US2191480A

US2191480A - Apparatus for manufacturing alloy ingots

Info

Publication number: US2191480A
Application number: US260892A
Authority: US
Inventors: Robert K Hopkins
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1939-02-23
Filing date: 1939-03-10
Publication date: 1940-02-27
Anticipated expiration: 1957-02-27

Description

'Feb. 27,, 1940; K PKINS 2,191,480

APPARATUS FOR MANUFACTURING ALLOY INGOTS Original Filed Feb. 23, 1939 2 Sheets-Sheet 1 INVENTOR ROBERT K. HOPKlNS 7 F BY l/Mifim ATTORN EY Feb. 27, 1940. i R. K. HOPKINS Q 2,191,480 7 APPARATUS FOR MANUFACTURING ALLOY INGOTS Original Filed Feb. '25, 1939 2 Sheets-Sheet 2 INVENTOR ROBERT K. HOPKINS 3 mm 25m ATTORN EY Patented Feb. 27, 1940 PATENT OFFICE APPARATUS FOR. mnumcroamo mo! moors Robert 1:. Hopkins, West New Brighton, Staten Island. N. Y.. assignor to M. W. Kelloggflo New York, N. Y., a corporation of Delaware Original application February 23, 1939, Serial No.

Divided and this application March 10, 1939, Serial No. 260,892

'3 Claims.

This invention relates to apparatus for emciently and economically making consistently uniform semi-finished alloy products, such as slabs and billets, from raw materials in a single continuous operation, and in such a manner that these products will be substantially free from external and internal defects, and in such condition that they may be readily fabricated into final products of various kinds. This application is a division of my copending application Serial No. 257,886 filed February 23, 1939 which in turn is a continuation-in-part of my application Serial No. 187,104 filed January 27, 1938.

One of the principal objects of my invention is to provide apparatus for the formation of such semi-finished products continuously and solidifying them while being formed, and in and by which the forming operation can be accurately controlled in all its various phases, and further to prevent any deleterious substances entering into the semi-finished products without the loss of any of the constituents used in making them.

A further object is to provide such, control for my apparatus as to enable the production of semi-finished products having a wide range of analysis.

The use of my invention eliminates-the many serious difliculties heretofore experienced and losses suffered in making alloy ingots and converting them into final products.

The above, as well as the further objects and advantages of the invention, will be better ap preciated from a consideration of the following description of preferred modes of carrying it out in practice taken with the accompanying V drawings in which Fig. l is front view, partly in section, of apparatus embodying my invention,

Fig. 2 is a fragmentary front sectional view illustrating .the use of an elongated mold, and

Fig. 3 is a sectional view takenon lines 3-3 of Fig, 2.

The invention is of general application and may be successfully employed in the production of both ferrous and non-ferrous alloys. novel method is especially applicable to the production of ferrous alloys, particularly those containing comparatively large proportions of alloying elements such as chromium, nickel, manganese, vanadiurn,,silicon, tungsten, molybdenum, columbium, either alone or in combination. Of the latter class of alloys, the corrosion resistant alloys, such as the chrome steels and the chromeiactory surface characteristics.

The

nickel steels, are particularly suited for production by the novel method.

In practicing the invention, the constituents of the alloy, in comparatively inexpensive and readily available commercial forms, are fed, in

' the proportions required to give the desired analysis, to a mold in which they are fused, by

an electric current discharge that is' submerged beneath a blanket of protective flux, to form the alloy of desired analysis. The submerged electric current discharge generates heat at extremely high temperatures so that conditions are ideal for the complete intermingling of the constituents into homogeneous metal and the refinement thereof to a high degree in a very short interval'of time. Since the flux envelops the electric discharge it too is subjected to the extremely high temperature heat and is fused and heated to very high temperatures thereby, in actual practice temperature readings taken at the surface of'the molten flux have ranged from 3000 F. to over 4000 F. The temperature of the molten metal beneath the flux exceeds the flux temperature by probably from 200 F. to 500 F., or more.

The highly heated-molten blanket, which extends across the full cross-section of the mold, conducts high temperature heat throughout the cross-section of the mold with the result that the commingling and refining effect of the electric current discharge is prolonged and the formed alloy reaches the mold sides in a highly heated and extremely fluid condition, in which condition it will conform'to the contour of the mold and produce an alloy body of highly satis- In the condition stated of the fused metal and fused flux, impurities readily pass from the metal to and will be taken up by the flux so that extremely clean metal results.

