LD CONVERTOR

                     STEEL MAKING 

LD CONVERTOR:- 

                                     LD full form is Linz and donawinz a place in austria in 1952

INTRODUCTION:-           

                                       The furnace is very similar in design to that of Bessemar convertor except that the bottom is solid and oxygen is blown vertically from top. 

      All oxygen steel making process are autogeneous like bessemer and need matten pig iron as a change material. 

Steel scrap is used as a coolant since excess heat is available in this processes. The refining is complate in about 20-25 minutes time of 40-60 minute is needed. 

Charge material used in LD Convertor:- 

1.) Refractories in convertor

2.) Hot metal

3.) Fuxes

4.) Steel scrap and ore

5.) Oxygen

Refractories In Convertor:- 

                                                          The total weight of refractory material required for lining is nearly the Three time. 

  First an inner leval of " magnisite " burn dolomite bricks is mades gaps between the bricks and the shall is fillded with the tar dolomite remaining mass the same remaining composition is use for making of the second intermedeate layer the upper working layer is made of magnesite carbon bricks they are performance of refracrory line life of the lining or by the construction of refractory per tonn of the steel production. 

  These refractories are selected the following condition:- 

a) Furnace atmosphere

b) Composition of slage

c) Mechanical stresses. 

d) Thermal shock

e) Effect of high temperature

f) Geomatry of the vessel 

h) Operational Procedure and blowing process 

I) Qualities of Refractories 

Hot Metal :- 

                        The charge consist old " Pig iron " Steel scrap limestone dolomite CaF2 and Feo like [ Boxite, gaseous, oxygen, etc. ] 

                  This process is use to make of soft steel for the product for transfer product. Sulphur 0.02% The adoption of continuous casting also need that the sulphur should be below 0.02% . 

 Being very fast in refining the LD process does not find enough time for effective sulphur removal during refining. The oxidising condition of LD process ore not at all conductive to de sulphurisation any attempt to bring about sulphur removal in LD refining necessitates high basicities and for which extra lime will have to be  charge for making the slag and which on the whole is detrimental. A high magnesia is also attandance to reffers to de- phosphurisation in the bath the LD process is removing then 90% of phosphorus. 

The analysis of iron used in LD processes is as follows:- 

S. No.                   Required%              Range use% 

1. Corbon               4.1- 4.3                   4.00-4.50

2.  Phosphorus      0.1-0.25                   0.05-0.45

3.  Silicon                0.5-0.85                   0.40-2.50

4.  Maganese          0.5-08                       0.40-0.06

5.  Sulphur              0.02-0.03                  0.02-0.06

      The temperature of the hot metal at the time of charging is usually around 1250-1300°C the proportion of hot metal in the charge varies in the range of 75-90% ie 10-12% scrap depending upon its availability. 

Flux:- 

              Efficiency and economic process is very much depends of formation of the flux oxidizing and basic slag as early as a possible during of flow a lumpi lime in lower dessolving slag. 

    Them powder lime conversion refine powder tendency to below of a small granular from of use time 2.5% of the metal charge for some communicate quality the size distribeyion of losses to iginition of to molten. 

Steel scrap and Ore :- 

                                          These are used at the utiliser the axis heat energy available during refining process them tal to tap 25% of the metal charge as scrap since oxygen gas is used on oxidising agent. 

       Iron are is not required for the same purpose the scrap is not available iron ore is added as a coolant. The charge is nearly to the 3.5% steel scrap. 

Oxygen:- Nitrogen content of the bath increasing with decreasing oxygen the during the de-carborization. 

Composition of Required Iron or Hot Iron:-------

Si   = 0.5-0.8

C    = 4.1-4.3

P    = 0.1-0.25

Mn = 0.5-0.8

Composition of slag:- 

Cao = 45-55%

P2O5 =18-22%

Feo =15-18

Sio2 =5-10%

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