DE2018283A1 - Process for the production of stainless steel - Google Patents

Description

Patent attorneys Dipi.-Ing. A. ünhocker

Dr.-Ing. H. Kr -! -: ϊ ' ^: γ_
DtAn-J. Λ · ν. '■ ■ ■: "■">"
8 Munich 23. tu .. ,. ·. . '.) "·'" · «■

15. '4 1970

P 3195 - / F

Allegheny Ludlum Steel Corporation 2000 Oliver Building, Pittsburgh »Pennsylvania 15222, USA

Process for the production of stainless steel

The invention relates to a calibration Saueratoffveredelungsverfabren (Oxygen Refining Method) "for producing roetreiea steel, in particular to such a method · b" i atm an electric furnace or a basic oxygen furnace (Basic Oxygen Furnace) reaches mr application.

The manufacture of stainless steel requires a lengthy and costly process _for recovering the chromium from the slag. When oxygen is added to the molten metal bath, carbon, iron, and magnesite are converted into slag .. thermodynamic is given for "of Kohleno? ono2cyd knew this be prevented would if the oxygen at temperatures in dor order of sloo ^to-0 C, set, since the carbon to chromium at these temperatures preferentially oxidized. The use of such temperatures, however, is not yet open to discussion today, since there is fire. solid materials »that could withstand these temperatures and would be compatible with the production of stainless steel» are not yet commercially available «

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The invention is based on the object of specifying an oxygen refinement process for the production of stainless steel, with the aid of which the chromium content from the slag can be recovered economically without a process consisting of several steps and at which the temperature is so low that the refractory materials of the boiler are not attacked. In addition, the process should allow "last chemical additives to be added to the container" ie the steel ladle that rivets the molten metal out of the boiler. can be considerably shortened at the side »Until now, H» lsB «it« tt (furnace refining tines) ear Veredelang _aij * J> tahJL * tUr were considered necessary to obtain »high quality stainless steel SM ·

This object is achieved according to the invention in that the metallic melt containing chromium and licks-forming additives with a carbon content of 0.15 # oxygen is supplied, and that the oxygen is added to the melt with the chromium and the other metallic or non-metallic additives to form reaction products , dieJ.zuV · _ sansäen bit the slag-forming additions form a slag, is reacted _r that the supply of oxygen is interrupted in the boiler when the temperature of the metal reaches a value of about 1 SO ° C and the coals'? - 'oxygen content below about 0.15% is ₅ that thereupon a "sufficiently large Mange is the Schlack® reducing agent added" to this inabesondere _t whose metal content reduced seu, and that the slag will be strongly mixed ₉ ata this reaction aar recovery of ^ Ilachen shares .. »us der Schlack® in .accelerate« * »·

0098 50/13 9S

Using the drawing and the description below The invention is to be explained in more detail below.

The figure is a graphic representation of the dependence of the percentage of chroa in the reduced Slag aged as a function of the slag base Invention·

The following description refers to processes as they are used as the type of basic oxygen furnace can reach, as this is the largest part of the oxygen refinement process out · Bs will, however, always refer to the electric furnace whenever it is relevant »

The process carried out with the help of basic oxygen furnaces begins with the formation of an initial batch of liquid substitute metal and cold or preheated scrap and the reducing agent "the relative proportion of liquid Binaatsaetalls and the scrap as well as their composition Bind theraiech balanced, so that the Bndteaperatur de · eauerstoffgeblasenen metals (see welter below) at about 1780 ⁰ Cr. is preferably between 1880 ° C and 1980 ° C. The starting batch should contain at least 50 % liquid Bineatzmotall in advance. A higher percentage of scrap can be used if it is preheated. The liquid insert metal can be free of chromium or contain chromium. A typical analysis for a chromium-free insert metal contains 4.25 % C _% 0.5 Ji Si, 0.5 % H », less

