DE2146923A1 - Process for deoxidizing molten metal - Google Patents

Description

DIPL .-. 'NG. Λ. QRÜNECKER f <goo monks i-a

DR.-1N0. H. i'iNKFLDPV ΜοχΙιηΙΙίοηιΙπιβ 43

Call 297100 / ίίί7 «

DR .-! F * "3. W. STOCKMAIR, Ao. E." al ..- .. "st.ο * τγ _λ -. _(Μ ., Wag ™", "" η ^,>",. «=. *:,.

PATEf.'T / .MVV ^ LTEi. ΤβΙοκ 05-26380

Godparents iari η: ^ i du ng

2H6923

l '-'! - 214- ^ 0 / Ml September 20, 1971

Allegheny Ludlura Industries, Inc. Oliver Building

JLl ^ Mb ¹ AyIaLr. Pennsy lvania 15222 USA

Process for deoxidizing molten metal.

The invention "relates to a method for deoxidizing molten metal and in particular a method for Deoxidation of molten metal, ie the carbon content of the molten metal kept at a value "or on a value is lowered which is the same as or less than that present at the beginning of the deoxidation.

2098U / 0999

2H6923

Current metal, ζ.-S. Steelmaking processes include often a deoxidation treatment. It is extraordinary It is desirable to reduce the oxygen content of a melt, since oxygen dissolved in the melt is in the form of non-metallic ones Inclusions can precipitate that adversely affect the properties of the metal.

'Various methods of deoxidation have been used in the past. In one of these methods, highly reactive elements, such as silicon, titanium and / or aluminum, are used, which can combine with the oxygen present in the melt to form oxides, which are then deposited from the melt. Sufficient time must be allowed for the separation of the oxides and the melt. In a second method, a predetermined amount of carbon is mixed with the melt and a dynamic hydrogen atmosphere is added to regulate the "carbon boil" or decarburization.

^ turns. This method can be used to determine the oxygen content effectively reduce, but the use of this method often adversely affects the achievement of the desired low carbon content (see e.g. U.S. Patent 5 188 198). With a third, especially for alloy steels With a high »carbon content effective method, the carbon monoxide partial pressure in the vessel (reaction vessel) is reduced.

2088U / 0966

ßÄD ORIGINAL

2U6923

Reducing the carbon dioxide partial pressure shifts that DC rectification ratios and lowers the achievable final carbon content without necessitating excessive oxidation of the metallic components and thereby sets carbon for the union with oxygen in the melt free »The Reduction of the »Koehler -ionoxyapartialdrucks can by decreasing doc total pressure in the vessel and / or by introducing Argon can be reached into the vessel. With this third method, however, the theoretically expected results lance themselves not or not completely, as the carbon-acid off ~ - Reaction does not proceed completely. Seen thermodynamically the system behaves as if it were under a higher pressure.

Another rather interesting prior art method is described in an article by VF Moore entitled "Deoxidation Techniques For Vacuum-Induction Melting""published in The Journal of Metals, 1963, pages 918-921 The method described there is used natural gas, which consists of 9 ^, 9 vol. # CE ₄ , 3.2 vol.% C ₂ H ₆ , 1.0 vol.% C ₃ Ii ₈ , 0.1 vol.% C ₃ H ₄ , 0.6% by volume of CO ₅ , 0.1% _{by volume of H 2} 0 and 0.1% by volume of Hp + CO consists in order to deoxidize the melt. The results obtained with this process were promising in terms of the degree of deoxidation, disappointed

20 9 8 U / 0966

BATH ORIGINAL

2Η6923

■, however, the manufacturers and processors who deal with steel both need low carbon as well as oxygen content. (Hit the natural gas was an excess of carbon in the Melt introduced, which increased its carbon content).

The present invention is therefore based on the object of creating a method which makes it possible to melt a metal to effectively deoxidize and at the same time to regulate the carbon content so that it is about the same. or even lower than the carbon content before the corrosion treatment is.

It has been found that this task is in principle thereby can be solved by using at least one deoxidizing agent Hydrocarbon as well as at least one diluent gas is used, the diluent gas makes it possible to use small amounts of hydrocarbon deoxidizer to work and thereby avoid blowing too much carbon into the melt, while at the same time a gas injection speed can be maintained which is sufficient to achieve a sufficient Mixing of the hydrocarbon._des_Qv: ydating agent with to ensure the melt. One can thus control the feed rate of the hydrocarbon oxidizing agent decrease without reducing the speed of the conversion of the acid

2098U / 0966

Stoffs slit to reduce the carbon by working with the hydrocarbon desoxidizing agents. introduces a dilution gas.

