US3693582A

US3693582A - Apparatus for applying a metal coating to an elongated metal article

Info

Publication number: US3693582A
Application number: US10169A
Authority: US
Inventors: Leon Joseph Eugene Delcour; Dominique Thomas Franco Streel
Original assignee: Cockerill SA
Current assignee: Cockerill SA; Cockerill Ougree Providence et Esperance Longdoz
Priority date: 1969-02-24
Filing date: 1970-02-10
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: FR2031254A5; JPS4817695B1; DE2006866A1; DE2006866B2; NL7002193A; LU60206A1; GB1277375A; CH520784A; BE728876A

Abstract

An apparatus for applying a metallic coating to an elongated metal article. The article to be coated is transported through an enclosure with closure gates at the ends. A source of ionized metallic atoms is positioned around the article. Also within the enclosure is a tubular deflection screen at a potential which is of the same polarity as the ionized atoms. The deflector screen deflects back towards the article the ionized atoms produced by the source which do not strike the article when emitted by the source.

Description

United States Patent Delcour et al.

[ 1 Sept. 26, 1972 154] APPARATUS FOR APPLYING A METAL COATING TO AN ELONGATED METAL ARTICLE [72] Inventors: Leon Joseph Eugene Deleour, Liege; Dominique Thomas Francois Streel, I Cointe-Sclessin, both of Belgium [73] Assignee: Cockerill-Ougree-Providence Et Esperance-Longdoz, en abrege Cockil .stre n l Belgium [22] Filed: Feb. 10, 1970 [21] Appl.No.: 10,169

[30] Foreign Application Priority Data Feb. 24, 1969 Belgium ..42,121

[52] US. Cl ..118/49.5,.118/634 [51] Int. Cl ..C23c 13/12 [58] Field of Search ..1 18/48-495; 117/93.4 R, 107.1

[56] References Cited UNITED STATES PATENTS 1,710,747 4/1929 Smith "118/49 UX 2,437,606 3/1948 Kaufman 17/9344 X 2,994,618 8/1961 Landgraf "117/9344 3,000,752 9/1961 Jackson et a1. 17/9344 X 3,192,892 7/1965 Hanson et a1 ..l18/49.1 3,250,694 5/1966 Maissel et al.18/49.1 UX 3,324,825 6/l967 Brumfield ..1 18/49.5

3,361,591 1/1968 Dill et al. ..l 18/49 .l X 3,395,674 8/l968 Burham et a1. ..l18/49.l 3,432,335 3/1969 Schiller et al. ..l...1 17/107. 1 X

2,382,432 8/1940 McManus et al. ..1 18/49 X 2,206,509 7/1940 Lederer ..l l8/49 X 3,288,638 11/1966 Van Paassen et al..l l8/49.1 X 3,386,909 6/1968 Hough ..l 18149.5 X 2,621,624 12/1952 Chilowsky ..1 18/49 X 2,771,568 11/1956 Steigerwald ..1 18/49 X 3,556,048 1/1971 Frazer ..l l8/49.5

FOREIGN PATENTS OR APPLICATIONS 665,540 9/1938 Germany ..1 18/49 Primary Examiner-Morris Kaplan Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT An apparatus for applying a metallic coating to an elongated metal article. The article to be coated is transported through an enclosure with closure gates at the ends. A source of ionized metallic atoms is positioned around the article. Also within the enclosure is a tubular deflection screen at a potential which is of the same polarity as the ionized atoms. The deflector screen deflects back towards the article the ionized atoms produced by the source which do not strike the article when emitted by thesour e 7 v 1 1 Claims, 3 Drawing Figures APPARATUS FOR APPLYING A METAL COATING TO AN ELONGATED METAL ARTICLE This invention relates to apparatus for applying to an elongated metal article a metallic coating obtained by condensation of metallic atoms produced by evaporation under vacuum of a metal heated to a temperature above its vaporization point.

