DE1583713A1 - Continuous casting process for the production of gas bubble-free cast steel bars - Google Patents

Description

PA T EN T A NW ALT E

PATENTANWÄLTE LIGHT, HANSMANN, HERRMANN β MDNCHEN 2 THERESIENSTRASS6 33

DipL-Ing. MARTIN LICHT Dr. REI N HOLD SCHMIDT ■ Dipl.-Wirtech.-lng ;, AX E L Ή A N S M A N N Dipl.-Phys. SEBASTIAN HERRMANN

Munich, the jJ-'i. August i'Jb?

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Patent attorneys DipL-Ing, Martin Licht, Dipl.-Wirtsch.-Ing. Axel Hansmann, Dipl.-Phys. Sebastian Herrmann

8 MUNICH i _f THERESIENSTKASSE 33> Telephone: 292102 · Telegram address: Lipatli / Munich

Bank details fr Deutsche Bank AG, Munich branch, Viktualienmarkf Dep.-Cashier, Konfo-Nr. 70/30 Ä38 Bayer. Vereinsborik Munich, branch. Oskafvon-Millef-Ring, toilet no. 882495 Postal check account: Munich No. 143397

Oppenauer OFFICE: PATENT ADVERTISER DR, REINHOLD SCHMIDT

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be kept animal. Hand-held steel blocks, which represent the largest IclI uus utahles for the production of υ punching and> ve ißbieeheii, are characterized by a clean surface free of, among other things, in ~. -JChlUtjsen "relatively small carbon -.- j the inside of the blocks has gas inlets or voids and has a higher carbon content than the surface, /.ar producing high quality itatids tahlü iat it is necessary to observe the desired structure of the ütahies, itauds taiilbiocice usually have 0, 03-0 ", 1 ^ 5 (jewiohtspro / uut r.oliiuus to f I, about 0 2 to U, b weight percent manganese, and less than υ, 02, but preferably not more than 0, ul" weight percent silicon. The essential ingredient for the ^ e lüohb i ö <-Ke has a relatively high, but precisely determinable oxygen content, which causes the desired ttaiidbiletting in the ingot mold. Lin soichor otahl is converted from an itahlbChmeizoi'en into a ^ bstich {(i "Anne with a pig Material content filled in, which is greater than the required amount in the casting mold, metallic deoxygenation agent is usually added in the opening arm in order to lower the oxygen content to the desired level before the tank is poured into the mold. Preferably xkluiuinium is used as a deoxidizer, whereby aluminum oxide is formed; Most of the aluminum oxide flows to the top of the steel in the pan and forms a smear or foam. The proportion of alurainiunioxyd retained as a line in the colum block is small and has none

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disadvantageous importance for the steel quality. Ls is avoided Silicon as a deoxidizer for Iland steels use ', since the resulting silicon oxide inclusions have a detrimental effect on the steel quality. Residual silicon, the proportion of which is the maximum possible amount of 0, Ü2 V ° in edge steels creates too many inclusions because of the relatively high oxygen content in the steel.

Killed steels were obtained using conventional methods if a steel was to be obtained free of gas bubbles or voids. These steels have less than 50 parts per million oxygen. In the manufacture of these steels, large amounts of .il.

Mau can also avoid the occurrence of gas leakages, if you keep the carbon content of the steel below about 0.02 Holds weight percent. With this small amount of carbon Does not form carbon monoxide regardless of what is in the steel contained oxygen; accordingly there are no gas bubbles educated. Steels with such a low carbon content are However, comparatively weak. The requirement therefore arises of steels with a higher carbon content ..

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It has long been shown to be desirable. stole iiii Strahggußverfähre to manufacture, since during the continuous casting process less labor is required than with the Production of steel blocks in conventional cast shapes or * Chill molds; However, so far it has not been satisfactory Steelmaking process developed for sheet metal and '.veifibiech production to manufacture suitable steel blocks. The processes involved in the manufacture of edge steels and capped Steels in conventional molds are by no means suitable for the production of steel in the continuous casting process. In the continuous casting process The blocks produced must be free of gas inclusions. Gasbiaseti or gas inclusions in Gußsträttgen are a great disadvantage, since gas bubbles on the surface of the strand adversely affect the quality and finish the surface or * has to be cleaned, gas inclusions inside the steel reduce the thermal conductivity of the cast strand and make it necessary to work with low casting speeds. The requirement to avoid gas inclusions or voids in cast strands makes it necessary to use a steel with an oxygen content which is lower than that of rare steels and cover steels. The use of conventional, metallic , Deoxidizer, d »h. Aluminum and silicon can be in your The extent to which this reduced oxygen content can be achieved is not be tolerated, since this is associated with the creation of too large quantities of uroxide is used as the only deoxidation agent, then forms

