US2445177A - Method and apparatus for depositing metallic layers - Google Patents

Description

July 13, 1948. .H. L. LINDBLAD METHOD AND APPARATUS FOR DEPOSITING .JTALLIC LAYERS F' d April 24, 1944 I /menuo L. Ma-91.40.

Patented July 13, 1948 METHOD AND APPARATUS FOR DEPOSIT- ING METALLIC LAYERS Harald L. Lindblad, Chicago, lill., assignor to Metallizing Company of America, Chicago, Ill.,

a copartnership Application April 24, 1944, Serial No. 532,450

2 Claims.

This invention relates to the art of cladding the surfaces of conducting material and is directed more particu-larly to a novel method of and apparatus for so treating said surfaces.

The present invention is characterized particularly by the fact that when utilized to treat the surface of conducting materials such as metals the result represents a distinct improvement over treatment by means of the well known spray type of gun or treatment by the well known arc welding processes.

With the present invention it is found that any arcing which takes place between the electrode and the surface of the work is incidental and is not a factor in the production of the desired surface. In other words, it is not incumbent upon the operator to maintain an are of a given dimension in order that the surface be properly treated or in order that the end of the electrode be prevented from freezing upon the work surface. I

With my invention the possibility of electrodes freezing upon the work has been eliminated and furthermore the process may be performed successfully without the operator giving any attention whatsoever to the degree of arcing between the electrode and the surface of the work piece being treated.

The invention is particularly adapted to the deposit of built up surfaces upon the initial surface of a conductor, these built up surfaces being in thickness approximately 0.001 inch to 0.010 inch.

In building up the surfaces of articles in the past, it has been found that while the initial body of the article, previously made from an entirely different process, is free from pits and thus is of a density adapted to machining, the deposited surface is usually of considerable less density and full of voids. Furthermore, by previous methods such as by spraying or arc welding, it has been found that an initial deposit of considerably more than the above thickness must first be made before the treated article is in condition for further treatment. With the present invention, however, the initial deposit may be made of approximately the desired depth to require a minimum of machining and wastage. Such a process has been found invaluable in the reconstruction of parts which have become worn 1 due to bearing action and for the repair of iissures which have occurred in an article due to excessive strain.

From the foregoing it Will be seen that the advantages to be obtained by the use of my invention are those not to be realized by the use of spraying methods or by the use of mere short circuiting methods which result in the deposit of a spongy, excessively thick layer.

Another advantage obtained by the use of my invention is the elimination of the use of oxygen, acetylene or other combustible, corrosive gases whereby the surfaces of deposited molten particles are oxidized to detract from proper deposition of subsequent particles thereon to provide the desired density.

Still another advantage attending the use of my invention resides yin the maintenance of the surface of the work piece at a relatively low temperature at all times even during the deposit of metal particles thereon, whereby the work piece is not distorted or otherwise detrimentally affected by high temperatures.

To the end that the above advantages may be obtained and as a further object of my invention, there is provided herein an improved apparatus for performing the method of my invention which comprises a combination of factors including a head member for advancing a wire or the like of metal to be deposited, means for imposing a low voltage, high amperage current upon the wire and in circuit with the conducting work piece, means for vibrating the head with the wire and means for discharging an envelope of a gas such as air toward and around the end of the wire simultaneously with the resistance heating thereof by the current and with the vibration thereof by the vibrating means.

It is another object of the present invention to provide an improved mechanism of the above character and a new method for depositing a dense built up layer upon the surface of a conducting material whereby the development of distorting heat and a corrosive atmosphere is avoided.

I am aware of the previous use of vibration in conjunction with a resistance heated wire Whereby the end of the wire is caused to jump from spot to spot upon the work surface and upon each individual movement, to deposit on the surface a protuberance. However, with such an apparatus and process it has been found that voids between the protuberances are not iilled in by subsequent overlying operations but rather are merely sealed over by the subsequent operation. Thus this deposit, while it has certain attributes in conjunction with subsequent processes, fails to provide a dense, underlying layer of the character here obtained.

I am also aware of the use of the stream of heated gas 'which aids in a puddling operation in conjunction with high temperature deposition of metal layers upon a work surface. However, such processes involve temperatures of such a nature that the work piece is subject to warping and the deposited layer is necessarily of a thickness much greater than that desired by the use of my apparatus and process.

