US2129702A - Process for making metal products - Google Patents

Description

Sept. 13, 1 938. J. M. MERLE 2,129,702

PROCESS FOR MAKING METAL PRODUCTS Filed May 5, 1954 2 SheetsSheet 1 gawk .Joscyab M. Marie;

Sept. 13, 1938. J. M. MERLE PROCESS FOR MAKING METAL PRODUCTS Filed May 5, 1934 2 Sheets-Sheet 2 de M. w J

Patented Sept. 13, 1938 mocsss ron mama METAL monuo'rs Jmpil. M. Merle, Tarentum, Pa. Application May 5, 1934, Serial No. 724,188

Claims.

The present invention relates to a method of manufacturing cutting tools and other metal products from molten tool steel or other metals or alloys.

With the exception of those metal products made from powdered metals sintered under heat and pressure, such products are customarily made from molten metal poured into a metal mold, sand mold or rotary mold, or are forced under mechanical or air pressure intoa mold or die. In every case of a metal product made from molten metal as above indicated, such molten metal reaches the mold or die in a liquid state and, while inside such mold or die, passes from the liquid state to the solid state, this change of physical condition involving well known phenomena which vary somewhat depending upon the specific metal or alloy involved.

This common method of production of metal products has a determining influence upon the physical and other properties-and characteristics of all commercial metal products either in their cast condition or in their worked condition resulting from forging, roiling, pressing, extruding or mechanical forming, as well as in their heat treated conditiomthe finished product retaining some of the characteristics of the crystals formed and propagated through the molten metal.

An object of the present invention is to avoid the conditions which take place when molten metal passes from the liquid to the solid state in a mold or die since I have observed that by forcing molten high speed steel or other steel into molds or dies not in the liquid state but in a fine atomized spray of undercooled but still plastic particles propelled at a relatively high speed, such particles would impact together when contacting with the mold wall or with a section of the prodnot already formed. The tools so formed disclose a different structure and difierent properties than tools made of ingot steel of the same composition but which have been produced by pouring liquid steel into an ingot mold, the ingot being subsequently hammered and/or rolled.

l have also observed that in steel or other metal products so made each of the undercooled atomized particles solidifies spontaneously upon impact while aggregating to other particles previously impacted thereby forming a metal product or increased density and cohesion, homogeneous in structure and free of the conditions occurring within an ingot when a large mass of molten metal passes from the liquid to the solid state, namely, dendrites, segregation, pipe and heterogeneity, and further that the grain size of the metal product so formed may be controlled by regulating the size of the atomized particles.

Also I have observed that the same structure and conditions are obtained by forcing the undercooled atomized particles not into a mold but through. a die, out of which the formed metal product is drawn or stripped at a rate corresponding to the amount of atomized metal forced into it, thereby forming metal products in bars, strips, sheets, or shapes in continuous lengths.

Furthermore, I have observed that steel and other metal products so formed have physical properties no longer comparable to the same metal as at present commercially cast, but better than the properties of the some metal commercially worked by iorging, rolling, or extruding. More specifically, cutting tools formed by this method are much better and can withstand a cutting speed two to three times as great as the cutting speed obtalnable with tools made of steel of the same composition as at present commercially produced.

In metal products so formed the latent heat of the molten metal is completely dissipatedbefore atomizing and each atomized particle is undercooled slightly below the ireezing point, so that a crystal nucleus, extending to a part of or entirely through the particle, has been formed and upon colliding and impacting with other particles, the metal atoms can find satisfactory arrangements, thus giving a structure free of internal stresses. Each particle also spontaneously crystallizes upon impact without iurther disturbance due to latent heat dissipation through the crystals formed, thus making metal products of a distinctive and physically new structure, which is retained through subsequent mechanical working operations or heat treatment. This structure for all metals and alloys is characterized by minute spheroid cells of identical size, free of dendritic needles, with impurities located at the grain boundaries, as well as supersaturated alloy components concentrated at the grain boundaries and with precipitating components uniformly distributed as minute particles throughout the product formed. Thereby a meta1 product is formed which is uniform in structure under any magnification, more dense and stronger than similar metal products of the same composition, having the same strength, elongation, elastic limit and reduction of area in every direction and will give a non-directional iracture. Furthermore, the metal products are not subject to any chilling efiects from metal molds and are free from dendrites, flow lines, segregation, pipes, shrinkage cavities, etc, and they have the same chemical composition throughout the entire section or any part of the product. This special structure is retained after forging, rolling, heat treatment and even after welding when using the metal product as a welding rod.