The heat generated by the electric current discharge passes from the flux and the deposited alloy to the mold and out from -it. 'Since the alloy forming is a continuous operation, as opposed to a batch operation, heat loss takes place before the total heat necessary for the operation is supplied. Consequently, cooling and solidification of prior deposited alloy takes place simultaneously with the deposition of subsequently deposited alloy. This results in a progressive filling of the mold as well as in a progressive solidification of the deposited alloy from the bottom of the mold upward.

Impurities or extraneous material rejected by the alloy during crystallization easily pass through the highly fluid supernatant alloy and are absorbed in the flux and eliminate defects in the product. By reason of the highly fluid supernatant alloy, piping and porous formations are eliminated.

By adjustment of the rate at which heat is supplied and the rate at which heat is removed from the mold, the depth of molten alloy in the mold as well as the rapidity of solidification and crystallization of the alloy may be controlled within wide limits. With corrosion resistant alloys, such as the chrome-steels and the chromenickel steels, a rapid solidification'is highly desirable as it results in a refined crystal structure which can be broken down by working operations without failure much in the same manner as carbon steel. In actual practice, by rapid solidification eighteen (18%) per cent chromium, eight (8%) per cent nickel steel billets have been produced in which the coarse dendridic crystal structure characteristics of cast 188 was practically eliminated. These billets showed an extremely fine grain structure extending inwardly a considerable distance from the skin. The fine grain zone provides an envelope which safely withstands the working forces without rupture. Copper molds were used which were cooled by sprays of water played on their sides and the stools upon which the molds were supported, the water being sprayed at a rate to allow from one to four inches of deposited alloy to remain molten after-the operation had attained equilibrium. This range of depth of molten metal is generally satisfactory for the production of highly refined homogeneous alloy of uniform analysis throughout; When less rapid cooling rates are desired, steel or cast iron, ceramic, or other molds may be used, these latter may be water cooled, if this is necessary, to give the desired results. In choosing the mold material, it should be of such character that it does not combine with the deposited alloy. Thus, in the production of low carbon corrosion resistant alloys the use of materials, such as cast iron, should be avoided because of the possibility of carbon pick-up.

The flux blanket should be of such character and deep enough to submerge the electric current discharge and cover the cross-section of the mold so as to effectively exclude the atmosphere. Flux blankets of from one to three inches in thickness have given satisfactory results. Thicker blankets will function satisfactorily but their use is not generally economical since electrical energy is wasted in fusing the excess flux.

The flux employed should be one that will not add to or remove substantial quantities of constituents from the deposited alloy. However, it should be such that it will readily flux out impurities. Certain silicates have been found to be satisfactory fluxes. -The silicates of calcium, magnesium, and manganese, either alone or in combination, and with or without additions of A; and T102 have been used successfully. In the production of corrosion resistant alloys a non-oxidizing calcium silicate flux, containing a suflicient proportion of calcium di-silicate to render it self-disintegrating and a small proportion of calcium carbide to render it slightly reducing, has been found satisfactory. Fluxing material may, if desired, be continuously, or intermittently, added during operation to maintain equilibrium in the flux blanket and the alloy.

The raw materials are generally readily available and relatively cheap articles of commerce 'or rates.

that are made up entirely of the constituents of the desired alloy. Thus, in the production of ferrous alloys, the preferred raw materials will be steel or iron and the ferro-alloys, such as ferro-chrome, and ferro-manganese, that contain high percentages of the alloy element. When the alloy element itself is commercially available at a comparatively low cost, as in the case of nickel, it may be used. Low price scrap alloy material has sometimes been satisfactorily employed to supply a large proportion of the constituents, the remainder of the constituents required having been supplied from ferro-alloys.

