US1998496A

US1998496A - Process of surface plating of metals with alloys

Info

Publication number: US1998496A
Application number: US481160A
Authority: US
Inventors: Fiedler Marcell
Original assignee: Individual
Current assignee: Individual
Priority date: 1929-04-09
Filing date: 1930-09-11
Publication date: 1935-04-23
Anticipated expiration: 1952-04-23

Description

April 23, 1935. FlEDLER PROCESS OF SURFACE PLATING OF METALS WITH ALLOYS \w w 5 Q? QN ---nnn m QN sw i -F ATTORNEYS Patented Apr. 23, 1935 UNITED STATES PROCESS OF SURFACE PLATING OF METALS WITH ALLOYS Marcell nearer, Bound Brook, N. J.

Application September 11, 1930, Serial No. 481,160

In Canada April 9, 1929 11 Claims.

This invention relates to surface plating or coating of one metal or alloy upon another and has for its object, more particularly, the process by which said coating is accomplished, and the l securing of a firmer bond between the base metal and the coating. The application is a continuation in part of my copending application Ser.

No. 274,162 filed April 30, 1928.

An object of the invention isthe production of a composite metal article having a base of one metal and a coating of another with an alloy or diffusion zone of the two metals therebetween and one of the advantages is the economy to be derived by my process in the saving of energy by the use of high frequency electric currents which produce an intense heat on the surface of the metal being coated, and also in the coating metal to cause rapid diffusion therebetween and so that the temper or other characteristics of the base metal are not detrimentally affected.

Another object of the invention is to apply the heat of high frequency induction currents to the meeting line of the base and coating metal so as to bring about a diffusion or alloying of the two metals, while limiting and controllingthe exposure of heat to thereby prevent adversely affecting the temper, tensile strength etc., of the base 'metal.

A still further object is to produce a surface plating or coating of an alloy of a high chemical, and mechanical, quality upon a base metal of lower quality, thereby greatly improving the life and usefulness of the base metal and at the same time effecting considerable saving in the substitution of inexpensive material for the inner body portion of a high grade material. In some cases where the mechanical strength is important, we can have a base of cast iron or steel and cover it with chromium or nickel, for instance; we not only have the-skin of the metal more resistant to corrosion or chemicals, butwe have on the inside the original steel which is strong and cheap and is substantially unaffected by the heat treatment.

These and other objects will appear as I relate the process in details of which the following is a specification.

In the drawing which shows a diagrammatic form of embodiment of apparatus suitable for practicing my invention,

Figure 1 is a part sectional view of one form of furnace suitable for treating pipe tubing and bars according to my process.

Figure 2 is an enlarged or magnified diagrammatic cross section of a coated metal article before heat treatment.

Figure 3 is a view similar to Figure 2 after heat treatment.

The base metal to be coated or. plated is first 5 covered with another metal by spraying, dipping, plating or the like, preferably with one which will compose an alloy or eutectic or chemical compound with the base metal, and it is then treated in an electric induction furnace, the tem- 1o perature being raised to the required degree necessary to cause the metals to diffuse together at their meeting line.

