2022年8月30日星期二

Vertical Semi-continuous Casting

Vertical Semi-continuous Casting

Vertical Semi-continuous Casting

The semi-continuous casting method can be divided into horizontal and vertical semi-continuous casting according to the operation mode of the slab.

Regardless of the horizontal or vertical semi-continuous casting method, in order to achieve a continuous and stable solidification and crystallization process, the total heat brought by the melt into the mold per unit time must be kept with the heat lost to the space through cooling channels such as mold and cooling water. Balance, otherwise, the normal process will be disrupted. The process characteristics of horizontal or vertical semi-continuous casting are:

(1) The reasonable configuration between the pouring system and the crystallization during the ingot casting process reduces the splash and disturbance of the metal liquid, and prevents the mixing of harmful substances such as oxide film and slag inclusion;

(2) The molten metal can be continuously and stably injected into the mold, so a lower pouring temperature can be used for casting, which is conducive to eliminating the pores and loose defects of the ingot;

(3) Using water as the cooling medium, the solidification and crystallization of the ingot is completed under extremely strong subcooling conditions. The ingot has a dense crystalline structure, and because the crystallization always maintains the order of crystallization, it has obvious directionality, which is conducive to removing Shrinkage and shrinkage defects;

(4) The length of the ingot is long, and it can be cut reasonably according to the process requirements of the processing workshop, which can reduce the loss of the cutting head and the cutting tail.

(5) The ingot casting method with the same pig iron mold is better than the working conditions. 


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2022年8月26日星期五

What is the Function of an Electric Arc?

electric arc

What is the Function of an Electric Arc?

The electric arc is a gas discharge phenomenon, an instantaneous spark created by the passage of an electric current through some insulating medium, such as air. The electric arc is self-sustaining gas conduction (electrical conduction in an ionized gas), and most of its charge carriers are electrons generated by primary electron emission. Electrons escape from the metal surface of the contact due to primary electron emission (thermionic emission, field emission, or photoemission), and gas atoms or molecules in the gap will generate electrons and ions due to ionization (collision ionization, photoionization, and thermal ionization). In addition, the bombardment of the emitting surface with electrons or ions can in turn cause secondary electron emission. When the ion concentration in the gap is large enough, the gap is electrically broken down and an arc occurs.

Conditions under which arcing occurs

1. The occurrence of arc when the circuit is broken

When the contacts begin to separate, the contact pressure acting between them will decrease, the contact area will also shrink, and the contact resistance and heat released in the contacts will increase. Heat is concentrated in a small volume, and the metal is heated to high temperatures and melted. A liquid metal bridge is formed between the contacts, and finally, the metal bridge is pulled apart, creating a transitional or stable arc between the contacts. If the discharge is stable, it is called breaking the arc. Discharge stability is related to many factors, such as the current being interrupted, the characteristics of the contact circuit, the speed of contact separation, etc. In order for the arc to ignite, a certain minimum current value is required.

2. The occurrence of arc when the contacts are closed

3. Breakdown of vacuum and gas gap

4. The transition from glow discharge to arc discharge

5. The transition from spark discharge to arc discharge

Classification 

Arc Spray Metal Anticorrosion

(1) According to the type of current, it can be divided into AC arc, DC arc, and pulse arc. 

(2) According to the state of the arc, it can be divided into the free arc and compression arc (such as the plasma arc).

(3) According to the electrode material, can be divided into melting electrode arc and non-melting electrode arc.

Functions

It has strong electrical conductivity, concentrated energy, high temperature, high brightness, lightweight, volatility, etc. 

The electric arc can be used as an intense light source such as an arc lamp, an ultraviolet source such as a sun lamp, or an intense heat source such as an electric arc furnace.

The arc has a thermal effect.



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2022年8月23日星期二

Control and Application of Electrodes for LF Refining Furnace

Electrodes for LF Refining Furnace

Control and Application of Electrodes for LF Refining Furnace


As a widely used out-of-furnace refining equipment, the LF ladle refining furnace takes the electrode regulator as the core and needs to realize reasonable control of the electrode position in order to keep the arc length constant. However, at present, affected by various factors such as feeding, argon blowing, and stirring, the arc length is prone to change, resulting in a change in the arc power, which not only impacts the power grid but also causes excessive electrode loss. Therefore, the research on the electrode control strategy of LF ladle refining furnaces should also be strengthened in order to make the equipment run stably.

