MANUFACTURING CAPABILITIES

Induction Furnace

evolution

Capacity – 25 MT

The paramount advantage of the Induction Furnace is its low capital cost compared with other types of Melting Units. Its installation is relatively easier and its operation, simpler. Among other advantages, there is very little heat loss from the furnace, as the bath is constantly covered, and there is practically no noise during its operation.

The molten metal in an Induction Furnace is circulated automatically by some electromagnetic action, so that when alloy additions are made, a homogeneous product is ensured in minimum time. The time between tap and charge, the charging time, power delays, etc. are items of utmost importance when it comes to meeting the objective of maximum output in tones/hours at a low operational cost. The process for manufacturing steel may be broadly divided into the following stages:

When the furnace is switched on, current starts flowing at a high rate and at a comparatively low voltage, through the induction coils of the furnace, producing an induced magnetic field inside the central space of the coils where the crucible is located. The induced magnetic fluxes are generated, through the packed charge in the crucible, which is placed centrally inside the induction coil.

As the magnetic fluxes are generated through the scraps and complete the circuit, they generate and induce eddy current. This induced eddy current, flows through the highly resistive bath of scrap, generating tremendous heat and starting the melting. It is thus apparent that the melting rate depends primarily on two things: (1) The density of the Magnetic Fluxes and (2) The Compactness of the Charge. The charge mixed arrangement has already been described. The magnetic fluxes can be controlled by varying the input of power into the furnace, especially the current and frequency.

In a medium frequency furnace, the frequency range normally varies between 150-10K cycles/second. This heat is developed in the outer rim of the metal in the charge, but is quickly carried to the center by conduction. Soon, a pool of molten metal is formed at the bottom, causing the charge to sink. At this point, any remaining charge mixed, is added gradually. The eddy current which is generated in the charge, has other uses. It imparts a molten effect on the liquid steel, which is thereby stirred, mixed and heated more homogeneously. This stirring effect is inversely proportional to the frequency of the furnace, that is selected in accordance with the purpose for which the furnace will be utilized.

The melting continues until all charge is melted, and the bath develops a convex surface. However, as the convex surface is not favorable to slag treatment, the power input is then naturally decreased to flatten the convexity and to reduce the circulation rate while refining under a reducing slag. The reduced flow of the liquid metal accelerates the purification reactions by constantly bringing new metal into close contact with the slag. Before the actual reduction of steel is done, the liquid steel which might contain some trapped oxygen is first treated with some suitable deoxidizer. When no purification is attempted, the chief metallurgical advantages of the process that can be attributed to the stirring action, are uniformity of the product, control over the super heat temperature and the opportunity afforded by the conditions of the melt, to control de-oxidation through proper addition.

As soon as the charge has melted and the de-oxidising ions have ceased, the objectionable slag is skimmed off, and the necessary alloying elements are added. When these additives are melted, and diffused through the bath, the power input may be increased to bring the temperature of metal to a point that is most desirable for pouring. The current is then turned off, and the furnace is tilted for pouring into a laddle. As soon as pouring has ceased, any slag adhering to the wall of the crucible is scrapped out, and the furnace is readied for charging again.

As the furnace is equipped with a higher cover over the crucible, very little oxidation occurs during melting. Such a cover also prevents cooling by radiation from the surface heat loss, and protecting the metal is unnecessary, though slags are used in special cases. Another advantage of the induction furnace is that there is hardly any melting loss compared to the arc furnace.

The temperature of liquid metal can rise in the furnace till the correct pouring temperature is achieved, which is checked with the help of the Immersion Pyrometer. The hot metal is poured with the hydraulic system into the preheated laddle, after adding certain fluxes to it, so that the temperature is maintained at about 1600°C. The laddle is then carried by EOT crane to the con-cast machine and (crucible is made free for further charge of the next batch) kept above the tundish of the con-cast machine. The bottom of the laddle is opened by the hydraulic system, and hot metal starts pouring out into the con-cast machine.

The molten steel from the IF after attaining the required temperature and chemistry poured into the pre heated ladle. The ladle is carried on to the continuous casting machine with the help of EOT crane. After making the machine ready for casting the molten metal from the laddle is opened from the bottom of the laddle with the help of slide gate system operated by Hydraulic Machine into Tundish. The molten metal from the Tundish is taken into the two stands consisting of required size of moulds kept in position. On proper cooling the metal gets solidified and taken to the conveyer with the help of dummy bar. The casted billets is cut into the required lengths and allowed to the rolling mill for hot rolling.

The casting operations consist of the following: –
  1. The process is continuous because liquid steel is continuously poured into a ‘bottomless’ mould, at the same rate as a continuous steel casting is extracted.
  2. Before the casting begins, a dummy bar is used to close the bottom of the mould.
  1. A laddle of molten steel is lifted above the casting machine and a hole at the bottom of the laddle is opened, allowing the liquid steel to the required shape.
  2. In the bottom of the Tundish slide gates are to open one by one to allow the liquid metal to enter into the mould for both stands.
  3. As the steel’s outer surface solidifies in the mould, the dummy bar is slowly withdrawn from the machine, pulling the steel along with it.
  4. Water is sprayed along the machine to cool/solidify the steel.
  5. At the end of the machine, the billets are cut into the required length of 6 metres or 12 metres.
  6. Sized billets are lifted by crane to the finishing yard, for inspection/storage /dispatch.

Rolling Mills

rolling-mill

Capacity – tons/annum

A Rolling Mill mainly consists of three separate units, capable of manufacturing re-bars of different diameters/sizes.

The sequence of the three mills is:

  1. Roughing Mill
    • 20 inch Three High Mill 1 number
    • 14 inch Two High Mill 4 number
  2. Intermediate Mill
    • 12 inch Two High Mill 4 number
  3. Finishing Mill
    • 10 inch Two High Mill 6+2 number

The automatic mill is from  M/s. Navbharat Engineering Works, Ghaziabad, one of India’s most reputed rolling mill equipment manufacturers.

ARS Steel manufactures TMT Rebars of dimensions ranging from 8mm  to 32mm.

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