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a great deal of Aluininiumoxydschauin; a large. share this smear or foam is trapped in the surface of the cast strand when it is in the mold forms. The surface must therefore be treated by cleaning will. The use of silicon alone as a deoxidizer. medium im.Stranggußverfahren has also proven to be disadvantageous proven. The judgment required for deoxidation - IaUt one Steel with unacceptable, high hardness is produced. When silicon is added, silicon oxide inlots are also formed, which affect both the surface quality and the quality of the internal structure in the strand. Silica inclusions are particularly common in hot processed Sheet metal disadvantageous.

It has also been suggested to use vacuum deoxidation of the Stahles perform to the oxygen content before continuous casting to reduce. The percentage of oxygen which is economically Reasonable speeds is achieved, however still too high for gas entrapment to occur avoid whenever the proportion of carbon in steel is above about 0.02 weight percent. The Vakuuin ~ Deoxydatiou therefore cannot be used alone to generate the oxygen ■ Antßil to be lowered to the desired level.

Since there is no cast strand with known steel deoxidation processes good quality for sheet metal and tear sheets can be achieved

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a new procedure is required by which

gas-bubble-free cast strands with a low oxygen content '' '

and only a small proportion of non-metallic inclusions can be manufactured.

Erfiuduugsgeraäß is with the present invention a Process for continuous casting created by which gas bubble-free steel blocks or steel strands with a low Proportion of inclusions to be produced. The procedure persists avis the introduction of molten steel with a carbon content of at least about 0.0 ^ weight percent and with an x part of dissolved oxygen in a vacuum - ventilating * / one. The proportion of dissolved oxygen exceeds that given by the equation:

ppm of O ₉ = 5.7

and 75

specified xin part. The carbon and oxygen des react under vacuum in the steel contained in the degassing zone with each other until the oxygen content is not significantly greater is than that by the equation:

ppm of 0 "= 8.7

0.75

specified proportion. The degassed cxtahl is covered with a metallic Deoxidizing agents are deoxidized in order to reduce the proportion of dissolved

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s further reduce. Then the degassed and deoxidized / Steel in a Strangguükbkille abegosseil, whereby the partially hardening steel cools down in the mold. then is a partially hardened Güüstraiig continuously from removed from the mold. This strand ranges from about 0.02 to about 0.15 weight percent carbon, no more than about 0.1 Weight percent silicon and no more than about 0.15 weight percent Aluminum on.

Furthermore, according to the invention, a continuously degassed and continuously cast Guiistrang is obtained, which consists essentially of about 0.02 to about 0.15 percent by weight of carbon, of about 0.1 to about 1 percent by weight, manganese, of not more than about 0.1 weight percent silicon, no more than about 0.15 weight percent aluminum, no more than about 150 parts per million oxygen with the remainder made up of lisen and in purities. The steel has a bonded proportion of no more than about one million files per million silicon oxide and silicon oxide iron. .

Erfindungsgeniaß was found that clean üuüstränge can free of üaseinsohlusscn by \ Aktium-Kohlt'iis t ο 1 are yes lertigt i desoxidation *, soft a deoxidation with one or more, metal 1 isclien Desoxydatiousmi t stuffs follows, although with no üesoxydationsmittel alone solejie

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Strands can be achieved. ,

According to the invention, carbon is deoxidized under vacuum, by a considerable proportion of the oxygen content

to remove. The degassed steel is then deoxidized with one or more metallic deoxidizing agents furthermore the proportion of dissolved oxygen before each decanting of the steel. The deoxidized steel is then poured into a water-cooled continuous casting mold, from which a partially hardened strand is pulled downwards.

The degassed cast strands produced using the continuous casting process of the present invention are characterized by low oxygen content and good nature the surface, which is free of alurainium oxide and small amounts of silicon oxide and aluminum oxide inclusions. The total amount of oxygen in the strands manufactured in the continuous casting process according to the present invention is less than about 150 parts per Million; the one not bound to silicon, aluminum or manganese The percentage of oxygen is no more than about 20 parts per million (ppm). The amount of bound silica and Alumina inclusions is no more than 150 parts per Million (ppm).

