CA1088755A - Method of extra-blast-furnace treatment of liquid iron in vessels - Google Patents

Abstract

METHOD OF EXTRA-BLAST-FURNACE TREATMENT OF LIQUID
IRON IN VESSELS

Abstract of the Invention According to the proposed method of extra-blast-furnace treatment of liquid iron in vessels solid particles of a magne-sium-containing reagent are introduced into the liquid iron in a hydrocarbon gas stream. The gas/solid reagent ratio varies from 15 to 600 1. of the hydrocarbon gas per kilogram of the magnesium-containing reagent.

Description

1(1~87S5 ~ he present invention relates to methods of extra-blast-furnace treatment of liqu~d iron and may be particularly use~ul ~or desulphuration~ denitration~ deoxidation and inoculation of cast iron.
Enown in the art are method~ of treating liquid iron with powdered magnesium mixed with lime or dolomite, with magnesium-aluminum allo~s, granulated magnesium, in which a magnesium-containing reagent i8 introduced into the melt with the aid o$ a carrier gas stream. In said prior-art methods compressed air, nitrogen, ar~on or other inert gases --are employed as carrier gases.
However, using compressed air as the carrier gas introdu-ces air oxygen into the melt which diminiæhes the efficie~c~
of desulphuration~ since it gives rise to magnesium losse~
owing to its oxidation with air o~ygen~ Moreover, a disad-vantage of the compressed air technique resides in that at low concentrations of magnesium in the c~rrier gas, this being required on ~ome occaslons to render the proces~ less vigorous~ magnesium loæses increase owing to magnesium oxida-tion with air V gen.
~ he application of air or nitrogen as a carrier gas leads also to the bloc~ing of denitratio~ processes in view of the presence of ~itrogen in the gas pha~e. ~-As to the use oi argon or other inert gases as a carrier gas when treating iron with magnesium-containing reagents, it

- 2 -' -1()8~755 would have ~timulated iron denitration and contributed to a higher degree o~ magnesium utilization, but it would add great-ly to treatment costs.
The main object of the present invention i8 to enhance the degree of utilization of magnesium in metal and of iro~
denitration.
~ his object is accomplished by that in a method of extra-blast-fur~ace treatment of liquid iron in ve~sels, in which ~olid particles of a magnesium-containing reagent are intro-duced into the liquid iron with the aid of a carrier gas stream~ according to the invention~ a hydrocarbon gas i8 employed as the carrier gas, the gas-to-solid-reagent ratio being equal to 15-600 l. of the hydrocarbon ga~ per ~ilogram ~;
of the magnesiumcontai~ing reagent.
~ he herein-proposed method o~ the extra-blast-furnace treatment o~ l~quid iron makes it pos~ible to e~ha~ce substan-tially bhe degree of utilization of magnesium and to denitride the melt.
~ he application o~ the hydrocarbon gas as the carrier ~as with the propo~ed ratio of the con3tituents obviates magne~ium losses (it~ o~idation) which pro~ides a higher degree of magne-~sium utilization ior desulphuration purposes.
~ ~aseous phaRe fo~med concurrently i~ the liquid iron and con~i~ting of magnesium and hydrogen vapours, the hydrogen ~apours being the product of the hydrocarbon gas decomposition,~

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., - - - ~ . . : -creates a vacuum for nitrogen dis~olved in iron, a feature which contributes to ~itrogen evolution from the melt.
When using the hydrocarbon gas as the carrier gas, a de-crease in magnesium concentration in the gas-powder mixture do-es not lead to magnesium losses due to it~ oxidation. ~owever, with the gas/solid reagent ratio exceeding 600 1. of the gas ~ -per ~ilogram of the solid reagent extend~ the proces~ time and results in inefficien~ drop in the iron temperature. A too low gas/solid reagent ratio, below 15 1. per kilogram of the solid reagent, adversely affects the conditions of pneumatic handling of the reage~t.
The propo~ed ga~/~olid reagent ratio ~aryi~g ~ithin 15--600 1. per kilogram o$ ths solid reagent pro~ides a reliable intriduction of the reagents into the liquid iron, creates a sufficient b reducing atmosphere in and above the melt and mo-re favorable conditions in the reaction zone for the binding of sulphur with magnesium and for the removal of sulphides from the melt.
The gas/solid reagent ratio can var~ from 15 to 85 1. of the hydrocarbon gas per kilogram o~ the magnesium-containing reagent. In this case it i8 e~pedient that the magnesium--contai~ing reagent be a miYture, with the ~ollowing weight perccntage of its constituents:
mag~e~ium, 20-35 lime or dolomite or carbide slag, the balance.