The alloy producing operation is carried out in such a manner that there is substantially no addition or removal of constituents by extraneous factors. The analyses of the alloys pro duced depend solely on the constituents used and the rate at which they are supplied to the" electric current discharge. While many ways may be devised for passing the raw materials at more or less constant rates through the flux blanket to the arc, I have found in actual practice that a satisfactory way is to form one of the raw materials, the steel, iron, or alloy scrap, into a hollow electrode from whose end the electric current is discharged and pass the other raw materials in particle form through the hollow electrode to the electric discharge. When the raw materials used make it possible all of them may be formed into solid electrodes; also, one or more solid electrodes may be used in combination with hollow electrodes. The use of one or more hollow electrodes, through which some of the raw materials are passed, alone or in combination with one or more solid electrodes, is a simple expedient for accurately securing constant rates of feed for each of the raw materials, which may be varied over wide ranges at will. Constant feed of the raw material, or materials, supplied in electrode form is obtained by maintaining the characteristics of the discharge constant; constant feed of the raw materials supplied in particle form through the hollow electrode, or electrodes, is obtained by metering them at a constant rate, A change of rate of feed of the raw materials supplied in electrode form is obtained by changing the characteristics of the discharge, thus, by reducing the amperage, the rates of feed is reduced and by increasing, the rate of feed is increased. The rate of feed of the raw materials in particle form may be changed by changing the metering rate. Thus, an alloy of predetermined analysis may be' continuously produced or alloys of different analysis may be successively produced with the same set of raw materials.

One form of apparatus embodying my invention includes a structural support Ill provided with horizontal I-beams ll upon which a bridge I2 is mounted for movement (Fig. 1). A truck I3 is mounted on bridge members l2 for movement along their length. Thus, truck l3 may be moved in any horizontal direction. An electrode forming and feeding mechanism I4 is supported on truck [3 and is movable vertically, manually or by motor operated means, relative to truck l3. The mechanism l4 includes a plurality of rollers i5 which are adapted to form a flat strip I6, supplied from a coil l'l, also supported on truck i3, into a hollow electrode l8 of substantially closed contour. Rollers l5 are driven by a variable speed motor which is are controlled as is common in the electric furnace art, to form and feed electrode 18 as required to maintain an electric discharge of constant characteristics from its end. By this control electrode l8 may be fed at any predetermined rate and the rate maybe changed at will by merelychanging the amperage setting of the electric current supply.

Electrode I8 passes through a contactdevice 1 19 which is supported from mechanism 14. A cable 20 connects device i9 to one side of the electric current supply.

A housingv 2i is supported above coil i1 and in it are positioned a plurality of metering devices. six are included in this apparatus. Each of the metering devices is arranged to receive granular material from a hopper, such as

hoppers

22, 23 and 24, and feed it at a constant but adjustable, rate to tube 25 that leads from housing 2| through rollers I 5 into electrode l8. By this construction constituents of the desired alloys in particle form may be supplied to the and ceramic, but which'in the production of cor-' rosion resistant alloys'such as chronic steels and chrome-nickel-steels, where rapid cooling is de-' sired and where it is important to avoid carbon pick-up, it may be made of copper of comparatively small thickness. Mold 26, of the desired cross-section, is provided at its bottom end with a flange 21. Mold 26 is held in position on stool 28 bybolts that pass through flange 21. Mold 26 is surrounded by pipecoil 26 through which water is passed. Coil 29 is perforated at spaced intervals so that the water may spray against the sides of mold 26. The water passes from the sides of mold 26 to the top of stool 28 from whence it passes through an outlet pipe 30. A cable 3| connects mold '26 to the other side of the electric current supply. I

The rates of feed per unit of time for each of the raw materials may be easily ascertained as there is substantially no loss or gain of constituents in the operation. Thus, in the production of 18% chromium, 8% nickel, 1% manganese alloy with 0.04% maximum carbon content, it will be well to supply per unit of time 18 weight units of chromium,- 8 weight units of nickel, 1 weight unit of manganese and 73 weight units of iron. Commercial ferro-chrome containing 70% chromium and having a carbon content of 0.06%

is a comparatively cheap material and is used as the raw material forthe chromium; 25.75 weight units of this material will supply 18 weight units of chromium as well as 7.75 weight units of iron and 0.0156 weight unit of carbon. Commercial ferro-manganese containing 80% manganese and having 0.10% carbon is a satisfactory raw material for the manganese. 1.25 weight units of this material will supply a 1 weight unit'of manganese and in addition, 0.25 weight unit of iron and 0.0014 weight unit of carbon. The nickel may be supplied by using commercial nickel shot containing 0.10% carbon. 8 weight units of the nickel shot will supply the required nickel and 0.008 unit of carbon. The iron may be cheaply supplied by using low carbon iron, such as the readilyavailable Armco iron, or by using low carbon steels. Armco iron may be obtained containing-0.02% carbon maximum and can be purchased in strip form. 65 weight units of such Armco iron will supply the remainder of the iron and 0.0130 weight unit of carbon.

