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Steel Making in India Technology Scenario Changes

INTRODUCTION
The world at present is having considerable reforms in regard to technology for steel manufacturing – its changes & developments. In the 18th & 19th century the mass production of steel was developed by using liquid Pig Iron in the Bessemere Converter where air was blown from the bottom at high pressure. The oxygen in air oxidized the impurities such as high carbon, silicon etc.. It was noted that this steel could not remove all impurities. The German scientist Siemen developed Open Hearth Furnace where the furnace was having rectangular shallow Open Hearth bath and the hot gases produced from coal gas producer were made to impinge on the hearth for ˝ hour from one side and then for ˝ hour from the other side to heat surface . face of the bath and reduce the impurities. It took 8-10 hours to produce good quality steel. The Pig Iron which contained high Silicon, Carbon etc was refined by oxidizing these elements such as silicon, carbon & phosphorous. The Siemen Open Hearth Furnaces of bigger capacities were installed all over the world. These are still used. Thus for over 100 years Siemen’s process of making steel in Open Hearth Furnaces was the main technology used for making steel.

L.D. PROCESS
Subsequently in early 1950’s L.D. Process was developed by Liz of Germany and Donwitz of Austria to make steel. The oxygen instead of Air was blown in the L.D. converter from bottom similar to the Bessemere converter. Very violent exothermic reactions took place. Thereby reducing Carbon, Silicon, sulphur and Phosphorous in one operation. The process was faster. The chemistry of bath could be adjusted. This process has become now the mainstay of making steel, known as BOF. For Basic Oxygen Furnace technology, very big Capacity Basic Oxygen Furnaces have been developed. Thus a revolution has taken place in steel making in the world. Over 75% of steel in the world is now made by BOF route and the rest by Open Hearth Furnaces and Electric steel making route.

SPONGE IRON
The technology Is also changing as far as manufacture of pig iron is concerned. Very high quality of coking coal is needed for making the coke as redundant in the blast furnaces. The coking coal reserves in the world are decreasing. In view of the same, technologies have to be developed to use non-coking coal as redundant for the Iron Ore. Sponge Iron is produced from iron ore by using low quality coal. Big rotary kilns are used where the iron ore, coal and limestone are fed from one end of kiln. The hot air is injected in the kiln from various zones, which heat the raw materials, and a temperature is reached where the iron ore gets reduced leaving solid contents along with gange material. The hot reduced material is discharged from the other end of kiln, which is cooled. The gases emitted from the Kiln have high calorific value containing Carbon Monoxide, methane and ethane etc. These are used for generating Power and in reheating furnaces of rolling mills.

PIG IRON
Iron ore of particular grit sizes is used in Blast Furnaces. Thus the Iron Ore mines have lot of fine Iron ore dumps collected at mine heads. In order to utilise fine iron ore dust, scientist are busy in developing processes to utilise fine iron ores and convert them in to pig iron. Pig iron making processes such as “Romelt Process” has been developed in Russia. In India, National Mineral Development Corporation have put up a Romelt process technology plant in the state of Chattisgarh. The capacity of experimental plant is 0.3 million tonne but work is also going on a 1.5 million tonne plant. This pig iron will be of high quality. Austria has also developed a technology called Hishmelt process. After the first product is made at Bailadila by Romelt process its efficiency will be known.
In Austria a process by name COREX has been developed. Jindal Vijyanagar in the state of Karnataka have installed the COREX plant. The non-availability of coking coal in this region, the soft iron ore is pelletised and fed in the closed furnace. The Corex by-product gas is used as fuel. The liquid pig iron is taken to BOF to make steel.

ELE CTRIC PROCESS OF MAKING STEEL
Due to shortage of Steel in the Country, Government of India allowed a number of Electric Arc Furnaces (EAFs) to produce steel in the Secondary Steel Sector by recycling the steel scrap. Since early 70"s to 1985, nearly 150 EAFs were installed with a capacity of over 9 million tonnes in various parts of the country. However, in the meanwhile the Medium Frequency Induction Furnaces technology came into the country in early 80’s. Electric Induction Furnaces have been installed in all states in India and India is perhaps the only country in the World using Induction Furnaces on a large scale to manufacture secondary steel.
Electric Arc Furnaces of bigger capacities say 150 tonnes/charges have been developed. The recent developments in EAF technology are the increased oxygen consumption, reducing power consumption and tap to tap time and the increased hot metal proportion to reduce power consumption and control ‘Cu’ content which comes from steel melting scrap to produce higher grades of steel. At present nearly 30% of steel is produced by EAF route in the world. This is because of more and more availability of steel scrap.