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«A. ty m ■

The invention becomes with reference to the accompanying drawings explained;

Figure 1 is a graph of oxygen or * the proportion of dissolved oxygen in the presence of various oxidizing agents

B "■ -

. 1 ' ¹ Ig ₄ 2 is a schematic view of the device used according to the invention »

In order to obtain a steel which is free from voids, it is necessary either to lower the carbon content of the steel to less than about 0.02 "/ o or to reduce the oxygen content to a level before solidification of the steel where there are no entrapment form se * the exact carbon content of the steel, in which to cavities no longer form, varies slightly by 0.02> since the formation by variables _(such as the manganese content of the steel is influenced "the present invention refers to Method of reducing the oxygen content of the steel to such an extent that a void-free steel is obtained In Fig. 1, the area of the composition within which no inclusions are formed by the steel is through that on the left-hand side and below: the curve A indicated range * The curve A shows the highest possible oxygen concentration for each carbon content in the range from about 0.02 to 0.16 by weight per cent. This

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maximum oxygen content varies from about 10 to 50 parts per million, depending on the carbon content. The curve A relates to a stationary oussforra or chill mold * As will be shown in the course of the description, in the case of btranggußgeblöoken liquid closures can be achieved with an oxygen content like that which is shown by the curve Λ, provided that the oozing speed is greater ge, know., minimal size, which depends on the concentration of the yellowest building material.

Line produced in a conventional Stahihochöfen bchmelze erfinduu may _like sgemuß continuous casting in koh "blocke of sheet metal and the btahl is from a ätalilsehmelzof s iii iu a ladle Ii are cast reinstblechformat * (flg. 2) cast at a temperature which usually above 1049 ^, although the temperature can be slightly higher or lower *

The cut off ^ taiii has an amount of carbon which has a black block with about 0.02 to 0.15 per weight per inch Carbon content after carbon deoxydation under vacuum gives »The amount of carbon is given by dt-n respective Purpose of the steel product controlled. There , the Kohienstoffaateil to about υ, οΐ to U, u5 uewiciitsprozeut des ütahlfes is reduced, usually contain v), 02 to u, ü3 üewiülitspro2Giit de »btahles about 0.04 to υ, Ι? Weight percent Carbon »The oxygen content of the 10 ab- *

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Chiseled steel can vary from a maximum of more than 600 parts per million if the carbon content is 0.0 ^ weight percent is up to about 120 parts per million when the carbon content is about 0.17 weight percent amounts to. The oxygen content of the steel tapped from the furnace is roughly represented by curve B, which the Amount of dissolved oxygen in equilibrium with dissolved oxygen Represents carbon at atmospheric pressure and 10 ^ 9 C.

small proportions of metals, i.e. up to 1.0 percent by weight manganese, not more than υ, Ι percent by weight silicon and up to about 0.02 weight percent aluminum can also be contained in the steel, if this from the melting furnace 10 is cut off.

After the steel melt has been poured from the steel melting furnace 10 into the ladle 11, it is moved along a path 12 to the sub-boron site of a continuous casting tower 13, as can be seen in Figure 2. The continuous casting tower consists of a degassing vessel ik ,. from four open, tubular and water-cooled extruded mold 15, from a number of support rollers Ib and from driving roll 17.

Additives in the form of metallic oxidizing agents Alloy elements can be added in the ladle 11. From the point of view of the purity of the steel, it would be advantageous to use the

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Do not use deoxidizers in the pan. The use of metallic deoxidizers in the tapping pan is desirable, however, as this avoids the occurrence of uncontrolled heat development, i.e. the formation of melts with an excessively high oxygen content in the ladle.The use of metallic deoxidizers is also advantageous because larger quantities of steel can be produced by partially transferring the deoxidation from the degassing vessel Ik to the tapping pan 11. Since the use of deoxidizing agents in the tapping pan 11 increases connections and the formation of foam, only limited amounts of these deoxidizing agents are used in the pan 11. The amount of oxygen remaining in the steel when the steel is tapped from the ladle 11 into the degassing passage Ik is essentially greater than that indicated by the curve C in FIG. 1 quantity shown. Curve C represents the oxygen content which can be achieved in economically justifiable amounts by carbon deoxidation carried out under vacuum.