In the case of high speed steel, the hard carbide components are disposed in a network around each martensitic crystal thereby imparting to each grain a cutting edge around its periphery and thus accounting for the better cutting properties over steel of the same composition as present commercial products. The distribution of the carbides is entirely uniform, and, in the case of chromium stainless steel, the same structural disposition accounts for better resistance to corrosion.

Molten substances such as molten glass or rocks so formed are also given a distinctly new structure and new properties.

I have also observed that cutting tools can be formed of a layer of high speed steel made from impacted undercooled. atomized particles and a layer of strong and tough alloy steel made in the same manner of impacted undercooled particles, the two layers being perfectly bonded together by this method and beingstrong enough to withstand, without breaking, increased cutting speeds.

Furthermore, finely powdered particles of tungsten, tantalum, titanium or other metal carbides, either one kind or several kinds at the same time, as well as finely powdered particles of diamond, can be dispersed through the atomized particles of high speed steel or other metal, the latter forming a matrix around the hard carbide or diamond particles which impart to the tools very desirable cutting properties. By undercooling the molten metal below the freezing point before atomizing and impacting the particles, 9. spongy metal product can be formed with voids uniformly distributed, the size of the voids being controlled by the regulated size of the atomized particles.

I have observed also that nickel, copper, zinc, cadmium, brass, etc. so formed into metal products have very desirable properties for the plating industry, as anodes so formed, on account of their homogeneous fine structure, will corrode uniformly in the plating bath, without leaving any deposit in the tank, thus eliminating the use of diaphragms as at present used, and making a more uniform deposit on the-plated product, free of trapped gas pockets, which will last longer and look better than the deposits as obtained from present commercial anodesi The physical conditions previously described under which the molten metal is forced into molds or dies or through dies, can be produced by various methods. Several methods are illustrated diagrammatically in the accompanying drawings, it being understood that other methods of undercooling, atomizing and propelling the molten metal can also produce the same results.

In order to more clearly understand the invention, particularly the tools and products, and the method of making them, it will now be described with reference to the accompanying drawings, in which:

Figure 1 is a horizontal top view of a rotary atomizing disc and a part of a stationary circular receiving mold,

Fig. 2 is a vertical'sectional view through the rotary atomizer and mold of Fig. 1 and through the receptacle feeding molten metal to the atomizing disc,

Fig. 3 is a vertical sectional view of an inclined atomizing disc with a different mold which can be stationary or rotary, to receive the atomized particles in a spiral spray,

Fig. 4 is a cross sectional view of a product obtained in the machine of Fig. 3,

Fig. 5 is a vertical sectional view of the atomizing disc of Fig. 1 showing the spraying of the atomized metal into a rotary mold for shaped Fig. 6 is a cross section of a formed tool, made of two metal layers,

Fig, 7 is a cross section of a tool made of three layers of steel,

Fig. 8 is a vertical sectional view of a belt shaped undercooler and atomizer and showing a cross section of a water jacketed mold for continuous metal products,

Fig. 91s a cross section of the metal belt undercooler and atomizer of Fig. 8,

Fig, 10 is .a horizontal elevation of the belt atomizer and mold of Fig. 8,

Fig. 11 is a vertical sectional view of two belt atomizers and a mold for continuous bimetal products; and

Fig. 12 is a part sectional and side view of a modified type of machine, similar to Fig. 11 but for metal coatings.

The various parts of the machine can be described by detailing the operation of the machine, and as to Figs. 1 and 2 it is as follows:

The molten metal I 4 in the receptacle l3 runs out through a series of orifices l5, whose number, size, and shape have an influence on the degree of undercooling desired. This molten metal contacts with a rotating disc I along a circumference line 2, Fig. 1, this part or section of the disc having already a considerable peripheral speed which prevents the molten metal from adhering to or burning the atomizing disc which would probably take place if the metal contacted with the center of the disc. The atomizing disc I is composed of two parts, an upper part 6 and a lower part i spaced from each other to provide a space 8 therebetween into which cooling fluid such as water may be fed. The water or other cooling fluid is fed to the receiving space 8 by the pipe 9 disposed within shaft 9 on which the disc is mounted and runs out of space 8 through the space 9 in the shaft between the stationary water pipe 9 and the center bore 9 of the shaft. The water flow will maintain the atomizing disc at substantially a constant temperature by taking up the heat imparted to the disc by the molten metal.