1. Electrode control requirements of LF ladle refining furnace

In terms of production control of the LF ladle refining furnace, only by keeping the input power in the furnace constant can the arc length be kept constant. In the arc collection, it is necessary to use the constant impedance constant factor to realize the input power control. However, in actual production, the temperature in the furnace will continue to change, the ratio of arc voltage to current is not fixed, and the constant impedance adjustment will produce deviations, resulting in the arc voltage failing to meet the control requirements. Using the electrode adjuster, the electrode position can be adjusted, so that the ratio of arc current and voltage can be adjusted, and the arc length control can be enhanced by adjusting the arc power. With the electrode regulator, the arc gap length of each electrode needs to be adjusted to ensure a safe distance between the electrode and the molten steel and to determine the best working point for arc heating. At this stage, the PID control method is mostly used for electrode adjustment control, which can observe the deviation signal through proportional adjustment, reduce the error by controlling the input and output error signals, and optimize the dynamic characteristics of the regulator. However, in practical applications, the electrode regulator is time-varying and cannot meet the electrode control requirements in most cases.

2. Electrode control problem of LF ladle refining furnace

At present, there are three main problems in the electrode control of the LF ladle refining furnace. First of all, under the condition of high arc temperature, the electrode will sublime, resulting in large end face consumption. Due to the low pre-arc temperature and thermal stress, the slag-liquid contact surface in the electrode end is prone to decompose, resulting in excessive current fluctuations, resulting in excessive current density, resulting in unbalanced stress at the end, and prone to end face peeling. Second, the problem of oxidative depletion occurs on the surface of the cylinder on the side of the electrode. During normal operation, the pressure in the furnace remains stable, and a chemical reaction occurs between the electrode surface and the circuit. When the temperature reaches 400 °C, the surface of the electrode will be penetrated due to oxidation, and the problem of surface area oxidation will occur. Furthermore, the electrodes are prone to breakage and consumption. Under the action of the electrode column, the highest joint and joint seat position will break. Because the joint between the electrodes is not tightened tightly, small cracks will appear, which will lead to contact resistance between the electrodes, resulting in local overheating of the connection position, which affects the thermal insulation performance of the refining furnace. At the same time as the breaking consumption occurs, there will be a three-phase current imbalance problem, causing the electrode to face the risk of high-risk fracture. The occurrence of low-level breakage is related to the loosening of the butt joint, and the electrode is easy to fall into the molten pool, resulting in the occurrence of carbon increase problems.

3. Electrode control strategy of LF ladle refining furnace

3.1 Electrode regulation control strategy

Combined with the requirements of electrode adjustment control, a PLC adjustment system equipped with switch and analog input and output templates can be used to realize current and voltage signal adjustment control, and control the input and output of related switch quantities. In the electrode lift adjustment, it is necessary to complete the setting of the proportional coefficient of the independent impedance controller, and use the PI control algorithm to achieve automatic adjustment to achieve the goal of automatically adjusting the electrode impedance. On the secondary side of the transformer, the voltage detection box can be connected to detect the arc voltage, and the standard signal can be obtained by converting the voltage transformer. The neutral point of the transformer can be set at the intersection center point of the contact position between the wheel of the ladle car and the rail, and the detection box can be connected by a cable. Using the system "power circle diagram" tool, it can realize the calculation of the best working point of each gear. The operating point is located on the tap curve of the transformer, and the tap changer can be used for gear switching, and the operating point on the tapping circle is determined according to the power factor and the intersection of the power curve to adapt to different operating conditions.

3.2 Electrode protection control strategy

In terms of electrode control of LF ladle refining furnaces, various protection control strategies need to be adopted. First of all, it is necessary to implement overcurrent protection. When the arc current is detected and found that the arc current exceeds the maximum set value, the system overcurrent protection function is used to realize the simultaneous emergency lifting of the three-phase electrodes. When the arc current fed back by the electrode is larger, the lifting speed is also faster. In the current detection, there is a difference between the limit value and the arc current, and the PI regulator needs to be used for the integral calculation to realize the output limit and ensure that the three-phase electrodes are in a reasonable motion state. Through the statistical analysis, the maximum three-phase electrode current can be determined, which is used to realize overcurrent control and avoid the overload problem of the electrode. Secondly, it is necessary to strengthen the electrode short-circuit protection. When the impedance is lower than the minimum set value and exceeds the protection time, the short-circuit control function needs to be automatically turned on.