Silicon was preferred as a deoxidizer in the Parting knife 11 used. Silicon is a mild deoxidizer and can be added in amounts that match the silicon content not more than 10% by weight of the total amount of silicon Allow (free and bound silicon) to grow. Usually enough silicon is added to make up the silicon content of the steel to at least 0.2% by weight, where-

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is achieved by suitable deoxidation. A higher proportion of silicon is avoided because of the greater hardness and poor tensile qualities of the resulting steel. Up to 1.81 kp silicon can be added per ton in the tapping pan without exceeding a silicon content of U, Iu ⁰ Jo in the product. The apparent discrepancy between the amount of silicon added and the resulting silicon part of the steel is explained by the fact that part of the silicon oxide floats on the surface of the steel in the fan and is not included in subsequent analyzes, silicon can In the tapping pan 11 in the form of an alloy, such as errosilicon or manganese silicon.

By adding silicon to the tapping cup the oxygen content is lowered to a level which is represented almost by the curve D in ^ i gV 1. uie curve D shows the proportion of dissolved oxygen under equilibrium in steel with different concentrations of dissolved (elemental) Silicon in the range from about U, Ul to 0.15 percent by weight at 1597 C in a containing 0.4 percent by weight manganese Stole. The temperature and the manganese content are typical conditions in the tapping pan. The amount of dissolved Oxygen decreases as the amount of silicon added increases. The amount of building material is in equilibrium of the steel less than at the time of tapping, however

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considerably larger than the oxygen content after degassing; a considerable amount of the elemental silicon remains in solution, and as silicon becomes an increasingly effective deoxidizer as the temperature of the steel drops, the dissolved silicon is available for further deoxidation of the steel after it has been degassed and cooled.

Aluminum is a powerful deoxidizer which is found in small quantities up to 0.339 kg per ton of steel in the ladle 11 can be added. Larger amounts do not advertise added, dm to avoid the formation of too large amounts of aluminum oxide. Aluminum additions in the ladle are undesirable from the point of view of the purity of the steel. Although the aluminum oxide formed flows to the top of the pan, a small portion of the aluminum oxide is mixed with the steel by the process. finally leads and settles in the mold, whereby the Casting surface is affected, In addition, Ffannen-ALuminium ineffective and not determinable as a deoxidizer. A certain one -uiteil \ vLrd consumed e.g. by air oxidation, without taking into account the content of dissolved oxygen in the btahl to reduce.

From the standpoint of the unit of steel it is desirable do not add any oxidizing agent "in the pan 11. This process removes the inclusions of bilizum and aluminum oxide reduced to a minimum. A certain amount of

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Deoxidizing agents are nevertheless desirable in order to avoid uncontrollable development of etching, i.e. melting which contain too large a proportion of dissolved oxygen in the steel.

Usually, manganese is added to the pan 11 in an amount having a manganese content of 0.1 to 1.0 percent by weight of the block results. Manganese is in the form of an alloy, for example added as ferromanganese or mangate silicon. Part of the added manganese is oxidized to manganese oxide, MnO.

The steel is continuously withdrawn from the tapping pan 11 into the degassing vessel 1'i. This is done according to llinzu-. Succulent of oxidizing agents and the alloying of the elements in the ladle 11 when these additions have been made. The steel withdrawn from the tapping pan 11 into the venting vessel Ik contains 0.0 to about 0.17 percent by weight of carbon, about 0.1 to 1.0 percent by weight of Maugau, less than about 0.5 percent by weight of aluminum, not more than about 0 .10 weight percent silicon and about 120 to 100 parts per. Million .. oxygen. Whether or not ladle oxidizing agents are used, the proportion of dissolved oxygen in the steel when this i: i d.ib Lutgasuugsgei'ass ik is poured off must be significantly higher than that indicated by curve 0 in i-'ig. 1 is oxygen-low so that the degassing vessel can be used effectively and the amount of inclusions that can be removed by use

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metallic deoxidizers are created to a minimum can be reduced.

The reduction in temperature of the steel in the tapping pan should be kept as small as possible. This drop in temperature averages 55.5 °, although I can change this amount. For example, steel is withdrawn from the melting furnace IU at a temperature of 16.9 ° C. or a little more and passed into the gas suction vessel 14 at a temperature of about 1593 ° C.

The; nlg £ isungsgefaß Ik is at a maximum pressure of about younges iHiu, lUi'gks-Ilber absolute and preferably mercury absolute operated at about 3 m ^111th.. The high vacuum prevailing in the degassing vessel Ik removes considerable amounts of oxygen from the steel together with some carbon; This results in a degassed molten steel, the oxygen content of almost of those / ig by the curve (J shown in Figure 1 ^v amount of oxygen corresponding to this curve can be represented by the following equation...:

ppm of oxygen = 8.7

(^ C) 0.75

This equation gives a jauerstolf salary for an affiliate degassing vessel again, which with reasonable ije-sc-hwind iskei t works. The Glei chscewiohtsk concentration of

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Oxygen under high vacuum in a steel bi-gas furnace lies below curve C, but is of no practical importance, since the equilibrium only occurs at low degassing ■ ■ ■ ■ speeds can be achieved which are suitable for industrial purposes doesn't seem practical.

