material science and metallurgy :: ON SOME THEORETICAL PROBLEMS CONNECTED WITH TREATMENT

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22.08.2009 07:40 - ON SOME THEORETICAL PROBLEMS CONNECTED WITH TREATMENT

Автор: bogomil Категория: Технологии

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ON SOME THEORETICAL PROBLEMS CONNECTED WITH TREATMENT

OF MULTICOMPONENT MELTS ON Fe-C BASIS WITH

VOLATILE ELEMENTS (N etc.)

Dr.Eng.Bogomil Velicov Kolev - Institute of Metal Science -BAS, 67 Shipchenski prohod str,

Sofia ,1574, Bulgaria

Summary

We worked out and enriched new characteristics (parameters) theoretical model, connected with mechanism of process of gas absorption S? (N?) by nnilticoniponent melt of Fe-C basis. We Introduced new parameters characterizing heterogeneous process: pressure "P", difference in pressure "AP" giving movement of gas S (N2) balloon, sure-face tense "a", diameter of balloons "d", depth of

bath (layer) - "X", thickness - "p", add alloying, diffusion coefficient "D", number free places in melt clusters "n", time "x", availability of

active surface elements, earth speed "g", T°C, etc. On basis on newly formula "vacuum-pressure" which model in embric Nature processes are ideas presuposing possibilities to create new ecology -technology schemes to work new machines, installations and other device for metallurgy and casting according to today"s development , of civilization and challenge of 21 century.

1.Introduction

The problems concerning mechanism and kinetics of processes of absorbing equilibrium and above equilibrium contents of N and other volatile, but also alloyed elements have topical scientific theoretical and application importance. They are connected not only with possibilities to make new alloys alloyed with volatile elements, but also with determining technological aims and economical use of the methods of treating melts as well as determining some perspectives for technological development of metallurgical and casting production [1-8]. This work is an effort to create new characteristics (parameters) of theoretical models of the period 1968-1980 [9,10,13] connected with mechanism of absorption of gas (N etc.) by multi-component alloys. It is result of years of absorblion and study. On basis of newly introduced formula and analysis it"s possible to make new ecology- technological schemes to work new machines and devices for metallurgy and founding with today"s development of civilization and the challenges of 21 century.

^ 2. Models of treatment and casting of melts

Possible variations: a) treatment and casting under classic pressure [1]. b) treatment and casting by methods of treatment of materials with gas counter-pressure (MTMGC)[l-8j. c)New ideas ecology-technological schemes and prognostications[l-9]. Type of gas medium to treat the melt and above: a) air mixture: N2, O9, H7,

H2O, H2 etc. b) work with active and non active gases: Ajt, He, N?, O2, CI2, F2 [2-4, 6]. Gas mixtures can introduce alone or togheder in a given ratio in different or the same quantities, i.e. in combinations 1, 2, 3, 4 etc. These mixtures can use to blow the melt to aim cleaning of gases and non metal inclusions. Mixes of active and non active gases can be put to aim, regulating partial pressure of active gases. Sources to saturate the melt with gas: a)active gas like - S2 (N2, O2, H2, CI2, F2..). Putting alone or in different combinations between it with non-active b) solid substances: non-metal general formula A_xSy (nitrides, nitrates, hydrides, oxides,

metals-general formulae - Me^Sy (nitrides, N-ferroalloys, ligatures, oxides, hydrides...), complex - general formulae Me_xCy (carbides,

carbonitrides, cyanides, oxyhydrides, oxinitrides...). Putting other substances - agent (R) - alloyng carbo and carbonitride forming, degaseous-reducers (deoxidisers, denitriders , dehydrators...). Absorbing gas S2, as well as its opposite process are complex

heterogeneous processes, fig. 1.