The atomizing disc I is journalled in ball bearing l0 and other bearings, not shown, and is driven (at a high rotative speed) by suitable means, not shown, associated with the shaft 9. The molten metal falling on the revolving disc on the circular line 2 forms a film which spreads out over the surface on the upper part 6 of the disc extending from the line 2 to the periphery of the disc, and while in such film state the metal loses heat by contact with the cooled surface of the disc and is thus undercooled. The thus undercooled metal film on leaving the periphery of the disc breaks up into a fine spray of atomized particles which are propelled at a high speed in a direction precisely at relative to the axis of rotation of the disc. The particles of metal traveling as a spray and at high velocity enter the stationary circular mold I6 through a circular slit it! which is exactly in the path of travel of the particles. These particles are solidified and united with each other under impact in the mold and fill up the mold cavity 4.

In the form of construction shown in Figs. 1 and 2, the exact amount of molten metal sufficient to fill the mold cavity is poured into the receptacle l3. When all the molten metal has been atomized and sprayed, the top part I 6 of the mold I6 is lifted from the bottom part II. The cast product, which may be formed as an integral circular unit or in two or more sections, three being shown in Fig. 1, by placing separating pieces 5 in the mold, is stripped from the part I1. The casting or the sections may have a fin molded thereon corresponding to the feeding slit if excess metal has been poured, but since the slit is only a few thousandths of an inch wide, the fin can easily be broken or cut away and the sections may be straightened in straightening rolls, if necessary. The plates II and I! on the mold parts l6 and I! completely close the space in which the disc rotates, and no air is admitted while the molten metal is being poured. In this way the atomized particles, while being propelled at high velocity as a spray from the disc to the mold cavity, are not subjected to possible oxidation, and preferably the air contained adjacent the disc is pumped out by means of pipe l9, so that the undercooling, atomizing, and impacting are carried out in a vacuum. If desired, hydrogen, a mixture of hydrogen and nitrogen, illuminating gas, or blue gas can be forced into the space adjacent the disc and in the mold cavity, if such gases are beneficial to the metal being sprayed and cast.

The undercooling of the metal, the size of the atomized particles, and the velocity at which the particles are propelled can be regulated at will. The fiow of molten metal from the receptacle l3 depends on the number and cross sectional areas of orifices l5 and can be made of such size and number as to feed from to 500 lbs. or more of molten metal per minute. disc having an outside diameter of 12", the molten metal can be made to drop on the circular line 2 on the upper part 6, which line may vary from 2" to 10" in diameter. This varies the time during which the film of moving molten metal is in contact with the upper surface 6 of the disc I. The temperature of the surface 6 of the disc may be regulated by varying the flow of water through space 8, and can be maintained at a low value or at a temperature of about 300 F. The speed of the rotary disc can vary in practice from 1,800 R. P. M. to 6,000 R. P. M., as the higher the speed the thinner the film of metal formed, and the smaller the size of the particles of metal sprayed from the disc, the greater their velocity and impacting power.

With these regulations, the grain size of the metal product can be controlled and products of increased density and increased strength over present commercial products can be produced. Furthermore, by reducing the flow of molten metal from the receptacle and increasing the length of its travel over the surface of the disc, the metal is undercooled, that is, the metal is cooled to a temperature below its freezing point and, the film breaks into particles already partly solid or entirely solid, and these particles, due to their velocity, unite by impact with each other into a solid but spongy metal product with uniform voids between the particles.

If, for instance, the undercooled solid particles are not collided and impacted together within a short distance after leaving the rotary disc to form a solid product, but are allowed to travel a distance of several feet before impacting against the walls of the chamber, they will not impact together but will be collected as powdered metallic particles. Depending on the speed used and the amount of undercooling, these particles may be .in Fig. 2, being made either in an airtight space or When using a rotary chamber or under a vacuum, or in a chamber filled with a neutral gas, the granules or particles are not subject to oxidation; Furthermore, a special gas, such as ammonia gas, can be used which will dissociate under the heat of the particles, and when using steel or another alloy capable of being nitrided, the granules or particles will attain a hard nitrided surface which is useful in several commercial applications.

