DESC:FIELD OF INVENTION:
This invention relates to the metallurgical cored wire used in manufacturing of steel in steel melting shops. The cored wire consists of filler material covered with steel strip. Conventionally, there used to be only one steel strip covering the filler material for manufacturing cored wire.
An earlier invention has developed a cored wire where two or more steel strips are used to cover the filler material in manufacturing of cored wire.
This invention related to such cored wire which are manufactured with two or more steel strips cladded together.
More specifically, this invention relates to the width of the steel strips used in manufacturing of such cored wires and use of steel strips having different widths; the inner steel strips being of lower width compared to outer ones.
Hence, this invention relates to the reduction in ratio of steel weight to filler weight and thereby reduction in steel consumption and thus cost of production.
This invention also relates to consequent beneficial impact on environment by reducing the consumption of steel, conserve resources and reducing carbon footprint by the reduction of cored coil weight for a unit weight of filler material.

BACKGROUND INFORMATION:
Steel making is essentially an oxidation process where the impurities of molten metal are preferentially oxidized to join the slag along with fluxes. The major challenge to steel makers is to reduce oxygen and inclusions, which are formed due to subsequent de-oxidation as they may remain intact after casting process & are thus detrimental to the product quality

The use of calcium is beneficial but its introduction in liquid steel bath is very difficult due to its low density and high vapour pressure. The advent of cored wire injection technology and development of calcium bearing material like calcium-silicide, calcium-iron, pure calcium cored wire etc. have enabled steel plant operators to introduce calcium efficiently in steel bath

A cored wire is a continuous steel tube filled with either a calcium bearing material or a ferroalloy material. The steel tube is usually made of a single strip. In general thickness of steel strip used in industry is 0.3-1.2mm and width of steel strip used is 30-70mm for cored wire. There is a patented cored wire which uses two or more steel strips cladded together.

The efficiency of calcium treatment of steel melt is measured by the yield (or recovery) of calcium after cored wire injection. This yield of calcium can be defined as the ratio of calcium retained in steel to the amount of calcium injected. The yield of calcium in the cored wire injection process is at the most 40% and sometimes it becomes as low as 2% depending on grades of steel processed and the operating conditions. The low yield of calcium is due to its high vapour pressure and low boiling point (14390C). As this temperature is lower than the working temperature of liquid steel, calcium vaporizes as soon as it is released in the liquid steel.

Thus, the calcium yield and its consistency are of paramount importance to the steelmakers for producing high quality steel with least cost. Achieving consistent and good calcium yield with least possible cost is major challenge for a steelmaker. The present invention aims at reducing the ratio of steel strip weight to filler weight which in turn reduces the steel consumption & cost of cored wire to enable steelmakers with an efficient and cost-effective calcium treatment process.

SUMMARY OF THE INVENTION:
Cored wire consists of filler material covered with one or more steel strips of lower width in inner strip compared to outer strips. Width of inner steel strips are lower as they do not need extra material for locking. Outer steel strip is wider and locking is done with this outer strip only.
The main object of this invention is to reduce the consumption of steel strip when compared to consumption of conventional cored wires. This reduction in steel consumption reduces the cost and thus makes the cored wire injection process more cost efficient. The width of steel strips may vary between 10 mm and 120 mm

DETAILED DESCRIPTION OF THE INVENTION:

The liquid steel is carried in a ladle to the secondary treatment unit after the steel is made in the primary steel-making vessel. The main purpose of the secondary treatment unit is to further refine the steel, adjust the bath temperature and chemistry to suit the demand of the next processing unit i.e. casting unit. The presence of dissolved oxygen and inclusions in the liquid steel poses problem to the smooth operation of casting and also deteriorate the product quality. The calcium treatment of the steel, thus, becomes essential to control the dissolved oxygen level as well as the shape and characteristics of the inclusions. The liquid steel is treated with the calcium and / or other additives bearing cored wires in the secondary processing units. Cored wire is injected into the ladle through wire feeder which is capable of feeding cored wire at a very controlled rate into the steel-melts. The efficiency of calcium treatment of steel melt is measured by the yield (or recovery) of calcium after cored wire injection. This yield of calcium can be defined as the ratio of calcium retained in steel to the amount of calcium injected.
It has already been established that, the yield of calcium and other additives is maximum when the material is released form the cored wire close to the bottom of the ladle.
In the current invention, different widths of steel strips have been used for inner and outer layers; inner layer(s) being always of lower width. The width of inner steel strip(s) has been planned in such a way that it covers the filler material to a maximum extent without covering the area of filler material which is lying just below the locking zone of the outer most strip. By leaving a gap for locking area which is covered by the locking of 3 folds of outer strip thereby enabling near uniform cross section of the coil without getting overlapped on the inner strip. This modification, for instance in one such design where two steel strips are cladded, allows over 20% reduction in steel consumption in comparison to conventional cored wire with single steel strip. The reduction in steel strip consumption reduces production cost of the cored wire.

Experimental production:
Production of cladded steel strips with different width has been taken up to validate the hypothesis of reduction in steel strip consumption
Assume strip thickness as ‘b’ in the conventional product and the thickness of cladded two strips as ‘b/2’ in the innovative product. Similarly assume width of strip as ‘a’ in the conventional product and the width of inner strip as ‘a-y’, width of outer strip as ‘a’ in the innovative product
Considering volume calculations for conventional product as W1 and innovative product as W2
W1=a x b,
W2= a x b/2 + (a-y) x b/2
Reduction in volume in case of innovative product is over 20% compared to conventional product. Comparison is done for steel used in innovative product and conventional product as shown in Figure 1

Fig.1: Comparison between steel used in innovative and conventional Cored Wire

Innovative Cored Wire reduces steel consumption by over 20% compared to conventional product

SPECIFICATION:
? Finished Cored wire diameter: 4-18 mm
? Width of Steel Strip: 10-120 mm
? Difference between width of inner strip and outer strip: 5-50mm
Cored wire consisting of filler material covered with inner steel strip of lower width compared to outer strip reduces steel consumption by over 20% compared to conventional product.

,CLAIMS:1. A cored wire injection process for introducing fluxes and alloying additives in liquid steel bath after adjusting bath temperature and the chemistry of liquid steel in a secondary treatment unit according to requirements: characterized in that said additives are released close to the bottom of the ladle by injecting at a predetermined speed a prefabricated cored wire of appropriate dimensions, depending on the grade of liquid steel, treatment temperature and ladle size / liquid column height
2. The process as claimed in claim 1, wherein a cored wire of filler material covered with two or more cladded steel strips.
3. The process as claimed in claim 2, wherein of two or more cladded steel strips different width are used.
4. The process as claimed in claim 2, wherein the inner steel strips are of lower width compared to outer ones.
5. The process as claimed in claim 2, wherein the width of inner steel strip is between 10 mm and 60 mm.
6. The process as claimed in claim 2, wherein the width of outer steel strip is between 30 mm and120 mm.
7. The process as claimed in claim 2, wherein the difference between width of inner strip and outer strip is in between 5 and 50 mm
8. The process as claimed in claim 2, wherein two or more cladded steel strips of different width is used for producing cored wire, there is a reduction in overall steel consumption during manufacturing of the said cored wire by over 20% in comparison to conventional cored wire.
9. The process as claimed in claims 2 to 8, wherein the reduction of steel consumption in Cored Wire by over 20%, it helps in minimizing carbon emission and contributing towards achieving sustainability goals