DE1533902A1 - Method and device for degassing molten metal - Google Patents

Description

Description of the patent application

of Dravo Corporation, Dravo Building, Fifth & Liberty Aves.,

Pittsburgh, Pa./USA

concerning:
"Process and device for degassing molten metal"

The invention relates to a method and a Device for degassing molten metal, in particular steel, in a vacuum. It is an improved one Device and a method for continuous vacuum degassing and for conveying the metal from a vessel, e.g. from a ladle, into a receiving element such as a sprue, a continuous casting mold, a sequence from standard molds or another casting vessel.

With the demand for purer steel and more thorough quality controls, especially in connection with it With the continuous casting process, degassing molten steel to remove oxygen, recovers hydrogen and any nitrogen that is present is becoming increasingly important.

Until recently, oxygen was obtained by adding Aluminum and silicon are removed to the molten metal prior to tapping. In this way so-called killed steel was created generated. Some of the aluminum and silicon went in contact with the oxygen, and the presence of the oxides destroyed the purity of the steel. The remaining unoxidized

Metal is desirable as an alloy component. By the Vacuum discharge «ground the silicon and the aluminum only required as alloy components, and the formation of oxides these elements are avoided.

The term "continuous degassing" is used when the metal flows continuously through the degassing chamber, as distinct from a discontinuous or intermittent process, with the metal as a dormant Melt bath exposed to the vacuum in a degassing chamber and then removed from this. Referred to as "current degassing" a process in which the Netall is under the action of the Gravity falls from a container through an evacuated space into another receptacle. These procedures are Currently in use, but they all have specific ones Limits. -

Continuous casting, in which the metal is transferred from a ladle through the degassing device to a casting mold is passed on, mass the alloy components To be added to the ladle before degassing with the result that "the steel calms down." and global degassing just like removing hydrogen effective 1st.

With continuous degassing, in which the Metal In one leg of a degassing vessel In one Degassing chamber moved upwards and out of the other leg while maintaining a vacuum in the degassing chamber emerges, whereby the metal either flows into the ladle from which it is removed, or is weltergeleltet to another ladle, casting mold or a continuous casting device, so far is the length of the leg or inlet channel through which the metal is lifted to the degassing chamber has been limited, by the height of the metal column, which is from the barometric pressure can be maintained »which acts against the reduced pressure in the degassing vessel, which is a Thighs Inlet duct length equal to the barometric altitude

minus the depth of the metal in the degassing chamber

009808/0531 --S *

BADORLGiNAL

means. This sets you a limit to the depth of the ladle, which is used to move the ketall from the ladle into another ■ bring type of receiving element «i. Eb also limits that Control over the flow rate and the flow time in the degassing systems fromGedbt «. In a so-called direct degassing control system, this is absent of monitoring and adaptability of the entire application the device narrow limits. This one! Can not laugh in satisfactory heat by requiring the metal from The cup to a cupboard or a similar shallow cup is then avoided for a gas hazard «Ground, since the heat loss is too f-roB and that! Ictall one «Purulent source of contamination by the refractory Lining exposed 1st.

The invention permits the task of creating a degassing device and a method that results in a far more efficient adjustment and control system, especially in the case of a direct throughput of the exhaust gas to be degassed z.Ii. a ladle is conveyed to another receptacle, although the invention is not necessarily limited thereto. For this purpose, more of the rare contained in the retail should be carefully used for lifting the metal into the development of the smoke. In doing so, certain elements are also said to have been used, which remove some contaminants from the melted heat during the opening, whereby provision is also made to compensate for loss of income. Le-ieruni-components or additional materials should only be introduced into the metal in the first stages of degassing and mixed with it should rfindun ^ should iectiümte nechaniscr.e advantages th & s "eiterhin the i-tertachunτ and control uerden improved by Ale • Ir.tracun-rc-vorri.chtunr of rietailflueses - * rlehtunr after?..

409808/0537

The method for degassing molten metal, particularly steel, in a degassing device with a Vacuum chamber and an inlet channel according to the invention is characterized in that the inlet channel with its lower End is immersed in a molten metal bath that a negative pressure is generated in the chamber compared to the atmosphere and that the molten metal under the action of barometric pressure in the channel to a level below the top of the Channel and above the level of the molten bath is drawn in, and that the molten metal continues through itself Expanding gases in particle form are thrown up into the chamber and collected there as they fall and again is peeled off / to keep the top of the channel free of buildup of molten metal. After another With this method, the molten metal is also drawn from the degassing vessel into a vacuum under reduced pressure Brought a receptacle, from which it is drained through an outlet opening in the bottom, while the metal mirror above the ' The outlet opening is always kept at such a height that the ingress of air into the receiving vessel is excluded.