The apparatus shown permits the handling of 10 metals or alloys of low melting point, as well as metals or alloys of high melting point, byadapting the conditions of flow, undercooling and atomiz-jl. ing to suit the various metals or alloys. It is further noted that practically none of the molten l5 metal is lost as by heads, pipes, or grates, which have to be cut oif from the solid product formed.

Fig. 3 shows a rotary atomizing disc as used in connection with a billet or slab mold, but in this instance, the disc instead of being set at 90 to 20 the axis of the shaft rotating it, is set at an angle to the shaft, the amount of angularity depending upon the height of the billet or slab to be made in mold 20 and 2| whose cavity is in a plane at right angles to the shaft. In this arrangement 25 the spray of metal on leaving the rotary disc I travels in a straight line, indicated by the arrows, exactly 90 to the axis of rotation of the shaft, and will build up the section of the billet or slab by evenly distributing the particles in a. spiral 3 path throughout the height or width of the product formed. The mold parts 20 and 2| are stationary or can be rotated at low speed. The billets formed have good surfaces, are of uniform structure, free of pipe shrinkage cavities, and are 35 ready for rolling. A vertical shaft is shown, but in view of the high velocity used, gravity has no effect on the molten metal poured'over the rotary disc, and therefore the shaft of this disc can be in any position which may be more convenient 40 for the operation of the process.

Fig. 4 shows a section of a product or casting made by pouring successively into receptacle l3 of Fig. 1, first one type of metal, for example stainless steel 24, then another type of metal 25, 45

such as low carbon steel, then stainless steel 24 again, if desired, so that a billet or slab is formed in the mold of Fig. 3 having a core 25 of low carbon steel and faces 24 of stainless steel, the

layers being perfectly bonded together by the 5 velocity of impact without any impurities, slags,

or oxides at the junction of the various layers.

junction between the distinct metals or alloys is free of gases, oxides, and other impurities and the products may be rolled or forged without any rupture or separation at the junction of the distinct metals.

Fig. '5 shows the same rotary disc and pouring receptacle as Figs. 1 and 2, but the atomized spray is received in mold 2'! and 28 which is also rotated by means of pulley 32, the direction of rotation being the same or the opposite to the direction of rotation of the rotary disc. The mold 21 and 28 has cavities each corresponding to the shape of the formed tools or other products, there being two or more of these cavities to receive the spray from the rotary disc. When making cutting tools of two layers of steel, first high speed steel of any of the commercial compositions is poured into receptacle l3 and this steel is formed into a film, undercooled and atomized, and these particles when reaching the mold cavities on account of the rotation of mold 21 and 28 form a layer 35 parallel to the axis of rotation of the mold. Then a tough alloy steel, such as chrome-nickel steel or chrome-vanadium steel is poured into receptacle l3 and also undercooled and atomized, and this steel is sprayed into a layer 36 adhering to the layer 35 of high speed steel until the tool cavities of the mold'are filled up. The second steel is poured in the receptacle before the high speed steel has entirely drained out, so that particles of both kinds of steel are intermingled at the junction of one to the other through a thickness of a few thousandths of an inch, thus making the two layers so inseparably bonded that they cannot be parted by any mechanical means. To receptacle l3 may be attached another receptacle 26, through which finely powdered material such as diamond powder or pulverized metallic carbides can be introduced at the same time that the high speed steel is poured, so that the pewdered material will be carried out on the film of molten metal and evenly dispersed into it. When the metal breaks into a spray, the atomized metal particles and the powdered carbides are both propelled together at the same speed and will impact and aggregate together in the layer formed in the rotary die or mold. This provides the tool with hard particles uniformly dispersed through a matrix of either high speed steel or some other binding metal, such as cobalt, nickel, high strength bronze, etc. Through receptacle 26 another molten metal can be poured, for example lead, and through receptacle l3 bronze can be poured, so that an. increased amount of lead can be dispersed through the bronze base metal as finely divided particles to improve the properties of the bronze for bearing purpose. Finely powdered graphite can be used for the same purpose and dispersed through the base metal. The foregoing describes some of the products which can be produced by building them of undercooled atomized particles instead of starting from a molten metal poured into a mold.

Milling cutters, hobs, rock drills, core drills, rotary saws, and other tools can be formed in the same manner having a hard cutting steel alloy or abrasion resisting alloy on the outside surface, and a core of tough and strong steel or other metal inside. Furthermore, as in ordinary die casting machines, inserts, of metallic or other suitable materials, can be placed in the die to become a part of the casting after the metal particles have been consolidated therein under impact.

