United States Patent 1 Bernsmann Dec. 11, 1973 METHOD FOR TREATING METALLIC MELTS [75] Inventor: Gert P. Bernsmann, Pittsburgh, Pa.
[73] Assignee: Jones & Laughlin Steel Corporation,
Pittsburgh, Pa.
[22] Filed: Dec. 11, 1970 a 21 Appl. No.: 97,384
Related U.S. Application Data [62] Division of Ser. No. 802,518, Feb. 26, 1969, Pat. No.
[52] U.S. Cl 75/58, 75/129, 75/130 [51] Int. Cl. C2lc 7/00, C22c 33/00 [58] Field of Search 75/58, 129, 130, 75/130 R, 130 B [56] References Cited UNITED STATES PATENTS 2,781,260 2/1957 Grandpierre 75/130 B 3,642,466 2/1972 McCaulay 75/130 B 2,776,206 l/1957 Klingbeil 75/130 B 2,871,008 l/1959 Spire 75/130 R 3,598,575 8/1971 .larysta 75/130 B 1,562,655 11/1925 Pacz 75/58 2,085,802 7/1937 Hardy 75/58 2,698,749 l/1955 Fishell 75/130 B X 3,251,680 5/1966 0055 et a1. 75/59 3,634,075 1/1972 l-loff 75/135 3,666,449 5/1972 Alt 75/130 B FOREIGN PATENTS OR APPLICATIONS 972,708 10/1964 Great Britain 75/130 13 Primary Examiner-Charles N. Lovell Assistant ExaminerPeter D. Rosenberg Atl0rneyT. A. Zalenski [57] ABSTRACT Method and apparatus for treating a metallic melt, such as molten steel in a ladle, are disclosed. The apparatus includes an inner tubular member, through which an additive is delivered to within the melt, and a coaxially disposed outer tubular member, the annulus between the two tubular members serving as a passageway for gas delivered to the melt. The gas is introduced into the melt through a porous refractory element positioned about the ends of the tubular members.
7 Claims, 2 Drawing Figures PATENTED BEE] I 1975 METHOD FOR TREATING METALLIC MELTS This is a division of Application Ser. No. 802,518, filed Feb. 26, l969, now US. Pat. No. 3,615,085.
This invention relates generally to method and apparatus for treating a metallic melt and, more particularly, to method and apparatus for effecting an efficient and controlled deoxidation of molten steel.
Controlled and uniform deoxidation of molten steel in a ladle can be realized by simultaneously delivering to a spot deep within the melt through a lance submerged therein a deoxidant, such as aluminum, and an argon gas stream. Employing the apparatus of the present invention, the deoxidant is maintained out of contact with the molten steel until it exits from the submerged lance whereupon it dissolves and reacts with the oxygen in the steel. The argon gas stream is passed from the lance to the deoxidant melt reaction zone through an inherently porous refractory element or a refractory element made porous by the provision of a plurality of fine passageways therein. The gas issuing from the porous element is in a finely subdivided state, thus promoting the stirring of dissolved, unreacted deoxidant throughout the melt and enhancing removal of deoxidation products to the melt surface. The subdivided gas particles also protect the porous element from overheating and early destruction from the reaction heat generated by the deoxidant and liquid steel.
The present invention is also useful in making additions to molten steel of materials, such as lithium and magnesium, which react violently with the molten steel or which possess high vapor pressures. By submerging the lance within the melt, initial contact and reaction between the additive and the molten steel is constrained to occur at any desired depth, obviating the dangers of a violent surface reaction and the complete oxidation of the additive before it has penetrated the melt to any appreciable degree.
The present invention is also used to make alloy additions to molten steel. Uniform distribution of an alloy throughout a melt is insured by its introduction deep within the melt and the dispersing action of the finely subdivided gas stream.
Preferably, the additive is fed to the molten steel through the lance in the form of a continuous rod so that a controlled feed rate is readily maintained. This permits deoxidation of the melt to be closely controlled so that it can be accurately deoxidized to any desired degree. For purposes of this disclosure, the term rod also includes shapes referred to variously as wire and bar. As-cast rods as well as rods formed by mechanical working are used. In addition, rods formed of particles of an additive or additives held together by a suitable binder are employed. Accordingly, a rod can be homogeneous and comprise a single additive or be heterogeneous and comprise several additives.
An object of the invention is to provide method and apparatus for simultaneously introducing an additive and finely divided gas stream to metallic melts. Another object of the invention is to provide method and apparatus for effecting controlled deoxidation of molten steel. Yet another object of the invention is to pro vide for such controlled deoxidation by simultaneously feeding a deoxidant, in the form of a rod, and argon to the molten steel in a ladle.
These and other objects and advantages of the invention will be more apparent from the following detailed description thereof with reference to the drawing in which:
FIG. 1 is a longitudinal view, partly in section, of a first embodiment of the invention; and
FIG. 2 is a longitudinal view, partly in section of a second embodiment of the invention.