As distinguished from prior apparatus and processes, my invention is directed to a concept by means of which there is deposited upon the Work surface a relatively thin, dense layer of metal Without the generation of high temperatures in the work piece, the deposited metal being free from pits and in fact possessing a density on the order of that of the work piece itself.

As an example of the density developed by my process I have deposited on a portion of a piece of cast aluminum, a built-up layer of aluminum from an aluminum electrode in my apparatus. ;v

The entire surface of the piece including both the coated portion and the uncoated portion is then covered with a viscous material and air pressure is impressed against the rear side thereof. It is then found that bubbles develop in the cast metal beneath the viscous material to show passage of air therethrough while no such bubbles are developed at the portion thereof upon which a layer has been deposited by my novel process. of cast aluminum the deposited layer is of a considerably greater density than that of the base.

Other objects and advantages of my invention will become apparent from the following description and accompanying drawings in which:

Figure 1 is a partially diagrammatic view of one type of apparatus which may be used to carry out the deposition of a metallic coating according to my invention;

Figure 2 is an enlarged, longitudinal cross sectional view of the head mechanism shown in Figure 1, showing particularly the passages for the metal rod or wire and compressed air and also the electrical connection thereto; and

Figure 3 is a Vertical section taken along the line III-III of Figure 2 showing the control valve for regulating the rate of speed of the metal rod or Wire.

It will, of course, be understood that various details of the process and apparatus may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessita-ted by the scope of the appended claims.

While, of course, it will be understood that the apparatus disclosed herein may be traversed manually over the surface of a particular work piece, there is shown in Figure 1 an arrangement wherein the work piece ID, for example, a Worn bearing or the like is mounted on and rotated by the mechanism of a lathe II. The wire I2, constituting the source of metal for the coating, has its end I3 directed toward the work and is mounted in the wire feed and compressed gas distribution device generally indicated at I4. As better shown in Figure 2, the head Il! has three principal parts, the rear part I5 which comprises a housing having an air turbine driven wire or rod feed mechanism, a section I6 for controlling the flow of compressed gas forwardly and a nozzle I T. It will be understood that while have shown herein an air driven feed, any other known conventional wire feed may be used.

This indicates clearly that in the case The mechanism I4 is preferably mounted upon a traveling base I8 on the lathe which is insulated therefrom by means of disks I9 and 2 and bolt 2 I. It will be seen that the resiliency of this insulated mounting enables the full effect of a vibrating assembly to be described presently to be transmitted to the entire mechanism and thus to the working end of the rod or wire I3, and not to the parts of the lathe II.

Preferably an alternating current of low voltage and high amperage is passed through the work piece I and the wire I3, this current being taken from a transformer 22 by means of a conductor 23 to the lathe II which is electrically connected to the work piece I and by means of conductor 24 to the terminal 25 secured to section I5 of the mechanism I 4.

As shown herein the terminal 25 is secured to the mechanism I4 by the fitting 26 through which fed compressed gas, such as compressed air, from a suitable source through filter 2l, pressure regulator 2B and tube 29 into air passage 30 (Figure 2) in section Iii of the mechanism I5. The air flowing through passage 33 passes through duct 3l to the annular recess 32 in the end of section IG and thence through a plurality, in this instance four, ducts 33 in the nozzle I'I.

It is to be particularly noted that the ducts 33 in the nozzle I'I converge so that the air stream therefrom is directed toward the work and also toward the wire or rod extending through the axial ypassage 34 and beyond the end of the nozzle Il, thus to form an envelope around the wire or rod I3 and to strike the surface of the work in the immediate vicinity of the part thereof against which the end of the Wire I3 is directed during the'deposting or cutting operation.

Air leakage between section I6 and nozzle Il is prevented by having their cooperating surfaces adequately ground and held in close contact by a coupling member 35.

Compressed air from passage 3d also passes through duct 36 into the body of a conventional needle valve 31 installed in section IB, and thence by valve seat 38 (Figure 3) through duct 39 into passage 40 which leads to the conventional air turbine (not shown) actuating the wire feeding mechanism (also not shown). The holes 4I are merely for the purpose of securing sections I5 and I6, as by cap screws 42 (Figure l). It will be apparent from the above that the rate of feed of the wire I2 can be readily controlled by means of the valve 3T.