3.3 Electrode monitoring management strategy

Using the pressure transmitter, the pressure value in the hydraulic cylinder can be converted into a standard signal to realize PLC chain control. When the steel slag is crusted on the molten steel surface, the electrode cannot be lowered, and the pressure of the hydraulic cylinder continues to drop, which easily causes the electrode to break. When the adjustment system detects that the pressure of a certain phase is lower than the set alarm value, the control electrode is quickly raised, and then the arc is dropped again. If the arc is unsuccessful three consecutive times, the system will raise the three-phase electrode to a high position, and then issue an audible and visual alarm that the electrode is in contact with a non-conductive object. During system operation, screen monitoring and analysis need to be implemented. Combined with the system monitoring data and display status, the setting of parameters such as transformer gear and voltage value can be completed, so that the automatic and manual status switching can be completed when the current reaches the maximum. According to the fault problems prompted by the screen, the system report data analysis can be realized, which can optimize the system operating properly. If the power transmission gear is optimized, a small current is used to preheat the cold electrode for the first power transmission to reduce the thermal shock and fall off of the electrode surface.

4. Conclusion

To sum up, in terms of electrode control of the LF ladle refining furnace, it is necessary to strengthen the control of electrode lift adjustment. The use of a complete set of PLC control systems can effectively control the arc length in each smelting stage, and successfully shorten the arc stabilization time in the arcing stage. Adopting corresponding protection and control strategies can strengthen various protections such as electrode overcurrent protection and short-circuit protection, reduce the loss of electrodes, and avoid electrode breakage through monitoring and management, thereby improving the service life and efficiency of the equipment.


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2022年8月18日星期四

Ladle Furnace Refractory

Ladle Furnace Refractory


Ladle Furnace Refractory


Ladle furnace, called LF furnace, is currently the most widely used out-of-furnace refining equipment. The LF furnace strengthens the thermodynamic and kinetic conditions of the metallurgical reaction by means of arc heating, reducing the atmosphere in the furnace, white slag refining, gas stirring, etc., so that the molten steel can achieve deoxidation, desulfurization, alloying, heating, and other refining effects in a short time. Ensure that the composition of molten steel is accurate, the temperature is uniform, and the inclusions are fully floated to purify the molten steel. At the same time, the steelmaking and continuous casting processes are well coordinated to ensure the continuous casting of multiple furnaces.

In recent years, the LF furnace is the most used device for the secondary refining method at home and abroad. The basic trend of the refractory materials used in the ladle furnace is the basicization and amorphization of the ladle material, so as to improve the service life of the ladle and reduce the consumption of the refractory materials of the ladle furnace.

(1) Refractory for slag line

The LF slag line area is under the condition of high basicity slag and high stress, and the damage is very serious. Therefore, more high-quality magnesia-carbon bricks with corrosion resistance and thermal shock resistance are used.

(2) Refractory material for furnace wall

LF furnace walls generally use high alumina bricks. However, although the traditional high-alumina bricks have good corrosion resistance, the slag penetration is serious, causing structural spalling and unstable durability. In addition, the slag penetration part shrinks and causes cracks, resulting in damage. Generally, carbon and MgO materials need to be added to overcome. The lining of refining furnaces has developed from shaped products to amorphous products. From the material, there are magnesium-carbon, aluminum-magnesium-carbon, aluminum-spinel castables, etc., and magnesium-calcium materials are also the development direction. The LF furnace adopts different grades of magnesia-carbon bricks and magnesia-alumina-carbon bricks or aluminum-magnesium-carbon bricks for comprehensive masonry lining, which has better benefits.

(3) Refractory material for furnace cover

Castable is used for the lid of the ladle furnace of the LF refining furnace. The castables for the furnace cover developed by Luo Nai Institute, etc. are made of fused corundum and Yangquan super bauxite as the main raw materials, pure calcium aluminate cement (4%-8%) as a binder, and added (8%-12%) Silica and alumina ultrafine powder and a small number of additives and superplasticizers make the thermal shock resistance and spalling resistance of the castable meet the requirements.

(4) Refractory materials for the bottom of the package and the breathable brick

The large-scale LF ladle bottom ladle furnace is used for pouring large bricks. The main component is Al2O3-MgO.Al2O3 and the permeability are good. The bottom of the LF furnace bag also uses high calcium dry ramming material.


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2022年8月15日星期一

Ladle Furnace Electrode Consumption

Ladle Furnace Electrode Consumption


Ladle Furnace Electrode Consumption


1 Introduction

Ladle Furnace electrode consumption: Graphite electrode is the main heating component and indispensable consumable material for electric furnace steelmaking and ladles furnace refining. In 1982, the output of electric furnace steel in the world was 160 million tons, and the consumption of graphite electrodes was 1.2 million tons. In 1985, the world produced a total of 1.4 million tons of graphite electrodes. It is estimated that by 2000, the output of electric furnace steel will reach 280 million tons, and 1.9 million tons of graphite electrodes will be required then.