0 0 9 8 5 0/1395

bath

ala 0.085 % S, less than 0.03 Ji P, wad the remainder Elsen. Am · typical · ·· Analy FTIR "in containing chromium metal is k% C, 0.2 Ji Να, 1.00 S S, 11.65% Cr, 8.9 * Ni, less than 0.03 Ji P, Less than 0.03 Ji ^s and the remainder bis-chromium-free insert metal is to be preferred, as it allows greater flexibility in the Schm "lawerk" 0 scrap is preferably made of stainless steel and / or chromium. Other sources of scrap are chromium-containing materials such as chromium-silicon (ferrochromium-IIIcon) and chromium ore. 01 «Auegangscharg« can also contain chromium with a low C content and / or metallic chromium Considered very economically · Chromium-free scrap can be set if «containing chromium ·· bloom metal is used · The liquid binocular metal and / or the scrap can also contain nickel! Nickel-containing materials or nickel sintered come into question if a chromium-Hickel steel is to be produced.The average content of nickel in the melt is preferably in the desired analysis in the final product, but may be due to non-nickel-containing materials added later in the process, i.e. chromium ions with low C content, 1 to 2 % higher than in the last analysis. The relative composition of the melt, i.e. the scrap and the original input metal, is of little importance.

Loads may be slag-condensing Additives and slag formers added. You can do this both before and during the supply of oxygen (see below) can be added. Typical slag-forming additives are quick lime and dolonite quick lime. They are added to their predetermined

009850/1395

Slag value of at least 0.5 »but preferably 1.0 to 2.0 after the reduction (see below) reach eu · Dmr minimum value of 0.5 and the minimum predicted value of 1.0« are set because they Set the maximum amount of chromium in the reduced slag. The Zeicing inclines how the chromium content in the reduced slag changes with the slag base. A minimum basic value is also advantageous, since refractory lining is less severely attacked compared to acu high basic values. The upper preferred value is set to 2, since slags with higher basic values bring back only a slightly larger proportion of chromium to the molten metal and a considerably larger amount of slag-forming additives, ie "make lime" necessary, cause greater amounts of slag-forming In addition, larger quantities of slag can also lead to a "slag overflow" over the boiler or container. "Soil token overflow" is dangerous for the operating personnel and can also lead to a considerable loss of slag residue with the proportion of chromium contained therein. In order to prevent the layer containing the slag from becoming thick and prevent the passage of oxygen during its supply, slag conditioning additives can be used. Typical slag conditioning additives are pluorite, sodium carbonate, aluminum dross, cryolite and sodium nitrate.

The oxygen is in the melt from Binsat »metal and scrap blown in from above, i.e. from a certain height above the predetermined level of the sleeper * layer or by blowing from a height below the level of the slag layer or a combination of both. The height of the temperature and the formation of the

009850/1395

ie the number of DUs in their directions, determine their distance in the case of bubbles from above. Όβτ blown in · Oxygen reacts with the chromium, iron, magnesium, silicon and carbon of the liquid 'insatxcetails, releasing energy that increases the temperature of the liquid filler metal * and the scrap · The supply is interrupted when the carbon content of the melt reaches • inen beard below O, 15%, is preferably below protected from 0.10%, and when the final temperature of the molten metal at least at 1790 ⁰ C, preferably between 198061legt 187Ο C and. The melt can be heated up «if the temperature is too low or the carbon content is too high · To the desired ·. To reach temperature «the heating can be supported by adding silicon to the melt. Molten metal is at temperatures below 1790 ° C. not conducive to late treatment. This temperature is not high enough to absorb the necessary amount of reducing agent in order to achieve the required composition. In addition, chromium, manganese and iron would prefer to oxidize at low temperatures · Low temperatures favor the oxidation of chromium, manganese and iron, higher that of carbon «

The boiler, a reducing agent is added to correct the LegierungszusamBiensetssung, when the carbon content of the melt below 0 _t 15% and the temperature of the metals wenig0tensi79O ^o Cbetr8gt. The amount should be high enough to really reduce the oxidized chromium, magnesium and iron. Preferred reducing agents are materials containing SIl i sin ta. Typical silicon-containing materials are silicon iron and chrome iron wire.

009850/1395

siu «. Because reducing agents can give you scrap, ie chrome iron and stainless steel old, low C-content and slag-forming agents contain an auf veniger ala 176O ¹ L The scrap can also contain Niokel, ie nickel-containing materials or nickel interiors * if a chrome-Miekel steel is produced.

koadltionieraaeätae such as fluorite. Matriarchal carbonate, A £ *. ■ Bluagrus, Cryolite ad Vatrl «« nterstlltaea entered the Beductlon.

