Abstract final job master Kuzminov А.V.:
"The use of scoop slag is for desulphurization cast-iron on the chamfer of high furnace"


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Introduction

      In world metallurgical practice the question on necessity of secondary treatment of pig-iron which is basic charges a making part of steel-smelting manufacture is is univocal solved. Steel-making iron improvement in quality allows to stabilise process of smelting of the hoist, to lower power and material inputs of the smelting rehash, to improve ecology. Substantial improvement of quality of a steel-making iron and finishing of its characteristics to the level matching to demands of steel-smelting manufacture, is attained by secondary processes of a sulphur removal, deformation and desiliconization. Application of methods of a secondary sulphur removal of pig-iron as raise of its quality combines with growth of productivity of ovens which are freed from emerge - and material-intensive operation of disposal of sulphur from metal in a slag phase is especially effective. To the present time the big know-how of application of secondary treatment of metal melts is saved up, developed theoretical grounds and industrial technics, convincing demonstrations of efficiency of their use at the iron and steel industry operations are gained. In our work trying is made to present the most widespread ways of secondary treatment of pig-iron, to show their refining abilities and reserves. The considerable attention is given also to the new processes, differing by the raised technical-and-economic indexes. Some metallurgical aspects of these processes are discussed.
The purpose of my work is definition of physic-chemical properties scoop slag at the temperature, pig-iron tapped from a blast furnace.

Review part

Now the most widespread in iron and steel industry are next ways of a sulphur removal of pig-iron:
• the secondary sulphur removal of pig-iron sodium and calcium-kept materials;
• the secondary sulphur removal of pig-iron a magnesium;
• the secondary sulphur removal of pig-iron slags.

At a secondary sulphur removal of pig-iron sodium and calcium-kept materials apply:

• the Soda which sulphur removal spend in ladle pots. However in connection with high cost and deficiency of the soda, the sped up lining wear of ladle pots under the influence of alkalis, necessity of careful flushing of the completed soda slag for prevention of return transition of sulphur in metal, complexity of provisions on protection of a circumambient and a labour safety use of soda for a pig-iron sulphur removal in some cases is restricted.
• Not melting reagents: lime, calcium carbide, sianomid calcium and various mixes on their ground which feeding into is carried out by their inflation through a submersible lance or batch on a melt surface more often. Among used in metallurgical practice calcium-containing of desulphurizers of pig-iron possesses the greatest desulphurizing power of calcium carbide which reacts with stressing of harmless steams thanks to what circulation of metal without use of a considerable quantity of carrying gas improves, in the capacity of which dry compressed air, nitrogen, rock gas is applied. It can delete a sulphur significant amount at small specific charges, forms very strong bridgings of sulphur that expels possibility of its return transition in pig-iron. Calcium carbide application in the capacity of desulphurizer manages a little bit more expensively, than to exhaust, however processed metal thus is less chilled.

Secondary sulphur removal of pig-iron a magnesium. The magnesium is one of the most effective desulphurizers of pig-iron. At him the low specific charge in comparison with other reagents (0,3-1,0 kg/t of pig-iron) it is possible to remove from metal to 90 % of sulphur and to gain pig-iron with contents S to 0,005 % with the minimum losses of iron and absolutely insignificant quantity of formed slag (0,5-1,6 kg/t of pig-iron). Ways of feeding into of a magnesium applied now in industrial conditions in pig-iron can be devided on four groups:

- Supply bullion a magnesium with adjustable linear speed mechanical proportioning device at independent of magnesium feeding into having blown gas in the evaporator (a so-called way "magnesium-gas");
- Supply bullion or a lumpy magnesium with an exicipient, braking process of transpiration of a magnesium (passive a magnesium, makgoc, magdolimit, pelamag, etc.);
- Inflation gascarrier small (grained or milled) a magnesium through a lance entrained in melt;
- Supply of a magnesium in the form of a powdered wire.
Pig-iron treatment by these ways is carried out in open ladle pots or in mixer cars in capacity to 250 т. The magnesium moves in pig-iron melt on the greatest possible depth by means of special immersion devices with extending drag.

      At a secondary metal working in a steel-teeming ladle or the assembly the oven-ladle is formed high-basic slag (the basic capacity is approximately equal 4) in quantity 20кг/1 metal ton. By explorations it has been fixed, that ability of this slag as desulphurizer use on 10-20 %, that is this slag could be used again in the capacity of desulphurizer and pig-iron. Chair «Electrometallurgy» had been offered and protected by the copyright certificate a way of a sulphur removal of pig-iron on a blast furnace spout. My problem are chemical compound explorations scoop slag, a melting temperature of slag, viscosity of slag and a sulphur partition ratio between scoop slag and pig-iron. The slags melting temperature is at present investigated.

The slags melting temperature

N melt N probe T melting, °C
2801374 1 1445-1453,2
2801433 2 1348,2-1355,3
2801376 3 1463-1469,5
2801375 4 1448,2-1456,1
2801373 5 1487,2-1471,7
2801400 6 1385,5-1353,3
2801368 7 1462,4-1463,8
2801401 8 1373-1351,3
2801342 9 1351,2-1360,9
2801344 10 1475-1489,2

Conclusion

      We suppose that the use of scoop slag is for desulphurization cast-iron on the chamfer of high furnace allows to reduce maintenance grey in him on 50%.

Library


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