Between 1980 and 1989, the consumption cost of graphite electrodes, although decreased by 3.56%, still accounted for 6% of the total cost of EAF steel. Therefore, metallurgists are working hard to reduce the consumption of graphite electrodes.

There are two ways to reduce EAF & ladle furnace electrode consumption: one is to improve the quality of graphite electrodes as much as possible; the other is to use all possible operating techniques in electric furnace steelmaking and ladle furnace refining to reduce graphite electrode consumption.

2. Factors Affecting the Consumption of  EAF & Ladle Furnace Graphite Electrodes

There are two types of electric furnaces that use graphite electrodes for steelmaking: AC electric arc furnaces and DC electric arc furnaces. Most of the ladle refining furnaces using graphite electrodes are three-phase AC ladle furnaces.

In the smelting process, the consumption methods of graphite electrodes mainly include end consumption, side consumption, graphite electrode breakage, and electrode residual head consumption. For the ladle refining furnace, the use of graphite electrodes has the characteristics of intermittent operation. The graphite electrodes are more severely subjected to thermal shocks of rapid cooling and rapid heating, and the phenomenon of end scattering is prone to occur. Therefore, the end consumption is more serious than that of electrodes used in general electric arc furnaces.

Taken together, the factors affecting the consumption of graphite electrodes can be divided into electrical, mechanical, oxidative, and management aspects according to their properties.

2.1 Electrical Factors

2.1.1 Electric Power

The optimal power system is adopted, that is, the highest possible voltage-to-current ratio and short thermal shutdown time are used to maintain full-load power operation so that the electric energy is in a state of high utilization. This reduces EAF & ladle furnace energy consumption and graphite electrode consumption.

As the current increases, the temperature of the entire graphite electrode alumni association increases. Therefore, the side consumption of the graphite electrode is also affected.

The heat generated by an increase in current obeys Joule's law. The current density of graphite electrodes and their joints has a certain limit. If the limit value is exceeded, the possibility of graphite electrode cracking, residual head consumption, and fracture rate will increase.

2.1.3 Arc Length

Increasing the arc length means that the penetration diameter of the graphite electrode to the charge is larger, so the possibility of the graphite electrode breaking due to the collapse of the material is also reduced accordingly. The long arc operation accelerates the melting of the charge, but after the furnace is melted, the heat radiation on the furnace wall is also greater. Generally, the appropriate furnace type (water-cooled furnace wall, furnace cover) and operation mode (foaming slag and reverse time reduction voltage should be used) tap).

2.1.4 Graphite Electrode Adjustment

The fracture of the graphite electrode is largely caused by the misoperation of the graphite electrode adjustment, so all the mechanical and electrical components of the adjustment system should be in good working condition.

The lifting operation of the graphite electrode should conform to the characteristics of the adjustment mechanism, especially to avoid mechanical breakage when the graphite electrode is lowered to the charge, and the lowering speed should be as uniform as possible. The overload current signal that causes the graphite electrode to rise rapidly may reduce the breakage of the graphite electrode when the charge is collapsed. Various graphite electrode protectors that operate by controlling hydraulic pressure, motor current, matching current, or cable tension can play a positive role in preventing the graphite electrode from falling onto non-conductive materials and breaking.


2.1.5 Electromagnetic Phase Rotation

When a large electric furnace uses a large current, choosing the correct electromagnetic phase rotation direction will also help to avoid loosening of the graphite electrode joint connection. Looking down from the top down, the phase rotation direction should be counterclockwise.

2.1.6 Electrode Holder 

The contact resistance between the electrode holder and the graphite electrode is particularly important for high-power electric furnaces.

Under the water cooling system, choosing the appropriate clamping force and clamping surface can prevent the graphite electrode clamping part from overheating due to the increase in contact resistance.

2.2 Mechanical Factors

2. 2. 1 Feeding Method

In addition to the adjustment of graphite electrodes, the fracture rate of graphite electrodes is also closely related to the feeding method in the smelting operation. During the charging process, efforts should be made to: avoid the collapse of heavy materials; the graphite electrode does not contact non-conductive materials; the melting time of the charge is the shortest.

2.2.2 Furnace Condition and Specific Operation

There is also a certain influence on the consumption of the graphite electrode. In order to reduce the consumption of the electrode, the following aspects should be paid attention to the whole graphite electrode should be well positioned longitudinally; the width of the gap between the graphite electrode and the furnace cover hole is moderate, and the graphite electrode is in the center of the furnace cover hole; the graphite electrode is in the center of the furnace cover hole; The mechanical vibration of the electrode and the cross arm of the graphite electrode may cause the jacket to break or the side of the electrode to be impacted. The tilting of the furnace, the rise, and rotation of the furnace cover should be as gentle as possible; after charging, the scrap falling on the upper edge of the furnace shell should be removed. , so that the furnace cover is in a normal horizontal position; when the furnace is tilted, the furnace cover must not slide.