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- ' . ~ : ' ~ he gas/solid reagent ratio may al~o vary between 50-600 1. of the hydrocarbon gas per kilogram o~ the magnesium--containing reagent. With said gas/solid reage~t ratio it is advisable that the mag~esium-containing reagent be either essentially pure magnesium in pulverized state or granulated magnesium of the following composition (percent by weight):
metallic magnesium, 85-98 oxides and salts of al~ali, alkali earth metals and magnesium, the balance.
With said gas/solid reagent ratio magnesium alloys with aluminium and zi~c can be also employed as the magnesium--containing reagents, the weight percentage o~ the consti-tuents in said alloys being as follow~:
magnesium, 50-96 aluminium, 4_50 zink, traces-10.
The low gas/solid reagent ratio~ are e~pedient when opera-ting with the lower magnesium content limits in the magnesium-containing reagent and with high-molecular hydrocarbon gaseæ.
~he high gas/solid reagent ratio are preferable when using the magnesium-containi~g reagents ~ith a hi~h magnesium content and light-weight hydrocarbon gases and when treating liquid iron in vessel~ accommodating over 120 t. o~ metal or in torpedo (submarine) ladles.

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- - : . -It is sound practice that liquid iron be treated with the magnesium-containing reagents introduced with the aid o~ the hydrocarbon gaQ stream with such a consumption oi the magne-sium-containing reagents and hydrocarbon gas that the amount of magnesium vapours formed thereof and that of the hydrocar-bon gas introduced thereinto would ensure a treatment inten-sit~ of 1.2-'l.0 Vg.s.
Said rate provides sufficient stirring of iron in large vessels and its continuous renovatio~ in the reaction zone.
The lower limits characteristic of the intensity of intro-ducing mag~esium with the hydrocarbon gas stream are to be emp- ~-loyed when treating cast iron in small vessels, such as, ladles up to 80 t. of liquid iron capacit~ and when using high-molecu-lar hydrocarbon gases. The upper intensity limits are e~pedient for treating iron in up to 120 t~vessels and in the torpedo ladles.
The proposed method of treating liquid iron affords the possibilit~ of decreasing the rate (intensit~) of introducing magne~ium (without loosi~g it owing to oxidation) and retaining the total rate of introducing the magnesium vapours formed the-reof and the hydrocarbcn gas of from 1.2 to 4.0 l/g.s. This ~ll provide a ~ore complsta utilization of magnesium.
It is advisable that prior to and upon feeding magnesium-containing reagents into the liquid iron the h~drocarbon gas must be introduced deep into the melt at a rate of 0.4-1.0 l/g. s.

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m e adopted conditions of treating liquid iron allow prior to feeding magnesium reducing ferrous oxide present in the metal and slag, creating a reducing atmosphere in and above the melt, providing a turbulent motion of the metal in the ladle, preparing thereby the melt for assimilation of the reagent, this enhancing the degree of utilization of magnesium.
This is achieved because the hydrocarbon gas decomposes in the liquid iron with the formation of hydrogen and a considerable increase in volume (two-fold and over).
me completion of the iron treatment by blowing the -~
metal with the hydrocarbon gas only, with the proposed inten-sity, accelerates the floating up of residual sulphides from the liquid iron into the slag ensuring thereby a higher degree of utilization of magnesium.
The efficiency of treating iron with a hydrocarbon gas prior to and upon feeding a magnesium-containing reagent, particularly when the process is carried out in large vessels, is determined by the rate of introducing the hydrocarbon gas.
With the rate of introducing said gas below 0.4 1/t.s.
the object of both preparative and post treatment of the melt with the hydrocarbon gas is not achieved, since it fails to provide the requisite stirring of the entire volume of the liquid iron in the vessel and because the processes of deoxi-dation of both the metal and slag are not developed in this case.
When used in the present disclosure and in the appen-ded claims, the unit l/t.s. means liter/ton.second.

