Intermediate Frequency Furnace VS Electric Arc Furnace?

Intermediate frequency furnace 
Intermediate frequency furnace is a power supply device that converts 50HZ power frequency alternating current into intermediate frequency (above 300HZ to 20K HZ). It converts three-phase power frequency alternating current into direct current after rectification, and then converts the direct current into adjustable intermediate frequency current. The medium frequency alternating current flowing in the capacitor and the induction coil generates high-density magnetic lines of force in the induction coil, and cuts the metal material contained in the induction coil, which generates a large eddy current in the metal material.

This kind of eddy current also has some properties of intermediate frequency current, that is, the free electrons of the metal itself flow in the resistive metal body to generate heat. For example, if a metal cylinder is placed in an induction coil with alternating intermediate frequency current, the metal cylinder is not in direct contact with the induction coil, and the temperature of the electrified coil itself is already very low, but the surface of the cylinder is heated to redness or even melting , and this redness and melting speed can be achieved only by adjusting the frequency and the strength of the current. If the cylinder is placed in the center of the coil, then the temperature around the cylinder is the same, and the heating and melting of the cylinder will not produce harmful gas or bright light to pollute the environment.

Smelting furnace characteristics of intermediate frequency furnace series:

(1) High melting efficiency, good power saving effect, compact structure, strong overload capacity

(2) The temperature around the furnace is low, there is less smoke and dust, and the working environment is good.

(3) The operation process is simple and the melting operation is reliable.

(4) The metal composition is uniform.

(5) The melting temperature is fast, the furnace temperature is easy to control, and the production efficiency is high.

(6) The furnace utilization rate is high and it is convenient to change the varieties.

(7) The long arc-shaped yoke shields the magnetic flux leakage and reduces the external magnetic resistance. There is magnetic leakage at both ends of the shielded coil. The inner side of the yoke section is arc-shaped and seamlessly adheres to the outer wall, which increases the effective magnetic permeability area and makes the lower ring Get better support. The unique positive and negative coils greatly improve the efficiency of the system.

Intermediate frequency furnace series diathermic furnace features:

●Fast heating speed, high production efficiency, less oxidation decarbonization, saving materials and forging die costs

●Excellent working environment, improving workers' working environment and company image, no pollution, low energy consumption

●The heating is uniform, the temperature difference between the core and the surface is very small, and the temperature control accuracy is high

Intermediate frequency furnace heating device has the advantages of small size, light weight, high efficiency, excellent thermal processing quality. It is rapidly eliminating coal-fired furnaces, gas furnaces, oil-fired furnaces and ordinary resistance furnaces. It is a new generation of metal heating equipment.

The intermediate frequency furnace is the main equipment of the foundry, forging and heat treatment workshop. The stability, reliability and safety of its work are the guarantee for the normal and stable operation of the casting, forging and heat treatment production line of the flow operation.

Electric arc furnace

An electric furnace for smelting ores and metals using the high temperature generated by the electrode arc. The energy is concentrated when gas discharge forms an arc, and the temperature of the arc zone is above 3000 ℃. For smelting metals, electric arc furnaces are more flexible than other steelmaking furnaces, can effectively remove impurities such as sulfur and phosphorus, furnace temperature is easy to control, and the equipment occupies a small area, which is suitable for smelting high-quality alloy steel. Electric arc furnaces can be divided into three-phase electric arc furnaces, consumable electric arc furnaces, single-phase electric arc furnaces and resistance electric arc furnaces according to the arc form. The furnace body of the electric arc steelmaking furnace is composed of a furnace cover, a furnace door, a tapping trough and a furnace body, and the furnace bottom and furnace walls are built with alkaline refractory materials or acid refractory materials.

Electric arc steelmaking furnaces are divided into ordinary power electric arc furnaces, high power electric arc furnaces and ultra-high power electric arc furnaces according to the transformer capacity per ton of furnace capacity. Electric arc furnace steelmaking is to input electric energy into the electric arc steelmaking furnace through graphite electrodes, and the electric arc generated between the electrode end and the charge is used as the heat source for steelmaking. The electric arc furnace uses electric energy as the heat source, and the atmosphere in the furnace can be adjusted, which is extremely beneficial to the smelting of steels that contain more oxidizable elements. Soon after the invention of electric arc furnace steelmaking, it was used to smelt alloy steel and has been greatly developed.

With the improvement of electric arc furnace equipment and the improvement of smelting technology, the development of electric power industry, the cost of electric arc furnace steelmaking continues to decline. Now electric arc furnace steelmaking is not only used for the production of alloy steel, but also for the production of ordinary carbon steel. The proportion of output in the total steel output of major industrial countries continues to rise.

The cost of electric arc furnace is very expensive, but the product quality is good, the public frequency furnace consumes the most electricity, the intermediate frequency furnace is 800-900 degrees/ton below 2000KW, and the large furnace is 600-700 degrees/ton. These are just normal conditions, plus human factors ( operation proficiency, equipment maintenance level), equipment aging, various compensation, harmonic control, and other factors will affect power consumption.

