Comparison and Analysis of Long and Short Processes in Iron and Steel Industry

Comparison and Analysis of Long and Short Processes in Iron and Steel Industry

There are three processes in the production of iron and steel industry: blast furnace-converter process, electric arc furnace process, and special smelting. The blast furnace-converter process is also called the long process. The steel produced is called converter steel. It is molten iron with iron ore and coke as the main raw materials and then converter steel. The electric arc furnace process is called a short process, and the steel produced is called electric furnace steel, which is made from scrap steel as the main raw material.

Comparative Analysis of Process Technology

The converter process and electric arc furnace process are two main production processes in the iron and steel metallurgy industry. The main differences in steelmaking are as follows:

1) Main steel materials used are different. Converter steelmaking mainly uses molten iron as raw material and about 15% scrap steel. In recent years, the low price of scrap steel and high profit per ton of steel provides conditions for a high proportion of scrap steel used in converter steelmaking. The proportion of scrap steel consumption has been greatly increased, even up to 40%. However, there is insufficient heat in the converter. Solving the heat problem in the converter is the key to improving the scrap steel ratio. Electric arc furnace steelmaking is mainly based on scrap steel as raw material, and scrap steel substitutes such as hot metal (pig iron), direct reduction iron, decarburized granular iron, iron carbide, and composite metal material.

2) Main energy sources are different. Converter steelmaking is mainly physical and chemical heat of molten iron. Electric arc steelmaking is mainly physical heat of electric arc, physical and chemical heat of raw material, auxiliary chemical heat, and residual energy of recovered flue gas. Auxiliary chemical heat mainly refers to oxygen jet carbon powder and gas burner. The residual energy of flue gas includes physical heat and chemical heat of flue gas.

3) Main operating objectives are different. Converter steelmaking is a metallurgical operation to complete decarburization, dephosphorization, and temperature control within a given time, achieving hit of composition (carbon, phosphorus) and temperature; Electric arc furnace steelmaking is to complete heating, melting, and overheating of scrap steel in a given time under the condition of all scrap steel. In the case of adding hot metal and other scrap steel substitutes, there is also a requirement for partial decarburization. In addition, EAF steelmaking can control the composition and temperature separately.

4) The process development direction is different. Converter steelmaking mainly achieves a high efficiency of converter production through measures such as high-efficiency blowing technology to improve oxygen supply intensity, fully automatic blowing technology for carbon and temperature hitting rate, fast tapping technology for non-inverting tapping, off-furnace treatment, and hot metal pretreatment to relieve the metallurgical load of the converter, realizing cleanliness of products through close balance smelting process, high-efficiency dephosphorization process and slag retaining technology for steel tapping. Low-cost and negative-energy steelmaking can be realized by slag reduction and slag return, alloy element melting reduction (Cr, Mn) ore, water reduction for dry dedusting, residual heat recovery from gas, etc. Electric arc furnace steelmaking is mainly based on the enhanced energy supply (including enhanced power supply and auxiliary energy), environmentally friendly scrap steel preheating system, preheating scrap steel and water process, and increasing physical and chemical heat. Continuous smelting technology that can still be electrified without furnace cover and when steel tapping is adopted to effectively reduce non-energizing time, and flat-bath smelting technology with a large amount of steel retained about 50% or higher, so as to reduce the damage of arc radiation to refractory materials and reduce electrode consumption during the smelting process. The application of the above technology shortens the smelting cycle, realizes high-efficiency production of steel-making, and reduces energy consumption per ton of steel.

5) Differences in metallurgical quality. Residual elements in steel (Cu, Ni, Mo, As, Sb, Bi, Sn) are different. The content of residual elements in steel is high due to the repeated recycling of waste steel in electric arc furnaces. Nitrogen content in steel is different. High nitrogen content in steel is caused by air ionization in the arc zone and high nitrogen content in raw material. Although the electric arc furnace operates in a large amount of flat molten pool and is sealed for smelting, which is conducive to reducing nitrogen content, it is still unable to compare with the capacity of converter steelmaking to carry nitrogen removal by CO bubbles.

Comparison and Analysis of Steel-making Costs for Long and Short Processes

2.1 Cost Analysis of Steelmaking Process

For bar and wire smelting, the cost components of the LF process of the converter, electric arc furnace, and electric arc furnace (30% molten iron) include two parts, i.e. different cost items and the same cost items.

The different costs of different steelmaking processes are mainly manifested in the consumption of iron and steel material, electric energy of electric arc furnace, electrodes, refractories, lime, and other auxiliary materials, gas, cooling water, and energy recovery, especially consumption of iron and steel material, electric energy of electric arc furnace and electrodes. The differential cost of the LF process for converter, LF process for electric arc furnace, and LF process for electric arc furnace (30% molten iron) is 226.96 yuan/t, 3049.84 yuan/t, and 2819.30 yuan/t respectively.

The same cost for different steelmaking processes is 346.77 yuan/t, including alloy consumption, LF refining costs (power consumption, auxiliaries, ladle refractories, cooling water, fuel vapor), continuous casting costs, wages and benefits of personnel, manufacturing costs (depreciation, maintenance, freight and other) and spare parts.

Based on the above analysis, under the condition that the scrap steel price is 2400 yuan/t and the hot metal price is 1948 yuan/t, the steelmaking costs of three processes (converter LF, electric arc furnace LF and electric arc furnace LF (30% hot metal) are 2563.73 yuan/t, 3396.61 yuan/t, and 3166.07 yuan/t respectively.