The rate of introducing the hydrocarbon gas exceeding 1.0 l/t.s. causes a substantial decrease in the iron tempera-ture.
The required stirring of the entire volume of the liquid iron in the vessel, as well as the acceleration of dif~usion processe~ associated with carrying the melt coLstituents to the reactio~ zone is provided by blowing ths liquid iron with the h~drocarbon gas at a rate o~ 0.4-1.0 l/t.s.
The nature of the invention will be clear from the follo~-ing detailed description of particular embodiments thereo~, to be had in conjunction with the accompa~ying drawing, in which:
~ ig. ~ i8 a layout of a de~ice for erfecting a method oi e2tra-blast-furnace treatment of liquid iron in vessels, accor-~ding to the invention.
~ or realizing the method o~ the inventio~ use is made of a device~ comprising a feeder 1 which is a metallic pressurized vessel ~hose bottom portion accommodates a proportioner 2 for adiusting the rate oi feeding solid particles of a magnesium-containing reagent into a mixing chamber 3, where a gas-po~der mi2ture o~ a solid reagent with a hydrocarbon gas of a re~uisi--te concentration is prepared. As for the proportio~er 2, use can be made of a proportioner of any desig~, such as, a rotor one~ pneumatic, etc., enabling the intensity of introducing the magne3ium-containing reagent into liquid iron to be ~d-iusted during treatment withi~ the requisite range. The device ' comprises also a tuyer~ 4 which is a hollow tube with a c flare at its outlet to form an evaporative chamber 5. The tuyere 4 ensures the introduction of the reagents deep into the liquid iron contained in a ladle 7.
A pipeline 8 co~municates with a source of the hydrocar-bon gas and is adapted to feed it into pipeline~ 9 and 10.
The pipeline 9 is in communication with the feeder 1 for supp~
ing therein the hydrocarbon gas that is required for feeding the magne~iu~-containing reagents into the proportioner 2.
The pipeli~e 10 communicates with the mixing chamber 3 and is adapted to feed therein the hydrocarbon gas. ~ pipeline 11 connectes the miYing chamber 3 to the tuyere 4 and i~ adapted to feed the hydrocarbon ga~ or the gas-powder mixture into said tuyere 4.
~ val~e 12 and a non-return valve 13 are adapted for cut-ting-off the entire device *rom the hydrocarbon ga~ source. A
valve 14 is adapted for cutting off the feeder 1 from the hydro~
carbon gas source after the treating operation has been brought~
to a close, when charging the magnesium-containing reagents in-to the feeder 1, and for adjusting the pressure of the hydro-carbon gas in said feeder 1 with the device in operation. A
valve 15 is adapted to cut of~ the tuyere 4 from the hydrocar- ~--bon gas source after the treatment of the liq~id iron has come to an end for removing the tuyere 4 from the metal 6; it ser-ves also for adju~ting the consumption o~ the hydrocarbon gas _ g _ .

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that is fed into the miY ng chamber 3 which makes it possible to vary the intensity of feeding the hydrocarbon gas into the liquid iron during its treatment, the total rate o$ introduc-i~g magnesium vapours with the hydrocarbon gas stream and the gas/solid reagent ratio. After the treatment of the liquid iro~ ha~ beed completed and when the magnesium-containing reagent i3 charged into the feeder 1 the gas is discharged from said feeder 1 through a valve 16.
Pressure g~vernor~ 17 and 18 are adapted to sustain a re-quisite pres~ure o$ the hydrocarben gas in the pipeline~ 9 and 10 ~ith the device in operation. -~
Pressure gauges 19 and 20 mounted on the pipelines 9 and 10 check the pressure in said pipelines while a pressure gauge 21 set up on the feeder 1 is adapted for checking the gas pres-sure therein.
A flow-rate meter 22 mounted on the pipeline 8 is adapted for determining the consumption o$ the hydrocarbon gas for treating the liquid iron.
~ dynamometer 23 ~rom ~hich the $eeder 1 is suspended is adapted for determining the amount of the magnesium-containing reagent fed into the iron being treated.
~ he magnesium-containing reagents are loaded into the feeder 1 through a branch pipe 24. The dust-laden carrier gas, as ell as the hydrocarbon gas are discharged from the feeder 1 through a branch pipe 25.

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-As to the hydrocarbon gas source, use can be made o~ theplant network of natural gas or of cylinders with hydrocarbon gas.
The de~ice ~or carrying into ef~ect the proposed method of treating iron in vessels must be preferably arranged on a special trestle un~er which the liquid iron i8 treated, said trestle being disposed on the way of conveying iron ~rom the melting to the consumption zones, e.g., intermediate o~ the blast-furnace and steel-melting shops.
The method o~ extra bla~t-furnace treatment of liquid iron with magnesium-containing reagents introduced with the aid of a hydrocarbon gas stream, according to the in~ention, ~-is realized in the following manner.
Liquid iron i8 poured into the ladle 7 which i5 carried beneath ~aid trestle to the liquid iron treatiDg zone. The solid magnesium-containing reagents are loaded i~to the ~eeder 1 in pulverized state through the branch pipe 24 by resorting to Rn~ 0~ the prior-art methods (by pouring, pneumatic handl-ing, etc.).
As to the ma~ne~ium-containing reagents, use ca~ be made of, e.g., either pure or granulated magne~ium with the metallic magnesium content varying from 85 to 98%, the bala~ce being the oxide~ and salt~ of alkali and al~ali earth metal~ and mag-ne~ium, or magnesium alloys with aluminium and zinc having the following composition: magnesium, 50-96%~ aluminium, 4-50~0;