Compared with electric arc furnace, the cost of intermediate frequency furnace steelmaking is lower, and it is suitable for small and medium-sized enterprises (small workshops). However, the steel produced by it has many impurities and high carbon content, so the steel produced is not pure, and those with low requirements can choose The steel produced by the intermediate frequency furnace is usually more than 3 tons in volume. Therefore, the electric arc furnace is only used by enterprises with a certain scale, and the steel produced by it is relatively pure.

The electric arc furnace uses power frequency electricity, while the intermediate frequency electric furnace uses intermediate frequency electricity.


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Electric Arc Furnace Steelmaking Process

1. Feeding

The operation of adding molten iron or scrap steel to the electric furnace is the first step of the electric furnace steelmaking operation.

2. Slagging

The operation of adjusting the slag composition, alkalinity, viscosity and reaction ability in steel and iron production. For example, the oxygen blowing operation is to generate slag with sufficient fluidity and alkalinity, which can transfer enough oxygen to the metal surface, so as to reduce the sulfur and phosphorus below the upper limit of the planned steel grade, and the amount of splashing and slag spilling during oxygen blowing should be minimized.

3. Slag discharge

It refers to the slagging operation taken during the smelting process in the electric arc furnace steelmaking according to different smelting conditions and purposes. For example, when single slag method is used for smelting, oxidation slag must be removed at the end of oxidation; when double slag method is used to make reduction slag, the original oxidation slag must be completely released to prevent phosphorus from returning.

4. Molten pool mixing

Supply energy to the molten metal pool to make the molten metal and slag move to improve the kinetic conditions of the metallurgical reaction. The stirring of the molten pool can be achieved by means of gas, mechanical, electromagnetic induction and other methods.

5. Dephosphorization

It’s the chemical reaction to reduce the phosphorus content in molten steel. Phosphorus is one of the harmful impurities in steel. Steel with too much phosphorus, when used at room temperature or lower, is prone to brittleness, which is called "cold brittleness". The higher the carbon content in steel, the more serious the embrittlement caused by phosphorus. Generally, it is stipulated that the phosphorus content of ordinary steel does not exceed 0.045%, and high-quality steel requires less phosphorus.

6. Electric furnace bottom blowing electric furnace bottom blowing

Blow N2, Ar, CO2, CO, CH4, O2 and other gases into the molten pool in the furnace through the nozzle placed at the bottom of the furnace to accelerate the melting and promote the metallurgical reaction process. The use of bottom blowing technology can shorten smelting time, reduce power consumption, improve dephosphorization and desulfurization operations, increase the amount of residual manganese in steel, and increase the yield of metals and alloys. And can make the molten steel composition and temperature more uniform, thereby improving steel quality, reducing costs, and increasing productivity.

7. Melting period

The melting period of steelmaking is mainly for open hearth and electric furnace steelmaking. The melting period of electric arc furnace steelmaking starts from the time of electrifying to the time when all the accompanying materials are melted, and for open hearth steelmaking, it is called melting period from the end of hot metal mixing to the end of furnace burden melting. The task of the melting period is to melt and heat up the charge as soon as possible, and make the slag in the melting period.

8. Oxidation period and decarbonization period

The oxidation period of ordinary power electric arc furnace steelmaking usually refers to the process stage from dissolution of the charge, sampling and analysis to the completion of the oxidation slag. Some think it started from blowing oxygen or adding ore to decarbonize. The main task of the oxidation period is to oxidize the carbon and phosphorus in the molten steel; remove the gas and inclusions; make the molten steel uniformly heated. Decarburization is an important process in the oxidation period. In order to ensure the purity of steel, the amount of decarburization is required to be greater than about 0.2%. With the development of refining technology outside the furnace, most of the oxidation refining of the electric arc furnace is moved to the ladle or refining furnace.

9. Refining period

The steelmaking process uses slagging and other methods to select some elements and compounds that are harmful to the quality of steel into the gas phase or discharge or float into the slag through chemical reactions, so that they are excluded from the molten steel. The continuous casting machine discharges the billet.

10. Restoration period

In ordinary power electric arc furnace steelmaking operations, the period from the completion of slagging at the end of oxidation to tapping is usually called the reduction period. Its main task is to create reduced slag for diffusion, deoxidation, desulfurization, control of chemical composition and temperature adjustment. High-power and ultra-power electric arc furnace steelmaking operations have canceled the reduction period.