It is a well known fact that the higher the frequency of the eddy currents induced in a body 15 of conducting material the more pronounced will be the skin' heating effect. This fact may be made use of in my process in which the greatest intensity of heat may be generated directly at the surfaces or interface of the base and coating 20 metal by using as high a frequency as permissible, causing the metals to fuse into an alloy at the meeting line of the base and coating metal without permitting penetration of the heat to the inside part or body part which is kept practically 25 cold, except at the surface or skin whereby the temper of the base or body metal remains substantially unaffected. The penetration of heat into the base or body part may be further limited by moving the pieces rapidly through the 30 zone of the heating coil or by artificially cooling the one side of the base or body part by a current of air, water, or other suitable cooling medium. However, in most instances the extremely high frequencies needed to produce such ex- 35 treme skin effect are not necessary. Frequencies of a lower order of magnitude, but high as compared with ordinary 60-cycle current, e. g. 960- cycles, may be used with equally satisfactory results. With frequencies of such lower order of 40 magnitude the heating is very rapid, and while the base may, and usually will, be heated throughout the exposures necessary are so short that the properties of the base are not detrimentally affected. Therefore for most purposes the skin effect of extremely high frequencies is not necessary in thepractice of this invention. In the drawing, I8 indicates a piece of pipe or tubing undergoing treatment. This pipe is preferably of a material of relatively high strength such as iron or steel but may be formed of copper, brass or any other suitable material. A coating l8a of chromium, nickel, cobalt, or other alloying material is formed on the surface of the tube I 8 by spraying, dipping, electroplating or the like to form a solid substantially uninterrupted coating giving a continuous mechanical as well as an uninterrupted electrical conducting wall, and the coated tube is passed through the coil 20 of a high frequency induction furnace. The coil 20 is preferably water cooled as indicated at 20b and the tube I8 is shielded by a quartz or other chamber 20a having end closures 20d which form a wiping fit with the tube [8 which permits the use of a neutral or deoxidizing atmosphere within the chamber 20a, if desired. Rolls 200 are provided for moving the tube l8 rapidly through the furnace, and telescoping air or water spray nozzles 2| may be provided to spray the inside of the tube with a cooling medium.

For example, a base metal of iron or steel coated with nickel or chromium by electroplating or dipping when subjected to an induction current of 1500 cycles for 4 seconds, the skin effect is sufficient to cause diffusion or alloying of the base and coating layer without softening or otherwise adversely affecting the mechanical properties of the entire article.

Figure 2 shows the base 18 and coating lBa before passing through the zone of the furnace in which the coating forms a substantially uniform line on the surface of the base. Figure 3 shows the same section after passing through the zone of the furnace in which it will be noted that the coating and base metal have diffused together along the meeting line [8b forming a strong interlocked bond which will prevent separation of the base and coating metal even under such severe conditions as are induced by repeated heat- -ing and cooling and which will protect the base from corrosion. At the same time it will be noted that the grain structure of the base has not been materially disturbed, and the temper and strength of the base has not been materially affected, due to the short time the metal is in the heating zone.

In treating a steel tube having an outside diameter of one (1) inch and a wall thickness of one-sixteenth g) inch, with a chromium plate 0.0002 inch in thickness in a furnace having a power input of 22-23 K. W. and a coil of five and one-half (5 /2) by one and five-eighths (1%) inches with a frequency of 30,000 cycles per second, the optimum diffusion or alloying is secured when the tube is fed through the coil at a rate of 0.4 to 0.55 inch per second. A 300 K. W. input and only 500 cycles per second will cause the same effect when the tube is passed through the coil of a speed of five (5) inches per second. The frequency may be lowered as the input is increased, the higher the frequency however, the higher the skin effect and the lower the degree of heating of the entire body portion. The speed at which the tube is passed through the furnace also limits the penetration of the heat into the body of the tube.

In order to make coated articles of desired composition, layers of the different metals may be placed on the base metal and fused. For instance, a cast iron base is first chromium plated then cobalt plated to produce a chromium-cobalt-iron alloy on the surface of the cast iron base.

It might be remarked that the coating is of a more uniform composition the thinner the layers of the covering are. In cases where the first metal applied is of a lower melting point than the base, for instance, zinc base plated with bismuth or cadmium and then copper plated on top,

will give a zinc-bismuth-copper alloy or zinccadmium copper alloy.

In case the applied covering metals and the base metal do not alloy readily, but one material only penetrates into the other one, then we use this process only to let one metal penetrate into the other one and we may heat treat it in any regular furnace to secure the desired alloying.

While it is preferable to use a high frequency alternating current to produce the skin heating of the metal, it is possible also to use an interrupted direct current in which the interruption is at a sufficiently high frequency. The process may be used for treating tubes, plates or irregularly shaped articles by shaping the coil in a circle, fiat spiral or the like to conform to the shape of the article and focus its induced currents on the surface thereof.