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zinc, traces-10%, as well as mixtures of powdered magnesium with lime or dolomite or carbide slag, the weight percentage of said constituents being as follows: magnesium, 20-35%, lime or dolomite or carbide slag, the balance.
The hydrocarbon gaæ is fed from its supply source (not shown in the drawing) along the pipeline 8 and then along the pipeline 9 into the feeder 1 to blow it through with a view to evacuati~g air. In this case the valves 12, 14 and 16 are open and the valve 15 is closed. On completion of the blowing proce-~dure of the feeder 1, the valYe 16 closeæ. A requi~ite pressure is built up in the feeder 1, said pressure being determined by the ferrostatic pressure of tha liquid metal at the depth of immersion of the tuyere 4, whereupon the valve 14 is closed.
Next th~ valve 15 is open and the hydrocarbon gas is fed through the pipeline 10 into the mixing chamber 3, pipeline 11 and the tuyere 4. By adjusting the consumption of the hydrocar-bon gàs with the help of the valve 15, the gas feed rate vary-ing from 0.4 to 1.0 l~t.s. i8 established, the gas being introduced at this rate into the liquid iron 6 contained in the ~es~el 7, whereupon the tuyere 4 ~s immersed into the melt to a m~imum depth. During ~aid treatment in case of insuffi-cient rate of the proceRs (the iron stirring in the vessel being insufficie~t) the supply of the h~drocarbon gas must be increased, the treatment being carried out at the upper limit of the proposed intensity range.

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' In the evaporative chamber 5 o~ the tuyere 4 the hydrocar-bon gas decomposes with the formation of hydrogen VapoUrQ whicb reduce ferrous oxide present both in the metal and in slag. The bubbles of the hydrogen vapours floating up in the iron cause its stirring and create a protective atmosphere under the surface layer of the melt. Moreover, owing to flotation the hydrogen vapours ensure the removal o~ oxide~ from the melt and acting as a vacuum for nitrogen dissolved in the liquid iron the~ contribute to its erolution from the melt.
Upon introducing the prescribed amount of the hydrocarbon -~gas into the iron 6 being treated, the supply o~ the solid rea-gent i~ initiated, said reagents being fed ~rom the feeder 1 into the mi~ing chamber 3 with the aid of the proportioner 2. -In said mixing chambsr 3 the particles of the solid reagent are entrained with the hydrocarbon gas stream whose consumption is adjusted b~ the valve 15 so that the gas~po~der mixture is fed within the range of the proposed gas/solid reagent ratio o~ 15-600 l. o~ the h~drocarbon gas per ~ilogram of the magne- -- -sium containing reagent along the pipeline 11 through the tuyere 4 into the evaporative chamber 5, where magnesium is melted and ev~porates on the s~rface of the liquid iron and the hydrocarbo~ gas decomposes. The mixture of magne~ium and hydrogen vapours and carbon are admitted deop into the liquid . .
iron whsre the~ iateract with the melt constituents. ~loating up in the iron the mixturo vapour~ intermiY it and contribute .. . . . . .
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., . , -.
- - : ~ . - : -, . . ~ . . : . -.-- ': '' ' '" ' ~ ', : ~ ' .. . . . , ~ . . . .
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~ 75 5 to the removal of nitrogen, oxides~ sulphides, nonmetallics and graphite from the melt.
Depending on the nature of the iron-treating process (it being either calm or vigorous), it is possible to adjuste the minute consumption of the magnesium-containing reagents with the help of the proportioner 2 and valve 14, while the valve 15 i8 employed for adjusting the consumption of the hydrocarbon gas to provide the requisite ratio, varying within 15-600 1.
of the hydrocarbon gas per kilogram o~ the magnesium-contain-ing reagent, and an optimum intensity of introducing magnesium vapours being formed and of the hydrocarbon gas being fed the-rein ranging within 1.2-4.0 l~t.s.
When using pure powdered or granulated magnesium of mag-nesium allogs of the above-specified compositio~ as the magne-sium-containing reagents, the gas/solid reagent ratio is sus-tained within 50-600 1. of the hydrocarbon gas per kilogram of the magnesium-containing reagent. And when using a mixture of magnesium ~ith lime or dolomite or carbide slag, said ratio must vary from 15 to 85 1 of the hydrocarbon gas per kilogram of the magnesium-containing reagents.
Low gas/solid reagent ratios lging within the recommended limit~ are applicable in case of the magnesium-containi~g rea-gents with the lower magnesium content and with the ~essel 7 being filled with a great amount of the li~uid iron 6 contained i~ said vessel during treatment.

