US2230296A - Method of casting metal bodies - Google Patents

Description

Patented Feb. '4, 1941 y Y 2,230,296'

UNITED STATES PATENT OFFICE y, v METHOD OF CASTING METAL BODIES All/obert K. Hopkins, New York, N.' Y., assignor to The M. W'. KelloggCo., New York, N. Y., a corporation of Delaware Application February 10, 1937, Serial No. 125,024 2 Claims. (Cl. 22-216) This invention relates in general to the cast- The further objects and advantages of the ining oi' metal bodies and in particular to an imvention will be readily appreciated from a conproved method for casting metal bodies in which sideration of the following detailed description of a maximum of dense sound metal is produced the mode of `carrying it out in practice taken from the metal cast. with the accompanying drawing, in which,

Metal sold in the form of worked shapes is Fig. 1 is a view partly in side elevation and generally cast into ingots preparatory to the partly in vertical section of a mold of the present working operations. The casting of the ingots is practice showing the use of a hot top, p a very important operation as the quality of the Fig. 2 is a view similar to that of Fig. 1 ilfinal product as well as the saleable yield is largely lustrating my invention, 10 determined by the quality of the ingots. A great Fig. 3 is a view similar to Fig. 2 but showing deal of .time and effort have been expended in the use of hot top or shrink head, and

perfecting ingot molds and ingot casting tech- Fig. 4 .is an enlarged fragmentary sectional nique with the result that in the present practice view illustrating the deposition of the fusing many of the causes of unsound ingot metal have metal. l5 been eliminated. One of the main causes for the The novel method of this invention may be lowering of the saleable yield, particularly with used in connection with the forming of metal killed steels and comparable materials, is the ingots in general and is not limited to any particucentral pipe or pipes that form in the upper end lar type of ingot or ingots of metal of any of the ingot during the cooling of the cast metal. particular composition. However, since it is 20 'I'he formation of a central pipe or pipes is inadmirably suited tol the formation of ingots of herent in the casting operation and results from partly, or completely, deoxidized steel it will be Athe manner in which the cast metal solidifies.. particularly described in connection with this I have found that the problem presented by type of metal. Y the piping of ingots may be solved in Van efficient In Fig. 1, is shown an ingot mold I 0 of the 25 manner. i, large end up type provided with a`hot top or According to my invention I provide a method shrink head il. Hot top il is usually made of for forming sound pipeless ingots in which the refractory material while the mold, iii is usually loss in volume oi the metal of the ingot, that made of cast iron. Ingot i2, as shown, is slightly takes place during the cooling thereof and that separated from the mold sides due to the shrink- 30 results in the usual pipe or pipes, is compensated age that takes place during theI initial cooling for by the deposition of molten metal in the ingot, and solidiflcation of the cast metal. The shrinkwhich molten metal welds to the metal of the age of the metal upon solidilcation also results ingot and thereby produces a sound pipeless inin the production of primary pipe i3 and somegot. The metal deposited is preferably deposited times in the production of secondary pipe lli. As 35 as fusing weld metal under the influence of a is Well known, the metal adjacent pipes i3 and discharge of electric current through a gap beit is generally contaminated with segregated imtween the end of the electrode and the ingot purities because of the fact that this metal, metal. The deposition is preferably carried out particularly that around secondary pipe il, is 4 under a blanket of fiux that protects the metal the last to cool. 40 f of the ingot and the deposited metal from the In carrying out my novel method any preferred atmosphere and also' absorbs or oats out imtype of mold and any preferred casting techpurities and segregations from the molten metal. nique may be employed. The mold i5 of Fig. 2 The deposition of the molten metal may be is generally the same as that of Fig. l but with initiated during the cooling and solidiflcation of the exceptions that hot top il has been omitted the cast metal or it may be initiated after the cast and that it is a big end down mold rather than a metal has been completely solidified. Also, the big end up mold. Big end up molds may be used novel method may be used with any preferred but since Vthis necessitates special arrangements type of mom, Thus, het tops, or sink hee-ds, or for the` removal of the mold relative to the ingot shrink heads may be used 'or omitted as prethe more simple type is shown. The metal to be 50 rerred. If the expedients, just mentioned, are cast, as for example carbon steel, is prepared as employed they need only be 0f small relative in the usual manner, i. e. the required additions size as the metal required to prevent the formaare made and it is either partly or entirely detion of pipes can more economically be supplied oxidized by addition thereto of ferro-silicon, as deposited fusing metal. aluminum, or other preferred deoxldizing agents, 55

and then allowed to come to the preferred pouring temperature. It is vthen poured into mold I5 and allowed to cool.

When the cast metal has cooled to such a point that the sides of the'ingot I6 have solidied and substantially all the molten metal that is left is Vto be found around the loci of primary and procedure.