0 «an appropriate reduction of office supplies is necessary Thoroughly mix the slag and the metal. This can be achieved in different ways. Bine Possibility is to have a pressurized atabend · *? Iuid

into the washed netall and the slag of above elnsublaaen '· dth. on one side there is a fixed distance above the pre-atlasite level of the slag stratified or by unaittelea Binblaaen, i.e. Bla «« n from a HBhe under the predestined state of sleep ' ckenschlcht or a combination of both Typical Fluids are dry air, i.e. air has a «dew point of less than about - 29 ° C, non-reactive gases, such as argon or nitrogen and their mixtures. Another or additional option includes defl the Do not tap the kettle through a hole, but through one Gutter takes place. As a result, slag and molten metal are mixed when the container is filled into the cue deoi kettle. Bins third possibility is the fluid. un ^ the pressure in which the sniffed metal and the slag, Pick up container asu epr it »while the stolen Metal and the slag are filled. This possibility

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2013 283

ness can work with any of the two options mentioned first been combined tu "an even more effective mixing to achieve" Additionally, mechanically or old means of an induction coil are stirred · The mixture la electric furnace is not sufficient · do a proper reduction to achieve ·

The molten metal and the slag are cleaned, i.e. poured from the boiler into the container, the steel ladle. The lacquer can be partially or completely reduced at this point , ie before the temperature drops below 1680 (Completed. The container can contain additives such as electrolyte manganese, electrolyte nickel and chrome iron, with low carbon content, which are introduced into the container before it is poured from the results of the analysis of test samples which are taken immediately after the supply of oxygen.After decanting, chemical, tests and tetrapperature measurements are first carried out and then the slag is removed, i.e. decanted or removed. In typical Che-Hisehen examinations, the content of C, Mn, P, S _f Cr, Hi, Mo, Pb, Cu and Sn is determined * A thin layer of slag It can remain on the molten metal until the chemical residues are present. Insulating materials, ie vermiculite, are brought into the container in order to reduce the thermal losses and the temperature of the molten material is high enough for the absorption of final additions to keep. This temperature depends, in addition to the initial temperature, on the amount and type of the last additions and is usually between 15 ° C and 1760%,

009850/1395 originally inspected

preferably between 1590 C and 1700 C. If the temperature of the molten material is too low to absorb the final additions in a satisfactory manner · it can be increased in a virulent way by the controlled addition of silicon-containing materials, ie silicon iron and brief oxygen supply · This oxygen supply causes, however, the formation of a Silialumsohlacke which should be removed before placing the final encores and the last Sohlnckenbestandteile · the recent additions such as chromium iron with low "Kohlenstoffgebalt, Blektrolytmangan, Biektrolytttickel, silicon iron and ^T i tan ei β en de" ge "* molten metal is added after the results of past studies conducted chemical, the chemical composition of the steel to adjust its determination * Schlackeflblld.ende additives such as quicklime and fluorite as Scblackenkonditionierzusätze can together mxx the last ingredients to be introduced "which si e form a final slag * Ea is favorable to move the molten metal, in order to support the melting and alloying of these! label. ', ingredients and the formation of a slag by liquefying the slag-forming additives. One advantageous way of bringing about movement is to inject a fluid under pressure. Typical fluids for this are dry air, ie, lütt

with a «dew point of less than. , Inerte _rr “. _f

Argon or nitrogen and mixtures thereof. Example ^ The following methods of injection come wisely

1. The fluid is through a porous seal, with which «the container is equipped, pressed;

2. The fluid is through a fireproof Bonrvin .. den Pressed container.

009850/1395

Other means of causing movement contain induction coils.

The molten metal in the container and the last slag are poured into a large container, a ladle, when the last chemical additives are ready and when the temperature of the molten metal is in the desired range. The desired temperature range depends on the chemical composition dea steel, and is usually LAT Bchenl480 ° C and L620 ° C, the melted metal Sm the second vessel! Rönnen last additives are still added, "when the molten metal enough even on a high temperature is in order to absorb them in a satisfactory manner. It is advantageous to add titanium substitutes to the second container, since these dissolve easily at low temperatures and are readily oxidized. The second container can be provided with desulfurize additives before the molten metal is poured to it during the pouring "to desulfurize * * The Metallschneize in dom second container can be held for a predetermined time is _t before it is poured into the final molds.