^ The device for carrying out the method according to the invention is characterized by an elongated chamber with its longitudinal axis inclined relative to a vertical plane with a hearth at its lower end, which slopes down from a higher side to an outlet opening on the lower side, and is much more characterized by a tubular inlet channel for the molten metal opening into the chamber on the higher side of the hearth and by a connection to a vacuum pump near the upper end of the degassing _{chamber 3} which has an inner cross section which is several times larger than the cross section of the inlet channel .

The invention also includes the use of a degassing chamber, preferably its vertical height Exceeds diameter, and from the lower end of a tubular leg with an inlet channel extends

009808/0537

bad u

is to be immersed with its end in the ladle with the steel to be degassed. This leg or the inlet duct contained therein is much longer than usual, over 1.524 m, which is about the height to which a column of liquid steel is raised by the barometric pressure under a vacuum of 0.5 mm HgS, whereby it has also been considered that the liquid level is not raised to the upper end of the inlet channel as the metal continuously passes through, where it opens into the degassing chamber. The expansion of gas present in the metal, with or without additional gas injected into this limited space , together with a vacuum present in the degassing chamber, throws the metal in droplets, mist and small particles of irregular size up to a height of one or more meters into the Degassing chamber. This process can be controlled by selectively injecting a gas into the inlet channel at one or more points. Means are preferably provided for selectively injecting a lifting gas into the inlet channel below the barometric height in order to increase the flow of metal into the degassing chamber. Another device is provided for the selective injection of gas ₇ , namely a so-called barrier or braking gas, into the leg or inlet channel above the barometric height in order to brake the flow of metal into the degassing chamber. The lift and brake gases can be the same or different gases, depending on various considerations discussed below. The term "barometric altitude" or the like, unless otherwise indicated, refers to the altitude to which a column of liquid metal is raised by atmospheric pressure when the column is exposed to the negative pressure prevailing in the degassing chamber.

Since the bottom or hearth of the degassing chamber is inclined towards an outlet opening, the rather finely divided ones fall Metal droplets and particles on the stove and flow as a stream out of the outlet opening, so that on the Hearth does not form a metal bath, as is usually the case, especially above the riser, and due to the degree of inclination and the

009808/0537

The diameter of the hearth determines to a certain extent the length of time the metal remains in the degassing chamber,

Although the degassed metal is also 1.52 * 1 m long outlet leg or duct is preferable, that it is discharged into an additional vessel of our own design, in which a vacuum is also maintained. d. Desirably, this vessel is designed so that in heat is added to the molten metal when required, a uniform and closely monitored casting temperature ensure, and to put the metal in circulation for better mixing with the alloy components.

The invention is hereinafter based on in the drawing illustrated preferred embodiments of the invention Device described in more detail. In the drawing show:

1 shows a vertical section through the device before it is put into operation,

2 shows the device in a similar representation in connection with a pouring pipe,

3 shows a more or less schematic representation similar to Pig. 2, although the relationship between the degassing device and the pouring ladle is also shown when it is almost empty: in this illustration the auxiliary or additional chamber has also been omitted and has been replaced by a second outlet channel or leg;

4 shows a more or less schematic section through Another embodiment of the auxiliary or additional vessel, in this also vertical Sectional representation shows only a fraction of the degassing device, and

009808/0537

- 7 - - O; "; at: -] AL INSPECTED.

Pig. 5 the performance curve of a typical, for the

Use on a gas injection device according to the invention suitable 'steam jet pump.

There are corresponding figures in the various figures of the drawing Parts are given the same reference numbers.