Fig. 6 shows a forming tool, finished to grinding size, having a. layer of high speed steel 35 with or without carbides or diamond powder dispersed therein and a. layer of tough steel 36 for the support of the tool.

Fig. 7 shows a bar for twist drills, made of a central layer 31 of high speed steel or other cutting material and two sectors 38 of a tough steel which will render the drill unbreakable.

Figs. 8 to 10 show a band undercooler and atomizer, the band being made of a steel or other metal ribbon similar to the band of a band saw or of some non-combustible material but preferably having a section as shown in Fig. 9. This band 42 runs over grooved pulleys 43 and 44 at high speed by means of a driving grooved pulley 45 which is connected to a motor or to a belt drive by means of shaft 55. The molten metal is poured into receptacle 39 whose nozzle contacts with the groove 51 of the band 42 at 4|. This receptacle 39 is supported over the frame 54 of the machine. A steady flow of molten metal is drawn through nozzle 56 and is propelled in the groove 51 of the band 42. The film formed in the band is very thin and when the band turns over pulley 44 this film under its velocity breaks into a fine spray of undercooled metal particles and is propelled into mold 41, thus forming a solid metal product of any desired section or shape depending upon the shape of the mold. This mold can be water-jacketed by means of the jacket 48 with inlet 50 and outlet 49 to maintain the mold at a constant temperature. A pair of rolls 52 and 53 draws the solid bar 5| formed at a rate of speed depending on the weight of metal flowing per minute from nozzle 4| and of the section of the metal product formed. The velocity of the atomizing band can be made to vary to correspond to the same peripheral speeds indicated for the rotary disc of Figs. 1 and 2, thus producing the same underccoling and atomizing conditions and the same characteristics as indicated in the foregoing in metal products formed in continuous lengths. The band 42 passes through a cooling liquid 46 in a depression 46' in the frame 54 to maintain the'band at a constant temperature to receive a film of molten metal, thus maintaining constant conditions of operation. With this design, strips of sheet metal or other shapes of any thickness and width can be formed. As indicated, the nozzle of receptacle 39 and the band are made wide enough to form the metal film in the proper shape, depending on the finished metal product desired. Furthermore, the rolls 52 and 53 will pull the formed strip, sheet or shape at a rate of speed depending on the amount of molten metal fed by the receptacle nozzle. The undercooled atomized particles can be thrown against the surface 'of a strip of metal and form a coating, or they can be collected as granulated or powdered metal particles if a long funnel is substituted in place of the mold 41.

Fig. 11 shows a construction in which two band atomizers 42' are arranged to spray a metal product 5| which is made up of two layers, and to form such product in a continuous length. Suitable covers 4'! keep the metal films free from contact with air and a vacuum can be created if desired, or some other gas can be forced into the space to prevent oxidation of or to induce desired chemical reactions with the molten metal used. The different metals are positioned in the receptacles 39' placed over the bands.

In Fig. 12 the parts of the machine, not shown, are understood to be the same as in Fig. 11. The band atomizer has a cover 41 to eliminate contact with air, and, as in Fig. 2, a tube such as that numbered I9 can be used to connect the space under the cover 41 to a vacuum pump or to introduce a supply of neutral gas into the active space under such cover. The two undercooling and atomizing bands 42' simultaneously form the atomized metal into a coating on both surfaces of a strip or sheet metal plate 52' which is drawn by bands 42'. The thickness of the coating is regulated by the flow of the metal from the receptacle nozzle and by the speed at which the strip or sheet is pulled by the bands 42'. This coating, being made of particles impacted under high velocity and free of oxidation, will form, on the clean surface of the sheet or strip,

a more adhering coating than by dipping the sheet in molten metal. This coating has distinctly new characteristics and a new structure and increased resistance to rust and corrosion on account of the fact that it is formed of atomized undercooled particles strongly bonded together under impact and further bonded to the metallic surface of the sheet or strip by pressure of rolls 53'. a

No claim is made herein either to the apparatus or to the product produced, such respectively constituting the subject matter of my copending applications Serial No. 33,157 filed July 25, 1935, and Serial No. 206,396 filed May 6, 1938.