The invention thus relates to a method for deoxyciating of molten metal, "in which the carbon content of the molten metal held at a value "or reduced to a value that is the same as" or smaller than the one at the beginning of the Deoxidation is present, which is characterized in that a hydrocarbon is added to a vessel containing the molten metal deoxidizer and. introduces a diluent gas, "wherein the hydrocarbon deoxidizer reacts with oxygen contained in the molten metal to form gaseous carbon compounds reacts, which escape from the vessel, thereby the effect of hydrocarbon deoxidizer and diluent gas "with regard to the carbon content of the molten metal "and the ratio of hydrocarbon deoxidizer to diluent gas regulates so that the "per unit of time the Average amount of carbon leaving the vessel is at least about as large as the average amount of carbon leaving the vessel per unit of time supplied carbon deficiency.

One might assume that the main disadvantage of the above discussed from the article published in the Journal of Metals

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BATH

2H6923

"known Verfah.rer. s-characterized corrected or could v.'orc.an avoided that ν blown into the melt Naturgasraenge erring ert. The naheliegensbe possibility, this zv reach," would be simply the Naturgaszufuhrgeßchv.rr : - to decrease the speed. However, this reduces the mixing effect caused by oil- gas injection and consequently also. the extent of the reaction between the. carbon evolving from the gas and the oxygen in the melt.

For the purposes of the invention, one or more hydrocarbon Deoxidizers can be used, consisting of a "wide range of different gaseous and liquid hydrocarbons." and substances containing hydrocarbons as well as one or more diluent gases that can be selected from a wide range of different substances.

Examples of suitable hydrocarbons and substances containing hydrocarbons are methane, ethane, propane, F ethylene, water gas and natural gas. Examples of suitable diluent gases are argon, nitrogen, hydrogen and carbon

• r

monoxide. When using liquid hydrocarbons and substances containing hydrocarbons, an additional measure must be taken nebulize the liquid into the diluent gas stream. The hydrocarbon deoxidizer and the

209814/0966

BATH

~ ι -

Diluting gas can be blown into the metal melt or on the surface of the melt can be inflated.

The boron effect of the hydrocarbon deoxidizer on the fluorine content of the melt can be determined from the initial and final analysis data of a previously deoxidized melt. A comparison of the initial and final analysis values, together with the feed rate and the analysis values of the carbon; hydrogen deoxidizer and / or diluent gas (diluent gas is not required in this case, as it is not necessarily a melt that must have a low carbon content ), provides the information required to determine the degree of utilization in which carbon from the deoxidizer combines with oxygen. The degree of utilization, in which carbon and oxygen combine, indicates how the ratio of hydrocarbon deoxidizer to diluent gas should be selected for subsequently deoxidized melts with the same chemical composition, which are to be deoxidized under the same or similar conditions, e.g. with the same gas injection speeds. For example, a carbon-oxygen reaction efficiency of 50% when deoxidizing a melt using 80% hydrocarbon deoxidizer and 20 % diluent gas indicates that subsequent melts using 4-0 % or less hydrocarbon deoxidizer and

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2H6923

50 % or less diluent gas deoxidized; should be _v if., the melts have the same chemical characteristics and are entorydated under the same conditions. v / should be grounded.

Although the method described above for determining dos Effect of carbon deoxy & atxonic agent far "Better than just sufficient, it is with an ITacli part afflicted. In this way, namely, the end point as a result of fluctuations in the analytical data of the melt, the temperature and the effectiveness or efficients of the gas blowing are not regulated or adjusted too precisely.

Another optional method for determining the effect of the hydrocarbon deoxidizer overcomes this disadvantage of the method described above. The latter method calculates, among other things, the rate at which carbon is introduced into the vessel and the rate at which carbon leaves the vessel. * The carbon feed rate can be calculated from the composition and feed rate of hydrocarbon deoxidizer and diluent gas. will. The carbon removal rate can be calculated from the analysis values and the removal rate of the gases leaving the vessel (a recorder system can be used to analyze the exhaust gases). The calculations make it possible to regulate the carbon content of the melt

209814/0966

1 BATHROOM A

the speed at which carbon pulls the vessel " is stirred to regulate.

In the following paragraphs, the types of roactions that occur in the anti-oxidation method according to the invention are described by way of example, as well as a method for calculating both the carbon supply and the carbon removal. As an example of a hydrocarbon deoxidation agent, methane, GH ₄ , is chosen for purposes of illustration.