2.2.3 Electrode Type and the Diameter 

In the choice of graphite electrode, the decisive factor is the electrical load and mechanical load of the graphite electrode. For a specific electric furnace, the diameter of the graphite electrode can be determined with reference to Figure 1. Ladle refining furnace The relationship between electrode diameter and current load is shown in Figure 2. At the same time, long graphite electrodes should be used as much as possible to reduce connection points and waste electrode residues.

2.3 Oxidative Factors 

The side consumption caused by the oxidation of the surface of the graphite electrode basically depends on the oxygen supply above 500 °C, the surface area of ​​the graphite electrode, the surface temperature of the graphite electrode, and the time that the entire graphite electrode rod is exposed to the oxidizing atmosphere.

2.3.1 The time from tapping to tapping improves the furnace operation rate, shortens the time from tapping to tapping, and reduces the unit consumption of electrodes. This can be achieved by using optimal electrical power, optimal smelting process, secondary or ladle metallurgy, and the use of auxiliary energy sources.

2.3.2 The partial pressure in the furnace is to accurately control the inner atmosphere and reduce the surface oxidation of the electrode. The negative pressure in the furnace should not exceed a certain limit value, which is generally about -150Pa.

2.3.3 Sealing of the Furnace 

The slag door and auxiliary door of the furnace should be kept closed as much as possible when the furnace is operating. In addition, pay attention to the sealing of the furnace cover ring, furnace cover hole, and water cooling ring or exhaust gas preheater.

2.3.4 Use of Oxygen Oxygen helps the charge to melt quickly, but the oxygen spray gun must not point directly to the electrode. In addition, during refining, oxygen should be blown into the molten steel below the slag line to avoid aggravating the oxidation of the electrode surface.

2.3.5 The dipping electrode of the graphite electrode must not be inserted into the molten steel, otherwise the consumption of the end of the graphite electrode and the residual head will be greatly increased due to the erosion of the molten steel. 2.3.6 The amount and composition of the slag should also be reasonably controlled, Generally, under the premise of ensuring submerged arc and refining needs, the amount of slag should be reduced as much as possible, and the erosion of oxidizing slag on graphite electrodes must be greater than that of reducing slag.

2.4 Management Factors 

2.4.1 Transportation and Storage 

Graphite electrodes and joints should be handled with care during transportation to avoid damage or breakage.

Graphite electrodes and graphite electrode connectors should be stored in a dry, dust-free place. If it can only be stored in the open air, the electrodes and connectors must be covered with waterproof canvas. Graphite electrodes or joints stored in the open air cannot be used directly but should be properly dried.

2.4.2 Assembling of Graphite Electrodes 

The ideal assembly means that the positions of the graphite electrode joints are symmetrically matched, so that the mechanical strength is uniform and the current transmission is good, which can prevent the graphite electrode from cracking or even breaking due to excessive thermal stress concentration, reducing the electrical conductivity. Extreme top and stump consumption.

2.5 Relevant Technologies for Reducing Electrode Consumption 

The successful application of some new technologies has effectively reduced the consumption of graphite electrodes. In terms of smelting operations and processes, there are eccentric bottom tapping, scrap preheating, water-cooled furnace walls and lids, and long arcs. Foamed slag operation and mineral fuel and oxygen fluxing, etc.; the production of electrodes includes advanced needle coke making graphite electrodes, large extruder (6000t) forming, water-cooled graphite electrodes, supplementary impregnation of graphite electrodes, longitudinal graphitization and graphite electrodes electrode coating, etc.

3. The current situation of production and quality of graphite electrodes in my country In the past ten years, the development of electric furnace steel in my country has been rapid. However, due to the fact that most of the graphite electrodes used in electric furnace steelmaking are ordinary power graphite electrodes, and the development of electric furnace steelmaking-related technologies has not kept up, the consumption of graphite electrodes is far from the foreign level.

With the accelerated development of electric furnace steelmaking in my country, the number of high-power and ultra-high-power electric furnaces newly built in various places has increased rapidly. Only in East China, more than 10 high-power and ultra-high-power electric furnaces will be newly built in the near future. After these large electric furnaces are completed and put into operation, only eastern China will need more than 10,000t of ultra-high-power graphite electrodes. Among them, Shanghai needs 4,000t of large-scale high-power graphite electrodes with a diameter of 650-700mm, and Jiangsu needs about 5,000t.