Compared with the total cost of converter steelmaking, the total cost of electric arc furnace steelmaking increased by 832.88 yuan/t and 602.34 yuan/t respectively under the condition of total waste steel and 30% molten iron.

Compared with the total cost of converter steelmaking, under the condition of total scrap steel and 30% molten iron, the cost of steel material accounted for 54.58% and 50.72% of the total cost increase respectively. The electric consumption of electric arc furnace smelting accounts for 25.93% and 27.44% of the total cost increase respectively. Electrode consumption accounted for 17.17% and 16.44% of the total cost increase respectively, with other expenses remaining. The cost increase is mainly steel material cost and smelting power consumption cost, followed by electrode consumption cost. Steel scrap price plays a leading role in steel material cost. Under the condition that power consumption and electrode consumption are basically unchanged, electricity price and electrode price are the main factors affecting cost increase. Therefore, to reduce the cost of electric arc furnace steelmaking, we should mainly control the cost of scrap steel (yield and unit price matching), power consumption, and electrode price.

2.2 Effect of Scrap Steel Price on Steelmaking Cost of Different Processes

The influence of scrap steel price on the steelmaking cost of three different smelting processes is studied under the condition that other indexes and prices remain unchanged. The total cost of steelmaking in different smelting processes is subtracted from the cost of scrap steel, and the price of scrap steel is set as variable x to calculate the relationship between the cost of steelmaking and the price of scrap steel:

1) When the price of scrap steel is lower than 1373.73 yuan/t, the cost of LF process steelmaking of electric arc furnace (all scrap steel) is lower than that of LF process steelmaking of converter, and that of LF process steelmaking of electric arc furnace (30% molten iron) is lower.

2) When the scrap price is 1373.73-1494.95 yuan/t, the LF process of electric arc furnace (mixed with 30% hot metal) has a low cost of steelmaking, and the LF process of electric arc furnace (all scrap steel) has a slightly higher cost of steelmaking than that of converter LF process.

3) When the scrap price is more than 1494.95 yuan/t, the cost of converter LF process steelmaking is lower;

4) When the price of scrap steel is more than 1707.07 yuan/t, the LF process of electric arc furnace (30% hot metal) has a low cost of steelmaking. When the scrap price is lower than 1707.07 yuan/t, the LF process of electric arc furnace (all scrap steel) has a low cost of steelmaking, which means adding hot metal is not conducive to the reduction of steelmaking cost. Therefore, the lowest cost of the steelmaking process is mainly dependent on the scrap price.

2.3 Effect of Electricity Charge Price on Steelmaking Costs of Different Processes

When the price of scrap steel is 100,200,300,400,500,600 yuan/t lower than that of molten iron, the cost of smelting the whole scrap steel and 30% molten iron is the same as that of the converter steelmaking process. The electricity price used in the electric arc furnace is shown in Table 3. It can be seen from Table 3 that when the price of scrap steel is higher than 1648.00 yuan/t, the cost of electric arc furnace steelmaking must exceed that of converter steelmaking. When the scrap price is 1548.00 yuan/t and the electricity price is 0.44 yuan/kWh, the cost of all scrap electric arc furnace steelmaking is equal to that of converter steelmaking. The electricity price is 0.23 yuan/kWh, which is equivalent to the cost of converter steelmaking with a 30% ferroelectric arc furnace. If the scrap price is further reduced and the corresponding electric price can be slightly higher, the cost of converter steel and electric arc furnace steel can be guaranteed to be equal.

On the premise that the price of scrap steel equals the price of molten iron, i.e. when the price of scrap steel is 1948 yuan/t, the cost of electric arc furnace steelmaking is higher than that of converter steelmaking. From the total cost of steelmaking in different smelting processes in Table 1 and Table 2, subtract the cost of electricity consumption in each process, and then set the electric price as variable x. When the price of scrap steel is 500 yuan/t lower than that of hot metal, i.e. the price of scrap steel is 1448 yuan/t, the relationship between steel-making cost and the electric price is calculated (Figure 3). It can be seen from Figure 3 that when the price of electricity is higher than 0.68 yuan/kWh, the steel-making cost of the converter LF process is the lowest. Electric arc furnace (30% hot metal) LF process has the highest steelmaking cost. When the electricity price is reduced to 0.68 yuan/kWh and higher than 0.43 yuan/kWh, the LF process of electric arc furnace (scrap steel) has the lowest steelmaking cost, followed by converter LF, while the LF process of electric arc furnace (30% molten iron) still has the highest steelmaking cost. When the electricity price is lower than 0.43 yuan/kWh, the LF process of the converter has the highest steelmaking cost, followed by the LF process of electric arc furnace (30% hot metal) with the lowest steelmaking cost, and the LF process of electric arc furnace (all scrap steel) with the lowest steelmaking cost.

2.4 Effect of Electrode Price on Steelmaking Cost

Compared with the total cost of converter steelmaking, the total cost of electric arc furnace steelmaking (scrap steel, 30% hot metal for electric arc furnace) increased by 832.88 yuan/t and 602.34 yuan/t respectively. Based on the data in Table 1 and Table 2, the relationship between the total cost increase of EAF steelmaking (compared with converter steelmaking) and the electrode price is analyzed. For all scrap steel of electric arc furnace and 30% molten iron smelting cost increases by 13.00 yuan/t and 9 yuan/t respectively for every 10,000 yuan increase in electrode price.