The degassing device according to the invention shown in pins 1 and 2 of the drawing consists of an elongated, upright structural unit. For operation with a 200-ton ladle, the total length of the device would be about 9 m, for example, but this value can change and is therefore only mentioned here to illustrate the size of such a device. The degassing device comprises an upper chamber, designated as a whole by 2, in the form of an upright, elongated hollow cylinder which is inclined with respect to the vertical position. This chamber can be circular, elliptical or more or less rectangular in section!:; be formed, but their longitudinal axis extends in the plane of the representation shown in FIG. The distance between the chamber side walls is about one meter or more and is, for example, of the order of 1.5 n. In general, the chamber has a metal jacket which is lined with a refractory material. The chamber has a removable dome 3, in which an opening ¹ I is located with a lock, as explained further below. In addition, the chamber has a floor or hearth 5 which slopes down from the higher chamber side to an outlet opening 6 in the side wall on the lower side of the inclined structural unit.

From the higher -: eler: enen side of the merde, a leg 7 lined with refractory material extends eccentrically to the longitudinal axis of the entire structural unit and has an inlet channel 8, the inner diameter of which is generally not less than about 15 cm. This Sdenkel with its inlet channel can be assembled from several sections, v. ^r ie in the

009808/053? 7 ~

Drawing ger, ei31. The leg has a cylindrical metal jacket, the Ulli: - Feusrfestern material is lined. At the bottom There is a replaceable end of the main part of the leg End section 9, md between this end section 9 and the The main part of the leg is a flange-like one Plate IG for the selective supply of gas from an external storage container or the like through the pipe 12 arranged therethrough. The lower end of the end piece 9 extends at an angle to the longitudinal axis of the leg or inlet channel, in a generally horizontal plane.

At a distance above the plate 10 is a second flange-like plate 10a, which also has gas inlet openings 11a for the selective supply of gas from an external gas supply through the pipe 12a. The two spaced apart gas inlet openings 11 and 11a in the leg 7 are arranged so that MIe are respectively below and above the surface or the level of the liquid metal normally present in the leg 7. This metal level is indicated schematically at AA and is normally about 1.5 to 152 cm above the ketal level in the container, for example the pouring ladle, into which the leg 7 or the inlet channel 8 is immersed. The gas inlet openings 11 are preferably arranged in the limb 7 near the lower end of the liquid metal column.

In the upper part of the V.'andunp of chamber 2 is a. Opening 13 is provided, from which a line, not shown, extends to a vacuum pump. teißr.ielsireise ^{leads to} a steam jet pump, of the kind that is generally used in the steel industry in connection with debris removal equipment. Chamber 2 has in hererr. Part above the hearth 5 up to the dome 3 expediently a height of about 3 m or more, while the legs 7 or the inlet channel 8 extend from the inner surface of the hearth up to the splashing area.

009808/05 3 _S ? _

Plate 10 desirably is considerably longer than 152 cm and the perpendicular distance from the opening at the end of the end piece to the hearth height exceeds 152 cm and preferably about two to two is two and a half times the barometric altitude. The height a column of molten steel, which is inside the leg or inlet channel by the atmospheric pressure at one in the Chamber 2 prevailing vacuum of 0.5 mm of mercury is maintained, is about 152 cm, and the inlet channel 8 should long enough so that the level of the metal barometric column is some distance below the hearth. The total length of the inlet channel 8 from the chamber hearth 5 to its lower end must be such that in the liquid metal to the full depth the ladle immersed leg 7 of the jacket of the degassing chamber does not yet come into contact with the upper edge of the ladle, but rather still a sufficient distance between both is present. For the purposes of the present invention, the total length of the leg 7 and that located therein should therefore Inlet channel 8 exceed the height of the barometric column.

According to the preferred embodiment of the invention shown in FIGS. 1 and 2 of the drawing, the outlet opening 6 opens into the interior of a closed auxiliary or additional vessel 15. This vessel 15 is detachably and sealedly attached to the main body of the degassing device. It has a bottom outlet opening 16, and an only schematically indicated wassergeküli ZTE Hetallabdeckung 17. In the lined with refractory material vessel 15 is a stopper rod 18 are arranged in the axial extension of the opening 16 ₅ which is passed through a stuffing box in the cover 17, and at the Devices for raising or lowering, as indicated schematically at 19, attack. An air- or water-cooled induction coil 20 is embedded in the refractory walls of the vessel 15 and surrounds the open chamber 21 in the vessel.

- 10 -

BATH

009808/053 7

The stopper rod 18 may be made of stainless steel tubing so that cooling water is passed axially through it can be. This tube, indicated at 18a, is surrounded by an insulating sleeve and an end section 18b. In the An opening 22 is provided on the upper cover 17 of the auxiliary or additional vessel.

