US3429565A - Metallurgical degasser vessels - Google Patents

Description

Feb. 25, 1969 N. NAPORA METALLURGICAL DEGASSER VESSELS Sheet Filed Dec. 23, 1966 M p H M m an; A A w M. X 5

Feb. 25, 1969 N. NAPORA METALLURGICAL DEGASSER VESSELS Filed Dec. 23, 1966 Sheet 2 of 2 M/VE/VTOR.

0 y f a? w ATTORNEY United States Patent 3,429,565 METALLURGICAL DEGASSER VESSELS Nicholas Napora, Pittsburgh, Pa., assignor to Harbison- Walker Refractories Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 23, 1966, Ser. No. 604,224 US. Cl. 26643 Int. Cl. C21b 7/06; C21c 7/00; C04b 43/00 ABSTRACT OF THE DISCLOSURE This invention relates to monolithic linings for degasser vessels which are anchored in place by hanger brick. The monolithic lining and anchor brick are both manufactured from fused magnesite-chrome ore grain.

BRIEF SUMMARY In a continuing effort to improve the quality of steel products, the steel industry has turned to vacuum degassing techniques. Vacuum degassing is performed by drawing molten metal into a refractory-lined vacuum chamber. There are currently several types of vacuum degassers, one of which is known as the DH Degasser in which the molten metal is repeatedly drawn up through a single snorkel from a ladle position below the degasser vessel and, thereafter, allowed to fall back. Another type of vacuum degasser, known as the RH Degasser, has two snorkels, one which is used to draw the molten metal up to the vacuum chamber, and another which allows the molten metal to return to its source. This invention pertains primarily to the refractory lining for the vacuum chamber portion of a vacuum degasser or similar metallurgical vessel.

The conditions within vacuum degassers have been found to be extremely damaging to refractory brick linings. In addition to the high temperatures (around 2900 F.) and chemical attack by siliceous and ferruginous slags, there are several other very damaging mechanisms. The continual washing action of the molten slag and metal is one most severe. Damage due to thermal shock is prevalent because the vessel is heated very rapidly when molten metal is first drawn into it. Also, the temperature of the vessel fluctuates rapidly in the DH Degasser between cycles.

ln copending application Ser. No. 350,630, filed Feb. 28, 1966, now Patent No. 3,216,540, and assigned to the same assignee as the present application, a lining for degasser vessels comprising chemically basic shapes and rammed portions made essentially of size-graded fused magnesite-chrome ore grain and an organic binder is taught. A novel feature of that invention is a ramming mix which was found to be as slag-resistant as burned brick contained in the lining. Because of its usual slag resistance, it was desired to line the entire bottom and lower side walls of a vacuum degasser vessel with such a ramming mix. This was actually tried.

For some reason not entirely understood, the entirely rammed bottom and lower side walls did not survive nearly as long as expected. It is thought the lining sintered at its exposed surface as monoliths normally do but then, unexpectedly, the sintered surface separated from the unsintered portion of the lining. When vertical cracks formed, hot metal entered the separation and floated the sintered surface away. By this erosion of sintered layers, the lining became too thin to be safe, and advantage of the superior slag resistance of the rammed lining was not realized.

It is an object of this invention to provide a vacuum 5 Claims "ice degasser bottom and lower side walls, the working lining of which is comprised substantially entirely of a fused magnesite-chrome ore grain ramming mix, which lining does not float away in successive sintered layers.

Other objects and advantages of the invention will become apparent from the following specification and claims and from the appended drawings which illustrate a preferred embodiment of a vacuum degasser having an anchored monolithic lining and incorporating the principles of the invention.

In accordance with this invention, there is provided a metallurgical vessel having an outer metal shell and a refractory lining therein. At least a portion of the lining, preferably the bottom area, is composed of fused magnesite-chrome ore grain monolithic material. Embedded within the monolithic material is a plurality of fused magnesite-chrome ore burned hanger brick to substantially eliminate erosion of the monolith during processing of molten metals.

DESCRIPTION OF DRAWINGS Referring to the drawings:

FIG. 1 is a vertical section of a vacuum degasser taken on line 1-1 of FIG. 2;

FIG. 2 is a plan view of a degasser vessel shown in section along line 2-2 in FIG. 1; and

FIG. 3 is a perspective view of a refractory hanger brick and metal anchor assembly.

DETAILED DESCRIPTION The general configuration of a DH Degasser vessel is best shown in FIG. 1. The vessel comprises a vacuum chamber 1 enclosed by side walls 2, a crown 3, and a hearth 4. The hearth has an opening 5 which is in communication with a snorkel tube 6. The hearth, crown, and walls of the vacuum chamber are comprised of an outer metal shell 8, an outer or insulating lining 9', and a working lining 10.