A metallic electrode I1 is then inserted into the ingot I6 at, or near, the center thereof and an electric current caused to flow through a gap between the end thereof and the metal of the ingot. Either before starting the electric current flow or just after the electric current flow is started the depression in the top of ingot I 8 is lled, or partly lled, with a blanket of ux I8 which may be either solid or molten. Preferably the flux I8 is heaped over the top of ingot I6, in such a case a proper dam I5' is employed to maintain flux I8 on ingot I6.

Electrode Il should be of such composition that the fusing metal deposited fro'rnit is of substantially the same analysis as that of the metal of ingot I6. Since there is generally a loss of electrode constituents the analysis of electrode I'I mayvary from that of the metal of ingot I8 as required to compensate for the losses. Electrode I'I may be covered or bare; electrode I1 may be solid or hollow. All of the required constituents of electrode I'I may be incorporated in the metallic portion thereof, or some of them may be included in the metallic portion and the remainder included in the coating of the electrode, if one is used, or passed to the region of the gap through which the current flows in any suitable way as for instance, by making electrode I'I hollow or at least trough-like and passing the remainder of the constituents through the hollow center, or also by passing said remainder of the constituents separately from the electrode as for instance through a hollow body which may be non-consumable or made of the same material as the electrode. 1

The ux I8 should be such that it is substantially non-gassing and will not remove substantial quantities of desired ingredients from the molten metal but will ux out impurities. A wide variety of fluxes may be used satisfactorily.

Silicates in general either simple silicates or mixtures thereof, or complex silicates or mixtures thereof, are satisfactory fluxes. Tantalates and similar compounds are likewise satisfactory. The uxneed not be composed of reacted materials but may be made up of the unreacted components thus, for instance, in the case of manganese silicate the flux may be made up of MnO and Sion,

At present, silicates, either simple or complex of the alkaline earth metals, manganese, aluminum and iron are preferred. ,Of these, manganese silicate is .preferred as it predominates in the desired characteristics. With any of the materials of the classes mentioned unreacted components that generate an excessive amount of gas either in reacting or at the temperature of the arc should be excluded. Thus,uncombined iron oxides, carbonates, etc., and water are undesirable. Flux I8 may also include constituents desired in the nal deposited metal or constituents such as ferro-silicometc., that facilitate the production of the final desired deposited metal. The slag produced during the manufacture of chromeiron alloys is also a preferred flux. This mate- Y rial compares favorably in required characteristics with the bestof the materials above noted and has the additional advantage that it is self disintegrating so that it does not require any comminuting to prepare it for use. The finishing slag'used in making the molten metal lthat is cast into mold. l5 may also be used as the ux. This may be done by ladling molten slag directly from the steel finishing furnace or by cooling the slag and then breaking it up into fine enough particle size to permit the formation of the protective blanket I8. `v

The electrode I'I is preferably fed to the gap at a predetermined rate and a predeterminedvvoltage and amperage maintained. This is accomplished by means of the usual welding head I9. Welding head I9 controls feed Wheel 20 that drives electrode I1 toward ingot I6. Welding headA I9 may include a welding current generator or the current may be supplied to it from a separate source. In any event, Welding head I9 is provided with the usual arrangements for controlling the voltage and `amperage of the welding current. One side of the welding current supply is connected to ingot I 6 by cable 2l and the other side is connected t'o a contact nozzle 22, through which electrode I'I passes, by cable 23. Contact nozzle 22 may be of any preferred construction but should be such as to assure the continuous passage of current to electrode I1.

The discharge of welding current through the gap between the end of electrode I'I and the metal of ingot I 6 generates heat which causes the progressive melting of electrode I1. The heat generated by the current discharge will also cause the fusion'of some of the metal of ingot I6 so that the metal melted from electrode I1 commingles I1 consumed untilthe pipe cavity is completely lled.

The heat generated by the current discharge remelts or renders more fluid, some of the metal of ingot I8. The metal thus effected is the metal in which segregation of unwanted materials is greatest. The action of the heat thus releases the segregated material so that it can come into contact with the supernatent molten flux and be absorbed. Thus, the metal of ingot I6 is further refined and purified by the action of the heat generated by the current discharge.

The flux I8, as above stated, is introduced into the pipe cavity and covers or blankets the deposi. tion of metal from electrode I'I so that it as well as the metal at the sides of the pipe cavity is protected from the atmosphere. The flux I8 however is also progressively melted by the heat ofthe current discharge, or when introduced in the molten condition rendered more fluid, so that in any case after the operation `has gone on a short time a molten layer of ux covers the molten metal. The molten ux is at a high temperature and, since it is not of high heat conductivity, prevents the rapid dissipation of the heat generated and assures the fusion and further refinement of the metal'at and adjacent the sides of the pipecavity even though such metal may not come into direct contact with the discharge of current. As the deposition of metal continues the progressive melting of the flux, when it is introduced in the solid condition, reduces the volume of the flux-so that it may be necessary from time to timeto add ilux in order to'maintain a proper blanket.