Since one purpose of the apparatus is to degas metal while it is being conveyed from one vessel, such as a ladle, to another vessel or receiving element, such as a continuous caster, FIGS. 1 and 2 show the top of a continuous caster shown schematically, and the outlet opening Vo is located centrally above the continuous casting mold A.

When putting the device into operation, it is advisable to preheat it / during preheating, heating devices such as an electrical heating device or a detector for liquid or gaseous fuel (either heating oil or gas) are inserted into the opening 4 in the dome of the de-airing device, and another heating device or a burner into the opening in the auxiliary or additional vessel 15. These burners are denoted in FIG. 1 by 23 and 24, respectively. When the system has been brought to operating temperature, these burners are removed and devices are inserted into the openings to monitor the work process in the vessels concerned. In FIG. 2, a television camera 25 for scanning or recording the interior of the vacuum chamber 2 is indicated above the opening 4, and an observation glass 26 is attached above the opening 22.

When operating the plant, a vessel with the melted Metal that is to be degassed and conveyed to a mold or other receptacle brought the degassing system and raised so far that the end piece 9 is only a small piece, for example 10 cm, immersed in the molten metal. A vacuum of the size

0 09808/0537

- 11 - BAD CrHG'NÄ!

Order of about 0.5 mm of mercury is used in the main degassing ungs chamber 2 maintained and lifts the metal due to the external atmospheric pressure in the leg 7 or Inlet channel 8 about 152 cm. This I! Etal3fräule ends in the inlet channel 8 below the gas supply openings 11a and below the stove, as stated above. Under these conditions the gases contained in the liquid metal are released from a considerable depth and with the rise of these gases towards the metal surface, the gas bubbles expand and gain speed. if they leave the surface of the ketal mirror, drift they get droplets or globules of the molten metal in at considerable velocity up from the inlet port the vacuum chamber 2. These droplets can practically vary in size from a vaporous distribution of the metal to Spheres are sufficient, which occasionally have a diameter of 2.5 cm to have. They are thrown upwards into the vacuum chamber at different heights and distances, but on average up to about 120 or lL> Ocm above the focus. Preferably reach they do not reach the height of the suction opening 13. -After they have reached their maximum height, they fall down onto the stove, v; o they are collected and drain through the outlet opening C by the inclination of the degassing device relative to the vertical position that falls in this way from the inlet duct Metal thrown into the vacuum chamber 2 does not return into the inlet channel 8, and its throw line is apart from the subsequent droplets or globules constantly spraying from the upper end of the inlet channel 8.

To increase the strength and speed with which the metal is thrown out of the inlet channel 8 into the vacuum chamber 2, gas from the supply line 12 is in the Splash 10 is initiated which then enters the metal near the bottom of the column. Preference is given for this purpose Uses argon gas, which is inert and not easily removed from it

- 12 009808/0537

molten metal is absorbed. For certain purposes, however, you can use oxygen, methane, or even a liquid Hydrocarbons can be injected instead of argon or together with argon.

If, for example, 150 liters of gas per minute are supplied by the injection pump, i.e. by the flange-like one Plate 10 are injected in the manner described above, this is the equivalent of about 6.58 g - Hol argon per minute (0.01 ^ 5 pound-mols of argon per minute). A 0.05 # carbon steel could be 500 ppm. Op in the form of CO at a working pressure of 0.5 mm of mercury in the degassing vessel. This is equivalent to about 45.3 g-moles of CO per minute (0.100 pound moles per minute of CO) when the steel flows through the degassing device at a rate of about 5 tons per minute. The gas contained in the steel in this example gives ten times as much expansion energy as the lifting gas supplied away.

It is known that finely divided steel particles must remain at the working pressure in the vacuum chamber 2 for about 0.25 to 7.0 seconds in order to achieve a practically useful equilibrium of oxygen content at a given carbon content and a given working pressure. The exact dwell time depends on the type of steel to be degassed. In the device described, the path of the droplets runs upwards into the degassing chamber 2 and downwards to the hearth 5 or the lower right side wall and finally into the receiving vessel 15. The average height and plug path of the droplets, The amount of time required to achieve the actual dwell time is determined partly by the heating and length of the degassing chamber and the core area as well as by the cross-sectional area of the kiln or additional chamber 15. Therefore, the metal can even then be sufficiently exposed to the vacuum when the indwelling ze it the iletalls on the stove is short in comparison with the method where _f with a metal bath in the degassing (~ operates efäßen.

