US1628375A - Apparatus for refining metals - Google Patents

Description

. 1,628 375 May 10,1927. l M. UNGER APPARATUS FOR REFINING METALS Filed Dec. 31, 1925 l-fs- 3o Fig. 2.

Inventor- Ilflc'gnus Unger,

HLS Attorny,

vPatented May 10, 1927.'

UNITED JSTATES lPATENT OFFICE. Y

IAGNUS UITGEB, OF PITTSFIELD, MASSACHUSETTS, .ASBIGNOR T0`r GENERAL ELFE- TBIC COMPANY, A COBIORATIONYOF NEW YORK.

Arranarus ron narrante Marlins.y

plantation and December s1, 1925. sum1 No. vaas?.

or control of the silicon content so that the product may be of uni-form quality as well as having the desired silicon content. vIn order to do this with certainty it is necessary to hold the steel in a molten condition for a suiiicient interval of time to enable lthe steel to be analyzedv to determine the amount of silicon and the amount of silicon regulated. if necessary. Furthermore, molten steel as received from the open hearth vfurnace or the Bessemer converter has been found to contain a considerable amount of gas which it has absorbed. The volume. of this absorbed gas at atmospheric pressure may be many times-the volume of the steel by which it isk absorbed. It is a further object of my invention to provide means` whereby the steel may be maintained molten for aconsiderable interval to permit 'this gas toescape.

In carrying out my invention in one form I reduce. the molten steel into a ladlev in which it remains for a considerable interval to rovide for the escape of as and for ana ysis. Associated with the adle I have provided inductive means whereby the steel may be heated to maintain its temperature or give it any desired superheat, the inductive means being also so arranged as to pro' duce a circulation, and thereby' thorough mixing, of the molten metal by electromagnetic repulsion.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a. vertlcal sectional view of apparatus for refining silicon steel embodying m invention; Fig. 2 is a sectional view a ong the,

line 2 2 of Fig. 1 looking in the direction of the arrows; Fig. 3 is a sectional view along the line- 3f-3 of Fig. 1 looking in the direction of the arrows; while Figs.' 4 and 5 are views showing details of construction. Referring to the drawing, in one embodi- ,which the ot' the greatest difficulties incident to the'makmg of silicon steel is the regulation i Y reservoir.

my invention I providea ladle in i molten steel 1s introduced and mamtamed for a considerable interval for rehnmg. 'This ladle comprises an inner heat insulated provide a ment of reservoir 11 for the metal and an annular channel 12 in which a portion of theA molten metal lforms a closed secondary for crucible l0 which is 'shaped toa primary winding 13 associated therewith.

The annular channel is arranged in a hori zental position, 1. e., with its axis substan-K tially vertical at one side of the reservoir l1 a slight distance above the bottom of the lt is connected with the reservoir .through three ducts provided in the refractory material of the crucible, two of these ducts 14 and 15 connecting the upper axial end of the channel and the third duct 16 connecting the lower axial end of' the channel with the reservoir. The two .ducts 14 vand 15 are each substantially one half the cross sectional area' of the duct 16 and are spaced apart laterally, i. e., in a direction-v at right angles to the axis of the channel, so as to communicate at opposite sides of the upper end of the channel. The lower duct 16 is situated laterally substantially midway between the two upper ducts, it being'spaced axially with respect to the other two duct-s as previously noted.

The crucible 10 is made from aA suitable refractory material lsuch as a mixture of fused magnesia, calcined magnesia,' and a with the reservoir binder. such as magnesium sulphate, as described and claimed in Patent N o. 1,444,527 to Scharschu dated February 6,1925. These materials are mixed in granulated or powdered form,l suiicient water being added to 'make a plastic mixture and the mass thus'.

formed is rammed` in place around a suitable core which .defines the reservoir, the

.channeland the ducts.v Preferably a hollow receptacle-like member 21 is provided as aY core for gie reservoir and the annular core is connec d to it by means of steel tubes los 22, 23 and 24 which define the ducts. ends of the tubes are butted or welded to the outer tube 18 and the receptacle 2l, and

communicate with the interiors thereof as indicated in Fig. 4. Surrounding the crucible 1() is a layer of suitable refractory heat insulating material 25, the whole being enclosed by an outer metallic casing 2G. ln constructing the ladle the insulating material 25 is built up inside the casing 26, suieient space being left for the crucible 10. rllhe bottom-layer of the crucible is then rammed in place after which the steel core for the channel, ducts and reservoir is placed on this bottom layer and the ramming in of the crucible continued until the desired thickness of material has been formed around the core. The heat insulating material around the upper portions of the crucible is then filled in and the remaining upper portions of the casing secured in place.

An aperture for the primary winding 1? is provided by means of a heat refractory cylinder 27, made of high grade fire clay, preferably having a high alumina conte at. This refractory cylinder 27 effectively protects the primary winding from contact with the molten metal in case of a'leak through the rammed crucible 10. A further protection is provided by a metallic tube 28 inserted inside the refractory tube 27, this tube 28 being split longitudinally at 29 to prevent its acting as a closed secondary for the primary winding. As shown, the primary winding is mounted on a` three legged core 30, the middle-leg on which the primary winding is secured passing through the metallic tube 28.

