US3479022A

US3479022A - Apparatus for vacuum treating liquid steel according to the circulation method

Info

Publication number: US3479022A
Application number: US560651A
Authority: US
Inventors: Werner Coupette
Original assignee: STANDARD MESSO DUISBURG
Current assignee: STANDARD MESSO DUISBURG; Standard Messo Duisburg Gesellschaft fur Chemie-Technik Mbh & Co
Priority date: 1965-07-01
Filing date: 1966-06-27
Publication date: 1969-11-18
Anticipated expiration: 1986-11-18
Also published as: DE1458936A1; GB1129298A; JPS4912B1

Description

V 8, 1969 w. COUPETTE APPARATUS FOR VACUUM TREATING LIQUID STEEL:

ACCORDING To THE CIRCULATION METHOD Filed June 27, 1966 highly heated 9 A ciPcu/ating gas United States Patent 4,067 Int. Cl. C21c 7/10; B011 7/00 US. Cl. 266-34 3 Claims ABSTRACT OF THE DISCLOSURE A degasifying vessel with two pipes extending into molten metal, especially steel melt, for vacuum treating according to the circulating degasifying method. Metallurgical reaction is made more versatile and intensive by providing the degasifying vessel with at least one adjustable plasma burner for blowing in a highly heated reactive gas able to flow around molten metal droplets due to splashing in the vessel. Heat energy of multi-atom inert gases is extremely high since the specific heat due to the increase in temperature is increased by dissociation and ionization energy; due to high temperatures at the phase borders, an intensive and quick reaction of the metal droplets is obtained. Heat losses occurring during the vacuum treatment are simultaneously obviated by radiation of the high temperatures, very favorable in a vacuum.

The present invention relates to an apparatus for vacuum treating liquid steel according to the circulating method, in which a degasifying vessel with two pipes extends into the steel melt. Devices of this general type for carrying out the circulating degasifying method are known. In order to induce the chemical reaction, it is known instead of conveyor gas to convey inert or reactive gases into the riser.

It is also known to carry out an inductive heating or a heating by means of a graphite rod in the interior of the degasifying vessel. These heretofore known devices, however, have the drawback that the method is difficult to carry out and involves considerable costs for the heating.

It is, therefore, an object of the present invention to make the metallurgical reaction more versatile and intensive than heretofore possible while permitting the employment of heretofore known degasifying vessels.

It is still another object of this invention to provide a device for vacuum treating liquid steel according to the circulating method, which will be relatively simple in construction and easy to handle.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing diagrammatically illustrating a device according to the invention for vacuum treating liquid steel.

The problem underlying the present invention has been solved by providing the degasifying vessel with one or more adjustable plasma burners for blowing in a highly heated gas. Modern plasma burners have a power of many thousand kilowatt and are able to produce gas temperatures up to 50,000 C. Such plasma burner or burners are arranged at the upper portion of the degasifying vessel so that hot gases conveyed from said burner or burners into the vessel almost flow only around the steel which splashes in the vessel. For purposes of degasification, small droplets down to 0.5 millimeter are very much desired in the vacuum chamber. However, they have the drawback that they cool off too quickly and thus give 06:

See

less gas and react in a poor manner. This drawback will be overcome when, in conformity with the present invention, the hot gases are able to flow around the said droplets.

Plasma burners are operated by means of inert gas, such as argon, or a reactive gas, as for instance, hydrogen, oxygen, methane, carbon tetrachloride, chlorine, sodium vapor, or the like, or mixtures thereof. The heat energy,

especially of the multi-atom gases, is extremely high since the specific heat due to the increase in temperature is increased by the dissociation and ionization energy. In view of the obtained high temperatures at the phase borders, an intensive and quick reaction of the steel droplets is obtained.

The heat losses occuring during the vacuum treatment are at the same time obviated according to the present invention, namely by the radiation of the high temperatures, which radiation is very favorable in a vacuum.