While the current input is largely determined by the amount of metal to be deposited and by the time available for its deposition, it is at present preferred to initiate the operation at high current inputs and gradually reduce the current input as the deposition progresses. Thus, for instance, the operation may be started at an amf perage in' the vicinity of 8000 amperes per inch diameter of electrode and finished at an amperage in the vicinity of 2000 amperes per inch of electrode. The amperage values just given are illustrative only and higher or lower values may be employed as required to obtain the .desired results, thus, the initial amperage maybe as high as 10,000 amperes or more and is limited only by the amount that the electrode can safely carry. The high initial current input is desirable since it provides for the generation of heat at a rate high enough to assure fusion of the bulk of the metal at the end of -the primary pipe and the metal at the situs of the secondary'pipe. The tapering off in current input on the other hand assures the solidication of the metal deposited at the upper end of the primary pipe at a rate that approaches the rate of deposition with the result that there is very little molten metal in the cavity at the end of the deposition of metal from electrode I1 and piping,segregation and porosity is avoided. The current may be tapered off to the value above given or to a much lower value as required to obtain the results just mentioned. A

To further assure complete fusion of the metal deposited from electrode I1 with the metal that forms the walls of the pipe cavity, electrode I1 may be given an oscillatory and/or rotary motion relative to ingot IS so that the region of the current discharge will come into contactV with or closely approach all portions of the sides of l the pipe cavity. For this purpose either ingot I6 or electrode i1 may be moved. Thus, ingot I6 may be supported on a turntable and rotated at a desired speed, also welding head I9 may be rotated and/or provided with'any of the usual electrode oscillating devices.

The method of this invention may also be employed to fill the pipe cavities of ingots, or cavities in metal bodies lof whatsoever character, such as castings, and the like, after all ofthe metal of the metal bodies. is solidified, or solidiiled and cooled to room, temperature. In the cases just mentioned, the procedure is the same as that Just above described however care should be taken to employ a sufllciently high initial welding current input to assure the meltingof a substantial portion of themetal at the bottom of the primary .pipe so that the metal at the situs of the secondary pipe may be melted and this source of imperfect metal removed.

v.The novel method may also be employed in connection with a hot top or similar device, however, ifja hot top is employed therelative volume thereof may be materiallyI reduced below that of the best present practice. Thus, in Fig.'- 3vmold 30 is provided with a hot top 3| that contains about 5% more or less of the metal of ingot I6'. In applying the method of my invention to this form of mold either of the procedures described above may be employed, however, the pipe cavity need only be lled to the crop line.

While the novel method of the invention has been disclosed in connection with ingots either prior to complete solidication or' after complete solidification; the novel method is of much broader application; thus, it may equally well be used in connection with cast bodies in general. Also, the method of the yinvention is not limited to cast metal bodies as it may well be used in the repair of wrought or otherwise worked bodies. Thus, the method may be used in the repair of imperfections such as porous areas, seams, cracks, etc. Therefore, the above description and inthe following claims the terms ingots and pipes should be taken as referring respectively to metal bodies of whatsoever character, and to holes, cracks, seams, porous areas, etc.

It is my present belief that in the operations above described the heat is generated by an arc discharge of the electric current. However, since the fluxes mentioned are current conductors when molten it has been advanced that thevheat is generated by the ow of the current through the molten flux. Since the present application is a disclosure of fact it is to be understood that I do not wish to be bound or limited by any theory advanced and that the appended claims are to be interpreted and construed in `the light of the factual disclosure and the prior art regardless as to the correctness of the theory underlying the generation of heat.

I claim:

1. A method of forming pipeless cast ingots comprising the steps of casting molten metal in a mold incorporating additional metal by electric energy and a fusible electrode, the energy input being-so controlled during the final portion of the deposition of the added` metal that said added metal is deposited at a rate less than that at which the molten metal solidifies `whereby at the end of said deposition only a small quantity of molten metal is present in the pipe cavity.

2. A method of casting pipeless ingots which comprises casting a molten metal in an ingot mold and depositing by electric energy weld metal from a fusible electrode into the pipe cavity formed in said cast metal and maintaining a flux blanket over the fusedmetal during the welding operation, the energy input being progressively diminished during the adding of the metal whereby the final portion of said deposition is effected at a rate which is less than the rate of so1idiilca tion. of the molten metal in the ingot.

ROBERT K. HOPKINS.

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