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108~755 High gas/solid reagent ratios are usable in case of the magnesium-containing reagents with the magnesium content at the upper limit9 when treating the liquid iron in vessels o~
more than 120 t, capacity, in torpedo ladles and with the pioeline 11 having a long len~th.
In ca~ the process is insufficiently intenæe, it i8 ne-cessary either to reduce the gas~solid reagent ratio or to in-crease the rate of introducing magnesium vapours and the hydro-carbon gas or to provide a more intense supply of said gas with out changing that of the magnesium vapours.
~ ith a vigorous process the gas/solid reagent ratio is in -~-creased, the total intensity of introducing magnesium vapours a~d hydro¢arbon gas being reduced.
Upon introducing a preset amount of magnesium into the iron being treated, the proportioner 2 stops ~eedi~g the solid reagent from the feeder~ ths valve 14 closes and further treat- -ment of the melt is effected as in the initial period only with the hydrocarbon gas by using the proposed rates. On compb-~tion of the treatment with the hydrocarbon gas, the tuyere 4 is taken out of the liquid iron and the ~uppl~ of the hydro-carbon gas i~ stopped by clo~ing to this end the valves 12 a~d 13 and discharging the hydrocarbo~ gas contained at a pres-sure in the feeder 1 with the aid of the valve 16 through t~e branch pipe 25. Thus, the process of treating the liquid iron is considered to be completed.

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The duration of the iron treatment by the proposed method depends on the ma~s of metal being treated, the requisite deg-ree of desulphuration and denitration o~ the iron.
Given hereinbelow are particular examples illustrating the treatment of liquid ~ound~y iron by the proposed method.
Example 1 ~ reatment was performed to desulphurize iron (to a maximum sulphur content of 0.015%) and denitride it.
~ he initial sulphur content in the iron before treatment was 0.053%, o~ygen content was 0.010% and nitrogen - 0.007%.
A ladle contained 60 t of iron (the rated ladle capacity being 72 t.).
A mixture of powdered magnesium with dolomite i~troduced into liquid iron with nat~ral ga~ wa~ employed as a reagent.
~ ho iron was treated by the method of the invention:
- prior to and upon introducing the magne~ium-dolomite mix~re into the li~uid iron natural gas wa~ injected deep into the melt at a rate o~ 0.5 l/t.s.~
- the employed magnesium-dolomite mi~ture contained 25% of powdered magnesium, the balance being dolomite;
- the gas/solid reagent ratio was egual to 20 1 o~ natural ga~ per kilogram o~ the magnesium-dolomite mixture;
- the rate of introducing magnesium and natural gas into the iron amounted to 2.1 l/t.s.

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Magnesium co~sumption amounted to 0.62 ~g/t.
The following results were obtained:
- final sulphur content in iron - 0.014%
- final oxygen content - 0.004%;
- final nitrogen content - 0.003%~
- iron desulphuration degree - 73.5~0~
- magnesium utilization degree in liquid iron (including magnesium consumption for binding sulphur, deoxidation of iron and iron saturation with magnesium) - 72.0%.
Treated iron ~as used for melting high-grade steel.
Example 2 ~ reatment was carried out to effect desulphuratio~ of iron (to a maximum sulphur content of 0.01~) and its denitration.
~ he initial sulphur content in the iron was 0.040%, oxy-gen content ~a~ 0.009% and nitrogen - 0.006%. A ladle contained 100 t of iron (the rated ladle capacity being 120 t.), said 100 t. bei~g subjected to ~aid treatment.
A~ for th~s reagent, use was made of a mixture of po~dered magnesium with lime, which was lntroduced into the iro~ with a stream of natural gas.
The iron w~s treated by the method of the invention:
- prior to and upon introduci~g the mixture of magnesium with lime i~to the liquid iron, natural gas was i~jected deep into the melt at a rate of 0.7 l/t.s.;
- the employed magnesium-lime mixture contained 33% of powdered magne3ium, the balance being lime;

