LD STEEL MAKING PROCESS

LD PROCESS

LD process is nothing but the first part of oxygen steel making process. The process was first patented at "Linz" and "Donawitzed" of Austria. It is a faster process of Steel making in which pure oxygen is utilities in refining process.
Following are the procedure steps involved in L.D process of Steel Making.


Furnace proper : 

The L.D furnace is made of a peared shape steel vessel is lined, inside this lining tar bonded, dead burnt dolomite and magnesite alnog with carbon (Magcarbor) bircks are placed which is known as refractory lining or Converter champaign. The Converter water cooled oxygen lance is used for blowing. Pure oxygen on to the surface of the liquid metal. The oxygen pressure applied is 7-11kg/cm2 and O2 consumption is 50 - 60m2 / tone of metal. Height of blowing is 1 to 2m from metal surface. A tap hole is located at the conical portion of the furnace.


PRINCIPLE of LD FURNACE


Pure oxygen (99.9%) is blown on the surface of the liquid metal to be refining. The pure O2 reacts with the impurities to form their respective oxidized. The oxidation product from slag combined with CaO addition in the bath and flux over the top of the metal oxide. The slag is removed after blowing and refining metal is tapped out.

Charged Material or Raw material of LD :

The L.D charge consist of molten pig iron, cold pi iron steel scrap, lime or limestone( in shortage of calciled lime) dolomite, florospare, iron ore, and pure oxygen with bottom argon purging. The recommended composition of metal chiled is...........

Material.          Required for L.D         Range used

Carbon                   4.1 to 4.3.                  4.0 to 4.50
Phosphorus        0.1 to 0.25.                0.05 to 0.45
Silicon                 0.50 to 0.85               0.65 to 1.40
Manganese        0.5 to 0.80                 0.40 to 2.50
Sulphur              0.02 to 0.03              0.02 to 0.08

Suitability of L.D Process to Indian Raw Materials

Indian pig Iron commonly average 0.30% P due to availability of high phosphorus raw material. So this pig Iron is unsuitable for steel making by acid and basic Bessemer process and acid open hearth, to produce low phosphorus steel. This is carried out in BOH process but it take longer time and very slow. So that L.D process is adopted to obtain low P steel which is much faster process and produce low nitrogen content steel also.


 Raw Materials For Steel Making :

Introduction :

The chief raw material for steel making are 
* Sources of metallic iron
* Oxidizing agent
* Fluxes
* Sources of heat
* Deoxidizer and alloying elements
* Furnace refractory

For any metallurgical process to final end product their are certain specific raw material are required in steel making progress.
Following are the essential material used for the process to perform.

1. Sources of metallic iron :  Molten pig iron, steel scraps, sponge iron etc

2. Oxidizing agent :  Iron oxide and pure oxygen air. Here iron oxide is used in the form of lumpy hematite ore and mill scale. Here nearly 25% of oxygen is required by the applying weight or present weight.

3. Fluxes :  lime and limestone And dolomite, ganister.

4. Sources of heat :  Exothermic oxidation of heat, solid pulverized fuel, liquid fuel like oils, tars and producer gases, water gas, coke oven gas, natural gas, B.F gas and pure oxygen also electricity. Some process like Bessemer, LD, Kaldo and rotor process, they are not requied heat. But when solid material used heat energy provides by fuel and electrical. Some electrical agents are induction heating, resistance heating, arc heating.

5. deoxidiser and alloying elements :  These are Al, Si, Mn, Zn, Ti, B etc.  Alloying elements are Ni, Cr, Ti, V, Mo, Cu, Co, C etc.

6. Furnace refractory :  These are silica, fireclay, chromite, dolomite, alumina, magnesite etc.

7. Sources of iron :   Mainly it devided in two type I.e. primary which is hot metal, liquid pig iron, sponge iron and secondary steel scraps.


   

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