In a preferred embodiment of the invention, a melt is used which contains at least 10 percent by weight of chromium and up to 1 % carbon and scrap which makes up about 10 to 40 percent by weight of the liquid Binsat metal. It comprises the following procedural steps:

1. The output batch of the 3ena «is · mam liquid *» and scrap is formed in the boiler}

009850/1395

BATH

2. Solvent-forming agents are added and an acidic current is directed to the bowl in the boiler, and the solute content of the bowl is reduced to below about 1 %

3 · The supply of oxygen through a JLanse protruding into the Sohmelse is continued until the carbon content of the liquid BinsatametaH is less than 0.10 %

4. Oxygen flow through the aforementioned into the narrow protruding lane is interrupted ι

5. Is becomes a reducing agent old one containing chromium Component specified ι

6. Be introduced a lana «protruding into the slag body and through this an inert gas is forced under pressure into the slag, whereby a mixture is achieved which is the reduction of the in the Schiackeenthai ^ enen ChroMS support

7 «The contents of the kettle are poured into a steel casting ptaane. poured ι

8 · Xn the contents of the steel ladle becomes an inert gas putted to the full reduction of the metallic Eliminate proportions in the slag and the steel bath regarding its chemical composition au hoeRygeni « sieren · The gas is fed through a refractory drill hole the contents of the steel casting ladle passed or passed through a porous opening in the steel casting ladle

009850/1395

9 · Dl · slag is decanted off

10. Κ «warden dl · last ingredients for · appropriately · chemically · Composition of the gowns forming the lacquer added 1

11 "Be becomes an inert gas" through a refractory pipe or el * ne porous opening within the steel gullet piles into it (• pumps around da «layers of steel and the movement of last slag tsu support f

12 · The contents of the steel ladle are poured into a ladle poured t

13 The melt is poured into the last mold

Liquid BinsatzMetall with an average phosphorus content of 0.05 to 0.5 % P and a high phosphorus content of 1.5 to 2.5 % P can be used to further develop the curve. Such liquid KInsatmetall requires at least one additional supply of oxygen, in order to decrease the phosphorus content below 0.05%, as a rule, before the ready Verfahrensabiauf described start "may · temperatures in the order of 137O ° C and 165o ⁰ C for withdrawing Phosphorus preferred. Slag-blocking agents such as burnt lime, dolosely burnt lime and materials containing beech oxide, as well as slag-condensing agents such as fluorite, are used in the metal. High levels of moisture, high FeO sleep and all other temperatures contribute to the reduction of the phosphorus content. However, if the temperature is too low, removing the slag from the melt can be difficult.

009850/1395

Prepare chains »In addition, causes a high content of Iron oxide has a low metallic yield.

The following examples illustrate some embodiments of the invention

Example I.

65500kg Ausgangscbarg · were given "ueanueen" it Spat 680 kg (savings) into a cauldron * The batch contained 47 x 500 kg Bin ^ Atxmetall and 18.OOO kg scrap · The composition dee Sinsatfwietalle was 4.44? C 6 ₁ 0 45 % Hi * 0.027 %? * 0.0i8 % S, o _e 36 $ Si, 0 _r 067 Ji Cr, 0.056 # Ni, 0.092 Jt.fü * 0.005 % Sn and AöefieZihenFe. The scrap contained 10,200 kg of 430 type stainless steel and 7,800 kg of high carbon chromium. Were on the snitch !. 183 »/ min of oxygen at a pressure of 11-3 kp / cm. blown "2,730 kg of quicklime _f il40 kg were added to the boiler; doloMitischeai lime and 680 kg iron granulate ssugesetst. The oxygen supply was interrupted when the temperature of the clioiolxenized metal reached iS> 40 ° C. A reducing agent was added to the kettle. Bs contained 7 * 950 kg; stainless steel (in plate form} of the type 430, 3830 kg chromium silicon and 500 kg of HOIS. The slag and metal were treated with argon mixed asu accelerate the reduction After mixing, the temperature was 178O ⁰ C. The slag and the metal subsequently released. The channel on the boiler was poured into the steel ladle. 227 kg of electrolyte · .manganese were poured into the steel pouring ladle before pouring · Argon was pumped into the pouring ladle during pouring. The slag was ebdekaotiert