11. Refining outside the furnace

The steelmaking process in which the molten steel initially made in a steelmaking furnace (converter, electric furnace, etc.) is transferred to another vessel for refining is also called secondary metallurgy. Therefore, the steelmaking process is divided into two steps: primary smelting and refining. Primary refining: The charge is melted, dephosphorized, decarburized and main alloyed in a furnace with an oxidizing atmosphere. Refining: Degas, deoxidize, desulfurize, remove inclusions and fine-tune the composition in a container of vacuum, inert gas or reducing atmosphere. The advantages of dividing steelmaking into two steps are: it can improve the quality of steel, the steelmaking workshop can shorten the smelting time, simplify the process and reduce the production cost. There are many types of out-of-furnace refining, which can be roughly divided into two types: out-of-furnace refining under atmospheric pressure and out-of-furnace refining under vacuum. According to different treatment methods, it can be divided into ladle processing type furnace refining and ladle refining type furnace refining.

12. Molten steel stirring

The stirring of molten steel during the refining process outside the furnace. It homogenizes the composition and temperature of molten steel and can promote metallurgical reactions. Most metallurgical reaction processes are phase interface reactions, and the diffusion rate of reactants and products is the limiting link of these reactions. When molten steel is in a static state, its metallurgical reaction speed is very slow. For example, it takes 30 to 60 minutes to desulfurize molten steel in an electric furnace; while it takes only 3 to 5 minutes to stir the molten steel in furnace refining. When molten steel is in a static state, the inclusions are removed by floating upwards, and the removal speed is slow; when the molten steel is stirred, the removal speed of the inclusions increases exponentially and is related to the stirring strength, type, and characteristics and concentration of the inclusions.

13. Feeding wire in ladle

Feed the steel ladle with deoxidation, desulfurization and fine-tuning powders, such as Ca-Si powder, or directly fed into aluminum wire, carbon wire, etc., to deep desulfurize, calcium and fine-tune the molten steel into the steel ladle The method of carbon and aluminum components. It also has the function of cleaning molten steel and improving the shape of non-metallic inclusions.



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How to Choose Cardan Shaft?

The choice of coupling mainly considers the speed of the required transmission shaft, the size of the load, the installation accuracy of the two connected parts, the stability of rotation, the price, etc. We should refer to the characteristics of various couplings, and choose a suitable coupling joint. The following points can be considered when making specific choices:

1. Due to manufacturing, installation, load deformation and temperature changes, it is difficult to maintain strict and precise alignment of the two shafts after installation and adjustment. There is a certain degree of displacement in the X and Y directions and the deflection angle CI. When the radial displacement is large, you can choose a slider coupling, and when the angular displacement is large or the connection of two intersecting shafts, you can choose a universal shaft. When the two shafts produce a large additional relative displacement during the working process, a flexible coupling should be used.

2. The working speed of the coupling and the centrifugal force caused by it. For high-speed transmission shafts, couplings with high balance accuracy, such as diaphragm couplings, should be used, rather than eccentric slider couplings.

3. The size and nature of the torque to be transmitted and the requirements for the function of damping vibration. For example, gear couplings can be used for high-power and heavy-duty transmission. For severe impact loads or transmissions that require the elimination of shaft torsional vibration, tire couplings can be used. Most couplings have been standardized or standardized. The designer's task is to choose, not design. The basic steps for selecting a coupling are as follows:

According to the size of the transmission load, the shaft speed, the installation accuracy of the two parts connected, and referring to the characteristics of various types of couplings, a common type of coupling is selected. The following points can be considered in the specific selection:

1) The size and nature of the torque to be transmitted and the requirements for the buffer and vibration reduction function. For example, for high-power and heavy-duty transmissions, gear couplings can be selected; for transmissions that require severe impact loads or to eliminate shaft torsional vibration, tire couplings and other couplings with high elasticity can be selected.

2) The working speed of the universal joint shaft and the centrifugal force caused by it. For high-speed transmission shafts, couplings with high balance accuracy, such as diaphragm couplings, should be used, rather than eccentric slider couplings.

3) The magnitude and direction of the relative displacement of the two axes. When it is difficult to maintain strict and precise alignment of the two shafts after installation and adjustment, or when the two shafts will have a large additional relative displacement during the working process, a flexible coupling should be used. For example, when the radial displacement is large, you can choose a slider coupling, and when the angular displacement is large or the connection of two intersecting shafts, you can choose a Cardan shaft.

4) The reliability and working environment of the universal joint shaft. Generally, couplings made of metal elements that do not require lubrication are more reliable; couplings that require lubrication are easily affected by the perfect degree of lubrication and may pollute the environment. Couplings containing non-metallic components such as rubber are sensitive to temperature, corrosive media and strong light, and are prone to aging.

5) Manufacturing, installation, maintenance and cost of couplings. Under the premise of meeting the convenience of use, couplings with convenient assembly and disassembly, simple maintenance and low cost should be selected. For example, rigid couplings are not only simple in structure, but also easy to assemble and disassemble, and can be used for low-speed, rigid drive shafts. General non-metallic elastic element couplings (such as elastic sleeve pin couplings, elastic pin couplings, plum-shaped elastic couplings, etc.), due to their good comprehensive capabilities, are widely used in general medium and small power transmission.

If you are interested in our Cardan shaft, please contact me.
Email: marketing2@hanrm.com; Whatsapp / Wechat: +8618392033938.

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