At present, there are only 7 large carbon factories producing graphite electrodes in my country, 19 medium-sized carbon factories, and more than 100 small carbon factories, with an annual output of about 170,000 tons of graphite electrodes, but 85% of the graphite electrodes produced by these factories are The above are ordinary graphite electrodes of small and medium size, and ultra-high power electrodes are seriously lacking. At present, there is only one domestic enterprise producing ultra-high-power graphite electrodes in batches, Jilin Carbon Factory, whose annual output can only reach about 1500t, and limited by the capacity of the press, only electrodes with a diameter of less than 600mm can be produced. Although Shanghai Carbon Factory has the most advanced presses imported from Germany and has mastered the complete process formula of ultra-high power electrode production, due to the backwardness of subsequent processes, it cannot form large-scale production capacity, and it can only produce high-voltage electrodes with a diameter of less than 600mm. power electrode. In addition, needle coke, the main raw material for producing ultra-high-power graphite electrodes, still needs to be imported from abroad.

In order to reduce electrode consumption and promote the development of electric furnace steelmaking, the Ministry of Metallurgical Industry promulgated 1992 the industry standards for ultra-high-power graphite electrodes and high-power graphite electrodes that have been implemented since July 1, 1993.

It can be seen from the table that the maximum diameter of ultra-high-power graphite electrodes in my country is only 500mm, while it has generally reached 700mm in foreign countries. At the same time, there is a certain gap between other technical indicators and foreign countries. Obviously, the localization of high-quality large-diameter electrodes cannot be solved in time, which will greatly affect the further reduction of electrode consumption.

4 Conclusion

(1) The consumption forms of graphite electrodes include end consumption, side consumption, breakage, and residual head consumption. The factors affecting the consumption of graphite electrodes can be divided into electrical, mechanical, oxidative, and management aspects according to their properties.

(2) The use of advanced operating technology and graphite electrode production technology is conducive to the reduction of electrode consumption.

(3) At present, the output of high-power graphite electrodes and ultra-high-power graphite electrodes in my country is seriously in short supply, and the quality of electrodes is lower than that of similar foreign products, and the specifications are not complete, which is difficult to meet the needs of current steelmaking production.

(4) Graphite electrode manufacturers should speed up technological transformation, actively adjust product structure, and focus on producing electrode products that are currently in short supply on the market.


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2022年8月11日星期四

Ladle Refining Furnace Diagram - Steelmaking

Ladle Refining Furnace Diagram


Ladle Refining Furnace Diagram


Ladle refining furnace multi-effect refining agent (auxiliary slag-making material) is applied to the molten steel refining process technology of foaming white slag in the reducing (or weakly oxidizing) atmosphere of refining slag. It is a low-cost smelting high-quality steel grade. The invention relates to a steel-making method, which belongs to the field of refining outside the molten steel furnace.

Ladle refining furnace, namely LF furnace (LADLE FURNACE), is the main refining equipment outside the furnace in steel production. Its main tasks are:

①Desulfurization

②Temperature adjustment

③ Precise fine-tuning of ingredients

④Improve the purity of molten steel

⑤ Slag making.

With the increasing demand of users for high-grade steel, especially clean steel with low nitrogen, hydrogen, phosphorus, sulfur, oxygen, and low inclusions, such as X65 anti-H2S submarine line pipe steel, X52QS anti-strong acid ultra-low sulfur line pipe steel, CS-110SS anti-corrosion oil casing steel, WB36CN1 nuclear power pipe steel, etc. These high-quality products have high requirements on the mass fraction of nitrogen and hydrogen in the steel, which are difficult to achieve by conventional ladle refining furnace refining technology.

The steel-making method of a ladle refining furnace includes the following steps:

1. Transfer the initial molten steel of the converter to the ladle refining furnace, start the electric heating at the refining station and add the slag for about 3 to 5 minutes, depending on the steel type, the converter endpoint [C], and the amount of slag. , according to the ratio of adding 0.25~0.5kg per ton of molten steel, a multi-effect refining agent is added at one time;

Described multi-effect refining agent, is prepared from the component that contains the following percentage by weight: CaC2--45~70%, SiC-5~20%, Al-5~15%, and slow release agent 10~20%.

2. In the refining process, adjust the slag according to the slag change situation; if the thickness of the slag foam can not be completely submerged arc or poor deoxidation, then add a multi-effect refining agent to adjust the slag, and add 0.05 to 0.20kg per ton of molten steel each time. The proportion of slag was added to adjust the slag. When the thickness of the slag foam cannot be completely submerged, the N and H2O in the air are dissociated into N and H atoms that are easily dissolved in the molten steel by the arc, resulting in a dramatic increase in the [N] and [H] content of the molten steel, which directly leads to the intrinsic quality and performance of use are degraded or deteriorated. When the deoxidation of the slag is poor, it is difficult to realize the metallurgical function of reducing the content of molten steel [0] through the diffusion deoxidation of the slag, which also leads to a decrease in the intrinsic quality and performance of the steel.

