US 3695337 A
A process for manufacturing plated products of metals in which a piece of one metal has its surface to be plated coated with a substance which decomposes releasing volatile organic compounds which protect the surface from oxidation by the atmosphere, while a second metal is cast adjacent the surface whereby a plating with high bond characteristics is formed.
Description (OCR text may contain errors)
United States Patent H 1 3,695,337
Grand Oct. 3, 1972 [5 PROCESS FOR MANUFACTURING 2,094,538 9/ I937 lngersoll [64/ I00 PLATED PRODUCTS 2,29l .026 7/ I942 Chace 164/102 Inventor: Rene Grand, Unieux France HOlmqulSt I  Assignee: Compagnie des Atelliers et Forges de FQREIGN PATENTS OR APPLICATIONS la Loire (SI. Chamond, Firminy, St. 70 03 3 1965 C d u 164 55 Etienne .lmbuolmr), Paris ana a France Primary ExaminerR. Spencer Annear  Filed: Oct. 7, 1970 Attorney-Wenderoth, Lind 8L Ponack  Foreign Application Pnority Data A process for manufacturing plated products of metals in which a piece of one metal has its surface to be Oct. 10, 1969 France ..6934722 plated coated with a substance which decomposes  US. Cl .164] 100, 164/55 relea ing volatile organic compounds which protect  hit. Cl. ..B22d 19/08 th rf fr m oxidation by the atmosphere, while a  Field of Search ..l64/55, I00, 10], 102 second m tal i a t adjacent the surface whereby a plating with high bond characteristics is formed.  References Cited UNITED STATES PATENTS 17 Claims, 5 Drawing Figures 2,042,800 6/1936 Pike ..l64/l0l X II I l I v I Y 2 '1" 3 \E i 5 I n as Mr PAIENTEDnma m2 Fl (3. l
PROCESS FOR MANUFACTURING PLATED PRODUCTS I BACKGROUND OF THE INVENTION This invention relates to a new process for manufacturing plated products of metals such as steels, alloys or pure metals and more particularly but not exclusively forming a composite product from;
steels such as structural steel and tool steel with stainless steels or steels which are resistant to high or low temperatures;
steels such as structural steel and tool steel with pure metals;
steels such as structural steel and tool steel with alloys based on nickel, chromium, molybdenum and tungsten, for example alloys comprising various proportions of these elements.
stainless steels with pure metals and alloys as defined above.
Such composite products can be made from any combination of steels, alloys and pure metals, including pure metals bonded with one another.
The use of products made of stainless steels, heat-resistant or low temperature-resistant steels, alloys or pure metals, plated on structural steels or with one another, has developed considerably in recent years in all branches of industry (petrochemicals, chemicals, electronics. household goods).
Different plating techniques are at present used, depending upon the products to be produced (type dimension, shapes).
The two industrial methods which are generally used are:
a. Manufacture of a composite metal from at least two separate metal strips, previously mechanically prepared to remove oxides and foreign matter.
The composite metal is produced by rolling in a protective atmosphere. The strips are passed into furnaces at temperatures selected to give to the final composite product the desired properties. This process is thus very limited in its possibilities.
h. Manufacture of composite metal by hot rolling. The constituent elements are prepared as a sandwich, with the interposition, on the previously mechanically prepared plating faces, of a deposit of electrolytic iron or nickel, for the purpose of facilitating the phenomena of chemical diffusion and preventing any oxidation during the course of heating. Use is made of various assemblies, with or without the interposition of a protective gas.
The application of this process is very difficult and its success depends upon the precautions taken throughout the whole production process.
From the metallurgical aspect, this process involves permanent risk of local failure to bond. in addition carbon diffusions, especially in the case of plating stainless steels. may preclude the use of this process in certain cases of special corrosion resistance.
A product particularly one designed to resist corrosion at low temperatures or at high temperatures is very often a steel having a high content of inoxidisable elements and in particular has a surface which, during the heating operations, becomes covered with a continuous film, adherent and impermeable to oxides, which arrests the diffusion phenomena and thus compromises the adhesion of the plating metal.
SUMMARY OF THE INVENTION The present invention has as an object the production of plated products, the plating obtained having high bond characteristics capable of resisting low or high temperatures.
A further object is the production of plated products of a wide variety of dimensions not just those which can be rolled.
A further object is to provide a plating process which is easy to apply and economical of time and materials.
Accordingly the invention provides a process for the production of plated metal products in which a first metal piece has its surface coated with a layer of a substance, and a second metal is cast adjacent that surface, said substance being such that it decomposes very close to the liquid front, releasing volatile organic compounds which protect the first metal from oxidation by the atmosphere, and which ensure a good contact of the liquid metal with the cleaned surface of the first metal.