As indicated previously, the vibration of the end I3 of the Wire I2 as it cooperates with the surface of the work piece upon which metal is being deposited, is a highly important factor contributing to the eiciency of my process and accordingly, there is provided herein a vibrator 50 which may be air driven or any other suitable type which is preferably started at the beginning of the operation and is continued as metal is deposited upon the work piece. Preferably the vlbrator 5U should be so constructed and arranged as to provide for exceedingly rapid vibration through a very small amplitude.

The magnitude of various factors such as voltage, amperage, air pressure and rate of wire feed are, of course, necessarily varied in accordance with the nature of the Work being done, the type of metal `being used and other conditions which change from time to time. The rate of feed is of course determined by the rate at which the metal is removed from the end I3 of the wire I2 and deposited upon the surface. Preferably I use current having a voltage in the range of 1.5 to volts and an amperage in the range of about 280 to about 1000 amperes, 3 volts and 600 amperes being typical values. The air pressure may vary from to 80 pounds per square inch, however, I prefer to use, under normal conditions, about to 40 pounds per square inch. The metal Wire or rod used may vary in diameter but'0.125 and 0.091 (11 gauge B. & S.) are especially suitable for ordinary use.

As an example of the use of my improved method and apparatus, from time to time in metal working a worker will accidentally grind down a surface too far or will disiigure an intended flat surface by indent-ing the same with the end of a drill or by compression. If it is desired to build up this surface or to fill in the indentation to the level of the remainder of the surface, apparatus such as that shown in the drawings may be supplied with the desired metal, the work piece may be connected in the electrical Icircuit and then the rod feed valve 31 regulated. When the air has been turned on, the apparatus is then ready for use and the operator places the end I3 of the wire l2 against the Work at the f point at which it is desired to build up the surface thereof. The wire end I3 is disposed at an angle to the work as shown in Figure l. The operator then, either freehand or by means of the lathe setup shown in the drawing, traverses the point of a r-od across the portion of the surface to be built up until it is slightly over-sized, whereupon a simple grinding or machining operation results in the provision o-f the desired surface free from pits which, as indicated above. is as dense as or denser than the original body of metal. During such an operation it is` desirable that the metal extend about one and one-quarter inches from the nozzle l1 of the mechanism M.

Thus it will be seen that with the end I3 of the wire protruding about the amount indicated and if the angle of the -wire is at about thirty degrees to the surface being Worked upon, the ilexibility of the rod will result in the desired degree of vibration whereupon a build-up of metal occurs.

If, upon positioning the Wire vertical to the surface, amperage is out down it is found that a very efficient forging action takes place. This is believed to be because there is suflcient current to render the deposited metal plastic while at the same time the combination of resistance heating, vibration and air flow results in a compression of the already deposited metal in a sense that it is forged or pressed against the work piece to increase the density thereof, to produce a more homogeneous layer and also to considerably iinish the surface of the deposited metal to smooth the same in readiness for a machining operation. Thus it will be seen that by proper regulation of the position of the tool and the amperage used, the novel combination I have provided affords a plurality of different operations, all of which contribute to the ultimate desired end, that is, the disposition of a thin, well bonded, dense, homogeneous layer of deposited metal upon the work piece. Of course it will be understood that the variation in rate of travel of they wire over the work pieces results in a variation in the rate of deposit whereby a mere dwell in this traversing movement will result in an accumulation of the desired deposit at a concentrated point. This principle is involved, for instance, in the .filling in of deep pits which have been made in the surface of the Work piece.

`From the foregoing it will be seen that by disposing the wire at a relatively acute angle to the work piece, and by impressing a relatively greater amperage through the parts, the operator accumulates a dense deposit upon the desired portion of the surface of the work piece. Thereafter, if the wire is directed at a vertical angle to the surface of the work and the amperage is somewhat reduced. the apparatus maintains successive parts of the deposited surface in a plastic or semi-plastic condition whereupon the combination of heat resistance, vibration and air action serve to forge the deposited metal to render the same more dense and to provide a relatively smooth uniform surface, Which condition is ideal for subsequent machining. This is possible because with my apparatus and method I do not obtain large puddles of molten material, but rather obtain a large number of minute, plastic deposits.