009808/0537

That through the inlet port 10 below the "barometric Height of the metal column in this injected lifting gas may only be necessary if the metal is calmed or semi-calmed or in similar cases where that contained in the steel Gas does not have sufficient energy to lift the metal the remainder of the distance into the degasser. In certain cases the lifting gas may only be required to facilitate the atomization and flow of metal balls or to initiate particles into the degasser initially. By the expansion of the lifting gas and that in the steel existing gases with an increase in the metal in the inlet channel 8, the metal flow into the chamber 2 can experience an acceleration. In order to monitor this acceleration, a second gas inlet opening 11a is at a point above the barometric altitude and preferably below the junction of the inlet channel 8 provided with the stove 5, namely for injecting a Gas into the ascending column of gas and steel particles to slow down the flow of these particles. The injected gas which can be argon or the like, acts to the effect that a pressure is generated in the inlet channel 8, against which the through the inlet duct 8 upward bäewing and expanding gases have to work, whereby the expansion and thus the acceleration the lifting gases and the gases already present in the metal braked and the metal flow is monitored. Thus, by selectively regulating the supply of the lift and brake gases to the Total flow or throughput controlled, is usually the volume of the braking gases is not sufficient to hold down the barometric metal column completely, although the total height the column can thereby be varied. The braking gas can be used alone or together with an externally supplied Hebeg-as although it is usually not necessary to use it, except when working with a lifting gas. Other means of regulating the metal flow are possible, such as controlling the vacuum in chamber 2 through the jet pump system, but is the method described

009808/0537 originally inspected

to be preferred because of its particular simplicity and economy. The monitoring and control of the metal throughput through the degassing device is important, both to a constant level in the Kilfs- or additional chamber 15 as well as avoid overfilling *, and continue to do so because in many cases the throughput must be matched to the capacity of a continuously operating continuous casting plant.

Fig. 5 of the drawing shows a typical performance curve of a four-stage steam jet pump which is suitable for use on an apparatus according to the invention. The effect of the braking gas on the vacuum in chamber 2 is shown on the curve of the first stage of the steam jet pump. Both the abscissa and the ordinate have a logarithmic scale. Point A on the curve shows a typical operating condition, with the working pressure in chamber 2 being 0.75 mm of mercury absolute, while gas from the steel plus lifting gas amounts to a total of 90 ₅ 7 kg / hour or £ .00 lbs / hr (corresponding to a dry air temperature of £ 1 ° €). When a braking gas is introduced into the upwardly directed inlet passage 8 at an amount of 45.4 kg / hour or 100 lbs / hr (corresponding to a dry air temperature of 21 ° C), the pressure above the metal in the limited space of the upward rises leading channel 8, but the suction chamber pressure increases only slightly because of the large volume of the suction caramer 2. The suction pressure can rise extremely quickly to about 0.8 mm of Quec-k silver, as shown at point B, but the suction chamber pressure and the amount of gas discharged will stabilize at a slightly lower point on the curve, as less gas is emitted the metal is withdrawn _s because the flow of metal is delayed by the supply of the brake gas. Using the braking gas it is possible to monitor and control the flow of metal while at the same time maintaining a substantially constant chamber pressure, whereby all of the metal experiences a very uniform degassing.

009808/0537,., _.._ '*

- 15 -

In the arrangement shown in FIGS. 1 and 2, the molten metal flowing out of the opening 6 reaches the Auxiliary or additional vessel 15. At the beginning of the degassing process the outlet opening 16 is closed. There are various possibilities for this, e.g. the one shown in the drawing Arrangement in which the stopper rod 18 is lowered against the inside of the outlet opening 16, while an aluminum plate covers the outside of the outlet opening in a sealing manner. Although the stopper rod cannot maintain a vacuum, it is however, able to prevent the hot metal from leaking through the outlet opening against the aluminum plate. The fact that the outlet opening 16 is sealed against the ingress of air and the outflow of metal acts the vacuum generated in the degassing chamber 2 also in the additional vessel, in which the metal is after its exit collects from chamber 2. If the depth of the metal bath in the additional chamber is the barometric height or about 152 cm reached, the stopper rod can be lifted from its seat, whereupon the molten metal with the aluminum plate comes into contact, melts it and flows into the mold. The size of the outlet port 16 should be adjusted and regulated so that the li level in the additional chamber is kept almost constant after the sprue. Solanne the metal in the additional chamber above a height of IL2 cn, from the outlet end measured, held ^ it flows through the outlet opening but prevents the surrounding atmosphere from ascending through the opening 16 into the metal bath, v / enn the depth of the Metal bath in the additional chamber is not sufficient to create a barometric column of liquid metal above the discharge opening 16, air would of course be drawn up through the molten metal.

