US3831915A

US3831915A - Closure for crucibles used for aluminothermic reactions

Info

Publication number: US3831915A
Application number: US00362310A
Authority: US
Inventors: H Guntermann
Original assignee: Elektro Thermit GmbH
Current assignee: Goldschmidt ETB GmbH
Priority date: 1972-06-22
Filing date: 1973-05-21
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: IT985446B; AT327643B; ATA513773A; BR7304400D0; NL7306788A; AR195717A1; GB1392894A; DE2230430B2; DE2230430A1; NL157527B; CH575108A5; ZA733318B; AU5615373A

Abstract

This invention relates to an improvement in a closure for crucibles used for aluminothermic reactions comprising a tap pin, a sealing material, and refractory sand, the improvement comprising a sealing material of inorganic fibers covering the tap pin.

Description

United States Patent [191 Guntermann Aug. 27, 1974 CLOSURE FOR CRUCIBLES USED FOR [56] References Cited ALUMINOTHERMIC REACTIONS UNITED STATES PATENTS [75] Inventor: Hans Guntermann, Essen-Steele, 2,024,132 12/1935 Sander 75 /27 Germany OTHER PUBLICATIONS [73] Asslgnee: E P GmbH Essen Publication: Thermit Mill and Foundry Practice; pages Steele, Germany [22] Filed: May 21, 1973 Primary Examiner-Gerald A. Dost [21] Appl' 362310 Attorney, Agent, or Firm]ames E. Bryan [30] Foreign Application Priority Data [57] ABSTRACT June 22, 1972 Germany 2230430 This invention relates to an improvement in a closure for crucibles used for aluminothermic reactions com- [52] US. Cl 266/34 R, 266/38, 75/27 prising a tap pin, a Sealing material, and refractory [51] Int. Cl. C2lc 7/00 Sand, the i rovement comprising a sealing material [58] Field of Search 266/38, 34 R; 164/53, 54, of inorganic fibers covering the tap pin 164/80, 123; 75/23, 27; 222/DIG. l9, DIG. 20

2 Claim, 2 Drawing Figures CLOSURE FOR CRUCIBLES USED FOR ALUMINOTHERMIC REACTIONS The present invention relates to a closure for crucibles used for aluminothermic reactions, composed of a nail-like tap pin, a sealing compound, and highly re fractory sand.

Employed for the purpose of carrying out aluminothermic reactions are generally conical crucibles composed of a sheet metal jacket, a refractory lining inserted into this jacket, and an exchangeable discharge nozzle which must be closed anew prior to each filling of the crucible. Serving as closure means are a nail-like tap pin, a sealing material, and refractory sand, for example corundum sand. The sealing material is asbestos which, when received, is prepared in the form of small plates, and the required number of the small plates, which latter are pulverized or ground to asbestos wool, prior to being used, is determined by the size of the cru cible.

In order to obtain, or bring about, the closure, the tap pin is suspended in, or placed into, the opening of the discharge nozzle; the head of the pin closing the opening of the nozzle is sealed with the pulverized asbestos wool, and the asbestos seal is covered with a layer of refractory sand.

The known crucible closure which has been made in this way for many decades involves a number of disadvantages which are due to the use of asbestos wool as a sealing material. It has been found time and again, for example, that portions of the finely pulverized asbestos fibers are pulled or carried along by the discharging aluminothermically produced steel and remain within the steel where they can give rise to defects.

Another disadvantage which is connected with asbes' tos consists in that it easily absorbs moisture, particularly when pulverized in moist surroundings, and moreover very frequently contains carbonaceous compounds. Both constituents may lead to the formation of gas during the aluminothermic reaction, and therewith to porous welds.

Added thereto more recently was the discovery that dealing with or handling asbestos which was heretofore indispensable for obtaining the crucible closure may cause an illness similar to silicosis, which is referred to as asbestosis.

It is the object of the present invention to provide a sealing material for the tap pin which is present in compact form while nevertheless being sufficiently flexible to accomplish the sealing effect without a pulverization of the material, which furthermore does not affect the aluminothermic reaction, and additionally is not injurious to health.

This object is obtained, in accordance with the present invention, with, or by virtue of, the use of inorganic fibers covering the tap pin. Small fleece plates, or platelets, made from these fibers have been found to be particularly advantageous for this purpose.

The invention will now be further described hereinafter on the basis of the accompanying drawings, wherein FIG. 1 illustrates a fleece plate 1 prepared from inorganic fibers, and

FIG. 2 illustrates the inventive closure means of a crucible used for aluminothermic reactions.

As shown in the drawing, the reaction crucible is composed of a refractory for example magnesite lining 4 which is inserted into a sheet metal sleeve 2 with an intermediate layer of sand 3. Inserted into the lower part of the crucible is an outlet nozzle 5 which must be closed anew prior to each filling or charge. For purposes of closing, a tap pin 6 is suspended into the opening of the discharge nozzle 5; the head of the tap pin 6 is covered with the inventive fleece platelet of inorganic fibers, and the fleece platelet 1 is subsequently covered with a layer of refractory sand 7, for example corundum.

It has been found that especially well suited for use in the present invention are inorganic fibers composed of approximately 43 to 52 percent by weight of Al O 46 to 54 percent by weight of SiO 0.06 to 1.0 percent by weight of B 0 and 0.1 to 2.0 percent by weight of one or more alkalies, such as Na O, for example. Such products are obtainable, for instance, under the trade names of Fiberfrax" or Kaowoolf The product may be prepared by melting a mixture of, inter alia, aluminum oxide, silicon dioxide, and small amounts of boric acid at about l,650C, and blowing the discharging melt apart by a strong air blast.

Subsequently yielded therefrom in a manner known per se is a fiber which is further processed for example to wool, mats, molding material, or fleece. It was particularly surprising to find that, when using this substance, the amounts of B 0 contained therein are absorbed by the slag and will not impair the mechanical properties of the aluminothermically produced steel, which is relatively sensitive to small boron additions. This phenomenon probably is due to the fact that the small plate of fiber fleece becomes coated with a slag layer and floats through the melt in the slag layer where it very frequently can be found again, practically undamaged.

It is equally possible to use small fleece plates of pure Si0 fibers. Of importance is the fact that the fleece platelets have adequate mechanical properties, but that a flexibility be retained which will assure a flawless sealing of the tap pin in the reaction crucible. It is particularly advantageous that the materials to be used according to the present invention can no longer adversely affect health, and that damaging inclusions in the steel are avoided. The latter was completely unexpected.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifica tions.

What is claimed is:

1. In a closure for crucibles used for aluminothermic reactions comprising a tap pin, a sealing material, and refractory sand, the improvement comprising a sealing material of fibers composed of A1 0 SiO B 0 and alkali.

2. In a closure for crucibles used for aluminothermic reactions comprising a tap pin, a sealing material, and refractory sand, the improvement comprising a sealing material of fibers of SiO

Claims

2. In a closure for crucibles used for aluminothermic reactions comprising a tap pin, a sealing material, and refractory sand, the improvement comprising a sealing material of fibers of SiO2.