Comparison and Analysis of Energy Consumption in Long-Process and Short-Process Steelmaking

The difference between the energy consumption of the long blast furnace-converter process and that of the short process is clarified.

1) Energy consumption of short process steelmaking in an electric furnace.

Under different conditions, the energy consumption of EAF short process steelmaking decreases significantly with the increase of hot charging molten iron ratio. Under the same conditions, the electric arc furnace without preheating and steam recovery have high energy consumption, followed by the waste steel reheating furnace and the lowest steam recovery process.

Using 15% pig iron with 85% waste steel and without preheating and steam recovery, the maximum energy consumption of the electric arc furnace smelting process is 90 kgce/t. The minimum energy consumption of the electric arc furnace smelting process with 50% hot iron and no preheating and steam recovery is 41 kgce/t.

2) Energy consumption of long blast furnace-converter process steelmaking.

Only consider the energy consumption of the blast furnace process is 390.63 (kgce/t).

For a 100t converter, the maximum energy consumption of the extraction process is -23.9 kgce/t.

The maximum energy consumption of the electric furnace procedure is 90 kgce/t.

Therefore, the energy consumption of long blast furnace-converter process steelmaking is much higher than that of short process steelmaking.

The main products of Hani Tech are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanmetallurgy.com/

                https://www.hanrm.com

Why doesn't the Water-cooled Cable Leak Electricity?

Why doesn't the Water-cooled Cable Leak Electricity?

Introduction to the Principle of Water-cooled Cables

Many devices will heat up after being used for a long time, and even cables will easily heat up if the current is large, and the occurrence of heat will affect normal work and service life.

Water-cooled cable is a kind of cable that uses water to cool down. Because of the problem of heating, the working strength and capacity of water-cooled cables are much higher than that of ordinary cables.

We all know that the water we see every day is conductive, so why doesn't the water-cooled cable leak electricity? What is the principle of water cooling cable?

 Water-cooled cable is a new type of cable. Its main feature is a hollow water passage. It is generally a special cable used in high-current heating equipment for medium-frequency and power-frequency high-current transmission. It usually consists of three parts: the outer sheath, the wire, and the electrode, that is, the cable head.

For ordinary water-cooled cables, the electrodes are welded with copper tubes and copper bars, which are not tightly connected to the equipment.

The wire is made of twisted copper bare wire, and the bending radius is large. The outer sheath is made of an ordinary rubber hose, which has low-pressure resistance. The sleeve and the electrode are fastened with ordinary clamps. The sealing performance is not very good, and it is easy to leak. Therefore, do not use water-cooled cables of poor quality. For water-cooled cables, the electrodes are made of integral copper rods by turning and milling, and the surface is also passivated or tinned.

The wire is made of tinned copper stranded wire or enameled wire, woven by a CNC winding machine, with a small bending radius and high flexibility. The outer sheath is a synthetic rubber tube with a reinforced interlayer, which has high-pressure resistance. Between the sleeve and the electrode is the copper clamp used, which is fastened by cold extrusion with professional equipment, has good sealing performance, and is not easy to leak.

Therefore, it is safer and more secure to use water-cooled cables.

The main products of Hani Tech are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

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

Email: stella@hanrm.com Or stellarollingmill@gmail.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanrm.com

Electric Arc Furnace Refining Furnace Conductive Arm

Electric Arc Furnace Refining Furnace Conductive Arm

The 75-ton horizontal feeding electric arc furnace conductive arm copper-steel composite conductive arm is a rectangular beam structure, which is welded by copper-steel composite plates. Due to the cancellation of the conductive copper tube and many insulation links on the traditional electrode arm, the structure is simplified, the conductive area is increased, the impedance value and maintenance workload can be greatly reduced, and it can be widely used in electric arc furnaces and LF ladle refining furnaces.

Characteristics and Composition of Conductive Arm of Electric Arc Furnace Refining Furnace

(1) The conductive arm is an indispensable part of the electrode lifting mechanism of modern electric arc furnaces. The conductive arm cancels the conductive copper tube structure so that the conductive arm can be used as both a supporting part and a conductive part, which simplifies the short-net structure. 

In terms of the arrangement, the conductive transverse arms of the two sides are symmetrically arranged relative to the conductive transverse arms of the middle phase.

The spacing should be as small as possible under the allowable conditions, which can reduce the size of the furnace structure, but the convenience of installation and adjustment of the column guide wheel must also be considered, so the size cannot be made too small. 

The elevation of the middle phase and the side phase is required according to the arrangement of the short grid, and the value of the elevation dimension is obtained from the calculation of the three-phase balance of the short grid. 

The advantages of using conductive arms are: high power input improves production efficiency; improves impedance and reactance indicators; good arc symmetry and stability, small pitch circle diameter, reduces refractory material consumption; Can be adjusted quickly without causing large system vibration; electrode arms are effectively cooled and insulated; maintenance effort is reduced. 

There are two types of conductive arms: copper-steel composite arms and aluminum alloy arms. Recently, copper-steel composite conductive arms are mostly domestic, and almost all of them are replaced by aluminum alloy arms in Japan. Especially since the DC power supply has no skin effect, the conductive arm of the copper-steel composite plate is not suitable. 