Metal is drained from the additional chamber when the level of the ketallic bath exceeds the barometric level. This is preferably started when the metal level in the suspension chamber has only reached a number of centimeters, for example 10 or more centimeters, above the barometric altitude. Thus ^the effective one ^arises

009808/0537 ' ^lS '

BAD OPiIGlNAL

Velocity level or the dynamic pressure of the through the opening 16 escaping metal only from the difference to the barometric pressure level, i.e. from the difference compared to a Height of 152 cm, which is why the metal exits through the opening at a low speed and into the one below the opening The foundry mold arrives. This slow speed is desirable because experience has shown that as a kind of general Usually the quality of the casting, the better the lower the speed, and vice versa, the worse the higher is the occurring speed. The method described above for flow monitoring and control and the appropriate one Device allow the effective metal level in the additional chamber at the desired level relatively keep close above barometric altitude to get a fairly steady flow of low velocity to achieve through the opening 16.

It is therefore essential for the operation of the present invention that the metal column is in the inlet channel held lower than this is long, but higher, than six feet and it is also important to ensure that the continuous flow of molten metal is maintained is without air can penetrate, which is achieved by the fact that the depth of the metal bath above the drain opening holds at least about 152 cm.

In the usual degassing technique, the molten metal is raised to a level in the inlet channel by the vacuum prevailing in the vacuum chamber. \: o there is a metal bath on the hearth of a degassing vessel above the upper end of the inlet duct, whereas the inclination of the hearth in the inventive device is such that the metal does not collect in a bath above the hearth to a level where it can prevent the droplets rising from the inlet channel of the degassing vessel from further rising.

BATHROOM CR) GiMAL - 17 -

009808/0537

Just as the metal level in the ladle lowers as the metal is removed, it becomes mutual Displacement between the ladle and the end portion of the inlet channel of the degassing device causes the Keep the end piece immersed in the metal at about the same height at all times. This can be done by lifting the ladle with a crane hook according to the sinking of the metal level. the ladle or by supporting the ladle for a vertical movement in any other way. To determine the change in the metal level in the ladle, one can look use various means, such as visual observation or a weight loss meter.

The heat equilibrium in the melt is caused by radiation and heat transfer losses and various exothermic and endothermic reactions that take place in the ladle, in the degassing device and in the auxiliary chamber. A useful heat loss can occur in some melt runs, which is why it is desirable to have devices for supplying heat to the metal in order to keep it at a suitable temperature for casting. In the described embodiment this is achieved by inductive heating of the MdHlIs in the additional chamber 21. By using a water-cooled one made of stainless steel Pipe with its covering made of refractory material As described above, only a small amount of the energy introduced is absorbed in the stopper rod. The induction coil can also serve to keep the metal in motion in the auxiliary vessel. This is particularly desirable when alloying materials or Additives are continuously introduced into the degassed metal. In FIGS. 1 and 2, an opening in the degassing chamber 2 is shown at point 27, through the alloy materials to the hearth introduced v / grounding ability. Such materials would then become more common at a uniform rate from a vacuum tight feeder

- 18 -

ORiUiNAL ii ^ -z

009808/0537

Kind be introduced.

If desired, an induction coil 28 can be provided be arranged around the lower end of the inlet channel 8 of the degassing device above the end piece 9. This induction coil 28 is water-cooled and can work as an electromagnetic split-phase induction pump that works in conjunction with the Argon or - if possible - instead of argon.

In Fig. 3, instead of an additional vessel for receiving the degassed metal from the opening 6, a tubular leg with an inner channel of sufficient length is shown to hold a metal column therein by the barometric pressure. This tube has an outlet opening 31 at its lower end, which serves to regulate the outflow of the metal according to the inflow rate, the metal column held above the outlet opening by the barometric pressure preventing the ingress of air into the degassing chamber »Ird. In this figure, 30 denotes the outlet leg and 31 is the outlet opening at the end thereof. The outlet leg 30 or the ^{channel provided 7} in has a length which is approximately comparable to the length of the inlet channel 8 and is at least long enough to hold a metal column slightly more than 152 cm in height below the outlet opening 6. This leg or the channel will of course usually not be longer than necessary, since, on the other hand, provision must be made to ensure that there is sufficient space for the continuous casting mold or another shape or a vessel into which the outlet channel releases the degassed metal.