It is known to protect the surfaces of metallic articles against corrosion by agents to which they are exposed, for the purpose of extending their useful life; for exam ple, steel or articles made of steel may be protected against corrosion by means of various coatings using various methods.

At the present time, the apparatus most in demand have to be simple, reliable, economic and must provide uniform layers which are not very thick, adhere well and are resistant to corrosion.

One known apparatus provides for metallization under vacuum, including placing the articles to be coated in an enclosure where there is a vacuum of approximately -4 Torr, into which enclosure, there are introduced metallic vapors constituted by the atoms of the metal required to form the coating, these atoms being produced by evaporation of the metal heated to a temperature above its vaporization point so that the vapors formed condense on the article to be coated.

This apparatus has the advantages that the coating obtained is homogeneous and adhesive and can be composed of an alloy, and that the method makes it possible to avoid the formation of fragile layers at the interface between the article and the coating.

However, several disadvantages then became apparent, due to the fact that in the high vacuum provided, the atoms arrange themselves in all directions along trajectories which may be considered as rectilinear. The atoms coming from source thus are arranged in the manner of luminous rays, and only those which directly strike the face of the article to be coated, i.e. visible from the source, contribute to the formation of the coating, whereas all the others are lost and are deposited on adjacent parts of the apparatus, where they condense. The non-visible surfaces of the articles receive some lost atoms, but the coating thus formed is quite inadequate, necessitating one subsequent orientation of these surfaces towards the source of atoms.

As a result, there is a considerable loss of vaporized metal, resulting in a low yield and the need to present two faces of an article to be coated successively to the source of atoms. In particular, for the coating of sheet strips this requirement means the construction of a plant of great length, and the machine has to be stopped frequently.

Moreover, when it is a matter of treating objects such as wires which present a small surface to the source, the yield is particularly low.

The present invention aims at overcoming or reducing the effect of these disadvantages.

The present invention consists in an apparatus for applying to an elongated metal article, for example a steel article such as a strip or a wire, a coating obtained by condensation of the metallic atoms produced by evaporation under vacuum of a metal heated to a temperature above its vaporization point, wherein the said article is arranged vertically in an enclosure under a vacuum of 10'] to 10 5 Torr, a source of metallic atoms is arranged around the article and metallic atoms from the source having passed the article and thus not directly condensed on the article, are deflected back towards the article.

In this way, it is possible to recover atoms which have escaped condensation on the article to be coated and to redirect them towards the article after deflection on a screen. In this manner the yield of the coating operation is considerably increased, and thus the method is particularly suitable for certain metallic products such as strips, rods, wires, i.e. elements having one dimension much larger than the other two, which, in the specification which follows, will be called elongated metallic articles.

In the accompanying drawings:

FIG. 1 is a diagrammatic view of one form of apparatus constructed in accordance with the present invention,

FIG. 2 is a partial diagrammatic view in perspective of the apparatus of FIG. 1,

FIG. '3 is a view in perspective of a portion of a modified form of apparatus for coating wire.

In carrying the invention into effect according to one convenient mode by way of example, FIGS. 1 and 2 show an apparatus for applying a metallic coating to a strip of sheet, which includes an enclosure 1 arranged vertically, i.e. whose longitudinal axis is vertical, the two ends being closed by

closure gates

2 and 3. Vacuum pumps, which are not shown, are attached to the said enclosure 1 and create there a vacuum generally of approximately 101 to 10-5 Torr. In this enclosure, a metallic strip 4, for instance of steel, transported by

drive cylinders

5 and 6 over a vertical path from the bottom of the enclosure to the top. Two

crucibles

7 and 8 composed of refractory material are located one on each side of the strip 4, the free side of each crucible beingin a plane perpendicular to the strip 4. The crucibles contain a metal which by two

electron guns

9 and 10, is raised to a temperature which is higher than its vaporization point. The crucibles are supplied continuously with metal by means of a cone device, which is not shown. The