There are many advantages to using aluminum alloy conductive arms in a DC arc furnace. Due to the lightweight of the aluminum alloy arm, the speed and control performance of the electrode lifting and lowering are further improved.

Since vibration attenuation can improve the stability of the arc and increase the arc power, this is the reason for choosing the aluminum alloy arm. 

The conductive arm is an important part of the electric furnace. A good conductive arm should have the advantages of excellent electrical conductivity, good processability, the long service life of each component, and convenient inspection and replacement of wearing parts. The structure of the conductive arm is described by taking the edge-phase conductive arm as an example.

(2) The Composition of the Conductive Arm

The conductive arm is composed of an electrode spray ring, electrode hoop, electrode chuck, electrode soot blowing device, electrode clamping system, arms body, water inlet pipe, return water pipe, oil inlet pipe, Metal hose, water-cooled cable connection plate.

The Conductive Arm Body

(1) The Shape of the Conductive Arm

The conductive arm is generally a rectangular body whose height is greater than its width. 

The cooling methods include hollow interlayer water cooling and integral water cooling, and most of them are made of integral water cooling for the inner and outer interlayers. 

In the early stage of the invention of the conductive cross-arm, the internal and external shapes of the hollow interlayer water-cooled conductive cross-arm were designed to be rectangular. 

Due to the existence of welds, water leakage often occurs under high temperature and strong water pressure, and under the action of frequent up and down irregular movements and vibrations. 

Once internal water leakage occurs, it is not only difficult to find the leaking point, but also very difficult to find and repair the leaking point. 

Moreover, there is a magnetic field inside the cross arm, which also causes the seal of the electrode clamping cylinder installed inside the cross arm to be easily damaged due to overheating due to the presence of eddy currents. 

Later, the material was changed to solve the problems of oil leakage and eddy current. 

Service life is greatly improved and maintenance is reduced. The interior of the overall water-cooled conductive cross-arm is filled with cooling water. 

In order to make the cooling effect better, the cross-arm is made into upper and lower compartments. The cooling water enters from the lower layer and flows out from the upper layer.

(2) The Material of the Conductive Arm Body

The conductive arm material is made of a copper-steel composite plate: the outer layer is the copper plate, the inner layer is a steel plate, and the two are welded together by the explosion. 

The outer part of the conductive arm is usually made into a rectangle, the outer copper plate is used for conduction, and the inner steel plate is used as the support arm. 

Use a copper plate instead of a conductive copper pipe. It can greatly increase the conductive area, greatly reduce the reactance and resistance value, and increase the power by 3%-6%.

The main products of Hani Tech are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanmetallurgy.com/

                https://www.hanrm.com

Smelting Process of Steel and its Chemical Reaction Equation

Smelting Process of Steel and its Chemical Reaction Equation

Steel-making begins with iron. Steel comes from iron. Pig iron produced by smelting with iron ore has a high carbon content (>2.08%) and contains many impurities (such as silicon, manganese, phosphorus, sulfur, etc.). As a result, pig iron lacks plasticity and toughness, and its mechanical properties are poor. Besides melt casting, it can not be processed under pressure, which limits its use.

In order to overcome these shortcomings of pig iron and make it play a more important role in the industry, it is also necessary to use various sources of oxygen at high temperatures to remove impurities to a certain extent in order to obtain a certain composition and quality of iron-carbon alloy - steel. This method of removing impurities from pig iron by oxidation at high temperatures is called steelmaking.

Basic Principles of Steelmaking

Various impurities in pig iron have a strong affinity with oxygen to varying degrees at high temperatures. They can therefore be oxidized into liquid, solid, or gas oxides, which act at high temperatures with the lining and the flux added into the furnace, combine to form slag, and are removed from the furnace when slag is scraped, and CO is carried out when the molten steel boils.

In the steel-making furnace, the oxidation of impurities is mainly realized by the presence of FeO.

2Fe＋O2→2FeO

2Fe+O2_2FeO

Oxidation of Silicon

Silicon has a strong affinity to oxygen, so it oxidizes very quickly and is completely oxidized at the beginning of smelting to produce SiO2:

>>Si+2FeO→SiO2+2Fe

>Si+2FeO_SiO2+2Fe

At the same time, SiO2 reacts with FeO to form silicates:

>>2FeO+SiO2→2FeO·SiO2

>2FeO+SiO2_2FeO.SiO2

This salt is an important part of slag. It reacts with CaO to form stable compounds 2CaO SiO2 and FeO, which are firmly present in the slag, while the latter becomes free in the slag and increases the content of FeO in the slag. It is advantageous to promote the oxidation of impurities. The reaction is as follows:

>>2FeO·SiO2+2CaO→2CaO·SiO2+2FeO

>2FeO.SiO2+2CaO_2CaO.SiO2+2FeO

Oxidation of Manganese

Manganese is also an oxidizable element. The MnO produced by it has a higher melting point. MnO is not soluble in metal solution, but it floats on the liquid metal surface with SiO2 forming compounds and forms part of the slag.

>>Mn+FeO→MnO+Fe

>Mn+FeO_MnO+Fe

>>2MnO+SiO2→2MnO·SiO2

>2MnO+SiO2_2MnO.SiO2

The oxidation of silicon and manganese emits a great deal of heat, which can rapidly increase the furnace temperature (which is particularly important for converter steelmaking) and greatly accelerate the oxidation of carbon.