In actual practice using the proportions and materials just stated, the alloy obtained had an analysis which did not depart from the predetermined analysis of 18% chromium, 8% nickel, 1% manganese and 0.038% carbon by more than an usual experimental error. Furthermore, the losses in this process are negligible. a

By the use of low carbon ferro-chrome, i. e,, the variety containing 0.03% carbon, the carbon content of. the 18-8 alloy stated above can easily be dropped to about 0.03% carbon. The

carbon content may also be further reducedto' the neighborhood of 0.02% by using carbon free nickel. 7

With the same ingredients given above and by changing the rates of feed, the whole series of corrosion resistant chrome-nickel steels maybe produced. I

The rates of feed in production of the chromesteels are also readily ascertainable. Thus, if it is desiredto produce 12%-14% chrome, 1% manganese steel, with a maximum carbon content of 0.05% the Armco iron strip, the 0.06% carbon ferro-chrome and the ferro-manganese. may be the raw materials. This analysis, fixing on 13% chromium, is obtained by feeding, per unit of time, 18.57 weight units of ferro-chrome, 1.25 weightunits of ferro -manganese and 80.18

weight units .of the Armco iron. The-resulting alloy'contains'somewhat less than 0.03% carbon. Again, the whole series of chrome steels may be produced by merely changingthe rates of feed of the raw materials. As before, lower carbon contents may be obtained by using the 0.03% carbon grade of ferro-chrome.

High speed tungsten tool steel, high siliconinch in diameter, I have deposited from 150- pounds to 200 pounds of 18-8 alloy per hour with a discharge of 2300 amperes; with the same electrode from 2504325 pounds per hour were deposited when the amperage was raised to 3700.

Within limits, the voltage of the discharge is of importance, and in general, the temperature of the operation, as indicated at the molten flux surface, increases substantially directly with the voltage. There are variations in the quality and properties of an alloy of given analysis when produced at different temperatures. In general, there is an optimum temperature, or optimum temperature range, for the production of each analysis. The optimum temperature, or optimum temperature range, can in each case be determined by trial and once obta ned canbe duplicated by merely adjusting the voltage of the electrical discharge. With 188 alloy, a voltage of.

about 40 volts gives good results, when ease of operation and quality of metal are balanced. At 40 volts, with water'cooling of a copper mold,

the flux surface temperature ranged from 3200f FJto 4000 After the rates. of feedjand the voltage and amperages have beenestablished, the metering devices and are control arrangements are adjusted to feed their respective materials at the .approaches the surface'of the plug and a wad of steel wool or similar arc starter interposed .between its end and the surface of the plug. A

flux blanket of from 1 to 3 inches is then placed in the mold to completely cover the bottom condition, in which condition its constituents quickly intermingle to form an alloy of uniform analysis.

The heat of the discharge also fuses the flux blanket and imparts to it an extremely high temperature. The highly heated flux not only excludes the atmosphere but maintains the high temperature of the surface metal of the deposited alloy so that it can flow in its highly fluid condition to the mold sides to conform to the contour of the mold with a surface remarkably free from folds, holes, cracks, segregations and other of the usual imperfections of cast metal. The highly heated flux, furthermore, makes it possible to prolongthe intermingling and refining action of the I is used in melting the flux, it is sometimes adable as with rapid crystallization the characterisvisable to maintain a water spray suflicient to prevent heating of the mold excessively. After the flux is molten the spray is increased to the ultimate required to maintain the cooling rate desired and an equilibrium between heat added and heat removed. With alloys that solidify with a coarse grain, especially the austenitic chromenickel steels, rapid solidification is highly desirtic dendridic structure is reduced to a minimum. In practice, I have found that highly satisfactory results are obtained by cooling at such a rate that a depth of molten metal ranging from one to four inches overlies the solidified metal. method of cooling produces small sized equiaxed grains which are very desirable for subsequen working operations.

The removal of heat by the water spray from the bottom. and sides of the mold at the rates stated, assures a continuous, upward solidification of the alloy while there is always highly heated metal above it which can move to compensate for shrinkage and thus prevent the usual porous areas, holes, pipes, etc. of the prior prac tice. The highly fluid supernatent metal, furthermore, prevents segregation of impurities as those that are thrown out of solution during crystallization canreadily pass through it to be absorbed by the flux.