The ladle is mounted on suitable rockers 31 and 32 which rest on tracks 33 and 34,.

and it may be tilted by means of a suitable hydraulic motor 35 in order to pour the metal from the spout 86.

After the crucible 10 is rammed it is allowed toI dry, this operation being completed by the application of heat. The drying or burning operation is carried out by means of suitable blow torches which are applied to the inner wall of the hollow core member, the flame of the torch being carried around through the hollow portions of the core member forming. the ducts 14, 15 and 16, and the annular channel 12. The annular portion'of the core member may be furit from the primary winding. During this drying or burning operation the hollow core member serves to protect the inner surface of the rammed material from injury by reason of direct contact with the flame of the blow torch and also serves to support the material. The material has a stage of great weakness during the drying or burning operation so that it might crumble if it were The"- unsupported. The hollow core member thus makes it possible to apply heat to dry the rammed material and at the same time it acts as a support for the material.

After the crucible has been dried, the ladle may be put in operation by pouring in a charge of molten steel which ills the hollow core member deiining the channel and the ducts. The primary winding is then energized whereby heating currents are induced in the section of the core forming the channel and in the molten metal contained therein. The core member is thus melted and mixed with the charge.

ln utilizing the ladle the molten steel may be introduced either from an open hearth furnace or Bessemer converter, er an electric furnace, a relatively small quantity being introduced at each time. F or example, with a 24 ton ladle the ladle will be initially filled and 8 tons poured at the end of the reining operation leaving 16 tons, and thereafter 8 tons will be added to the ladle. The steel is left. in Athis ladle for a considerable interval, for example, three or four hours during `which time the absorbed gases are caused to escape and the composition of the metal can be dcterminedand regulated as desired. .y

During this period the metal will`be maintained molten or superheated to a desired temperature by means of heat generated by the induced currents in the portion of the metal in the annular channel, these currents being induced by the primary winding.

Furthermore, the primary winding 1s so associated with the molten metal in the channel that a circulation is produced by electromagnetic repulsion. For` example, the primary winding may be displaced axially downward so as to exert an upward repulsive force. In` other words, the primary winding as shown in the drawing has its lower end projecting below the secondary channel so that its axial center isbelow the axial center of the secondary. This disposition of the primary winding results in upwardly directing the repulsive forces acting on the moltenv metal in the channel, these forces being cumulative in an upward direction sov that the metal in the upper axial end of the secondary channel is under a greater pressure than that at the lower end. This causes the metal to flow out of the secondary channel into the reservoir through the upper ducts 14 and 15, a return-flow of molten metal from the reservoir to the channel through the duct 16 being thereby produced. The circulation of the molten metal thoroughly mixes it as well as distributing heat generatedin the channel. The mixingeffect produced by the inductive heating apparatus is of great importance since the molten metal is maintained of uniform quality and any additional metal suchv as silicon added to raise Ithe silicon content, i's thoroughly mixed With the metal already in the crucible. V

In order to provide for the rapid escape of the gases from the molten metal, the metal isv preferably allowedto cool almost to the point of solidification after which its temperature is raised quickly for pouring.

While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since K various modifications thereof will suggest themselves to those skilled in the art Without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I. claimv as new and desire to secure by Letters Patent of the United States, is:

vl. A Crucible for molten metal comprising refractory material forming a reservoir for the charge and an annular channel in which a portion of the Charge forms a closed secondary, said refractory material providrmg two openings spaced 1n a directlon at i right angles to the axis of said channel connecting one end of said channel with said reservoir, and a single opening connecting .Y

the opposite endpof said channel With said reservoir, and a primary winding arranged to induce heating currents in said secondary and produce circulation of molten charge by electromagnetic repulsion.

2. A mixing and` refining Crucible for molten metal comprising refractory material forming a reservoir for the charge and lateral extremities of said channel and res-` ervoir and a single opening connectlng the lower end of said channel with said reservoir at a point laterally intermediate said upper openings, and a primary winding arranged to induce heating currents in said secondary and produce circulation of molten charge between said channel andreservoir by electromagnetic repulsion.

3. Electric induction heating apparatus comprising heat refractory material formf ing a reservoir for a charge and an annular channel having its axis arranged substantially vertical in which a portion of the charge forms a closed secondary, said refractory material providing spaced openings connecting the upper end of said channel With said reservoir and a single opening connecting the lower end of said channel with said reservoir, and a primary winding inserted in said secondary, said primary winding being axially displaced in a downward direction with respect to said channel whereby a magnetic repulsive force is exerted on said secondary in an upward direction to produce a circulation of molten charge between said secondary and said reservoir.

In witnem whereof, I have hereunto set my hand this 28th day of December, 1925.

MAGNUS UNGER.

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