The working lining is divided into two portions, the upper side walls and the lower side walls and hearth. According to this invention, the upper side walls 12 are comprised of suitable basic refractory brick, preferably basic brick having excellent hot strength at about 2900 F. The upper side walls are supported in part by an annular ledge 14 which is fixed to the outer shell 8. The lower side wall 15 is that portion of the side wall below the annular ledge 14.

According to this invention, the working lining of the lower side walls and hearth of the degasser vessel is comprised of a fused magnesite-chrome ore ramming mix bonded with an organic binder 17. The ramming mix is rammed about a plurality of hanger brick, which are burned fused grain magnesite-chrome ore brick 18. The hanger brick may be maintained in a fixed relation to the outer metal shell by anchors 19 which are fastened (for example, by welding) to the outer metal shell at one end and the hanger brick at the other end.

FIG. 2 schematically shows a suitable placement of hanger brick in the bottom and lower side walls of a DH-type degasser vessel. In FIG. 2 the anchors are arranged in concentric rows about the snorkel port. However, other configurations in which the hanger brick are about 24 inches apart are suitable.

FIGS. 3a and 3b are pictorial views of a typical refractory hanger brick having grooved sides 20, allowing it to become attached to ramming mixes which are rammed about it. Typically, hanger brick have a T-slot 21 at their base which allows them to be easily fastened to a metal anchor. FIG. 2b is a pictorial view of a preferred hanger brick for use in this invention.

The burned fused grain magnesite-chrome ore hanger brick used in the practice of this invention typically have 3 a bulk density of about 206 p.c.f. and the following chemical analysis:

The fused grain hanger brick are manufactured by first fusing a suitable magnesite and chrome ore batch, as by electrical fusion. A suitable batch contains from 50 to 80% high purity magnesite (at least 95% MgO) and from 20 to 50% refractory grade chrome ore (no more than SiO The fusion is then sized-graded to a brickmaking batch, formed into brick as by pressing, and fired or burned to form a ceramic bond,

A suitable fused grain ramming mix is prepared by first fusing a magnesite and chrome ore batch. The fusion is thereafter size-graded to form a ramming mix. The batch described as suitable for making fused grain for brick is also suitable for making fused grain for ramming mixes. The chemical analysis of a typical fused grain ramming mix used in the practice of this invent-ion is the same as that given for the fused grain hanger brick. Typically, the ramming mix will have a density of about 195 p.c.f. Suitable ramming mixes are described in copending application Ser. No. 350,630, referred to above.

As pointed out above, fused igrain ramming mixes have been found to be unusually resistant to slag attack in metallurgical vessels, such as vacuum degassers. The rammed portions of actual degasser vessels have been found to resist the action of molten slags better than brick portions of almost identical compositions, because the rammed portions contained no joints which are more readily attacked by slag. However, for some reason not entirely understood by the inventor, rammed fused grain linings tend to separate in layers and float away. This condition is avoided in hearths constructed according to this invention by the use of hanger brick which hold the sintered surface layer against the unsintered portion of the lining. This is the first use of hanger brick in a hearth of which I am aware. In fact, this is the first use of hangers, of which I am aware, to maintain a basic lining, This is probably because most basic brick do not have usually suitable hot strength to be used as hangers. However, burned fused magnesite-chrome brick are as unusual as fused grain ramming mixes. Their exceptional hot tensile strengths permit their use as hangers in monolithic linings. The fused grain hanger brick and ramming mix cooperate to provide a lining that is exceptionally slagresistant and in which no portion is more vulnerable to attack than another. Hence, a balanced hearth lining is provided which, of course, results in the most economic use of refractory materials.

While the invention has been described with respect to specific embodiments and examples, it should be understood that modifications, substitutions, and the like may be made therein without departing from its scope.

Having thus described the invention in detail and with suflicient particularity as to enable those skilled in the art to practice it, what is desired to have protected by Letters Patent is set forth in the following claims:

I claim:

1. In a metallurgical vessel having an outer metal shell and a refractory lining therein which is subject to attack by siliceous and ferruginous slags wherein at least a portion of the lining is composed of fused magnesite-chrome ore grain monolithic material, the improvement comprising a plurality of fused magnesite-chrome ore burned hanger brick embedded within the fused magnesitechrome ore grain monolithic material to substantially eliminate erosion thereof during processing of molten metals.

2. The vessel according to claim 1 in which the ramming mix and hanger brick analyze typically:

Percent SiO 1.3 A1 0 6.6 Fe O 11.7 CaO 0.5

MgO 62.1 Cr O 17.9

References Cited UNITED STATES PATENTS 2,713,787 7/1955 Rose 266-43 X 3,326,543 6/1967 Kienow 26643 X 3,330,546 7/1967 Bryan 266-43 X 3,350,085 10/1967 Over 26643 FOREIGN PATENTS 268,527 8/ 1961 Netherlands.

I. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.-

U.S. Cl. X.R. 26634

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