Oxidation of Carbon

Carbon oxidation takes up a lot of heat energy and must be carried out at higher temperatures. The oxidation of carbon is also an important reaction in steel-making:

>>C+FeO→CO+Fe

>C+FeO_CO+Fe

Because CO gas is produced when carbon is oxidized, it has a strong stirring effect when escaping from liquid metals, which is called boiling. The results of boiling can promote the uniformity of composition and temperature of the molten pool, accelerate the reaction between metal and slag, and also facilitate the removal of gas and inclusions in the steel.

Oxidation of Phosphorus Element 

Oxidation of phosphorus can take place at relatively low temperatures. The dephosphorization process is a combination of several reactions, the following reactions:

>>2P+5FeO→P2O5+5Fe

>2P+5FeO_P2O5+5Fe

>>P2O5+3FeO→3FeO·P2O5

>P2O5+3FeO_3FeO.P2O5

The following reactions occur when sufficient CaO is present in the alkaline slag:

>>3FeO·P2O5+4CaO→4CaO·P2O5+3FeO

>3FeO.P2O5+4CaO_4CaO.P2O5+3FeO

The resulting 4CaO.P2O5 is a stable compound that remains firmly in the slag and thus achieves the purpose of dephosphorization.

It must be noticed that iron silicate and ferromanganese etc. are added to the deoxidizing process of molten steel. As a result, slag often becomes acidic after deoxidizing, which destroys 3FeO.P2O5, from which P2O5 is reduced, while P2O5 is an unstable oxide, which is easily reduced by carbon and results in phosphorus return at high temperature. This also shows that it is very difficult to remove phosphorus in acid furnaces. In order to prevent this phenomenon, it is necessary to properly increase the alkalinity and quantity of slag and improve the oxidation of slag.

Oxidation of Sulfur

Sulfur is present in the form of FeS. Sulfur can also be removed when there is enough CaO in the slag as follows:

>>FeS+CaO→CaS+FeO

>FeS+CaO_CaS+FeO

The resulting CaS is not soluble in the molten steel, but slag floats on the surface of the molten steel.

The above reaction is reversible and takes place in the slag containing FeO. When FeO reacts with CaS, sulfur will return to the molten steel, so the desulfurization efficiency will increase with the decrease of FeO content in the slag. When there is enough carbon in the residue, the reaction is different:

>>CaO+FeS+C→CaS+Fe+CO

>CaO+FeS+C_CaS+Fe+CO

Because carbon robs oxygen from FeO and loses the possibility of interaction between CaS and FeO, the reaction can not be reversed, which is why desulfurization in electric furnace steelmaking is more complete than in the other two methods.

Manganese also plays a role in promoting desulfurization during the desulfurization process as follows:

>>FeS+MnO→MnS+FeO

>FeS+MnO_MnS+FeO

The resulting MnS is almost insoluble in molten steel and enters the slag. Therefore, desulfurization increases with the oxidation of manganese.

Deoxygenation of FeO

After the above series of oxidation reactions, although the impurities have been oxidized to achieve the purpose of removal, also because of the oxidation result, there is more FeO in the steel water, which means that there is a lot of oxygen in the steel water, bringing great harm to the steel, on the one hand, steel with a lot of air bubbles; On the other hand, it also causes hot and cold brittleness of steel, and the hazard increases with the increase of carbon content.

Therefore, at the end of the steelmaking process, it is also necessary to try to remove a lot of oxygen from the molten steel. The usual method is to add some deoxidizers such as ferromanganese, ferrosilicon, and aluminum to the molten steel. They strongly take oxygen from FeO to achieve the purpose of deoxidation. The reaction is as follows:

FeO+Mn→MnO+Fe

FeO+Mn_MnO+Fe

2FeO+Si→SiO2+2Fe

2FeO+Si_SiO2+2Fe

3FeO+2Al→Al2O3+3Fe

3FeO+2Al_Al2O3+3Fe

Effect of Slag

The whole steelmaking process consists of oxidation and reduction processes. Oxygenation of carbon, silicon, manganese, and phosphorus is usually called a reaction in the oxidation period and desulfurization and deoxidation are called reactions in the reduction period. As can be seen from the above reaction formulas, many factors must be considered in order to remove impurities from metals, but the most important ones are slagging and slag removal.

Slag Plays the Following Important Roles in Steelmaking:

(1) Slag shall ensure that the steelmaking process is carried out in a certain reaction direction (oxidation or reduction).

(2) Slag shall ensure the maximum removal of harmful impurities (phosphorus and sulfur) from metal and the prevention of gas (nitrogen and hydrogen) from furnace gas entering metal.

(3) Slag shall ensure minimal loss of iron and other valuable elements during operation.

Basic Methods of Steelmaking

1. Converter Steelmaking

Converter steelmaking is a steelmaking method that uses air or oxygen to oxidize elements in molten iron to specified limits by bottom, side, and top blowing, so as to obtain qualified steels.

2. Electric Furnace Steelmaking

Electric furnaces are steelmaking by converting electrical energy into thermal energy. There are two types of electric furnaces commonly used: electric arc furnaces and induction furnaces. The electric arc furnace is widely used and suitable for smelting high-quality steel and alloy steel. Induction furnaces are used for smelting high-grade alloy steels and non-ferrous alloys.

3. Open-hearth Steelmaking

With the development of industry, a large amount of scrap steel has accumulated in the metal processing industry. At that time it could not be converted back into steel, so steelmaking workers were looking for a method of making steel from scrap steel. Open-hearth steelmaking was invented by Martin in France in 1864.

