US3618924A

US3618924A - Method and apparatus for degassing liquid steel

Info

Publication number: US3618924A
Application number: US769793A
Authority: US
Inventors: Theodor Messing
Original assignee: STANDARD MESSO DUISBURG
Current assignee: STANDARD MESSO DUISBURG; Standard-Messo Duisburg Gesellschaft fur Chemietechnik Mit Beschrankter Haft Ung & Co
Priority date: 1967-10-24
Filing date: 1968-10-23
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09
Also published as: GB1187168A; FR1582311A

Abstract

A method of and device for degasifying liquid steel batch by batch by vacuum treatment in a gas extraction chamber filled with a suction intake pipe extending down into a ladle containing the liquid steel to be degasified, according to which while holding said ladle and said gas extraction chamber stationary, displacing a batch of molten steel from said ladle into said degasifying gas extraction chamber, degasifying said last-mentioned batch in said gas extraction chamber and releasing the degasified batch from said chamber.

Description

United States Patent Inventor Appl. No.

Filed Patented Assignee Priority METHOD AND APPARATUS FOR DEGASSING Primary Examiner-Donald R. Schran Allorney-Walter Becker ABSTRACT: A method of and device for degasifying liquid .steel batch by batch by vacuum treatment in a gas extraction chamber filled with a suction intake pipe extending down into ggfik n s a ladle containing the liquid steel to be degasified, according g g to which while holding said ladle and said gas extraction US. Cl 266/34 V chamber stationary, displacing a batch of molten steel from Int. Cl

2l 7/10 said ladle into said degasifying gas extraction chamber, degasi- Field of Search 26 /3 34 fying said last-mentioned batch in said gas extraction chamber V and releasing the degasified batch from said chamber.

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PATENTEDunv 9 1971 saw 2 OF 3 INVENTOR. 7 0 0 Mil/4r) BY the barometric column METHOD AND APPARATUS FOR DEGASSING LIQUID STEEL The present invention relates to a method of and a device for the removal of gas from liquid steel, batch by batch, by vacuum treatment in a gas extraction chamber fitted with a suction intake pipe extending down into a ladle.

For the removal of gas from a batch at atime, steel, tapped ofl into an ordinary ladle, through a suction pipe partially exhausted gas The molten steel rises the pressure difference tion chamber and the the liquid is conveyed in batches, extending down into the ladle, into a extraction chamber situated above it. initially in the suction pipe because of between the vacuum within the extracatmosphere over the bath in the ladle, of liquid steel usually attaining a height of about 1.4 meters. To remove the gas from the steel, either the extraction chamber or a ladle is raised and lowered, for example, by means of hydraulic equipment. As the extraction chamber is lowered or the ladle is raised, part of the molten steel rises into the extraction chamber, in which it yields up its gas. When the extraction chamber is raised or the ladle is lowered, this batch of steel, now freed from gas, flows back into the ladle. This process is repeated until the requisite degree of degassing has been achieved throughout the entire charge of steel.

in the method just described, for the removal of gas from molten steel in small batches, a great deal of power is needed for imparting relative motion to the refractory-lined gas extraction chamber, with the equipment mounted on it for the admission of fluxes and so forth, and to the ladle mechanism its entire charge of molten metal, all of which represent a very considerable deadweight. The moving mechanism, which is necessarily very robust because of the heavy nature of steelmaking work, is highly expensive and bulky.

Dust and heat reduce the life of this mechanism and give rise to heavy maintenance costs.

It is, therefore, an object of this invention to provide a method of and device for degasifying liquid steel, which will overcome the above-mentioned drawbacks.

It is another object of this invention to provide amethod of and device for batchwise removing gas from liquid steel by vacuum treatment, according to which it is no longer necessary to more the gas extraction chamber and the ladle in relation to each other while the gas is being removed.

These and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawing, in which:

FIG. l diagrammatically shows a gas removal device according to the invention, in vertical section, with the displacement vessel secured noncoaxially to the gas extraction chamber;

FIG. 2 shows in vertical section a gas extraction chamber according to the invention, with the displacement chamber flanged onto the gas extraction chamber coaxially with the intake pipe thereof;

FIG. 3 illustrates in vertical section a gas extraction chamber according to the invention with flange-attached cover, to provide a pressuretight closure on the ladle containing the charge of molten steel.

Taking as its starting point the existing methods whereby gas is removed from liquid steel by..the vacuum treatment of small batches in an extraction chamber fitted with a suction intake pipe extending down into the ladle, the invention achieves its purpose by virtue of the fact that the batches of molten metal are expelled from the ladle pneumatically or mechanically and thus raised into a gas extraction chamber situated above the ladle.

The particular advantage of the method here proposed lies in the fact that the only power it is now necessary to expend is that which is required to raise the sum of all the batches of molten metal. This advantage can best be demonstrated by the following numerical example. For adequately degassing 100 tons of molten steel, the method used hitherto entails raising the gas extraction chamber, which itself weighs approximately gas, is admitted, the molten suretight cover fitted with 40 tons, about 30 times. Making allowance in the calculation for a circulation factor of 3, the amount of steel treated in each instance in the gas extraction chamber is only (3Xl00)/3 =10 tons. Hence, if all that is lifted at each stroke is the batch of metal being degassed, instead of the extraction chamber itself, this makes a difference in weight of about 30 tons of each stroke.

in one advantageous fonn of equipment for putting the invention method into practice, a bell-type displacement vessel, open at the bottom and fitted at the top with a pressure feedpipe and a pressure relief pipe", extends down into the charge in the ladle, adjacent to the intake pipe of the gas extraction chamber. When this is used, it has been found desirable to connect the displacement vessel rigidly to the gas extraction chamber. When a fluid under pressure, such as air or an inert steel inside the displacement vessel is expelled, with the result that the level of the melt rises correspondingly in the ladle and in the gas extraction chamber. When the pressure in the displacement vessel is relieved, the melt flows back into the ladle again.