Kin preferably used degassing vessel for use .- in the present process consists of a continuous casting degassing device with an upper Ii In let opening 21 for non-degassed metal, with a discharge opening 22 located on the underside, which with the help of a hydraulic cylinder 2k movable Sehiebeventlls 23 is controlled, with a Uffining in the side wall of the degassing vessel l'i , "pouring metallic deoxidation agent into the amount 26 of the degassed steel accumulating in the degassing vessel l ^ i, and with a feed device 27 for degassing agent. According to a preferably shown design of the feed device 2'7'x 'for deoxidizing means, an option for feeding aluminum in wire form is provided, one that extends outward from the opening 2' 'and is sealed Line 29 and a seal J> 0 on the outer part of the line 29, with which the luminescent material can be introduced into the degassing vessel Ik , while at the same time a vacuum-tight seal is maintained. That. The gasification vessel has lines 3i and 32 which end on the opposite sides of a baffle 33 and are closed off at one of the lines of pressurized medium

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are. The Strargguß-Entgasungsgefaß Lk after rig. 2 is preferably used because of the slight decrease in the steel temperature in the degassing vessel. The temperature decrease in the degassing vessel 1Λ is usually only "about 5.55 C. Other degassing vessels can also be used, for example the known, pan-like Lehen insert degassing vessels. however, this is associated with a much greater temperature loss, ie 55.5 - · U or more.

The degassing in the degassing vessel l ^; i results in a reduction in the carbon content of the steel by about 0. Ui to 0.05 percent by weight, usually about 0.02 to about 0.03 percent by weight, based on the total weight of the steel, and a resultant reduction in building material of about L30 Parts per million 1'ü. for each 0.01 weight percent of the reduction in carbon content. The reduction of the oxygen content is caused by a reaction between oxygen and carbon monoxide to form carbon monoxide. If the carbon content is reduced by (0.02 weight percent, then the oxygen content drops by about 260 "files per million The dissolved oxygen content of the degassed steel is shown by curve C in FIG.

The tightness of the dissolved water remaining in the degassed otahl Oxygen is still so great that gas locks in it

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üußbloolc are formed so that the metal is further deoxidized must be before it hardens. An essential feature of the present invention ordered in the deoxidation of the degassed .Melt metal with one or more. Metal deoxidation average to reduce the proportion of dissolved oxygen.

- Preferably aluminum and silicon are used as deoxy- dation agents used, although of course other metallic ones Deoxidizing agents, for example Uor, are used equally can.

Aluminum is preferably used as a deoxidizer for degassed metal. Since aluminum is the strongest deoxidizer compatible with .Stal.il, the use of aluminum as a deoxidizer results in steel with the lowest possible proportion of dissolved oxygen. In addition, by using aluminum instead of silicon, a steel with the desired hardness is achieved with a minimum of silicon oxide inlusions. Aluminum can under vacuum in the degassing vessel described ik the degassed steel be added, or may be introduced at the 'Top of the mold-Ip. In any case, aluminum is preferably introduced into the degassed metal in the form of a wire. Since all of the. \ Luminiu: u supplied in the .vbstiehpXanue 11 is oxidized there, the substance / »light aluminum must be added to the degassed metal if the degassed metal is deoxidized with aluminum

8t

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is desirable. Aluminum is used in a more efficient way in the degassing vessel I ^ or in the Koitllle 15 than in the pan. Since most of the aluminum added in the ladle is consumed, most of the aluminum added in the degassing vessel Ik or the mold 15 is used to deoxidize the steel; only a small proportion is oxidized by oxygen supplied from the outside, for example by the oxygen in the atmosphere, which is also trapped in the mold when it is withdrawn from the degassing vessel Ik.

The aluminum added in the gasification vessel Ik reduces the oxygen content of the steel to a very low level, which is shown approximately by the curve E in FIG. This curve shows the equilibrium oxygen concentration as a function of the amount of dissolved (ie acid-soluble) aluminum in the steel. If enough is used, the formation of inclusions in the ingot is avoided.