According to one particular embodiment of the in vention, the layer of substance is a polyfluorethene. This may be applied by spraying or brushing on, of an aqueous or alcholised dispersion of a polyfluorethene. or by any other means.
In one form the process starts with a metallic core, the surface of which has been previously prepared and coated with a polyfluorethene, this core is then arranged inside an ingot mould or other mould, and a plating metal is introduced into the remaining part of the mould.
In the absence of a layer of substance such as polyfluorethene the metallic base piece, during the course of the casting, would be raised to a high temperature such that it would progressively oxidize in the air. The oxide formed on its surface would constitute a barrier to the diffusion phenomena and would compromise the adhesion of the plating metal.
ln the practice of the present invention during the course of casting, the substance such as polyfluorethene becomes progressively pyrolised at the front of the liquid metal and emits gaseous vapors which protect the surface of the base piece from oxidation. In this manner the adhesion of the plating metal to the base piece is ensured under excellent conditions.
The polyfluorethenes (for example the polytetrafluorethylene or the polychlorotrifluorethylene or their derivatives) give satisfaction under these circumstances because they possess simultaneously the following characteristics; high chemical stability; :1 product which is non-plastifiable at high temperatures; a product which is non-thermo-hardening and non-thermoplastic (a gel at high temperature, this gel having high viscosity); absence of a true melting point; decomposition by pyrolysis, giving rise to fluorinated or chlorofl uorinated compositions.
An important consequence of these properties is that the product decomposes at the useful instant (and not before), very close to the liquid front, releasing volatile organic compounds which protect the solid piece from oxidation by the atmosphere and which ensure a good contact of the liquid metal onto the previously cleaned surface of the base piece.
In a general way the derivatives of ethylene, in which the hydrogen atoms are partially or wholly replaced by atoms of fluorine and/or chlorine, (e.g. su-
perchlorinated polyvinyl chloride), possess to a considerable extent the properties described above and may thus be suitable for protecting the metal surface effectively from oxidation.
If an ingot, and not a casing, is used as the base piece, the composite ingot thus produced can then be rolled in accordance with normal techniques and taking account of the restraints which are necessary in dealing with the particular materials involved in the composite product.
The casting of the plating metal is preferably effective at source. However, this casting may be made directly and, if necessary, by means of a ladle with one or more nozzles.
The base piece can be plated on one or both sides as desired, or two base pieces can each be plated on a single face simultaneously in the same mould. Such two pieces may be in contact at their faces which are not to be plated and which are separated by an anti-sticking product, such as chromium oxide for example, or be assembled by a peripheral weld preventing any penetration of liquid metal and preventing sticking of the surfaces in contact, or both be coated with an anti-stick product and welded peripherally.
The casting of the plating metal may be carried out under the protection of an inert gas, such as argon. For this purpose the jet of plating metal at its exit from the casting ladle is surrounded by such an inert atmosphere and/or the mould is placed under such atmosphere.
The principal advantages of the process according to the invention at least in its preferred embodiments are:
case of application;
substantial economies compared with methods previously used;
substantially perfect plating;
extension of the possibilities of the use and production of plated products, by virtue of the improved properties resulting from the elimination of any harmful contact and other pollution.
Polyfluorethene coatings, due to their particular properties, both physical and chemical, enable exceptional cleanliness of the contact surfaces to be achieved at the moment of casting, thus facilitating the normal commencement of the diffusion phenomena leading to the production ofa plating with high bond characteristics.
Ultrasonic inspection of products formed by the invention exhibited a substantially perfect bond between the base piece metal and the plating metal.
Transverse sections made with a blow-torch using powdered iron confirmed perfectly the ultrasonic examinations and the substantially complete absence of non-cohesion, even partial or local.
in order to make the invention more easily understood, there will now be described by way of nonrestrictive example, four methods of realization of the invention, reference being made to the accompanying drawings, in which:
FIG. 1 is a perspective view showing one form of vertically sectioned ingot mould in which a base piece is suspended before casting;
FIG. 2 is a view similar to alternative form of mould;
FIG. 3 is a view similar to that of FIG. I further form of mould;
FIG. 4 is a view similar to that of FIG. I, with two contiguous base pieces to be plated; and
that of FIG. I showing an showing a FIG. 5 illustrates, in vertical section, of forming a plated cast piece.