Various modifications and changes may be made in the specific examples and apparatus shown, which are intended only to illustrate and not limit my invention, without departing from the spirit of my invention, or the scope of the appended claims.

I claim:

1. The method of causing penetration or diffusion of one substance into a metal base which comprises heating the skin of said metal base to a diffusion temperature in the presence of the penetrating substance .by the use of an induced high frequency current without heating the entire body of said metal base or affecting its temper, while artificially cooling the one side of the metal base to limit penetration of the heat into the bodyof themetal base.

2. The method of causing diffusion of one metal into the surface of another metal while applying the heat to the meeting surface of the metals which comprises bringing the metals into contact and subjecting the meeting surface of the metals to the heat of a high frequency interrupted current in a furnace while moving the metals rapidly through the furnace to cause heating of the skin only of said metals and artificially cooling one side of said metals.

3. The method of forming a non-corrosive surface on a base metal tube which comprises coating the tube with a non-corrosive metal and passing the coated tube through the coil of a high frequency induction furnace to cause diffusion of the coating and base together atthe meeting line and artificially cooling the tube to limit penetration of the heat thereunto, the movement of the tube through the coil being such that no structural change occurs in any other part of the base.

4. A method of adherently bonding a coating metal to a metallic base, comprising providing said base with a coherent layer of the coating metal, subjecting the coated base to a high frequency electrical field and thereby heatng the coating and the underlying base by high frequency electric currents induced therein, and continuing such heating for such a time as to cause adherent bonding diffusion between the coating and the base. 7

5. A method of adherently bonding a chromium coating to a ferrous metal base, comprising providing said ferrous base with a coherent coating layer of chromium, subjecting the coated base to a high frequency electrical field and thereby heating the coating and the underlying base by high frequency electric currents induced therein, and continuing such heating for such a time as to cause adherent bonding diffusion between the chromium coating and the ferrous base.

6. A continuous method of adherently bonding a coating metal to a metallic base, comprising providing said base with a coherent layer of the coating metal, progressively subjecting the coated base to a high frequency electrical field and thereby locally and progressively, heating the coating and the underlying base by high frequency electric currents induced therein for such a time as to progressively cause adherent bonding diffusion between the coating and the base.

7. A method of adherently bonding a coating metal to a metallic base, comprising providing said base with a coherent layer of the coating metal, subjecting the coated base to a high frequency electrical field, regulating the electrical power input and frequency of said field and the time of exposure of the coated base to said field to rapidly heat the coating and the underlying base by high frequency electric currents induced therein, and continuing such heating for such a time as to cause rapid and adherent bonding diffusion between the coating and the base without adversely ailectlng the mechanical properties of the base.

8. A method of adherently alloying a coating metal to a metallic base, comprising providing said base with a coherent layer of the coating metal, subjecting the coated base to a high frequency electrical field and thereby heating the coating and the underlying base by high frequency electric currents induced therein, and continuing such heating for such a time as to cause alloying between the coating and the base.

9. A method of adherently alloying a chromium coating to a ferrous metal base, comprising providing said ferrous base with a coherent layer of chromium, subjecting the coated base to a high frequency electrical field and thereby heating the coating and the underlying base by high frequency electric currents induced therein, and continuing such heating for such a time as to cause alloying between the chromium coating and the base.

10. A method of adherently alloying a coating metal to a metallic base, comprising providing said base with a coherent layer of the coating metal, progressively subjecting the 'coated base to a high frequency electrical field and thereby locally and progressively heating the coating and the underlying base by high frequency electric currents induced therein for such a time as to cause alloying between the coating and the base.

11. A method of adherently alloying a coating metal to a metallic base, comprising providing said base with a coherent layer of the coating metal, subjecting the coated base to a high frequency electrical field, regulating the electrical power input and frequency of said field and the time of exposure of the coated base to said field to rapidly heat the coating and the underlying base by high frequency electric currents induced therein, and continuing such heating for such a time as to cause rapid alloying between the coating and the base without adversely affecting the mechanical properties of the base.

MARCEIL FIEDLER.