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- , . ' - ' ~ - -- the gas/solid reagent ratio wa~ equal to 65 l of natu-ral gas per kilogram o~ the magnesium-lime mixture;
- the rate of introducing magnesium and natural ga~ was

3.0 l/t.s.
~ agnesium consumption amounted to 0.53 ~g/t.
The following results were obtained:
- final sulphur content in iron - 0.010%~
- final oxygen conte~t - 0.003~;
- ~inal nitrogen content - 0.004 - iron desulphuration degree - 75.0 - mag~esium utilization degree in liquid iron - 73-5%-Treated iron was employed for melting high-grade steel.
Exam~
60 t. of ~oundr~ iron were subjected to the proposed trea- -tment to ef~ect deep desulphur~tion (to a m~imum sulphur con-tent of 0.005~o) and denitration.
~ he initial sulphur content of the iron before treatment amounted to 0.035%, oxygen content was 0.008~ and nitrogen-a.oo7%.
The iron wa8 treated with pulverized essentiall~ puremagnesium introduced deep into the metal with propane by the method of the i~vention: ~ -- prior to and upo~ introducing magnesium into the li-quid iron propane was injected deep into the melt at a rate of 0.41 vt.s.

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10~755 - the gas/solid reagent ratio was equal to 200 l. of pro-pane per ~ilogram of magnesium;
- the rate o~ introducing magnesium and propane ~as 1.26 l/t.s.
Magnesium consumption for iron treatment amounted to 0~54 kg/t.
The ~ollowing result~ were obtained after treatment:
- final sulphur content in iron - 0.003%;
- final o~ygen content - 0.002%;
- final nitroge~ content - 0.003%J
- iron desulphuration degree - 91. 5~o~
- magnesium utilization degree in liquid iron - 87.0%.
After treatment the iron was cast into pigs by a pig ca~ting machine.
Exam~le 4 140 t of conversion iron were subjected to the proposed treatment to provide deep dosulphuration and denitration.
~ he initi~l sulphur content in the iron amounted to 0.040~, oxygen conte~t was 0~009% and nitrogen - 0.006%.
~ he iron, similarly to Example 3, was treated with pulve-ri~ed Lagnesium introduced with the aid o~ a prop~ne stream.
Treatment conditions and parameters corresponded to those specified in the ~ethod of the in~ention:
- prior to and upon introducing magnesium into the liquid iron propane ~a~ inje¢ted deep into the melt at a rate of 0.7 l/t.~.

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- the gas/solid reagent ratio wa~ equal to 500 1 of pro-pane per ~ilogram of magnesium~
- the rate of introducing magnesium and propane was 1.3 Vt.s.
~ agnesium cinsumption for iron treatment amounted to 0.56 kg/t.
~ he following result~ were obtained after treatment:
- final sulphur content in iron - 0.005%;
- final oxygen content - 0.002%
- *inal nitrqsen content - 0.003 - iron desulphuration degree - 88.0%;
- magnesium utilization degree in liquid iron - 82.5%.
The treated iron was emplo~ed for melting high-grade steel steel Example ,~
60 t of conversion foundr~ iron were subjected to the ~.
proposed treat~ent to provide it~ desulphuration (to a maxi- : :
mum sulphur content of 0~010%) and denitration.
~ he initial sulphur content in the iron amounted to 0.040% oxygen content wa~ 0.011~ a~d nitrogen - 0.007%.
The iron was treated with granulated magnesium introduc~d deep into the melt with tho aid of a natural gas stream b~ the method o* the invention:

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-- prior to and upon introducing granulated magnesium into the liquid iron natural gas was injected deep into the melt at a rate o~ 0.55 l/t.s.;
- the gas/solid reagent ratio was equal to 200 l of natu-ral gas per kil~gr~m of granulated magnesium;
- the rate of introducing magnesium and natural gas was 2.1 l/t.s.
Magnesium cons~mption for iron treatment amounted to 0.49 ~gJt.
~he ~ollowing results were obtained:
- final snlphur co~tent in iron - 0.007~0;
- final oxygen content - o.oo3%t - final nitrogen content - 0.003%;
- iron desulphuration degree - 82.5%~
- magnesium utilization degree in li~uid iron _ 90 0%
After treatment the iron was used for melting high-grade steel.
Exam~le 6 ~ or purpo~e o~ comparison iron from the ~ame heat produc-ed in a bla~t furnace, as in Example 5, was treated with granu--lated mag~esium taken from the same batch but with compressed air employed a~ the carrier gas. The rate of feeding magnesium into the li~uid iro~ a~ou~ted to 2.4 g/t.s. J magnesium concent-ration in the air being 6.0 kg/m3.