009850/1395 ^ ₀

Metal to a chemical test and "ister temperature measurement subjected · The choir niches investigations selgten that dan metal O _s O45% C, 0.39% ***. Contained 0.29 % Si, 11.68% Cr, 0.13% Ni and Best Biee ». 73 kg of aluminum were added to the molten metal in the steel casting ladle and the aisle of vermiculite (aenolite> covered "The temperature was read at 160 ° C." supply of argon was stopped and the remaining slag removed. the temperature was 159O ° C _S the metal was then * then eaten in a ladle "which 725 kg of titanium scrap, 36.4 kg of aluminum and containing 45.4 kg Cryollt" was followed d ^ r pour into the individual molds.

In Table I below are the Results of Example X plotted.

Wk

9k

ψ *

U) X
Oj

VO SO ΙΛ

* - Cl

OM rt

· «« I O I

• S I - »

Ο— I O ·

B I «<I

• Ε I * ι

O * - I O ι

SO NO «Λ

H Q

. j, ο ο ο

£ ο

MK I * I

OCt O I

• G (· I Ο— O

ΙΛ - * CO CQ

Ci K CO C4 I.

OQO O 1

»Β ·» I

Ο «- O O

m U \ ^ f ^ f

* ν ♦ »-

O O O O

Q '* O co tv

, S K ΙΓι - * J5

Of O £ O O O

ο «- · ο ο ο

ti <05 υ Λ *

• w «ta η

fi W «rt -H τ »

| Ä .J J ^

• «β O

w η ■ ic to te

Se-H h * t *

«Μ β M d U

0098S0 / 139S

- i6 -

Οίο Table X is the desired and obtained chetical composition · Result A means the cheap composition & ** «advise Qusses» Result I the JBusattMensetftung dee let and result C the marriage «i» che Xueaaneneetsung dee middle Qnsses. The procedure carried out in Beieplel Z gave 7 # 9 % Cbro «· and 90 * 6 % Netallau yield.

Example XZ

Aftsgangsekarge was placed in a cauldron containing 82 kg of quicklime · 22.6 kg of dolealtleehea keIk and 1 * 6 kg of fluorite. The aisle contained 11.SOO k * Binsataast · *! and 4000 kg scrap · The Zueaamensetsung dec Cins "itsjaetslls was 4.18 SC, 0.6L% Ha, 0.03% P, 1.34% 0i, ti, 55% Cr, 9:43 J * Hi and read Ilsen you · had a temperature of Ι3βθ ° € · The scrap was made of stainless steel of the type l8-8. The Scheel · · were 34 eV «in Seueretoff. 770 kg of quicklime, 101 kg of Useners granulate and 272 kg of Chroner * were added to the kettle. The oxygen supply was interrupted when the temperature at which the machine was being used was 189O ° C. Chemical tests were carried out on the fact that Netall 0.043 # C ₁ 0.28 % Nn, O, O4 Ji P, 7.53 % Cr, 10.32 Ji Mi and Itest * Bisen contained. Xn den Keeeel a reduction was given emit toi. It contained 900 kg of chrome iron, 1180 kg of chrome iron with a low carbon content, 36 kg of stainless steel, 68 kg of nangan silicon and 136 kg of fluorite slide slag and the metal was pre-washed with dry nitrogen and the reduction speed up su. For smelling the tea temperature was 1780 ° C. The Schlecke and Dae Netall were then via gutter <Ua Kessel in the

009850/1395

Cast steel ladle poured «100 kg of lead electrolyte manganese, 82 kg of electrolyte nickel and 83 * 6 kg of chrome iron hit low ·» The carbon content was previously added to the steel ladle * The chemical composition of Netalle was determined and the temperature was measured. The chemical tests showed that the metal was 0.051 % C, 0.90 % M ", 0.026 % P, 0.43% Si" 18 "3 [3] % Cr, 9,% 5 % Ni and R" and Bisen. The temperature was found to be 1680 ° C. The steel ladle was covered with vermiculite. Finally, alloying requirements were stated. The alloying requirements contained 11-3 kg of low-carbon chromium iron, 6.8 kg of electrolyte manganese, 9 kg of electrolyte nickel, 25 kg of 75% silicone iron and 31.6 kg of 70% titanium iron kg quick lime, ti, 3 kg fluorite, 32.6 kg slag flux and 9 kg aluminum granulate added · Argon was added to the molten metal in order to accelerate the mixing of the additions. * The argon flow was interrupted and the remaining slag was removed was 160 ° C. The metal was then poured into pouring spoons and then into the final molds.