ELECTRIC ARC FURNACES
Electric Arc Furnaces installed in India were of small capacities ranging from 5 tonne to 20 tonne per charge in early seventies. The reason was (a) non availability of big size furnaces (b) to cater the need of shortage of steel for construction industry as the product of Arc furnaces was not under govt. control of prices unlike steel produced by integrated steel plants. (c) Facilities provided by Government such as less excise duty of Arc furnace product.
Thus EAFs were installed in J & K, Punjab, Haryana, Himachal Pradesh, Uttar Pradesh, Rajasthan, M .P., Bihar, West Bengal, Orissa, Andhra Pradesh, Tamil Nadu, Karnataka, Maharashtra & Gujarat. There was a slump in 1975 to 77 and to rehabilitate them, the banks reduced interest rates and excise duty was also reduced in 1980. Finding shortage of steel melting scrap in the country, import of steel scrap was allowed at concessional custom duty rate. From1978 to 1985 EAF s did very well. Some of them started diversifying the product-mix made by them, some installed balancing equipment and continuos casting equipment. In mid eighties the profitability of EAFs upto 15 tonne/charge decreased particularly who were producing pencil ingots only. Some of EAFs did not take action to reduce power consumption etc. When the Induction Furnaces started producing steel from 84-85 period using less power, the competitiveness of EAFs became less and less despite steel Ministry not giving license to Induction Furnaces to make steel. However, EAFs were still favored by Steel Ministry in giving imported steel melting scrap, which was canalised by Government of India and allotted to EAFs only. But Induction Furnaces got import duty concession for importing steel melting scrap through MSTC Ltd. This made the production of EAFs for making only pencil ingots uneconomical. Only 35 EAFs are in operation at present who diversified their production or have started flat production – colour coating or galvanising them.

INDUCTION MELTING FURNACES
Induction melting furnaces in India were first installed to make stainless steel from imported SS Scrap. But in years 81-82 some entrepreneurs, who were having small size induction furnaces making stainless steel, experimented in making mild steel from steel melting scrap, they succeeded. More firms in northern India produced steel (Pencil Ingots) by using 500 kg to 1 tonne induction furnaces. The power consumption was found to be about 700 kWh/tonne, which was nearly 100 units less than EAFs. Bigger size Induction furnaces were then installed first in North India and then in other states of India. By 1985-86, the technology of making mild steel by Induction Furnace route was mastered by Indian Technicians. Induction furnace manufacturers saw the potential and started manufacturing bigger size/capacity furnaces. By 1988-89 period 3 tonne per charge induction furnaces were installed (became standard) all over India. The chemistry of melt was adjusted by adding mill scale, if opening carbon of bath was more. Good quality of steel melting scrap was used. In 1991-92, the Government license and control on steel making and rolling was removed. Then more induction furnaces were installed all over India. Backward and forward integration took place. The use of sponge iron made it possible to adjust chemistry of melt. Thus good quality of Mild Steel pencil ingots are being produced with no tramp elements.

INPUTS IN THE INDUCTION FURNACES
Induction Furnaces are using Steel melting scrap, Sponge Iron & Pig Iron/Cast Irons. On an average the ratio of these items is 40% sponge Iron + 10% Cast Irons or Pig Iron. The technology of melting these input materials varies according to the availability of raw materials and location of the plant and inputs of sponge iron consumed is as high as 85 % as charge mix on bigger furnaces.

TECHNOLOGICAL UPGRADATION
The old slogan that in Induction Melting Furnaces you do not “make” steel but only “melt” which is like “Garbage in” and “Garbage out” has been proved wrong. The ingenuity of making all types of steels has been mastered by technologists of Induction melting Furnaces. Qualified metallurgists and experienced Engineers are employed by the industry. While industry is mostly producing Mild Steel and Carbon Steel, it has been noted that many units have started producing Low Alloy Forging quality steel, thereby, diversifying the product mix. A very careful control is exercised by the smelter in regard to chemistry of melt and quality of product. During the past six years over twenty Induction Melting furnace units have installed Ladle Refining equipment and Continuous Casting machines. There is upgradation of electronic circuit design to conserve energy. Some units have installed machinery for proper sizing of steel melting scrap, Electro magnet handling and feed hoppers for its chemical and mechanical treatment to improve density and quality by continuous feeding of charge. This has improved melting rate and productivity using less energy per tonne of metal produced. Power consumption is reported as low as 525 ~ 550 kWh (Units) per tonne.

PRESENT SCENARIO
After 2 years of depressed market, the steel market has suddenly shown competitiveness. It is noted that induction-melting furnaces in various parts of the country are at present operating to near capacity. However, the power is not supplied to the units fully. Against a capacity of 8.5 million tonnes in the year 2003-04, the induction furnaces are likely to produce nearly 5.2 million tonnes of mild steel ingots. the production of stainless steel may also be 3.5 lakh tonne. There are nearly 890 units of induction melting furnaces installed in various parts of the country and laboratories to produce cast iron, special cast iron, mild steels stainless steels and high & low alloy castings. There are nearly 650 induction furnaces installed in the country to manufacture the mild steel and stainless steel. Out of this nearly 560 induction furnace units are in operation at present.
The demand of steel has increased during the last one year, Mini Integrated steel plants have come up in some states of India. These plants, according to our information have been installed at Durgapur zone in West Bengal, Chhattishgarh, Jharkhand, and in a big way in Orissa. It is also noted that many units are installing furnaces of 16 tonne per charge to 22 tonne per charge. Induction melting furnaces use over 60% sponge, and have also installed mechanical devises to remove slag, then use LRF to make better quality steel. The refined steel will be poured in the concast machine to produce steel billets. It is expected that this system of manufacturing steel by these Mini Integrated Steel Plants with capacity from 0.25 to 0.50 Mil Tonne per annum will shortly present a totally new scenario. Very shortly MBF Mini Blast furnace is also going to be added to plants located near mines. These plants are generating their own power for captive consumption from the waste gas of sponge iron kiln. Revolution is taking place to make steel in India by utilising various technologies. India is therefore, emerging as a country with innovative idea to make steel, which is not followed by other countries in the world. In the first decade of twenty first century, major existing integrated steel plants will face a challenge in producing Long products from Induction Furnaces in producing steel economically and efficiently.

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