I claim as my invention:

1. A method of producing a metal product from molten metal, which includes the steps of producing a flow of molten metal in the form of a continuous stream, converting such fiow into a stream of film-like proportions, substantially abstracting the latent heat of all such metal as it moves in such film-like stream, and then subjecting the metal so cooled to a forming force while it exists at a temperature slightly below t freezing point of such -metal.

2. A method of producing a metal product from molten metal, which comprises producing a flow of molten metal in the form of a continuous consolidated stream, converting such flow into a stream of film-like proportions, supporting such film-like stream and simultaneously abstracting substantially all the latent heat from all the metal in such stream, projecting the metal so cooled in the form of a .mass of separate particiesand subjecting each such particle to a forming force while it exists at a temperature slightlybelow the freezing point and is plastic.

3. A method of producing a metal product, which comprises establishing a flow of molten metal infthe form of a continuous consolidated stream, converting such fiow into a film-like stream moving at a high velocity, uniformly cooling all the metal of such film-like stream and substantially abstracting the latent heat therefrom, then subjecting the metal so cooled to forming force while it is plastic and exists at a temperature slightly below its freezing point.

4. A method of producing a metal product,

which comprises establishing a flow of molten metal in the form .of a continuous consolidated stream, converting such flow into a film-like a batch of molten metal which includes the steps of establishing a fiow of such metal from such batch in the form of a continuous stream, converting such stream of molten metal into a continuous stream of film-like proportions moving at a high velocity, substantially dissipating the latent heat of such metal while moving at such high velocity by subjecting such film-like stream to a cooling medium, and in subjecting the thus partially cooled metal to forming force while it" exists at a temperature slightly below the melting point thereof.

6. A method of producing a metal product from a batch of molten metal which includes the steps of establishing a flow from such batch in the form or a continuous stream, converting such flow into a rapidly moving continuous stream of film-like proportions while supporting the same substantially extracting the latent heat from all the metal as it moves in such film-like stream, breaking the partially cooled stream of metal into a mass of separate particles while projecting each such particle at a high velocity, and consolidating such particles by impact while each such projected particle exists at a temperature slightly below the freezing temperature of such metal.

'7. A method of producing a metal product from molten metal, which includes the steps of establishing a continuous flow of molten metal from a batch of such metal, converting such ilow into a continuous stream of film-like proportions, moving in a straight line, continuing the straight line motion of such film-like flow while supporting the same and'while substantially dissipating the latent heat of all the metal constituting such stream, breaking the flow into a mass of separate particles of metal projected at a high velocity into a mold while existing at a temperature slightly below that of the freezing temperature of such metal, and subjecting each such particle to impact force while at, such temperature.

8. A method of producing a metal product from molten metal, which includes the steps of establishing a flow of such metal in the form of a film-like continuous stream moving in a planedefining direction, supporting such film-like stream during a substantial portion of its motion and while substantially withdrawing the latent heat of all the metal constituting such stream, then causing such metal to move while unsupported in the direction of its supported travel and while existing at a temperature substantially that of the freezing point of such metal, and subjecting the metal while slightly below such temperature to a forming force.

9. A method of forming a bi-metal product, which consists in establishing a fiow of molten metal in the form of a film-like continuous stream, supporting such stream while extracting substantially all of the latent heat of the metal constituting the same, breaking the stream into a mass of separate metal particles projected at a high velocity along the line of travel of' such stream and while each such particle exists at a temperature substantially equal to that of the freezing temperature of such metal, subjecting each such particle to an impact force while existing at a temperature slightly below the melting temperature of such metal, continuing such stream-like now without interruption thereof from a batch of different molten metal, converting such flow into a stream-like film constituting a continuation of the aforesaid film and while supporting the same and extracting substantially all of the latent heat of the metal constituting such film, breaking such fiow into a mass of metal particles existing at a temperature substantially equal to that of the freezing point of such last mentioned metal and causing the particles so projected to impact upon previously projected metal while the same exist at a temperature slightly below the freezing point of the last mentioned metal. q

l0. Amethod of producing a metal product as set forth in claim 2 wherein the metal from which the product is made is protected against oxidation from the time it leaves the molten batch until the metal product is fully formed.

JOSEPH M. MERLE.

CERTIFICATE-OF CORRECTION.

Patent Noo 2,129,702, September 15, 1958.

JOSEPH M. MERLE.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 16 for "grates read gates; page 5, second column, line L5,

before, "the" second occurrence, insert all; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of November, A. D; l958.'

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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