electron guns

9 and 10 which may be of a known type are provided with a deflection system effecting a deflection of on the electrons and a reciprocating sweeping device to cause the electron to pass alternately to each end of the crucibles, which ends are thus heated equally. In this manner the crucibles constitute a source of metallic atoms, which when emitted follow paths which are almost rectilinear, and some of them strike directly the two faces of the strip 4 where they condense and form a coating. The atoms which do not reach the strip directly, pass to one side of it and strike the internal surface 11a of a reflecting screen 11 forming a hood. This hood is brought to a temperature, called deflection temperature, by means of heating provided by a heating resistance 12 surrounding the hood and supplied from a source of current 13. The deflection temperature is selected in such a manner that the metallic atoms which strike the hood cannot condense there and are immediately deflected towards the strip 4 which is to be coated. Tests which have been carried out have shown that in general this temperature may be between seven-tenths and twelve-tenths of the value of the melting point of the coating metal. The best manner of operation in practice is to perform tests by subjecting the hood successively to various increasing temperatures from a value approximately equal to threequarters of the vaporization temperature of the metal, and to determine that which supplies the best yield.

Alternatively, deflector screen 1 1 may be heated in a totally different manner by passing an electrical current through it so that its own resistance brings about the heating. As a further alternative electron guns may be used, which may be the same guns for heating the crucibles, beams of electrons issuing from the guns being moved such that in turn they strike against the crucibles and the internal surface of the screen. Moreover, the heating of the screen by a particular means may even be omitted, since when the apparatus is operating, the crucibles heated by the electron guns emit thermal radiation sufficing in certain cases to heat surface with parabolic directrix.

Moreover, the hood 11 is connected by a circuit 14a to the positive pole of a source of current 14 and the metallic atoms emitted are subjected on issuing from the crucibles to the action of an ionization device 15 of a known type arranged immediately above the crucibles. Accordingly the atoms are transformed into positive metallic ions which by virtue of this device are repelled by the positive hood and returned to the strip 4 where they condense, which increases the yield. The' yield may be still further increased by connecting the strip 4 to the negative pole of a source of current, not shown. The value-of the potentials of the strip and of the hood depend in particular on the nature of the metal deposited and the operating conditions. Thus, for depositing nickel, it has been found that the strip should be at approximately 500V, the hood at approximately 100V and the vaporized nickel at earth potential.

Although this is not always necessary, in certain cases to ensure perfect adherence of the coating, the article may be heated to a temperature in general between one-fifth and-one-third of the melting point of the metal to be deposited. Thus, in FIG. 1, this heating of the strip 4 is obtained by a source of current 16 connected by conductors 17 to the

cylinders

5 and 6 driving the strip 4, which is thus heated by the Joule effect. The heating of the strip 4 may also be obtained by an electron gun 22 as shown in FIG. 2.

For the application of a metallic coating on a metallic wire, for instance of steel, use can be made of apparatus such as that partially illustrated in FIG. 3. In this case, the hood 18 forming the deflector screen has a cylindrical/conical shape and its opening 180 is directed downwardly. Following its axis, a wire 19 to be covered passes along toissue through the apex 18b, driven by a device not shown, analogous to the

cylinders

5 and 6. Two crucibles 20 of semi-toroidal shape surround the wire 19 and each is swept alternately first in one direction and then in the other by the electrons emitted by two electron guns 21 and deflected by a known device which is not shown. I

The apparatus of FIG. 3 also has an enclosure for the hood, a device for heating and polarizing the hood, a heating device for the wire, an ionization device for the metallic atoms, as in the apparatus shown in FIGS. 1 and 2 provided for coating a metallic strip.