The rapid development of oxygen top-blown converter steelmaking will replace open-hearth steelmaking. Oxygen top-blown converter and electric furnace are the main new steelmaking workshops in China.

With the progress of science and technology, new steel-making methods, such as vacuum treatment of molten steel, electro slag furnace smelting, and vacuum induction furnace smelting, have been used more and more.

The Casting of Steel Ingots

The molten steel obtained from the steelmaking furnace must be shaped into ingots for subsequent processing (rolling and pressing). This kind of ingot, which is in the middle of the molten steel and the steel from the factory, is called the ingot. The ingot is solidified by pouring molten steel (molten steel) into the mold through a ladle (also called a ladle).

The process of ingot casting by casting is abbreviated as ingot or die casting. The process of billet casting by continuous casting steel method is abbreviated as continuous casting.

Die Casting Process

First transfer the molten steel in the steelmaking furnace into the ladle, then lift the ladle over the ingot mold, and then pour the molten steel into one or more ingot molds intermittently. After the molten steel solidifies, the ingot is demoulded. After demolding, the ingot is cut to the end and sent to the heating furnace for heating. At last, the steel embryo is obtained by one or more initial rolling embryos.

The steel ingots used for bar and profile production are usually square sections (called square ingots). The steel ingots for plate production are generally rectangular sections (called flat ingots). The steel ingots for forging and pressing are square, round, and polygonal.

The ingot casting process is accompanied by various physical and chemical phenomena, such as heat conduction, volume shrinkage, liquid steel flow, carbon and oxygen reaction, component segregation, etc. This results in different crystalline structures and component distributions.

In the process of ingot casting, various defects will occur due to improper operation, improper injection speed, and improper temperature control. Common defects are ingot surface scarring, heavy skin, longitudinal and transverse cracks, internal residual shrinkage holes, subcutaneous bubbles, looseness and segregation, inclusions caused by refractories and slag, and dust mixed in steel, etc. These defects can greatly reduce the billet yield of the ingot and even scrap the entire ingot.

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

Email: stella@hanrm.com Or stellarollingmill@gmail.com

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Reactive Power Compensation for Submerged Arc Furnace

Reactive Power Compensation for Submerged Arc Furnace

---To Achieve The Purpose of Energy-saving and Efficiency

In the metallurgical industry, the high-energy submerged arc furnace has the characteristics of low voltage and high current, and the power factor is generally low, and the power factor is one of the important indicators of the overall electrical performance of the submerged arc furnace and is the main factor affecting the daily output and power consumption. 

Implementing reactive power compensation for the submerged arc furnace can improve the power factor and achieve the purpose of saving energy and increasing efficiency.

Scope of Application of the System

The reactive power compensation system of the submerged arc furnace is suitable for the submerged arc furnace of the ferroalloy system and the calcium carbide furnace of the chemical system. It can be used as auxiliary equipment for the electric furnace to improve the power factor and release the production capacity.

Composition and Appearance of Reactive Power Compensation System

The low voltage compensation system includes:

Compensation capacitor cabinet: built-in low-voltage compensation capacitor and special switching switch, etc.

High-current short-circuits: A reactive power compensation high-current short-circuit system connected to capacitors.

Automatic control cabinet: automatic measurement of compensation system, automatic switching, automatic control device.

Description of the Function and Effect of Adding Reactive Power Compensation

1. Improve power factor, increase active power, increase output, and improve furnace conditions.

2. Most of the furnace transformers are overloaded for a long time. After adding compensation, the furnace transformer can increase production by 8-10% without overloading. It reduces the vibration and noise of the furnace transformer and short net and improves the operating life of the main equipment.

3. Reduce the high-voltage line loss, and improve the primary voltage and electrode voltage. The electric furnace can still operate normally when the system voltage is low.

4. The influence of harmonics is reduced, the electrical parameters of the system are improved, and the power quality is improved.

5. Avoid electricity fines due to low power factor.

6. The compensation device controlled by a microcomputer can automatically print the daily report, automatically count the power failure time, automatically calculate and print the active and reactive power, and improve the management and operation level of the electric furnace.

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 mills, reheating furnaces, induction furnaces, intermediate frequency furnace, electric arc furnace, ladle refining furnace, blast furnace, continuous casting machine. 

Hani is the one-stop supplier able to design, manufacture, install and commission your hot rolling mill plant from A to Z.

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

Email: stella@hanrm.com Or stellarollingmill@gmail.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanrm.com

What is the difference between DC arc and AC arc?

What is the difference between DC Arc and AC Arc?

Recently, we received a message from some friends in the background asking about the difference between the DC arc and the AC arc. We believe that this is a common problem, and it is worth raising it separately for everyone to answer.  

The DC electric arc furnace has only one electrode, the negative electrode and the positive electrode. Its power supply system is different from that of the AC arc furnace.

(Alternating current arc) An arcing discharge between an analysis gap using alternating current. According to the voltage level, it is divided into high-voltage AC arc and low-voltage AC arc.

The former has a working voltage of 2~4kV, which can be used for direct arc ignition. The device is complicated and the operation is dangerous, so it is rarely used. Qualitative and quantitative analysis of trace elements in various materials, and quantitative analysis of low-content elements in metals and alloys.

