Anatoly Tuyahov, Alexander Ponomarenko
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World tendency in steel-smelting production - receipt of high-quality metal for all brands of staley. Quality of metal is determined by not only composition of the regulated components (With, Si, Mn, S, P)but also such harmful admixtures as non-metal inclusions (Al2O3, SiO2 and dr.) and dissolved gases (H, N, About).
At the front-rank metallurgical plant of Ukraine the vnepechnie methods of treatment of liquid metal are widely used, with the purpose of receipt of steel of high quality with low maintenance of non-metal inclusions and dissolved gases. To the number of such enterprises it is possible to deliver MK "Azovstal", "DMZ OAO" and row of other. Except for it at many metallurgical plant the distribution of setting "stove-scoop, electromagnetic interfusion of metal and influence on him of the electric field, was got. However, the use of vnepechnih methods of treatment of metal requires considerable primary expenditures on planning and editing of basic and auxiliary equipment. In addition, in the process of affinage of liquid steel the use of electric power and expensive rare gases is needed, mainly argon, that in the conditions of difficult finansovo-ekonomicheskogo situation of OAO "MMK" presents considerable difficulties.
Therefore the decline of energozatrat at the vnepechnom affinage of steel on "MMK OAO" can be attained due to dehydrogenizing from steel-smelting bath of basic technological aggregate. Most effectively it is possible to carry out dehydrogenizing from bath of martin stoves working with blowing of liquid metal out by oxygen through vaults furmi.
In steel-smelting bath the hydrogen acts from three basic sources:
- metallic and non-metal part of charge;
- atmospheres of stove;
- raskisliteley and alloying additions.
In metallurgical part of charge hydrogen is in an elementary form (the dissolved gas, or gas in shells and bubbles of cast-iron chushek) so in the chemically linked kind (for example, as a blight). On occasion it is necessary to be considered that the pieces of charge are painted, are poured by a fuel oil or resin. In liquid cast-iron the maintenance of hydrogen relies on partsialnogo pressure in the furnace of high furnace, which is determined by humidity of blowing and quantity of given in a stove fuel oil or natural gas and makes 3-7 sm3 / a 100ã metal.
The far of moisture can be borne in bath of stove by a lime, boksitom and iron-stone. Influencing of moisture of lime especially shows up, when she is loaded on the surface of liquid shlaka and metal.
The most intensive receipt of hydrogen in a metal is carried out from the atmosphere of stove, due to formation of aquatic steams at incineration of fuel.
Thus aquatic pairs, dissolving in shlake, pass the hydrogen to the metal. In addition, a metal directly co-operates with the atmosphere of stove at his baring during boiling or by means the shallow metallic drops thrown out from bath in the process of its intensive decarbonating.
Hydrogen gets in a metal also at his alloying and raskislenii. It is explained to those, that the used ferro-alloys frequently contain the far of gases. So, in 75 % - nom ferrosilitsii maintenance of hydrogen hesitates from 8 to 15 sm3 / 100ã, and in a blast-furnace ferromargantse ( 75 - 80% ) it makes 20 - 40 sm3 / 100ã.
It was incorrect to characterize melting as process resulting in the gazonasishennosti of steel. Along with the processes of enrichment of steel its degassing, which takes place thanks to education and selection of bubbles of oxide of carbon, which dissolved in a metal hydrogen passes to, develops by gases during melting with one or another intensity. Speed of this process is described by equalization:
( 1)
where Vc - speed of decarbonating of bath
to - constant relying on speed of massoperedachi in the volume of metal, I.e. from the radius of bubbles, depths of bath and dr.
[H] - middle maintenance of hydrogen in a metal.
It is visible from equalization (1), that speed of dehydrogenizing from a metal is determined by speed of decarbonating, and the last in same queue relies on intensity of blowing of bath out by oxygen.
Adopting on the basis of literary data the maintenance of hydrogen in a metal on melting 8 sm3 / 100ã intensity of blowing of bath out was definite by oxygen in the period of lapping in the interval of speeds of oxidization of carbon 0,1 - 0,5 % / ch. It was assumed thus, that 90 % oxygen on oxidization of carbon acts due to blowing out, and 10 % from the atmosphere of stove. Except for it was taken into account, that oxygen in a reactionary area was expended directly on the reaction of oxidization of carbon in a quantity 30 %.
Using dependence of change of maintenance of hydrogen in a metal from speed of burning down of carbon, got V.I. Yavoyskim for basic martin stoves was it is set, that oxidization of carbon with speeds 0,1 - 0,2 % /÷ conduces to satiation of metal by hydrogen, that corresponds to intensity of blowing out 1400 - 2800 m3 / ch.
Oxidization with speeds 0,3 - 0,5 % results in degassing of metal from hydrogen, that corresponds to intensity of blowing out 4200 - 7000 m3 / ch.
The decline of maintenance of hydrogen was the purpose of work in a metal due to blowing out by oxygen on 2 - 4 sm3 / 100ã with subsequent his degassing in a scoop in the conditions of "MMK OAO". Such decline of maintenance of hydrogen it is possible to attain at intensity of blowing out 4500 - 5000 m3 / ch. The rise of intensity of blowing out conduces to the further degassing of metal, however here the expense of oxygen increases considerably.
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