Silicon can also be used for degassing Deoxidize metal. The silicon suitable for this / awake can "consist of dissolved core silicate, which the steel in since * 'ivbs tiohpJtan-rie was supplied; "it can also work with silicon which the degassed metal either in the gasification vessel l-'i or · on the top of the mold 15 puffs se t / .t

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became. In any case, conventional silicon compounds such as errosilicon and manganese silicon are used. Silicon, which is added to the degassed metal, is somewhat more effective than the silicon added in the tapping cup 11.

As stated earlier, silicon is becoming a more effective one Deoxidizer when the temperature drops from Hillt. rfenη the Steel is cooled and solidified in or below the mold 15, another lteaktiou occurs between silicon and Oxygen, as a result of which the oxygen content is below that which can be achieved in the degassing vessel 14 (shown by curve C) Oxygen content drops, with no more connections form.

The total amount of silicon added in the section 11 and in the degassing vessel Ik results in a silicon content which is not greater than 0.10 percent by weight of the ingot. The largest possible silicon content decreases with increasing carbon content after animal bleaching:

■> Si + Ο, τ / οΟ = 0.11

For example, steel containing 0.12 yb carbon can contain an inaxijiium of 0.1 - / ο silicon. Steel with a carbon content of 0.06 / ι »should not contain more than (1.03 percent by weight silicon, while steel with 0.15 percent by weight carbon should not contain more than 0.03 percent by weight silicon.

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The content of dissolved oxygen, which by silicon is higher than that achieved with aluminum; it is "nonetheless deep enough to allow the formation of To prevent casting inclusions, provided that the further the casting speeds described in the grooves are adhered to, while the oxygen content achieved is often in the "calm" range below curve A (t'ig. 1) when using ■ aluminum is the Lnd oxygen content when using silicon more likely below curve A, so that the lowest casting speeds need to be maintained to the formation of Prevent inclusions.

Degassed steel is continuously withdrawn from the degassing vessel lh into the mold Ip. The outflow speed from the degassing vessel Ik corresponds to the influence speed during the pouring off. Lie mold 15 is a conventional, water-cooled and open continuous casting mold. A hardening coat made of metal forms in the mold 15 and becomes increasingly thicker as the extrusion sinks below the mold 15 until the strand is completely hardened.

When silicon alone is used as a metallic deoxidizer for degassed metal, it causes gradual Cooling and hardening of the strand is another reaction between the silicon previously added and the ■ dissolved in the otahl Oxygen; the oxygen content is lowered so far that

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■ more kc-jrie inclusions are formed, provided that the GuU-speed does not come to a critical minimum, which depends on the dissolved oxygen content of the steel.

UEDE limiting the amounts of silicon and .vluminium Walche, can be used as a deoxidizer, Al without ft s maximum of 0.1 weight percent silicon and 0.15 Nominal CHT / sjrroz ent to exceed for aluminum, the "formation, may VO- n cause melts which have enough yellowest oxygen that the _; Avoidance of gas inclusions cannot be guaranteed. It has been found, however, that these inclusions can be avoided, provided that there is a certain, lowest level of moisture content, which depends on the content of dissolved oxygen in the. ^c tahl depends, is retained, -for this reason, -from high GuOg.esctai.udig-. at low speeds. For example, the titration of inclusions in a melt that has 20 parts per million oxygen and is formerly not bound to aluminum, biium or manganese is avoided if the speed is at least 12 "cm per minute If the λιιΙ-οϊΙ of the chemically unbound acid is toi fes hpringer than 20 lei Ie per million, then the lowest, ei n / ul) eh; i L t ende GuUgescliwindi iikci t is correspondingly lower.

The cast strand has, when it is hardened, about 0.02 to about 1 ', i ^r ) weight s-percent carbon aut, not, more than about

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0.10 weight percent silicon, about 0.1 to about 1.0 weight percent Manganese and no more than about 0.015 weight percent aluminum. The total oxygen content is less than about 150 parts per million and is preferably less than 100 parts per million. The amount of the oxygen not chemically bound with aluminum, silicon and manganese is not more than 20 and preferably less than 10 parts each. Million. The total amount of silicon and aluminum inclusions is not more than 150 parts per million. The amount of silicon inclusions is less than 100 parts per million when the deoxidation process is using .aluminium is used in the degassing vessel.

Steel manufactured according to the invention is in particular suitable for forming into sheet metal and thin sheet, which can be produced by known processes. The mechanical Properties, i.e. tensile strength, hardness and elongation, are excellent for sheet metal and sheet metal sheets. The steel produced according to the invention has excellent tensile qualities on.