  

Generally speaking, the voltage fluctuation and flicker produced by the DC electric arc furnace is half of that of the AC electric arc furnace of the same capacity. Compared with the traditional AC electric arc furnace, the main features of the DC electric arc furnace are:

(1) The DC arc does not pass through the zero point, and there is no periodic ignition and extinguishing phenomenon, so the arc is stable.  

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

(3) The electrode loss is less, 50% less than that of the AC electric arc furnace. However, it has been limited to the DC power supply that cannot obtain high power, which has also caused it to fail to develop by leaps and bounds.

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 mills, reheating furnaces, induction furnaces, intermediate frequency furnace, electric arc furnace, ladle refining furnace, blast furnace, continuous casting machine. 

Hani is the one-stop supplier able to design, manufacture, install and commission your hot rolling mill plant from A to Z.

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

Email: stella@hanrm.com Or stellarollingmill@gmail.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanrm.com

Electric Arc Furnace for Sale

Electric Arc Furnace for Sale

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 mills, reheating furnaces, induction furnaces, intermediate frequency furnace, electric arc furnace, ladle refining furnace, blast furnace, continuous casting machine. 

Hani is the one-stop supplier able to design, manufacture, install and commission your hot rolling mill plant from A to Z.

 

We can also design, manufacture and revamp, upgrade your rolling mill plant according to your requirements. 

Upgrading your existing Bar and Wire Rod mills, to increase production and improve efficiency and product quality, is our specialization.

Our Rolling Mill Machinery not only has a ready installed in the domestic market but is also exported to Iran, Ethiopia, Kazakhstan, Thailand, Vietnam, Indonesia, India, Myanmar, and other countries and regions.

EAF Equipment Composition for Sale

Serial number	Name and Specification	Unit	Number
1	Furnace body unit (inner diameter of shell Ø3700mm）	set	1
2	Water-cooled furnace roof	set	1
3	Dump mechanism	set	1
4	Dump cylinder	set	1
5	Rotary frame and furnace cover lifting device	set	1
6	Rotating mechanism	set	1
7	Rotating base frame	set	1
8	Guide wheel device	set	12
9	Conductive Arm	set	3
10	Lifting column	piece	3
11	Column connection device	set	3
12	Electrode lifting cylinder	piece	3
13	Cooling water system	set	1
14	Hydraulic system	set	1
15	Soft connection compensator (T2 material)	set	6
16	Conductive copper tube (T2 material)	piece	6
17	Water-cooled cable (T2 material)	piece	6
18	Short mesh support (stainless steel)	set	1
20	High Voltage Switchgear (GG1A-10KV)	set	1
21	Transformer (10000KVA/10KV)	set	1
22	Low Voltage Power Supply and Distribution System	set	1
23	Automatic system	set	1

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

Email: stella@hanrm.com Or stellarollingmill@gmail.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanrm.com

How is Steel Made? - Converter Furnace and Open Hearth Furnace

How is Steel Made? - Converter Furnace and Open Hearth Furnace

In the last issue, we talked about the changes in cast iron smelting furnaces. In fact, cast iron is not easy to process. Before the Industrial Revolution, people tended to use pure iron, and the pure iron at this time was generally forged iron. The use of pure iron is very rare these days because people have found a better material, which is carbon steel.

The difference between cast iron and carbon steel is the carbon content. Generally speaking, cast iron has high carbon content and steel has low carbon content. The process of changing from cast iron to steel involves later converters and open hearths. Let's take a look at this process.

In fact, there are actually two routes from iron to steel. One is to start with cast iron. Since cast iron has a high carbon content, we can find a way to reduce the carbon content of cast iron. Another is to start from pure iron and obtain steel by increasing the carbon content in pure iron.

In fact, since pure iron was first used in the West, the latter route was the first in the attempt to make steel. This route is a forging and heat treatment route. In fact, in the forging of iron, due to the different carbon content of the iron block itself, coupled with the changes in the manufacturing and heat treatment process, during the long Iron Age, human beings can make it by accident. Steel. Of course, at that time, human beings did not realize the influence of carbon content on the strength of iron-based alloys, so whether or not steel can be made depended entirely on personality and experience.

This ancient smelting has a bit of metaphysical meaning like the compound crystallization made today. In order to smelt a ferroalloy with better strength, the ancients also prayed to gods and worshipped Buddha, and they used everything and even sacrificed swords. In fact, those famous swords in ancient times should be carbon steel from today's point of view.

Historically, the first steel produced on a conscious scale was the so-called Damascus steel. Similar to the fact that Arabic numerals were not invented by the Arabs, Damascus steel actually originated in India. 

Due to the characteristics of oriental smelting technology, the preparation method of this steel takes the route of starting from cast iron.

 The Indians first made cast iron, then heated and cooled it repeatedly to reduce the carbon content, and finally obtained steel with a carbon content of 1.5%, which is actually cast steel. 

Damascus steel was adopted by the Arabs as an excellent weapon and gradually spread to Europe. This is probably in the 7th century AD.

Damascus steel is civilized because of its unique pattern, but in fact, this is due to the lack of smelting technology. The cast steel smelted by the Indians is called Uzi steel, and the Arabs buy steel ingots from the Indians and then use them to make weapons. Because the carbon content of Uzi steel varies greatly, different steel ingots are repeatedly folded and forged, resulting in random patterns on the surface of the weapon.