3. Saturation of gas S2 at atm. and high pressure (P)

In today"s (classic-carbon) metallurgy are known oxidizing-reduction processes, based on interaction of elements of melt with 02- In that case introduction of gases "S" in general case can be called "gazing", just like "oxidizing". There are no such terms in works, however, because of lack of experimental data on new gas metallurgy. Working with gases S2, process of "giving- taking" of

electrons can be generally called "degazing". In this case we

conclude that new gas metallurgy (with volatile elements) has to

expect "gazing-degazing" processes. In private case N2 - nitriding-

denitriding process. Introducing agents R - there are these general

processes:

xR + yS R_xS_y(1)

We have products of gazing R_xS_y: oxides, nitrides, hydrides, oxihyd-

rides...The other basic process reduction can generally be shown

this:

- reduction with carbon(C)

R,S_y + kCo xR + C_kS_y(2)

where, R-agents: Li, Na, Ca, Mg, Al, M11, Cr, V, Nb....... Me.... and

S₂- N₂, 0₂, H,, CL. F₂..., QSy- are results products of C reaction,
-working with reductor metals - Me (Mn, V, Cr...).
R_xS_y + kMe xR + Me_kS_y(3)

where, Me*S_y - predicts of base of resp. element-metal. Combination reactions. Above are general reactions and have eutestic forecasts importance as for material - science as well as for general knowledge [1-9]. Example: working with H₂ we expect products of C^Hy type. These are carbonitrides with general formulae - CnH2n+2. Working with N we expect chemical composition in the resp thennodynamic conditions (carbonitrides). Working with O2, H2, No and reductor C we have basic elements of organic chemistry and organisms (DNA, RNA ). To these reactions can be put other biogenic gases- Cl₂, F₂. In practices, big interest is alloying with gaseous elements controlling (he quantity (N) of vacuuming. The above and long years of observation help us state prognosticate that as today"s classic (C) metallurgy has got trends of full burning (to make some special alloys) there is introduction to make mades of steels, cast iron, ferro-alloys ligature . So in new metallurgy we have aims to make vacuum metallurgy (to obtain max. lowN etc. content of gases to some ends) and the other hand-development of metallurgy under pressure to introduce air elements (N etc.) and make alloys of controlled N content (and C +N) steels, cast iron, ferro-alloys, ligatures alloys. Big possibilities- opening direction- epoch. There are two ways to saturate complex (N) trough the surface and by volume.

4. Stages of saturation processes (vacuuming) with gases.
Velocity

Analysis schemes of in fig. 1-4. On the bases of the above at saturating the melt gases can be identified by 7 basic stages. Every of which has own velocity (V): Making active- S₂ or non active gases or mix of them in combination in 2, 3,4 etc. to surface in zone "metal-gas". Adsorption of S₂ (N₂). Process velocity V|. Taking gases S₂ (N₂) by gas- containing substance to surface of zone -velocity Vi". Sum velocity V^V," +Vj". 2.Dissociation of active sources of gases on surface of zone: gaseous S₂- velocity V₂ solid (A_xS_y, Me_xS_y)- velocity V₂" .Taking atomic gas S (N). Formation of ball. Atomic N have certain life-time (to some min) after it connects in molecule [11]. Sum velocity process:V₂=V₂"+ V₂". As to our observation and studies the taking of balloons can be not only heterogeneous (of between interphas boundary but also homogenous. For embryos can be vacancies" V in clusters inch

(n=e°"^RT at to Frencel [2-9]. 3.Crossing of surface of cut in one
direction (in saturation with gases S) or in the other to vacuum) i.e.
diffusion of atomic gas (N) of surface of zone in volume of melt
(ionization), change of electrons. Velocity. V₃. Possible diffusion of
gases S (N) from melt in balloon. Velocity V₃. Sum V₃=Vj"+Vj". 4.
Diffusion reagent R- velocity V₄ and rest inclusions and solved
gases of volume melt to surface of zone "metal-gas" baloon).
Velocity V4-sum. V₄=V₄"+V₄". For example in balloon N2
diffusion of H2O etc.gases CO, Cl, F etc. This diffusion processes to
surface of zone metal gas can go to equaling balance concentration
of diffused gases with partial pressure of resp. gases in gas phase. 5.
Chemical reaction in surface of zone (balloon) between agent. R and
resp.gases. S (N). Processes according to reactions (1-3) Velocity
V₅". Sifm V₅ ■ Vj" + V₅". Those carry in macrosphere [1-9].
Known materials in period 1980-1987(90) are said to be true later
by experimental ways [1,2]. Diffusion on products of chemical
reaction (1) R_xS_y- velocity V₆" and reaction (3), Mei

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