Xn of Table II below are the results of example II summarized

Table II

£ & £ 1 Z £ £ r. Si

targeted ■ *,.

Result 0.07 1 * 00 0.% 5 0.03 0.025 l 8.35 9.50 (max) (max) (max)

Result 0.053 1.06 0.51 0.029 0.007 l8.65 9 35

bath 009850/1395

IX
The borrowed fegatrai * ® «<* 2k a <m is Example IX of the described method m & nl & n $

free warn S! »rc-; e ssic

Xl «• rides

Üsi® »$» a9iall la Eel

rand XZ in "is *" " the β

ir © »
In d «n

«Fi» tt

sslelit a ^ f dtai

il © r Be «cäs>'r-®ifeötte the inside mi®h in
be"

- Patent application -

009850/1395

Claims (1)

PttinttBiprQch « The process is carried out for a long time in consultation with the rest of the steel, which means that the metallic elements containing chromium and slag-forming steel have a carbon content of 0.15 tons of oxygen aetalllachea «dar aiohtaetallleehea closing the snow on Beaktiamapradaktan · dia anaa-tu alt dam eeblackenblldandan Swaltsaa elaa slag · a« eeet * t will, that the infttbr of Senerateff in the Keaael is interrupted if the Teaperatar is interrupted Vert of about 178O * C errelelit «ad the Kehlenateff content below about 0.55 % li« so that the Sehlaeke is then given a sufficiently large Manga idea aaaetat · «· theee« laahaaaada in it aietal proportion, of rednaierea · «ad that the slag in the process, it is heavily exhausted, "aaa reactions only lalekgavinnaag of the non-metallic Jaiteile ame der SehleekaV 8. Method according to Aaepntch 1, characterized in that the supply of oxygen takes place when the icalene content is less than about 0.10 % . 3 · Procedure similar to one of the approaches 1 or S, characterized by the fact that the drive from Saneretoff is interrupted when the temperature of Natalia is between 1880 ° C and 198O ⁰ C · % · Method according to wealgatans one of the pineapples 1 to 3, thereby keaaselchaet, deft the metallic Smae · Chrom «ad Mick ·! eathtlt. 009850/1395 5 «method according to at least one of claims 1 to 4 * characterized in that the additives forming slag are burnt lime or uolonitlsch burned. are lime and the reducing agent is a silicon holding material 1st « 6 · method according to at least one «of claims 1 to 5, characterized in that the reduced slag has a CaO ♦ MgO / SiO value of at least 0.9 owned. 7. The method according to at least one of claims 1 to 5 »characterized in that the reduced slag has a CaO ♦ MgO / SiOg value of approximately
1.0 to 2.0. 8 · Method according to at least one of claims 1 to 7 « characterized in that the strong mixing of the slag by blowing in one under Pressurized fluid is reached in the boiler. 9. The method according to claim β, characterized g β ke η η ζ λ, 1 ch-'net that the FluJLr * consists of dry air and / or non-reacting Ganen · 10 · Method according to at least one of Claims 1 to 9 *. characterized in _t that the metal melt after the strong mixing of the slag is poured into a container and that the lane is added into this container Legierungeasuegts *, us the Zusanaensetasung of the steels in desirable catfish in the sense of the Her "distribution of a stainless, steel at to enhance· 0 0-9S50 / 139 6 81 ~ 11. Method according to claim 10, characterized in that it is worthwhile that during d «a strong verse dar slag and de · discharging · the Sehaelse one under Pressure is injected into the keasel, and that the slag and the metal dea Keaeele is poured into the container 12 »Method according to Anapruch 10, characterized by this e t »that the metallic Sduaelae and the one in the container given ingredients are consumed in motion · around because · the cutting and sealing of the ingredients speed up the process. 009850/1395 Blank page