 3. 5~10 minutes before the end of the ladle refining furnace refining, add 5~Mkg/furnace bauxite or ferrosilicon powder or silicon calcium powder to break the slag, eliminate the CaC2 particles in the slag, increase the surface tension of the slag Promote the separation of steel and slag; at the same time, it can prevent slag inclusion in molten steel and promote the absorption of inclusions in molten steel by refining slag, and avoid carbonization of molten steel during vacuum treatment such as VD furnaces.

In the refining process, if the slag turns from white to gray-black carbide slag phenomenon, then add 5~15kg/furnace bauxite or ferrosilicon powder or silicon calcium powder to adjust the slag, and strengthen the ladle bottom blowing Ar stirring, to Maintain the foaming of the slag completely submerged arc and the stability of the white slag.

The chemical composition of the multi-effect refining agent is Ca-28~55%, A1-5~15%, C-15~30%, Si-3~15%, and slow release agent 10~20%.

Sustained release agents are oxides that significantly increase slag viscosity and surface tension and inhibit gas escape. Such as active BaO, CaO, MgO, etc.

During the specific operation, firstly, according to the oxygen content of the primary slag (FeO+MnO, etc.), the deoxidation ability of the deoxidizing elements, the gas generation amount of CaC2 and SiC, the requirements for the mineral phase composition of the white slag, the influence on the viscosity and surface tension of the slag Calculating the dosage of each deoxidizing element and corresponding components, that is, determining the specific weight percentage of each component of the multi-effect refining agent.

In order to effectively control the reaction speed of each foaming element, the generated gas sources C02 and CO (mainly CO) are sealed in the slag with high viscosity and surface tension for a long time. The particle size of the material can achieve a certain effect; second, by adding a slow-release agent that inhibits the foaming speed and gas escape, the viscosity and surface tension of the slag can be increased stably (the effect does not change much with temperature).

The best block degree or particle size range is: the ladle refining furnace multi-effect refining agent components are prepared, first each component is processed according to the following block degree or particle size requirements: CaC is 5~20mm, SiC is ≥ 3mm, Al is 1 ~5mm, slow-release agent≤5mm, then mix according to the design ratio and adopt the double-layer moisture-proof packaging of inner plastic and outer weaving, and the weight is advisable with 5 ~ 10kg/bag. Shelf life does not exceed 15 days.


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

2022年8月9日星期二

Working Principle of Ladle Refining Furnace

Ladle Refining Furnace


Working Principle of Ladle Refining Furnace

 

The ladle refining furnace is a device that refines in a ladle after tapping into an electric furnace or a converter.

The ladle refining furnace is composed of ladle, furnace cover, electrode heating system, and argon stirring system. The molten steel is stirred by blowing argon gas through the permeable brick installed at the bottom of the ladle to complete the reaction between steel and slag.

The function of the furnace cover is to close the refining chamber to maintain the reducing atmosphere.

Three-phase electrodes are used to make slag and increase the temperature of molten steel by arc heating, and a sliding nozzle is installed at the bottom of the ladle for pouring.

Equipment composition: ladle, ladle car, heating bridge and furnace cover lifting mechanism, water-cooled furnace cover, electrode lifting system, short net, argon gas, compressed air, water cooling system, hydraulic station, transformer, low-voltage control system, high-voltage system

The electric arc heating system used in ladle refining is the same as the steelmaking electric arc furnace. The arc generated between the three graphite electrodes and the slag molten steel is used as the heat source. The heating equipment is basically the same as the electric furnace. The difference is that there is no melting process in the LF furnace. The submerged arc heating method is used, so compared with the electric furnace, a lower secondary voltage and the smallest possible polar center can be used, and the submerged arc heating method has a protective effect on the furnace lining due to the small radiant heat. The thermal efficiency of heating is also relatively high, and the heat utilization rate is good.

The secondary side of the transformer used in the ladle refining furnace is usually divided into several levels of voltage, but it is not necessary to carry out on-load adjustment, so the equipment is relatively simple and the reliability is good.

When the ladle refining furnace is refining, the molten steel level is relatively stable, the current fluctuation is small, and there is no short-circuit impulse current caused by the collapse of the material when the electric furnace melts the charge, so the current density can be selected to be larger.

The adjustment system of the ladle refining furnace must have an automatic adjustment system with high sensitivity to reduce and prevent the carbon increase caused by the contact between the electrode and the molten steel.

