat:+8615877652925

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2021年2月23日星期二

EAF steelmaking

Advantages: by arc heating, high thermal efficiency, can adjust the furnace atmosphere, compared with open-hearth, converter, less capital investment, small area.

Disadvantages: the arc is a point heat source, high consumption of power, electrode and refractory, low productivity, and higher cost than the converter.

Introduction of traditional basic electric arc furnace steelmaking method and process flow.

Common smelting methods: generally can be divided into oxidation method, non-oxidation method, and return oxygen blowing method.

Oxidation process: after the furnace charge is melted, the operation of dephosphorization and decarbonization is carried out by adding ore or blowing oxygen into the molten steel, resulting in the boiling of the molten pool, removing [H], [n] gas, and non-metallic inclusions in the steel, and then tapping after deoxidization and decarbonization in the reduction period, adjusting the chemical composition and temperature of the molten steel. The characteristic of this method is that it can reduce [P], [S], [H], [n], [O] in steel to the specification range, so as to achieve the purpose of purifying liquid steel. Therefore, most steel grades are smelted by this method. The disadvantage of this method is that if there are a lot of alloying elements in the steel, it will cause oxidation loss and bring adverse effects on the operation. Therefore, carbon scrap is often used in general batching, which causes difficulties in later alloying.

Non-oxidation method: there is no oxidation period in the smelting process, which can fully recover the alloy elements in raw materials. After the burden is melted, the composition and temperature can be adjusted by reduction. The utility model has the advantages that a large amount of alloy steel cutting head, tail, scrap ingot, injection residue, soup channel, chip, etc. can be added into the furnace charge to reduce the consumption of ferroalloy and the cost of steel. The disadvantage is that it is impossible to remove P, gas, and inclusion in the smelting process, so it is required to add clean, rust-free, oil-free steel with low P and suitable C content, and to prevent excessive suction of liquid steel during smelting.

Return oxygen blowing method: a large amount of alloy steel return material is added to the furnace charge. According to the theory that the affinity of C and O is greater than that of some alloy elements and o at a certain temperature when the temperature of molten steel rises to a certain temperature, oxygen is blown into the molten steel, so as to achieve the purpose of decarbonization, degassing and impurity removal, and at the same time, the oxidation loss of alloy elements in the steel can be avoided. This not only reduces the cost but also improves the quality.

Free send inquiry to stella@hanrm.com if any needs.

Whatsapp/Wechat:+8615877652925

Energy Saving and Emission Reduction in Steelmaking Production

More News You May Interesting:

Alkaline EAF( Electric Arc Furnace) Oxidation Smelting Process

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2021年2月21日星期日

Advantages of DC Arc Furnace

Electric arc furnace is a tool for steelmaking. Different kinds of electric arc furnaces have different steelmaking methods.

Electric arc furnace is a steelmaking electric arc furnace that uses DC power supply to supply electric energy. Like AC EAF, it uses the arc generated between electrode and charge (or molten pool) to generate heat, so as to achieve the purpose of melting, and can be used to melt steel or alloy.

Compared with the traditional AC EAF, the main advantages of DC EAF are as follows

(1) The results show that the arc is stable and concentrated, the bath is well stirred, the temperature distribution in the furnace is uniform, and the erosion of the furnace lining is less;

(2) The current and voltage fluctuations are small, the impact on the power grid is reduced, and the cable life is extended;

(3) The electrode consumption is 50% less than that of AC EAF. The performance of the DC electric arc furnace is better than that of the AC electric arc furnace, but it has been unable to obtain a high-power DC power supply, so it has not been developed for a long time.

With the application of thyristor technology, the manufacturing technology of high-power DC power supply equipment has been solved. So in the late 1970s, the metallurgical industry re-launched the research on DC electric arc furnace. By the early 1980s, the technical problems of DC electric arc furnace construction and use have been solved one by one. The world's first DC electric arc furnace was built and put into operation in 1982 at Bush steelworks in Germany. In the following, six or seven years, the United States, France, Italy, and Japan successively rebuilt or newly built their own DC electric arc furnaces, with capacities ranging from 30t to 60t. In 1989, the Tokyo Iron and Steel Company of Japan built the largest DC electric arc furnace with a capacity of 130t at that time. In recent years, many DC arc furnaces with capacity from 60t to 180t have been built and put into operation. In 1989, the first small DC electric arc furnace in China was developed and put into operation in Taiyuan machinery foundry. In the same year, a 2000kVA submerged arc DC electric arc furnace was put into operation in the Xuanhua ferroalloy plant to produce ferrosilicon, ferromanganese, calcium silicon, and other ferroalloys. Since the 1990s, more and more attention has been paid to DC EAF. Shanghai No.3 iron and steelworks, Changcheng iron and steelworks, Qiqihar iron and steelworks, Jiangyin Yanshan iron and steelworks, and Shanghai No.1 Iron and steelworks have successively introduced large DC EAF with a capacity of 80-100t. Baoshan Iron and steel (Group) Co., Ltd. imported a set of 150t DC EAF equipment with a double furnace shell (one power supply) from France.

There is only one electrode above the DC EAF, which is the negative electrode, and the bottom electrode is the positive electrode. Its power supply system is different from the AC arc furnace. It is equipped with a rectifier and reactor. Contacts are installed on the bottom of the furnace to form a current circuit. The maintenance and service life of the contacts are the key problems in the operation of the DC arc furnace. Generally, the copper plate is placed on the steel plate at the bottom of the furnace to facilitate conduction. Three layers of magnesia carbon bricks are laid on the copper plate, and then refractory materials are knotted on it.

Hani Tech is a Hot Rolling Mill manufacturing company working mainly in the area of the bar and wire rod mills, high-speed wire rod mills, high-speed rebar rolling mills, TMT rolling mills, flying shear, cold strip rolling mill, reheating furnace, induction furnace, intermediate frequency furnace, electric arc furnace, ladle refining furnace, blast furnace, continuous casting machine.

Free send inquiry to stella@hanrm.com if any needs.

Whatsapp/Wechat:+8615877652925

Website: https://www.hanrm.com

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