Referring to FIG. 1, a lance embodying the principles of this invention is shown and includes a steel inner tubular member 10 and steel outer tubular member 11 concentric therewith. The annulus 20 between the tubular members is closed off at the top of member 11 by sealing means 12, comprising packing gland l3 welded to member 11, packing box 14 and packing 15.
A circular flange 16 is secured, as by welding, to the lower ends of tubular members 10 and 11, an opening 17 being provided in the center of the flange in line with the interior of member 10.
A porous head or stone 18 of refractory material, of the type known in the art, is positioned about the lower ends of tubular members 10 and 11. The porous head includes a centrally disposed cylindrical recess 19 forming a shoulder 20 in the head. The porous head is supported on flange 16 by its shoulder 20, and is firmly secured thereto by refractory cement 21.
To provide protection against the action of the molten metal, in which the lance in normal operation is submerged, a refractory sleeve 22 consisting of a plurality of stacked cylindrical tiles. 23-23 is provided about the tubular members 10 and 11, extending upwardly of said members from the porous head. The bottommost tile rests on head 18 and the stack is held in place by nut 24 which is threaded onto the exterior of tubular member 11 so as to bear down on washer 25 placed on the topmost tile. In addition, the joints between tiles are filled with a refractory cement.
A conduit 26 is tapped into outer tubular member 11 and is in fluid communication with annulus 29. In operation, conduit 26 is attached to a gas source.
Ports 27-27 are provided in outer tubular member 11 in the vicinity of porous head 18 to provide a passageway for gas to flow from annulus 29 into and through said head. Also, ports 28-28 are provided in tubular member 10 for establishing fluid communication between annulus 29 and the interior of member 10, enabling a positive pressure to be applied to said interior, preventing the ingress therein of the fluid in which the lance submerged.
In employing the apparatus described deoxidize a molten steel bath, the lance is lowered deep within the bath, an aluminum rod is fed downwardly from the top of inner tubular member 10, exiting from the bottom thereof through opening 17 and into the molten steel bath whereupon the aluminum reacts with the oxygen in the bath. Simultaneously, argon gas is delivered through conduit 26 into annulus 29. The argon passes from the annulus through ports 27-27 and then through porous head 18 into the melt. The finely subdi-- vided gas emerging from head 18 disperses throughout the bath, promoting stirring of the dissolved unreacted aluminum throughout the bath and removal of deoxidation products to the bath surface. The argon also protects the stopper head from overheating from the heat generated by the reacting aluminum and oxygen.
The argon gas flow rate is maintained at least high enough to establish, through ports 28-28, a pressure within tubular member 10 sufficient to balance the pressure within the bath at the level of the bottom of head 18. Entry of the molten metal into tubular member and the consequent reaction therein of oxygen and aluminum is thereby precluded.
The embodiment of the invention illustrated in FIG. 2, is similar to the embodient of FIG. 1, and the same reference numerals used in both figures refer to the same features in both. In addition to conduit 26, the embodiment of FIG. 2 has a second conduit 30, tapped into the wall of tubular member 10 and in fluid communication with the interior thereof. Conduit 30 is connected to a gas source independent of the source to which conduit 26 is connected and transports gas to the interior of member 10 to establish a positive pressure therein at least balancing the pressure of the bath at the level where the porous head is positioned.
The provision of a second conduit 30 and independent gas source associated therewith to maintain a suitable back pressure within member 10, enables the interior of the latter to be kept isolated from annulus 29 by eliminating the ports 28 provided in the embodiment of FIG. 1 for fluid communication between the two. As a result, with the embodiment of FIG 2, the gas flow rate to the melt through porous head 18 can be varied as desired, without concern for the pressure needed to prevent the entry of the material of the melt into member 10.
I claim:
I. A method of treating a metallic melt contained within a vessel, comprising delivering from outside the melt downwardly through the melt to a location deep within the melt an additive reactive with the melt, isolating said additive from themelt until the additive reaches said deep location, simultaneously establish a first gas stream outside the melt, introducing said gas stream into the melt at said deep location in a finely subdivided state by passing said stream thereto through a porous refractory head, and stirring the dissolved unreacted additive by means of said finely subdivided stream. I
2. The method of claim 1 wherein the metallic melt is molten steel, the additive is a deoxidant and the gas is a gas inert to the steel.
3. The method of claim 2 wherein the deoxidant is aluminum, and the inert gas is argon.
4. The method of claim 1 wherein the additive is delivered to the melt in the form of a rod.
5. The method of claim 4 wherein the metallic melt is molten steel, and the additive is an alloying material.
6. The method of claim 4 including delivering the additive to the melt through a tubular member open at the bottom thereof to the melt and establishing a second gas stream independent of the first gas stream within said tubular member.
7. The method of claim 6 including maintaining the pressure of the second gas stream at a value high enough to prevent the melt from entering the tubular member at its open bottom.