The ladle refining furnace has the functions of arc heating under normal pressure, bottom-blowing argon stirring, temperature measurement, and sampling fine-tuning of alloy composition, deoxidation, desulfurization to remove impurities, etc., so as to obtain molten steel with high purity.


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


2022年8月4日星期四

LRF Ladle Refining Furnace

LRF Ladle Refining Furnace

LRF Ladle Refining Furnace 


The LRF Ladle Refining Furnace is a device that refines in a ladle after tapping into an electric furnace or a converter. 
LF ladle refining furnace consists of the ladle, furnace cover, electrode heating system, and argon stirring system.
The molten steel is stirred by blowing argon gas through the permeable brick installed at the bottom of the ladle to complete the reaction between steel and slag. 
The function of the furnace cover is to close the refining chamber to maintain the reducing atmosphere. 
Three-phase electrodes are used to make slag and increase the temperature of molten steel by arc heating, and a sliding nozzle is installed at the bottom of the ladle for pouring.
The arc heating system used in the LRF ladle refining is the same as the steelmaking electric arc furnace. The arc generated between the three graphite electrodes and the slag molten steel is used as the heat source. 
The heating equipment is basically the same as the electric furnace. The difference is that there is no melting process in the LF furnace. 
Moreover, the ambush heating method is used, so compared with the electric furnace, a lower secondary voltage and the smallest polar center circle can be used, and the submerged arc heating method has a protective effect on the furnace lining due to the small radiant heat.
At the same time, the thermal efficiency of heating is relatively high, and the heat utilization rate is good.
The secondary side of the transformer used in the LRF ladle refining furnace is usually divided into several levels of voltage, but it is not necessary to carry out on-load regulation, so the equipment is relatively simple and the reliability is good. 
When the LF ladle refining furnace is refining, the molten steel level is relatively stable, the current fluctuation is small, and there is no short-circuit impulse current caused by the collapse of the material when the electric furnace melts the charge, so the current density can be selected to be larger.
The adjustment system of the LRF ladle refining furnace must have a high-sensitivity automatic adjustment system to reduce and prevent the carbon increase caused by the contact between the electrode and the molten steel.
The LRF ladle refining furnace has the functions of arc heating under normal pressure, bottom blowing argon stirring, temperature measurement and sampling, fine-tuning of alloy composition, deoxidation, desulfurization, and removal of impurities, so as to obtain molten steel with high purity.

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

2022年8月1日星期一

Aluminium Electrode Arms and Electrode Clamping Device

 

Aluminium Electrode Arms

Aluminium Electrode Arms and Electrode Clamping Device

The Aluminium Electrode Arms and Electrode Clamping Device have the following advantages:

  1. Due to the use of integral conduction and fewer contact connections, the contact resistance is reduced, the integral conduction eliminates the eddy current resistance generated in the prior art, and improves the utilization of electric energy.
  2. The design of the Aluminium Electrode Arms can have a small diameter of the electrode ring when a certain free space is required around the cross arm, which means that the baking of the electrode to the furnace wall will be small during use, saving refractory materials.
  3. Using water-cooled conductive copper block and water-cooled stainless steel ring, high conductivity, high mechanical strength, and long service life.
  4. Compared with the existing copper tube, the overall conduction reduces the vibration sensitivity of the cross arm, thereby reducing the possibility of electrode breakage.
  5. The insulation used in the chuck eliminates the danger of arcing between the chuck and the electrode.
  6. The solid box-type structure of the Aluminium Electrode Arms makes it able to withstand a high degree of bending and twisting pressure, which means that it can have a greater adjustment speed.
  7. The clamping and loosening mechanism is placed inside the cross arm to avoid electromagnetic interference and thermal baking.
  8. Using a special lightweight aluminium alloy structure, the weight is 40% lighter than the conventional Aluminium Electrode Arms, which increases the sensitivity of the adjustment system.
  9. Simple appearance, easy installation, and maintenance.


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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We are the manufacturer of Steel Rolling mills, Wire Rod Mills, TMT Rebar Mills, Electric Arc Furnaces, Flying shears, Continuous Casting machines, and spare parts. we can supply designing, manufacturing, installation and commissioning of the equipment with "turn-key" service. We can also design, manufacture and revamp other non-standard equipment according to the requirements of users. Free mail to Stella@hanrm.com for your rolling mill plant Solution  Whatsapp/Wechat:+8615877652925 https://www.hanrm.com/ https://www.electricarcfurnaces.com/ https://www.hanmetallurgy.com/ https://www.rollingmillmachine.com/ https://yfmetaltech.com/

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