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~ he rated capacit~ o~ the ladle, as well as the weight of the liquid iron in said ladle were sImilar to those of Example 5.
Hence, the initial co~ditions for iron treatment in Examples 5 and 6 were identical, but the techniques of extra--bla~t-furnac0 treatment did not correspond to the method of the inventio~.
The initial sulphur content in the iron prior to treat-ment was 0.038%, oxygen content was 0.011% and nitrogen --- 0.007%.
Magnesium consumption ~or iron treatment amo~nted to0.5 ~g/t.
~ he treatment results were as follows:
- ~inal sulphur content in iron - 0.013%i - final oxygen content - 0.006%;
- final nitrogen content - 0.007%~
- iron desulphuration degree ~ 66.0 - magnesi~m utilization degree in liquid iron - 64.0~.
Exam~la 7 120 t of cast iron were subjected to the proposed treat-ment to effect deep desulphuration and denitration.
~he initial sulphur content in the iron amou~ted to 0.035%~ o~ygen content was 0.008% and nitrogen - 0.006%~

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1~t3755 ~ he liquid iron wa~ treated with granulated magnesium with natural gas used as the carrier gas. The treatment tech-ni~ues corresponded to the method o~ the invention~
- prior to and upon feeding granulated magnesium into the liquid iron natural gas was injected deep into the melt at a rate o~ 0.9 l/t.s.;
- the gas/solid reagent ratio was equal to 400 1. o~ natu-ral gas per kilogram of granulated magnesium;
- the rate of introducing magnesium and natural gas was ~ --3-5 Vt.s.
Magnesium consumption amounted to 0.54 kg/t.
After treatment the following results were obtained: -- final sulphur content in iron - 0.003%~
- final oxygen content - 0.002~
- final nitrogen content - 0.003%;
- iron desulphuration d~gree - 91.5%;
- magnesium utilization degree in liquid iron - 87.0%.
The iron obtained upon treating was cast into pigs on a pig casting machine.
Exam~le 8 Treatment was performed to desulphurize iron (~or produc-ing commercial iron with sulphur contents o~ up ~o 0.02%) and to e~fect its denitration.

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lhe initial sulphur content in the iron amounted to0~065~o~ ox~gen content was 0.012% and nitrqgen - 0.007~0.
60 t of the liquid iron were subjected to said treatment.
As the reagent use was made of pulverized magnesium-aluminum alloy introduced into the liquid iron in a natural ga3 stream.
~ he liquid iron was treated by the method of the invent-ion:
- prior to and upon introducing the magnesium alloy into the li~uid iron natural gas was injected deep into the melt at a rate o~ 0~5 vt.s.~
- the employed magnesium alloy comprised essentially 50~ of magnesium and 50~ of aluminum (with traces o~ zinc);
- the gas/solid reagent ratio amounted to 50 1 of natural -gas per kilogram of the magnesium alloy~
- the rate o~ introducing magnesium and natural gas into the iron ~as 2.0 vt.s.
~ agnesium consumption wa3 0.52 ~g/t.
~he ~ollowing re~ults were obtained:
- final sulphur conte~t in iron - 0.020%;
- ~inal o~gen content - 0.006%~
- final nitrogen content - 0.003%~
- iron de~ulphuration degre~ - 69.
- magnesium utilization degree in liquid iron _ 93.o%.

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108~3755 On being treated the iron was poured into a mi~er and employed for melting steel.
Example 9 100 t of iron were treated to produce commercial, in terms of its sulphur content, iron, with a maximum sulphur content o~ 0.018% and decreased nitrqgen content.
The initial sulphur content in the iron amounted to Q.050%, oxygen content Was 0.011~o and nitrogen - 0.007~o.
~ he iron was treated with a secondary magnesium alloy which was introduced into the liquid iron with the aid of a natural gas stream by the method of the inventio~
- prior to and upon introducing magnesium into the liquid iron natural gas Was injected deep into the molt at a rate of 0.7 vt.s-;
- the emoployed magnesium alloy contained 82% magnesium, ~0% aluminum and 8% zinc;
- the ga~/~olid reagent ratio amounted to 250 l o~ natu-ral gas per kilqgram o~ the magnesium alloy~
- the rate of introducing magnesium and natural gas was - 2.7 l/t.s.
~ agnesium coLsumption ~or treating the iron was 0.47 kg/t ~he following re~ults were obtained:
~ al sulphur content in iron - 0.015%;
- final o2ygen content - 0.005%;
- ~ina1 nibroge~content - 0.003%;