In Fig. 4 there is a somewhat more or less schematic another embodiment of the additional vessel shown. This additional vessel 35 has a water-cooled Iletall cover 36. It is lined with refractory materials. A partition! * Or a weir 37 is provided between the ends of the vessel. which separates a container 38 into which the molten metal from the degassing device is first drained.

009808 / Q53 ¹ !

An air-cooled induction coil 39 surrounding this container, and the metal flows from the container into a second chamber 3 over ¹ J, the one or more Ablaßöffriungen may have in the ground, as shown hei ¹ Il. The outflow of the metal through the openings can be controlled by stopper rods 42, one for each opening. The seal can be exactly as described above in connection with FIGS. 1 and 2, or other temporary closures can also be provided for these openings. Chamber 40 is deep enough to contain molten metal at a height greater than six inches. In this figure, each opening releases molten metal in molds A used for multiple continuous casting. Instead of introducing the alloy material onto the hearth of the degassing chamber 2, as described above, it can also be introduced into the additional vessel in one of the various embodiments used here. That's in Fi * r. k , where ^ 3 shows an opening for the addition of Legleruncsnaterial in the metal contained in the container 38. Here the induction coil is again used to move the metal in order to finely distribute the alloy material in the metal, as well as for the supply of heat in order to reduce or partially replace heat losses occurring during degassing.

In Fig. 1 there is a nozzle in the bottom of the Zusatzp.efäßes shown by introducing argon gas to beep the ketal can be so as to ensure a more uniform distribution of the alloy components in the metal. This nozzle is at * 15 shown, with a similar arrangement also being made in Fir: · * J which is not shown there, however.

Each of the in one of the Fip. the drawing ^ Executions or arrangements can be made to the extent that it is is desired or appropriate to be exchanged with those in others The modifications shown in the figure are used.

- 20 -

009808/0537

BAD OFJiGINAL

Since only the lower end of the part 9 on the inlet pipe is immersed under the surface of the molten metal in the feed ladle, the main lung of the inlet leg or channel can be surrounded by a metal jacket, which is important _A for maintaining a barometric column of molten metal in the inlet duct as the refractory lining of the duct itself is porous. So far, no precautions have been taken to maintain a barometric column in such a leg, but the leg or channel has been immersed deep to the bottom of the ladle. Molten metal can be removed from the ladle close to the bottom by lifting the ladle in the described manner, while the height of the metal level in the leg or the inlet channel is kept the same.

With the present invention it is therefore possible to use such special refractory lining materials in the additional chamber, such as a rammed refractory lining made of calcium oxide. Calcium oxide reacts with the sulfur contained in the steel, and when the oxygen and sulfur levels are roring, nitrogen can be removed. By preventing the low degree of dissociation of calcium oxide (2 Ca 0 - 2 Ca + O _n ) in steels with a low oxygen content and the associated low release of gas into the melt, more effective degassing conditions can be maintained in the degassing vessel with the result that more nitrogen can be removed from the ground than using more conventional refractory lining materials. At the same time, the consumption of calcium oxide due to the reaction with sulfur is so low that its service life is not seriously impaired compared to that of other refractory lining materials. By using the calcium oxide on the inside of this vessel, it can be kept at such a temperature at any time that the lining does not absorb any atmospheric impurities and therefore does not swell and decompose. v: ie that is the case with calcium oxide, which can be used as a refractory lining

Exposed to influences if: t. _A. - οι -

009808/0537

BATHROOM OHiGINAL

The additional vessel allows alloying elements to be added to the metal while it is still under vacuum, however, in an environment where most of the gases present in the steel have been removed, so that these alloying elements during the direct passage of the metal from a ladle to a mold, strand, caster, or be added to another receiving device and mixed in without any noticeable oxidation of the alloy.

The numerical data contained herein relates to the treatment of steel as a metal. For the skilled person, however, it is It can be seen that other metals, such as copper and aluminum, may have somewhat different designs of the degassing device than require the illustrated. For example, denser metals have a barometric altitude that is proportionally lower than that of steel and less dense metals have a proportionally greater barometric altitude under the same vacuum conditions.