In the case of deoxidation with methane mainly the following reactions take place:

CH ₄ (gas) + 0 = CO (gas) + 2H ₂ (gas) CH ₄ (gas) + MO = M ₊ CO (gas) + 2H ₂ (gas)

The deoxidation reactions can be carried out at atmospheric, as well as at both below atmospheric and above atmospheric pressures.

The following reaction leads to the carburization of the bath: OH ₄ (gas) «CJ + 2H ₂ (gas)

Another carburization reaction that turned out to be intolerable! high levels can take place if too high an amount there is a presence of carbon deoxidizer, is following

209814/0966

(Gas) = C ι- 2H ₂ - (gas)

The hydrocarbon deoxidizer becomes go ω: · a el ·: fc and deposits carbon (soot) in the colder parts of the vessel.

The carbon feed as well as the carbon feed rate can be determined using the following equations:

The total atomic weight of the vessel

supplied to into the _{Λ mol of} carbon / Sg7 carbon = vessel put X X

amount fed ²² > ⁴ &»& ^{1 Mo1} methane £

atomic wt. of pounds of carbon total cu.ft. _{1 mole of carb (m}

introduced into "of methane X X

the vessel introduced ^ ^{60 cu} ' ^ft · ^{1 mole}

into the vessel

charcoal fed into the vessel

" Amount of carbon input £ kg J

speed? ^β

The carbon removal and the carbon removal rate can be determined from the following equations

209814/0968

BAD OftKSNAl

The vessel
leaving
Amount of carbon

to the CIL leaving the vessel, CO and Ov

1 mole

Atomic weight of carbon

Zcb.m7

TiQS Ol

carbon leaving
the vessel

Carbon removal rate

total cu.ft. of CH ₄ , CO and COp leaving the vessel

1 mole

atomic vrt »of carbon (lbs.)

360 cu.ft.

1 mole

Amount of carbon leaving the vessel /

Time

For the proportions of hydrocarbon deoxidizer No numerical values can be given for the diluent gas, as it occurs during the deoxidation treatment can change. In some cases it is even expedient to deoxidize in the final stage with and without an inert gas to carry out any addition of hydrocarbon deoxidizer. The inert gas reduces the partial pressure of Carbon monoxide, changes the equilibrium or Ratios and shifts the achievable final carbon content in the direction of lower values without a To make excessive oxidation of metallic components necessary, whereby carbon is released to deal with To combine oxygen in the melt. In addition, this causes a thorough mixing of the melt promotes or accelerates the carbon-oxygen reaction. As a general rule it can be stated that the

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2Η6923

Hydrocarbon Deoxidizer and the Diluent gas into the vessel at an average gas bite rate of at least about 0.566 cbm / hour be blown in. Preferably the average gas sparging velocity is at least 0.85 cbn / Hour. However, the invention also encompasses the use of lower gas injection bonds. An exact value cannot be specified for the minimum speed as it is related to the process variables, e.g. the depth of the Metal melt or the metal bath, fluctuates.

In the context of the invention, the final oxygen content can optionally also be regulated. You have to do this the oxygen content before the deoxidation treatment or know at a certain point of the deoxidation and mathematically the amount of oxygen leaving the system determine. The oxygen content of the melt can be determined by means of an electrical voltage cell (EMF cell) or by chemical analysis can be determined. The amount of oxygen leaving the system can be determined from the analysis data of the gases leaving the system (exhaust gases) and calculated with the aid of the following equations will:

209814/0966

BAD ORfGJNAt

From the
system
outgoing Sauex 'amount of substances / Έβ7

leaving the system

2U6923

Atomic weight
of oxygen

1 Hol

= Total amount X X

.-, p, _no . 22.4 / cbn7 average

/ Sg / liohes nol ^ l-axcx,

weight of the gases leaving the vessel

pound D of oxygen

total cu.ft.

1 mole

atomic \. ^r i \. of oxygen ()

leaving the system of CO, C0 _? and 360 cn.ft. average

H ₂ O leaving the molecular

system

wt. of gases
leaving the vessel

Oxygen removal speed

Amount of oxygen leaving the system / kg7 Time

If you take the measured oxygen content of the melt and the rate at which oxygen is released from the system, knows, one can easily determine the amount of oxygen still remaining in the melt at a certain point in time.

The following examples explain the invention using the method according to the invention on steel, which is the most common embodiment of the invention. However, the method of the invention can be applied to a ■; A wide variety of metals can be used, including, for example, both nickel and cobalt alloys.

'. 2098U / 0966

BATH

There are three £ 'j aiii melt (A, B wad C) & ακ korroc-ionsbestäiiuigem steel it with each of £ iiachf.tehc.ndan Table I to ersehenden carbon, oxygen "- entoxydiert xcacl Btickst held off.