The invention is described below with reference to The examples listed below are explained below.

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Example I.

Molten steel was withdrawn from an oxygen furnace 10 into a tapping pan 11. The carbon content in the ladle was 0.038 percent by weight, the proportion of the llestmaiigans was 0.27% and the temperature in the pan was L675 ° C. In the Abstiehpfanne were additions of 5, HSS kp Kohleu.s mean tof f-ferro-manganese per ton and 0.63 kg aluminum added per ton. This corresponds to 0.50 percent by weight manganese, 0.01 percent by weight carbon, 0.07 percent by weight aluminum and 0.01 percent by weight silicon. The carbon content of the steel after the additions was 0.043 "weight percent while the oxygen content was 217 parts per million.

The melt was degassed in the degassing vessel 14. Of the The gassing boiler was set to an absolute pressure of about 3 mm Mercury column held. In the degassing vessel 14, aluminum became with an aiif eye of 0.114 kp per ton in the Melt of degassed metal introduced; This amount was reduced to 0.054 kgf per ton during the degassing.

The degassed steel was continuously removed from the degassing vessel 14 poured into a continuous casting mold 15. This mold consisted of an open, tubular and water-cooled Casting mold. The molten metal started within the

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To harden mold walls. The partially hardened cast strand was at a speed of about 203 cm per minute withdrawn from the mold 15. .'If, the cast strand .below the mold was, it was further cooled with water and hardened. The cast strand was then cut into certain lengths cut and on, surface quality and internal structure examined. The surface was of good quality and required little or no cleaning. The interior of the cast strand was free of gas inclusions. .

An analysis of the cast strand showed about 30 percent by weight Carbon, 0. pO percent by weight manganese, U, .U22. Weight percent Silicon, 0.005 percent by weight aluminum.and Ils parts per million oxygen. This elemental analysis, includes both free and bound forms of the elements. The oxygen content was determined by vacuum melt analysis certainly. -.

Analysis of Inclusions by the Ester-Analog Extraction Process produced 67 parts per million. oxide, 57 parts per million .aluminium oxide and 152 parts per Million manganese oxides. The total amount of bound oxygen for these three oxides was 98 parts per Hillion.

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The SI raugguiiprodukt had a tensile strength of 16.52 kp / mm ", a tensile strength of 32.34 kp / ram, an elongation (50 yram) of 39» 6>, and a Rockwell 13th hardness of 35, 8 '/ «. ■ ■

Example 2

Line. Molten steel was drained from an oxygen furnace 10 into the tapping pan 11. The carbon content of the melt in the ladle was 0.0 ^ 3 '/ «; the proportion of kestmanganese was 0.27> and the temperature in the pan was 105S ⁰ C. ·,

The additions in the descent were Ί, 12 kp higher carbon 1'erromangans per ton, 1.1S kp 50 'own i'errosiliziums per ton and 0.635 kp aluminum per ton (ton). This corresponds to 0.36 percent by weight of manganese, 0.3 percent by weight of oil, 0.07 percent by weight of aluminum and 0.07 percent by weight of silicon. The Pfanneiizusätze increased the carbon content of the steel to 0.071 ',' c The SaiBrstof fgehal t of the steel Iietrug after addition of the additives and before degassing 217 parts per million.

The bchmel / .e was degassed in the degassing vessel I ⁷ I at a pressure of 3 mm of mercury; the carbon content of the steel was reduced to 0.057 y . It was

009835/0337

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No aluminum is introduced into the vacuum system during the degassing process. The steel was made as in Example 1 was cast at a rate of 208.6 cm per minute.

The weight percent analysis of the product was: carbon 0.055; Manganese 0, ki; Phosphorus 0.010; Sulfur 0.011; Silicon 0.05 and oxygen 0.0065. The inclusions in steel, determined by the ester-halogen extraction method in parts per million, were: SiO ^, 63; AIgO ,, 79; and MnO, 6l. The proportion of oxygen in silicon oxide, aluminum oxide and manganese oxide was 98 parts per million.