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10~37SS

- iron desulphuration degree - 70.5~0;
- magnesium utilization degree in liquid iron - 85.5%-On being treated the iron was poured into a mixer to beused for melting steel.
A~ shown by the foregoing Examples Nos. 1 through 5 and 7 through 9, the proposed method of extra-blast-furnsce treatment o~ iron allows treati~g great masses of the liquid iron, ensuring its desulphuratio~ within the required limits, as well a~ its denitration and deoxidation along with a high magnesium utilization degree.
A comparison of Examples 5 and 6 makes it possible to ar-rive at a conclusion that th departure from the proposed method of treating iron adversely affects the results of sald treatment: iron denitration in not effected~ iron desulphura-tion and deoxidation efficiency are diminished and the magne~
8ium assimila1,ion degree is abruptly reduced.

. . ,

Claims (14)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A method of extra-blast-furnace treatment of liquid iron in vessels, in which solid particles of a magnesium--containing reagent are introduced into the liquid iron with the aid of a hydrocarbon gas stream, a gas/solid reagent ratio being equal to 15-600 1. of the hydrocarbon gas per kilogram of the magnesium-containing reagent.

2. A method of Claim 1, in which the gas/solid reagent ratio amounts to 15-85 1. of the hydrocarbon gas per kilogram of the magnesium-containing reagent.

3. A method of Claim 2, in which as said magnesium-con-taining reagent use is made of a mixture having the following composition, percent by weight:
magnesium, 20-35 substance selected from a group consisting of lime, dolomite, carbide slag, . . . the balance.

4. A method of Claim 1, in which the gas/solid reagent ratio amounts to 50-600 1. of the hydrocarbon gas per kilogram of the magnesium-containing reagent.

5. A method of Claim 4, in which the magnesium-containing reagent is essentially pure magnesium in pulverized stats.

6. A method of Claim 4, in which as the magnesium--containing reagent use is made of granulated magnesium of the following composition, percent by weight:

metallic magnesium, 85-98 oxides and salts of alkali, alkali earth metals and magnesium, . . . . . . . . . . . the balance.

7. A method of Claim 4, in which as the magnesium-contain-ing reagent use is made of magnesium alloys with aluminum and zinc of the following composition, percent by weight:
magnesium, 50-96 aluminum, 4-50 zinc; traces-10.

8. A method of Claim 1, in which the introduction of said magnesium-containing reagents into the liquid iron is effected with such a consumption of said magnesium-containing reagents and of the hydrocarbon gas that the amount of magnesium vapors formed thereof and of the hydrocarbon gas introduced thereinto will ensure an intensity of 1.2-4.0 l/t.s.

9. A method of Claim 3, in which the introduction of said magnesium-containing reagents into the liquid iron is effected with such a consumption of said magnesium-containing reagents and of the hydrocarbon gas, that the amount of the magnesium vapors formed thereof and of the hydrocarbon gas introduced thereinto will provide an intensity of 1.2-4.0 l/t.s.

10. A method of Claim 5, in which the introduction of said magnesium-containing reagents into the liquid iron is ef-fected with such a consumption of said magnesium-containing reagents and of the hydrocarbon gas, that the amount of the magnesium vapors formed thereof and of the hydrocarbon gas introduced thereinto will provide the intensity of 1.2-4.0 l/t.s.

11. A method of Claim 6, in which the introduction of said magnesium-containing reagents into the liquid iron is effected with such a consumption of said magnesium-containing reagents and of the hydrocarbon gas, that the amount of the magnesium vapors formed thereof and of the hydrocarbon gas introduced thereinto will provide the intensity of 1.2-4.0 l/t.s.

12. A method of Claim 7, in which the introduction of said magnesium-containing reagents into the liquid iron is ef-fected with such a consumption of said magnesium-containing reagents and of the hydrocarbon gas, that the amount of the magnesium vapors formed thereof and of the hydrocarbon gas introduced thereinto will provide the intensity of 1.2-4.0 l/t.s.

13. A method of Claim 1, in which prior to and upon feed-ing said magnesium-containing reagents into the liquid iron the hydrocarbon gas is introduced deep into the melt at an intensity of 0.4-1.0 l/t.s.

14. A method of Claim 8, in which prior to and upon feed-ing said magnesium-containing reagents into the liquid iron the hydrocarbon gas is introduced deep into the melt at an intensity of 0.4-1.0 l/t.s.