Table I. Analysis (TpM) 18th 0 140 G 187 14-5 71 . 383 190 161 24-0

melt

Melts A and B are used for 30 minutes with pure methane decoxidized, while the melt C 30 min. With a Gas mixture of 2% methane and 98% argon (diluent gas) is deoxidized. The average injection speed for both pure methane (melt A and B) and also for the methane-argon mixture (melt C) " 1.02 cbm / hour each.

From Table II below are the carbon, oxygen and nitrogen analysis values of the deoxidized Seen melting.

2098.1 A / 0966

τ ..- -

Analysis (TpM) 2U6923 ToWlIe II 0 115 C. 86 κ 164 32 13th 440 84 10 43

ScliBielze

A comparison of the Tables I and II above values listed shows that "in the melts A and B, the oxygen content decreases as a result of the treatment, but the carbon content in each case increases, while in melt C both the carbon and the oxygen content is also considerably reduced in each case. The deoxidation of melts A and B does not take place according to the method of the invention, since pure methane is blown into the melt in each case. The deoxidation of the melt C, however, corresponds to the method of operation proposed according to the invention, since methane and a dilution gas are blown in.

20981 A / 0966

JBADQBiQiKAi.

Claims (14)

2U6923 P 42-14-50 / Ml. September 20, 1971 claims 1. Process for deoxidizing molten metal in which the carbon content of the molten metal increases a value "or is reduced to a value that is the same as or less than the one at the beginning, the deoxidation is present, characterized in that one is in a. A vessel containing molten metal introduces a hydrocarbon deoxidizer and a diluent gas, wherein the hydrocarbon deoxidizer with the oxygen contained in the molten metal to form gaseous carbon compounds reacts, which escape from the vessel, thereby the effect of hydrocarbon deoxidizer and Diluent gas determined with respect to the carbon content of the molten metal and the ratio of ) Hydrocarbon deoxidizer to diluent gas regulates so that the average amount of carbon leaving the vessel per unit of time (carbon removal rate) is at least about as large as the average for the vessel per unit of time Amount of carbon supplied (carbon supply speed). 20 9 8 U- / 0 966 2U6923 2. The method according to claim 1, characterized. That the "or the hydrocarbon deoxidizing agent and the diluent gas (s) blown into the molten metal. 3. The method according to claim 1, characterized in that that the hydrocarbon ™ deoxidizer and the diluent gas (s) be inflated on the molten metal. 4 ·. Method according to at least one of claims 1 to 3, characterized in that the deoxidation conditions and in particular the carbon deoxidizer-diluent ratio based on the effect of the hydrocarbon deoxidizer and diluent gas selects or determines the carbon content of the »melt, which is determined by first “the carbon content of a first molten metal in a vessel (Sample melt) determined analytically, the sample melt with the hydrocarbon deoxidizer deoxidized, the amount of carbon fed into the vessel containing the sample melt calculated, the carbon content of the deoxidized sample melt determined analytically and then the deoxidation efficiency of the carbon introduced into the first melt is calculated. 2098U / 0966 2U6923 5. The method according to at least one of claims 1 bin ^, characterized in that one the "effect of the hydrocarbon deoxidizer? and the diluent gas in terms of carbon content the molten metal determined by ie ar. the carbon feed rate and the carbon abtranspor {^ speed determined by calculation. 6.! ^ Experience according to claim 5? characterized in that one leaves the vessel Gases (exhaust gases) analyzed. 7. The method according to at least one of claims 1 to 6, characterized in that hydrocarbon deoxidizer is introduced into the vessel containing the molten metal and diluent gas at an average total feed rate feeds in at least about 0.566 cbm / hour. 8. The method according to claim 7 »characterized marked ψ is characterized in that an overall average feed rate is applied by at least about 0.85 cubic meters / hour. 9. The method according to at least one of claims 1 to 8, characterized in that a molten steel is used as the molten metal. 2098U / 0966 10. Verfahrsn according to pintlest-ons one of claims 1 to 9, characterized in that used as a coal earth; oi \ l "deso: xydat ± orisini" fcteX methane will. 11. The method according to at least one of claims 1 to 9, characterized in that a liquid hydrocarbon deoxidizer is used and nebulized into the diluent gas. 12. The method according to at least one of claims 1 to 11, characterized in that argon is used as the diluent gas. 13. The method according to at least one of claims 1 to 12, characterized in that the final oxygen content of the molten metal is regulated, 14. The method according to claim 13 »characterized that the final oxygen content of the metal melt is regulated by adjusting the oxygen content the molten metal is determined analytically and then the amount of oxygen leaving the vessel calculated. 209814/0966