Example 5

The procedure according to Ueispeil 2 was carried out with the exception that the pan additives consisted of the following: 3.72 kp carbon-rich i-'erromangans per ton, 2.45 kp 50 'own ferrous silicon per ton, and 0.3 ^ 5 kp aluminum per ton. This corresponds to 0.52 percent by weight manganese, 0.03 percent by weight carbon, 0.07 percent by weight aluminum and 0.13 percent by weight silicon. The carbon content in the tapping pan was 0.035 % and the carbon content after adding the additives was 0.065%

The product analysis showed in percent by weight: carbon 0.055; Manganese 0.44-; Phosphorus 0.010; Sulfur 0.010; silicon ; Aluminum (total) 0.002; and oauerstolT 0.0087. the

00983 5/0337

ORiaiNAL

Inclusions in the steel were determined by the ester-Halogeii Kxtraktionsraethode and consisted of: SiO _0, 120; λ-1 _ο 03, 27; and Mn.0, 92. The proportion of oxygen chemically bound in these oxides was 99 parts per million.

^009835/0337

Claims (10)

PATENTANWÄLTE .3θ · Dipl.-Ing. MARTIN LIGHT β Mönchen 2 - THEREsiENSTRAssE 33 Dipl.-Wirtsch.-Ing. AXEL HAN SMAN N DiPL-PHyS ₁ SEBASTIANHERRMANN UMITED STATES STEEL CORPORATION Pittsburgh, Pennsylvania Munich, August 24, 1967 William Penn Place 52p your _sign and "rz.ich _e " V. is. A. "~ ' ^Fc Patent application ; Continuous casting process for the production of gas bubbles free cast steel strands Claims i. Process for the production of gas bubble-free cast steel strands with a low content of inclusions, characterized by the following process steps: Introducing an otahlsehmelze with a carbon content of at least approximately 0.04 percent by weight and a proportion of dissolved oxygen, which the by the equation ppm of O ₉ = 8.7 0.75 significantly exceeds the specified proportion, in a vacuum degassing area, Reaction between carbon and oxygen of the steel located under vacuum in the degassing area, until the oxygen content is not significantly greater than that given by the equation ppm of O ₉ = 8.7 I '/ pü) 0.75 specified content, deoxidizing the degassed steel with a 009835/0337 Patent attorneys Dipl.-Ing. Martin Licht, Dipl.-Wirtsch.-Ing. Axel Hansmgnn, Dipl.-Phys. Sebastian Herrmann 3 MDNCHEN 2, THERESiENSTRASSE 33 · Telephone: 292102 · Telegram address: Lipalli / Munich Bank details: Deutschs Bank AG, Munich branch, double cash register Viktualienmarkt, account no. 70/30438 Bayor. Vereinshank Munich, branch. Oskar-von-Millor-Ring, account no. 882495 Postschedc account: Manchen No. 163397 OppenauerB0.ro: PATENT ADVOCATE DR. REINHOtD SCHMIDT • -. - "BAD.ORIQIMAL metallic, deoxidizer to the proportion of the dissolved To reduce oxygen further, to discharge it continuously of the degassed and deoxidized steel in a continuous casting ■ Killing, cooling of the partially solidified steel in the mold, and continuous pulling off of a partially solidified strand from the mold, the strand being about 0.02 to about 0.15 percent by weight Kohlens great, no more than about 0.1 percent by weight, silicon percent and no more than, about 0.01.5 percent by weight Has aluminum. 2. The method according to claim 1, characterized in that that a metallic deoxidizer added to the steel before it gets into the vacuum degassing area. 3- ancestor according to claim 2, 'thereby aekcnnzci fhtii 1, that silicon is used as a metallic deoxidizer will" 'i. Process according to Claim 1, characterized in that a metallic deoxidation agent is added to the degassed steel. 5. VtMlahreii according to Ansprudi k, characterized in that aluminum is used as a metallic deoxidizer. 009835/0337 ORIGINAL BATHROOM 6. The method ⁴ according to claim k , characterized in that the metallic deoxidizer is added to the steel while it is under vacuum. 7. The method according to claim 1, characterized in, that the cast product is about 0.02 to 0.10 percent by weight silicon having. . " S, method according to claim 1, characterized in that that the cast product comprises about 0.002 to about 0.015 weight percent aluminum. 9. The method according to claim 1, characterized in that ■ that the partially solidified Gußprödukt from the mold with is withdrawn at a rate no less than about 127 cm per minute. 10. Continuously degassed and cast steel casting, characterized by about 0.02 to about 0.15 percent by weight carbon, about 0.1 to about 1.0 percent by weight manganese, not more than about 0.1 percent by weight silicon, not more than about 0.015 Ge \ ^T maybe percent aluminum, not more than about 150 ppm oxygen, iron and incidental impurities are contained as a balance and the steel 150 having a composite weight of not Mohr ppm Siliziumoxyd- and aluminum inclusions. 00983 5/033 7 ■ '■ BATH Blank page