As indicated previously, it appears from investigation and experimentation that homogeneity and density of the deposited layer results from the elimination of voids in the deposited metal which is made up essentially of molten portions of the ends of the wire which have adhered to the surface being worked upon and then have been pulled away from the end of the wire by the vibrating action, this cycle being repeated with great rapidity to provide a very large number of adhered projections over the surface. These projections do not appear, however, to remain as such after the point of the wire has progressed to the next adjacent portion of the area of the work piece under the action of the vibrator, Rather, while still in molten condition these mounds or projections are forged by the air into a somewhat flattened, spread condition thereby to assume the character of fiat .layers rather than a plurality of projections. 1t is believed also that, governed by the rapidity of the vibration and the control of the traversing speed over the surface of the work piece, these initial projections are disposed close enough to one another so that when flattened o-r forged by the air into a dense condition they spread into one another to provide a continuous layer o-f deposited metal. Thus it will be seen that with the use of my novel method and apparatus embodying this `combination of factors above set forth, I am enabled to eliminate overhanging edges on the projections which define spaces that will be so protected by the overhanging edges that they will not be filled by a subsequent cycle of operation such as that described above. Furthermore, I am enabled to avoid the so-called mushrooming of the metal which comp-rises the disposition of overhanging globules at the ends of pointlilre projections during a subsequent treatment of a surface by my apparatus. This eliminates the further formation of spaces or pits in the layer.

1t will be understood, of course, that the concept set forth above actually occurs, in the practice of my method, on a very minute scale and with extremely rapid sequence, and accordingly other concepts than those set forth above may also be instrumental in affording the density and homogeneity of the metal deposited by my method and apparatus.

As indicated previously, by the use of my method and apparatus I not only obtain the secure bond of an extremely dense layer of metal against the surface of the work piece but also I have eliminated the production of high temperatures during the deposition of the metal whereby many well known detrimental effects are avoided. This reduced temperature of the entire process is brought about by the reduction in the arcing action and also by the action of the cold air stream upon the portion of the surface being treated. Additionally, the converging air stream which flows down the wire portion I3 impinges upon the deposited metal simultaneously with its deposition on the work piece to forge it in a manner described above.

From the foregoing it will be seen that I have provided herein a novel method and apparatus whereby there may be deposited upon a work piece constructed from conducting material, a thin, homogeneous, dense, well bonded layer of electrode metal which layer is admirably adapted to a subsequent machining operation to give a new surface which is, in effect, an integral part of the body of the article to which it has been added.

T. claim as follows:

l. A method of depositing a layer of metal on a fusible electrically conductive surface of a Work piece from a fusible consumable electrode, said method comprising the steps of traversing said electrode across said surface while holding the electrode against the same, passing electric current through said surface and electrode under conditions of resistance heating to bond metal deposited from said electrode to said surface, and at the same time blowing a gas non-combustible with air against the metal being deposited, and simultaneously rapidly vibrating said electrode through a small amplitude toward and away from said workpiece so as to make and break Contact between said electrode and surface and to forge the already deposited metal against the workpiece whereby the deposited metal is worked to compact the saine into a dense layer.

2. An apparatus for depositing a layer of metal on a fusible electrically conductive surface from a fusible consumable electrode, said apparatus comprising means to support an electrode so that the tip thereof can be held against the surface of a workpiece, said supporting means including a member having a channel through which said electrode extends, means to supply an electromotive force of the proper voltage and amperage for effecting resistance heating, means for connecting up said electrode as one terminal of said electromotive force, means for connecting up said surface as the other terminal of said electromotive force thereby to bond metal deposited from said electrode to said surface under conditions of resistance heating, said member having another through channel including a portion substantially parallel to the electrode channel and terminating at the same surface of said member as and near the termination of the electrode channel, means to supply a gas non-combustible with air to the second channel whereby said gas is blown against said surface in the region Where it is contacted by said electrode, and means for rapidly vibrating said electrode through a small amplitude toward and away from said surface so as to make and break contact between said electrode and surface and to forge the already deposited metal against the workpiece whereby the deposited metal is worked to compact the same into a dense layer.

HARALD L. LINDBLAD.

REFERENCES CITED The following references are of record in the iile of this patent:

TNITED STATES PATENTS OTHER. REFERENCES Construction Materials, Sept. 1942, "page 53.

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