Although various embodiments have been shown, it is clear that these modifications can be made without the To leave the scope of the invention.

Claims

- 22 -

009808/0537

Claims (13)

Claims 1) Method sum degassing of molten metal, in particular steel, in a degassing device with a vacuum chamber and an inlet channel, characterized ₃ that the inlet channel is immersed with its lower end in a molten metal bath, that in the chamber a negative pressure relative to the atmosphere is generated and that the molten metal under the action of the barometric pressure in the channel to a level below the upper end of the channel and above the melt pool level is pulled and that thereby the molten metal thrown by expanding gases in particulate form up into the chamber and is collected there as it falls and withdrawn again, so that the upper end of the channel is free of molten masses To hold metal. 2) Method according to claim 1, characterized in that the molten metal from the degassing vessel also at negative pressure is placed in a receptacle, from which it is drained through an outlet opening in the bottom, while the metal mirror is always kept above the outlet opening at such a height that the ingress of air into the receptacle is excluded is. 3) Method according to claim 1 or 2, characterized in that the metal is drained from the receiving vessel only when the metal level in it is above by the barometric Pressure level lies certain liiveaus, and that the amount of the through-degassing metal is controlled so that the metal level is kept essentially constant. 4) The method of claim 3 _9, characterized gekennzeichent that the control is effected by controlled supply of a gas into the intake port of the degassing below the metal mirror to increase the flow rate and by the supply of gas into the inlet channel above the metal beep els for braking the flow. 009808/0537 - 23 - BAD QiTiGi ^ AL. - 23 - 1533302 5) Method according to claims 1 to 4, characterized in that that the one lined with pounded calcium oxide The inside of the collection vessel is always on a sufficient one Temperature is maintained to prevent the liner from absorbing water or moisture. 6) Method according to claims 1 and 2, characterized in that that Wilrme is supplied to the metal in the receptacle will. 7) Device for performing the method according to one or more of claims 1 to C, characterized by an elongated chamber (2) π with its longitudinal axis inclined with respect to a vertical plane higher side to an outlet opening (6) on the lower side, and further characterized by a tubular inlet channel (8) opening into the chamber (2) on the higher side of the hearth (5) for the molten metal and by a connection to it a vacuum pump in the liilhc of the upper end of the degassing chamber (2), which compared to the cross-section of the channel (8) has a multiple diameter inner cross-section. G) Device according to claim 7, characterized in that the tubular inlet channel (8) has a ln-re i.at which is <~ _r above the pressure height until the metal in the channel ( 8) rises under the effect of atmospheric pressure when the channel (8) is immersed in the molten metal while maintaining the vacuum conditions in the chamber (2). 9) Device according to claim 8, characterized in that the rohrförir.ige inlet channel (8) is longer than l'i 2 cn. 10) Device according to one of the claims: odor 7 to 9, thereby characterized in that the tubular inlet channel (8) consists of one refractory materials liner with a metal jacket and also a replaceable refractory end piece (9) using refractory materials on both its interior and exterior 009808/0537 " ² "" BATH ORIGINAL on its outside for immersion in the molten metal on much st. 11) Device according to claim 7 or one of the following claims, characterized by a receiving device (15j30,35) for the molten metal, into which the outlet opening (6) arranged on the lower side of the hearth (5) opens, and which has a narrowed bottom outlet (l6,31 "" * H) and a depth such has that in its molten barometric pressure by a column metal maintained v. ^r ird. providing a seal against the ingress of air with an open outlet (16,31, ^ 1 ) and when the vacuum is maintained in the degassing chamber (2). 12) Device according to one of the preceding claims, characterized in that the tubular inlet channel (8) with an airtight refractory lining is provided. 13) Device according to claim 11, characterized by devices for setting and controlling the Iletallmenne entering the chamber (2). 1 * 0 device according to one or more of the preceding claims, characterized by a device for the selective introduction of an Eel erase into the Ijetall located in the inlet channel (8) in a height below the tc.rcr.etr: ¹ .see height of the metal column. H) Device according to one of claims 7 to your r.eLrcren Ik _t indicated by a "inrichtunr for selectively introducing a gas into the channel Linla.i above the barometric altitude of the ^{Ilet2llsc:...} .Ule. BATH 009808/0537 Blank page