In all these examples a solid base piece of carbon structural steel is involved, which receives a plating of stainless steel cast at the source, or indeed these two items may be reversed. The arrangements of FIGS. 1 and 2 are for the plating of stainless steel on the two faces 2 and 3 of a bloom 4 of carbon steel. For this purpose, a start is made with a bloom 4 of carbon steel of dimensions 1.700 X 0.850 X 0.160 meters, these dimensions constituting only an example, which is carefully cleaned and, if it is not to be used immediately, has its surface protected from oxidation and any external pollution by a coating of a currently used protective product. At the last moment before plating this protective product is removed by a special solvent and the bloom is coated, by spraying or brushing its faces 2 and 3 with a layer of polyfluorethene arising, for example, from an aqueous or alcoholised dispersion. This coating is then subjected to some fritting by moderate heating for a short period. The bloom is then carefully introduced into the ingot mould 5, either suspended so as to leave underneath it a space sufficient for the arrival of the plating metal (FIG. 1) or placed on the bottom of the ingot mould if the arrival or the plating metal from the source takes place at the sides (FIG. 2). The plating metal arrives during the course of casting through the base of the mould as indicated by the arrows and occupies the space 1. The jet of stainless steel, at its exit from the casting ladle, is protected by an argon atmosphere.
The arrangement of FIG. 3 is for forming a stainless steel plating on a single face of a bloom of carbon steel. A bloom 6 of carbon steel is prepared as before, but the polyfluorethen is applied to only one face 7. The bloom is then introduced into an ingot mould 8 in such a way that the large side 9 of the bloom 6 and the base which are not to be plated are placed up against one wall and the base of the mould. Stainless steel is then introduced as indicated by the arrow to fill the cavity 10.
According to a variant the items are transposed, that is to say a bloom of stainless steel is prepared, and placed up against one wall of the ingot mould, after its working face has been coated with polyfluorethene, and carbon steel is cast, at source, into the remaining space.
The arrangement of FIG. 4 provides for effecting simultaneously two simple platings. For this purpose, two blooms H and 12 of stainless steel are placed back-to-back, an anti-stick layer 13 being placed between them. They are if necessary held in this position by a peripheral weld 14. The face 15 of each bloom which is to be plated is coated with the layer of polyfluorethene, and the whole is introduced into an ingot mould l6, either suspended, or placed on the bottom. Carbon steel is then cast at source into the space 17. Clearly the carbon steel and stainless steel can be interchanged as before.
The arrangement of H6. 5 is for producing a plated shaped casting. First a carbon steel casting 18 is produced to the desired size and shape with the omission at the faces which are to be plated of a thickness corresponding to the desired plating layer. The surface to be plated I9 is then coated as described above. Finally, the cast piece 18 is placed around a mould core 20 and the stainless steel is cast at source to occupy the space 21 left between the mould core and the piece.
another method The process of the invention is applicable to the manufacture of numerous composite products such as castings, wire, strip, plates and tubes, with single plating, or double plating, or plating limited to certain parts of the desired final product.
l. A process for the production of plated metal products comprising coating the clean surface to be plated of a first metal piece with a layer of a derivative of ethylene, in which the hydrogen atoms are replaced by atoms of the group comprising fluorine and chlorine and casting a second metal adjacent to said surface so that said layer decomposes close to the liquid front of said second metal releasing volatile organic compounds.
2. A process according to claim 1, in which said derivative is superchlorinated polyvinyl chloride.
3. A process according to claim I in which said derivative is a polyfluorethene.
4. A process according to claim 1 in which the layer of said derivative is applied in the form of a dispersion in liquid.
5. A process according to claim I in which the casting of said second metal is carried out by top casting.
6. A process according to claim I in which the casting of the second metal is carried out directly.
7. A process according to claim 1 in which the second metal exits from a casting ladle in a jet which is surrounded by an inert atmosphere.
8. A process according to claim I in which the first metal piece is placed in a mould into which the second metal is cast and the mould is placed in an inert atmosphere.
9. A process according to claim 8 in which the inert atmosphere is argon.
l0. A process according to claim 1, in which the plating is carried out on two faces of the first metal piece.
II. A process according to claim I in which the plating is carried out on a single face of the first metal piece.
12. A process according to claim 1 in which the plating is carried out on a single face of two first metal pieces simultaneously, the two pieces being in contact at their faces which are not to be plated and being separated by an anti-stick product.
13. A process according to claim 12, wherein said anti-stick product is chromium oxide.
14. A process according to claim 12, in which the pieces are welded peripherally at their faces which are not to be plated, the peripheral weld ensuring slight separation which prevents direct contact between these two faces, thus enabling the two pieces to be subsequently separated after plating.
15. A process according to claim 1 in which the first metal piece is placed in a mould having walls and a base defining an aperture and the second metal is introduced into the mould through the aperture to fill the space between the mould walls and the first piece.
16. A process for plating a cast piece which comprises coating the surface of said piece to be plated with an organic substance which decomposes by pyrolysis to release volatile non oxidizing compositions, and then casting the plating metal to occupy the space left between the mould and the piece.
17. A process for plating a cast piece defining a cavit which co rises coa in the surfaceof said iece to b e plated wiili an organic s ubstance Wl'llCl'l deco mposes by pyrolysis to release volatile non oxidizing compositions, placing a mould core in the cavity, and then casting the plating metal to occupy the space left between said piece and said mould core.