In Europe in the Middle Ages, because they had not yet mastered cast iron technology, they used another process to make steel, that is, carburizing. On the basis of pig iron, carbon was added during forging to form steel, which is similar to today's low-carbon steel. Steel composition is close. Of course, making steel is very expensive. The price of steel was very high back then. Therefore, on many weapons, only the blade part is steel, and the other parts are iron.

It can be seen that before the Industrial Revolution, the efficiency of steelmaking was very low, and both forging and carburizing were intermittent operations, which could not be carried out with continuous output. All this changed during the industrial revolution. During the industrial revolution, the steelmaking furnace evolved from a stirring furnace to an open hearth, and the converter completely created the current iron and steel industry.

Let's first talk about the traditional stirring method, which uses a coke oven to make iron. Iron generally contains 1% silicon. In order to further obtain steel, it needs to be refined. 

Generally speaking, refining is divided into two parts, one is to oxidize silicon. , the second step oxidizes the carbon in the iron. In this process, the furnace shape originally used by humans was a reverberatory kneading furnace. Through this process, the carbon content of steel can be controlled at about 0.5%-1.2%. This technology has matured in 1850, and the melting temperature of the stirring furnace can reach 1400 °C.

The picture shows a reverberatory kneading furnace in the 18th century. Iron blocks were added to the furnace, and the combustion of charcoal was used to form a high temperature in the furnace. The air enters in two parts. The hot air enters from the air duct, which is used for charcoal combustion. There is also a cold air junction at the top of the furnace. After the cold air enters, it acts as an oxidizing medium to oxidize silicon and carbon in the cast iron. However, as the iron is purified, the melting point increases, causing the molten iron to have a tendency to solidify, so manual stirring is required, so it is called a stirring furnace.

On the basis of the stirring furnace, the current open hearth is formed by adding heat storage technology. Heat storage technology was first proposed by the Siemens brothers in Germany in 1856 (these two Siemens are not the Siemens we are familiar with).

The so-called heat storage is to use a part of the heat storage body, generally a silicate-free material, to realize the heat exchange between the furnace gas and the hot air, and save the energy consumption of the hot air. Due to the limitation of the temperature resistance of the heat storage material, the heat storage technology was first applied to the glass. Industrially, because the melting temperature of the glass is not high. But around 1867, this technology was used by the French Martin Martin for steelmaking, and finally evolved into the current open hearth. Due to the use of regenerators for heat exchange, the temperature of the open hearth can reach about 1700 ° C, which has reached the temperature of steel. Therefore, the open-hearth furnace no longer needs to be stirred, and it is also possible to smelt steel with lower carbon content.

This is the structure of the Martin-Siemens open-hearth furnace. The four grids below are the regenerators, which are grouped in pairs. The flue gas in the furnace is first heated by the first group of regenerators, but after the temperature of the regenerators reaches the requirement Pass the flue gas in the furnace into another group of regenerators. At this time, the air passes through the heated regenerator, the air is preheated, and the regenerator is cooled. Then switch to the gas furnace, repeat the above process, and indirectly use the flue gas to exchange heat with the air.

Almost at the same time, another method of steelmaking began to spread, and it is still in use today, that is, converter steelmaking.

Converter steelmaking is a very interesting subject, and here we analyze the process from the perspective of reaction engineering. First of all, let's do a heat calculation. There are two sources of heat input in this system: fuel combustion and exothermic reaction, and the other is oxidation reaction because the reaction between air and carbon is a process of releasing heat. What are the uses of this heat, the first is the heat required for the melting of iron blocks, and the other is the heat of air heating and furnace heat dissipation. Then the idea comes, if we increase the rate of the oxidation reaction, the heat release per unit time can be increased, and can we use less fuel?

The British at that time had this idea. They thought this way. In the early days, we all blew air directly into the container. The airflow can only react with the carbon on the surface of the molten iron, so the reaction rate is very slow. If the blowing tube can be inserted into the molten iron and bubbled in the molten iron, the reaction rate will be greatly accelerated.

The earliest experimental converter is called the bottom-blown air converter with today's viewpoint. After the air is compressed to 0.7-1bar, it is blown in from the bottom distributor, and the molten iron is stirred for reaction. Due to the violent reaction, the smelting time is only 1h.

The converter steelmaking experiment was conducted under the direction of Bessemer in 1856. The result was incredible. Due to the accelerated oxidation rate, the temperature of the molten iron could be maintained without the need for an external heat source. Danger. This experiment proves that without heating, as long as the steel contains enough carbon, it can be directly ventilated, and the heat generated by the direct reaction between the air and the carbon in the molten iron can be used to maintain the high temperature in the furnace. The temperature of the converter can easily reach 1600°C, which exceeds the melting point of the steel, so the steel can always be guaranteed to become liquid in the furnace during the smelting process. Compared with the kneading method, there is no need to stir, and the whole is more convenient, so it has a great response once it occurs.

Of course, in the early stage, there were some problems in converter steelmaking, and it did not completely replace the churning method. Therefore, the stirring method and the converter steelmaking have coexisted for more than ten years in history, but after 1880, the converter steelmaking has basically completed the replacement of the stirring method.

Later, with the advancement of electrical technology, new furnace types such as electric furnaces and induction furnaces appeared, and new technologies such as lasers also joined the smelting industry. Due to the emergence of these technologies, we can smelt more materials, and human beings have also ushered in Since the 20th century, the development of material technology has been blowout.

The main products of Hani Tech are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanmetallurgy.com/

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