When the mold is filled to the desired extent, the metering devices are stopped and the electric current opened but the spraying of the water may be continued until all of the alloy is solidified. After solidification of the alloy body, mold 26 may be separated from stool 28 and removed. The alloy body may be easilytaken from mold 26. Mold 26 may be then placed on stool 28 and This the production of another alloy body commenced.

The operation may be used not only in the production of billets but to form semi-finished alloy articles of any of the usual forms. Thus, in Figs. 2 and 3 is shown a mold 32 shaped to form a rectangular slab. As before, the mold may be cooled by water sprays from perforated coil 33. Mold 32 is of a highly conductive metal such as copper and is held on its stool 34 by bolts passing through flange 35. With molds of this shape a plurality of electrodes 36 are preferably used. The electrodes may all be hollow as is electrode I8 of Fig. 1, or one or more may be solid, or all may be solid, the raw materials being supplied at constant rates by and through the electrodes. Electrodes 3B maybe fed by arrangements carried on truck I4 in the same manner as described in connection with Fig. 1.

The billet molds 26 and the slab molds 32 may be of any size and length. Thus, semi-finished alloy bodies of the usual sizes are easily produced, and when required bodies weighing as little as only a few pounds may be produced.

The alloy bodies, whether billets, slabs, etc., after they have been removed from their molds, because of their substantially imperfection free surfaces, because of their'small crystal structure,

and because of the strong outer fine grain envelope, may be worked directly in the manner well known in the art, to flnal or further intermediate products with great facility. Thus, cogging and the diiflculties, losses and expenses attendant thereto are eliminated. While some trimming may be required, the finished article will be free from defects chargeable to the production of the original semi-finished alloy body.

I claim:

1. In combination in an apparatus for the production of alloy bodies directly from raw materials made up of the constituents of the desired alloy, a mold wherein the alloy may be produced and solidified into the desired alloy body, said mold being adapted to receive a blanket of protective flux to cover the alloy during its production and solidification, a metal electrode made up of constituents of the desired alloy, an electric currentsupply connected ,to the electrode and the mold, means for feeding the electrode into the mold through the flux blanket to maintain an electric current discharge of predetermined characteristics from its end through a gap beneath the surface of the flux, means for passing raw materials made up of constituents of the desired alloy at predetermined rates through the flux blanket to the electric discharge to be fused thereat with the metal of the electrode and intermingled therewith to form the desired alloy, and means to remove heat from, the mold to prevent fusion of the mold and to solidify the alloy formed from the bottom of the mold upwards during the filling of the mold, whereby to form a solidified,

alloy body that is removable from the mold.

2. In combination in an apparatus for the production of alloy bodies directly from raw materials made up of the constituents of the desired alloy, a mold wherein the alloy may be produced and solidified into the desired alloy body, said mold being adapted to receive a blanket of protective flux to cover the alloy during its production and solidification, a hollow metal electrode made up of constituents of the desired alloy, an electric current supply connected to the electrode and the mold, means for feeding the electrode into the mold through the fiux blanket to maintain an electric current discharge of predetermined characteristics from its end through a gap beneath the surface of the flux, means for passing raw materials made up of constituents of the desired alloy at predetermined rates through the hollow electrode to the electric discharge to be fused thereat with the metal of the electrode and intermingled therewith to form the desired alloy, and means for removing heat from the mold to prevent fusion of the mold and to solidify the alloy formed from the bottom of the mold upwards during the filling of the mold, whereby to form a solidified alloy body that is removable from the mold.

3. In combination in an apparatus for the production of alloy bodies directly from raw materials made up of the constituents of the desired alloy, a mold wherein the alloy may be produced and solidified into the desired alloy body, said ,mold being adapted to receive a blanket of protectiv'e flux to cover the alloy during its production and solidification, means for forminga metal strip made up of constituents of the desired alloy into a hollow electrode and feeding the formed electrode into the mold through the flux blanket, an electric current supply connected to the formed electrode and the mold, means for controlling the electric current supply and the forming and feeding means to maintain a discharge of electric current of predetermined characteristics from the end of the electrode through a gap beneath the surface of the flux, means for passing raw materials made upof constituents of the desired alloy at predetermined rates through the hollow electrode to the electric discharge to be fused thereat with the metal of the electrode and intermingled therewith' to form the desired alloy, and means to remove heat from the mold to prevent fusion of the mold and to solidify the alloy formed from the bottom of the mold upwards during the filling of the mold, whereby to form a solidified alloy body that is removable from the mold.

ROBERT-K. HOPKINS.