The advantage of the apparatus is that it applies simultaneously a uniform coating on the two sides of an extended metallic product such as a strip, a wire or a section of metal. Moreover, the yield is'increased and there is far less clogging of the apparatus, with the result that there are far fewer stoppages for cleaning and production is increased. 1

What we claim is: r

1. An apparatus includingan enclosure for applying ametallic coating to an elongated metal article said apparatus comprising:

a. closure gates at each end of the enclosure;

b. transporting means for transporting said elongated metal article through the enclosure along a vertical P 0. source means for producing metallic atoms, the

source means being positioned around the elongated metal article in a plane normal to the path;

d. ionizing means for ionizing the atoms produced by said source means;

e. tubular deflector screen means, surrounding in part the article passing therethrough for deflecting back towards the elongated metal article the metallic atoms which have passed to the side of the elongated metal article and have not condensed thereon, wherein the deflector screen means is positioned above the source means;

f. a dc. current source having one pole connected to the deflector screen means for applying a potential to said screen means which is of the same polarity as the polarity of i said ionized atoms thereby enhancing the deflection by said screen means; and:

g. means for creating a vacuum of from 10-1 to 10'5 Torr within the enclosure.

2. Apparatus as claimed in claim 1,- wherein the deflector screen means is arranged to be heated.

3. Apparatus as claimed in claim 2, wherein the deflector screen means is raised to a temperature eq ual to at least to seven-tenths. of the temperature of vaporization of the metal producing the metallic atoms.

4. Apparatus as claimed in claim 1, wherein the deflector screen means is defined by the internal surface of a geometrical body with edges.

5. Apparatus as claimed in claim 1, wherein the a source means of metallic atoms comprises at least one crucible'containing the metal to be vaporized under, said apparatus further including an electron gun for vaporizing the metal.

9 Apparatus as claimed in claim 1 wherein the section in the horizontal plane. deflector screen means is defined by the internal sur- T e apparatus 88 Set forth n C aim 1 herein Said face of a body of revolution. tubular deflector screen means has a circular cross sec- 10. The apparatus as set forth in claim 1 wherein said m the horizontal P tubular deflector screen means has a rectangular cross 5

Claims

1. An apparatus including an enclosure for applying a metallic coating to an elongated metal article said apparatus comprising: a. closure gates at each end of the enclosure; b. transporting means for transporting said elongated metal article through the enclosure along a vertical path; c. source means for producing metallic atoms, the source means being positioned around the elongated metal article in a plane normal to the path; d. ionizing means for ionizing the atoms produced by said source means; e. tubular deflector screen means, surrounding in part the article passing therethrough for deflecting back towards the elongated metal article the metallic atoms which have passed to the side of the elongated metal article and have not condensed thereon, wherein the deflector screen means is positioned above the source means; f. a d.c. current source having one pole connected to the deflector screen means for applying a potential to said screen means which is of the same polarity as the polarity of said ionized atoms thereby enhancing the deflection by said screen means; and g. means for creating a vacuum of from 10 1 to 10 5 Torr within the enclosure.

2. Apparatus as claimed in claim 1, wherein the deflector screen means is arranged to be heated.

3. Apparatus as claimed in claim 2, wherein the deflector screen means is raised to a temperature equal to at least to seven-tenths of the temperature of vaporization of the metal producing the metallic atoms.

5. Apparatus as claimed in claim 1, wherein the source means of metallic atoms comprises at least one crucible containing the metal to be vaporized under, said apparatus further including an electron gun for vaporizing the metal.

6. Apparatus as claimed in claim 5, further including means for moving the stream of electrons issuing from the said electron gun in a to and fro movement.

7. Apparatus as claimed in claim 5, wherein the crucible containing the metal has the form of a ring.

8. Apparatus as claimed in claim 1, wherein the deflector screen means has a cylindrical/conical shape.

9. Apparatus as claimed in claim 1 wherein the deflector screen means is defined by the internal surface of a body of revolution.

10. The apparatus as set forth in claim 1 wherein said tubular deflector screen means has a rectangular cross section in the horizontal plane.

11. The apparatus as set forth in claim 1 wherein said tubular deflector screen means has a circular cross section in the horizontal plane.