Referring now more specifically to the drawing representing a section through a degasifying vessel, the degasifying vessel 1 is in a manner known per se with its two pipes 2 and 3 immersed into a ladle (not illustrated) which is filled with liquid steel. By means of a conduit 4 communicating with the riser 2, argon or any other suitable gas is blown into the vessel 1 whereby in a manner known per se a circulation will be obtained. In the degasifying vessel 1, the steel is pulled upwardly and torn into droplets. Vessel 1 communicates with the vacuum pump through a connection 5 and a hose (not illustrated) which is connected to connection 5.

In conformity with the present invention, the degasifying vessel 1 is equipped with controllable plasma burners 6 arranged in the upper portion of vessel 1. Burners 6 are operated by an inert gas, or a reactive gas, so that the highly heated gas will be able to flow around the steel droplets. With a ton melt to be degasified, burners with a power of from 1000 to 2000 kilowatts will suflice. In order not unnecessarily to place the vacuum pumps under load, high gas temperatures are selected so that a high heat supply with a relatively small quantity of gas with a temperature of approximately 25,000 C. will be obtained. Advantageously, the supplied quantity of gas should not exceed 10% of the output of the vacuum pumps.

When employing hydrogen for deoxidizing disquiet steels, water steam is formed which with steam jet ejectors does not place a material load on the pump system, because water steam deposits in the condensator. It is important for the metallurgical reaction that gaseous products only form which cannot impurify the steel. Furthermore, it is advantageous for the vacuum gas metallurgy that all reaction products are immediately withdrawn at the border layers so that they cannot act against each other. Thus, with the device according to the present invention, it is possible to carry reactions of various types without the necessity of employing the greatly interfering metallurgical slags.

When employing a plasma burner, it is also possible to keep the degasifying vessel warm during treatment intermissions. This is particularly advantageous with a high grade lining because such linings are sensitive to temperature changes.

Plasma burners are generally Well known and have been described, for instance, in French Patent 1,311,252 which issued on Oct. 29, 1962. The power output of such plasma burners may be controlled in any convenient manner, for instance, by alternating current or three-phase current. This is particularly favorable when a plurality of such burners are employed since" with superposition of three-phase current the power of the burners may be increased to a maximum in a very simple manner, which is practicallynot possible with methods not employing superposition of three-phase current.

The control of such plasma burners is likewise well known and, for instance, described and illustrated in said French patent. A control circuit of this type is diagrammatically illustrated in the present drawing in which reference numerals 7 and 8 designate direct current generators respectively conductively connected to the

electrodes

9, 10 and 11, 12 of the two burners 6 shown in the drawing. There is, furthermore, provided a source 13 of threephase current, the three-

phase

14, 15, and 16 of which are respectively connected to electrodes 10 12 and a further electrode of a further burner (not shown).

It is, of course, to be understood that the present invention is, by no means, limited to the particular arrangement shown in the drawing but also comprises any modifications within the scope of the appended claims. Thus, while according to the drawing the degasiiying vessel is equipped with a plurality of plasma burners, it is to be understood that the arrangement would also operate properly with one burner only.

What I claim is:

1. An apparatus for vacuum treating liquid steel according to the circulation method for degasifying the steel, comprising a degasifying vessel, pipe means connected to the lower portion of said vessel and communicating with the interior thereof, said pipe means being immersed in a steel melt, conduit means communicating with said pipe means through which gas is admitted for withdrawing steel from the steel meltand throwingtthe same in form of droplets into said degasifying vessel, adjustable plasma burner means arranged at the upper portion of said vessel and operable by inert or reactive gas to convey highly heated gases into the interior of said vessel and around steel droplets thrown up into the flow of said highly heated gases, and vacuum creating means connected to and communicating with said degasifying vessel.

2. An apparatus according to claim 1, in which means for conveying high-heat gas is associated with said plasma burner which means is operable to furnish a small quantity of said gas at a temperature around 25,000 C.

3. An apparatus according to claim 1, in which a plurality of plasma burner means are associated with said degasifying vessel and arranged to supply hot gas flow around the droplets for intensive metallurgical treatment.

References Cited UNITED STATES PATENTS 3,147,330 9/1964 Gage 219-121 XR 3,320,053 5/1967 Lehman 7549 XR 3,342,250 9/1967 Treppschuh 7549 XR L. DEWAYNE RUTLEDGE, Primary Examiner J. E. LEGRU, Assistant Examiner U.S. Cl. X.R.