In another form of equipment, the molten steel is expelled from the ladle by a bell chamber lowered into the charge and raised from it by mechanical means.

In yet another form of equipment, the displacement vessel can be made coaxial with the extraction chamber intake pipe and flanged on to the extraction chamber along with this pipe.

in another advantageous arrangement for putting the invention method into practice, the ladle is provided with a prespressure feed and pressure relief pipes, the extraction chamber intake pipe extending down through the cover, into which it is sealed, into the molten charge.

With all three forms of equipment for putting the invention method into practice, the gas extraction chamber and the displacement vessel or cover should preferably be stationary, while the'ladle containing the charge of molten steel is raised once only from below to the appropriate height. Alternatively,

' it is possible for the extraction chamber, complete with displacement vessel and/or cover, to be mounted from above and secured to the charged ladle, this bring stationary.

- Referring now to the drawings in detail, and FIG. 1 thereof in particular, the equipment shown therein comprises a ladle 10 of standard type fitted with a stopper lifting rod 11, said ladle containing the charge of molten metal 12. Above the ladle 10 is a gas extraction chamber 13. At the top of the extraction chamber 13 is a dome 14, carrying a connection flange 15 for the vacuum pump connection or the like (not shown). Near the top or about halfway up, the extraction chamber 13 has a charging pipe 16 directed obliquely downwards and having mounted thereon a device 17 for gauging the charges of whatever additional materials are to be introduced. The base of the extraction chamber 13 carries a pipe stub 18, to provide a pressuretight connection for the intake pipe 19.

The displacement vessel 22, which is open at the bottom, is secured eccentrically to the gas extraction chamber 13 by means of the anchorage 2!. The top end of the displacement vessel is fitted with a pressure feedpipe 23 and a pressure relief pipe 24 with shutofi valves 25.

While the intake pipe 19 extends only a short way down into the molten steel 12, the displacement vessel 22 dips far more deeply into the steel. By the introduction of fluid under pressure into the'displacement vessel 22, the'molten metal in said vessel 22 can be lowered from its assumed level a to the level 1:, the level in the ladle thereby becoming adjusted to b. At the same time, the level of the steel within the gas extraction chamber 13, which at 0 corresponds to the vacuum P, will rise to the extent of h, the new level in the gas extraction chamber 13 now being b". As soon as the pressure fluid is allowed to escape from the displacement vessel 22 through the pressure relief pipe 24, the two levels of the steel, b and b", will drop again to the corresponding levels a and a. By virtue of the fluid being repeatedly pumped into and released from the displacement vessel 22, the entire charge of molten steel will be forced in successive batches into the gas extraction chamber 13, where its gas will be removed.

In the example shown in FIG. 2, the displacement vessel 32 is mounted coaxially about the intake pipe 19. The displacement vessel, along with the pipe 19, is by means of a pipe connection 33 flanged onto the pipe connection 18 of the gas extraction chamber 13. The rising and fall of the batches of metal is also in this instance effected in the manner described in connection with FIG. 1 by means of a fluid pumped into the displacement vessel 32 under pressure, which fluid is subsequently released.

in the example illustrated in FIG. 3, a cover 42 to provide a pressuretight closure on the ladle 10, is secured by the pipe connection 43 to the pipe connection 18 on the gas extraction chamber 13. [n this arrangement, after the tapping and charging of the molten steel 12, the ladle 10 is raised and forced up under the cover 42 to form a pressuretight seal with the aid of an interposed packing 44, which may be water cooled. It is also possible, of course, for the cover, along with the complete gas extraction chamber and intake pipe, to be placed upon the ladle and pressure tightly fitted thereon.

The raising of the batches of metal from the charge 12 into the gas extraction chamber 13 and their return to the ladle are in conformity with FIG. 3 effected by the admission of fluid under pressure to the container formed by the ladle l and its cover 42, following by release of the fluid. As the fluid is forced in, the level a of all the metal in the ladle will drop to b. In this example, the difference in level h within the gas ex traction chamber 13 now depends solely on the geometrical dimensions of the gas extraction chamber 13 and on the volume of steel expelled from the ladle l0.

It is, of course, to be understood that the present invention is not limited to the specific showing in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is:

l. A device for degasifying liquid steel batch by batch whereby part of molten steel is lifted by pneumatic displacement from a vessel into a degasifier vessel, which includes: a first vessel adapted to receive and hold a charge of molten steel to be degasified, gas extraction chamber means arranged above said first vessel and provided with downwardly extending tubular means extending into said first vessel, and a belltype displacement vessel closed at the top and open at the bottom and extending downwardly into said first vessel and fed at its upper portion with a feedpipe for selectively conveying pressure fluid into said bell-type displacement vessel to displace a batch of molten metal from said first vessel into said gas-extracting chamber, the upper portion of said displacement vessel also being provided with an adjacent exhaust pipe for releasing pressure fluid from said displacement vessel to release the degasified batch from said extraction chamber means.

2. A device according to claim 1, in which said displacement vessel is connected rigidly to said gas extraction chamber means.

3. A device according to claim 1, in which said displacement vessel is mounted coaxially about said downwardly extending tubular means and is flanged onto said gas extraction chamber means together with said downwardly extending tubular means.

Claims

2. A device according to claim 1, in which said displacement vessel is connected rigidly to said gas extraction chamber means.
3. A device according to claim 1, in which said displacement vessel is mounted coaxially about said downwardly extending tubular means and is flanged onto said gas extraction chamber means together with said downwardly extending tubular means.