US3474520A - Process for explosive bonding of metals - Google Patents

Description

Oct. 28, 1969 YU TAKIZAWA ET I 3,474,520

PROCESS FOR EXPLOSIVE BONDING OF METALS Original Filed March 2, 1965 2 Sheets-Sheet ll Il/z/l/l/l/rnl/z/z/z/zm1I/////////////////////////// Oct. 28, 1969 YU TAKIZAWA ET AL 3,474,520

PROCESS FOR EXPLQSIVE BONDING OF METALS Original Filed March 2, 1965 2 Sheets-Sheet 2 United States Patent PROCESS FOR EXPLOSIVE BONDING 0F METALS Yu Takizawa and Minoru Ikeda, Oita-shi, and Shoji Tojima, Nobeoka-shi, Japan, assignors to Asahi Kasei Kogyo Kabushiki Kaisha, Dojima Hamadori, Kita-ku,

Osaka, Japan, a corporation of Japan Continuation of application Ser. No. 436,544, Mar. 2,

1965. This application Nov. 20, 1967, Ser. No. 684,557 Claims priority, application Japan, Mar. 9, 1964, 39/12,818; Dec. 8, 1964, 39/158,683 Int. Cl. B23k 31/02 US. Cl. 29-470.1 9 Claims ABSTRACT OF THE DISCLOSURE A thin cladding metal layer is bonded on a metal base by adhering the cladding layer to a supporting plate, supporting the resulting composite plate with the cladding layer spaced from, facing and in substantially parallel relationship to the base, placing a detonating explosive on the exposed surface of the supporting plate, and initiating the explosive.

This application is a continuation of my application Ser. No. 436,544, filed Mar. 2, 1965, now abandoned.

The present invention relates to a novel process for bonding together two or more metals by explosive pressure to form a multilayered body and in particular for explosive bonding of a thin layer of a metal to a surface of a base metal and to novel articles of manufacture which are produced by this process.

One of the methods for bonding together two metals to fornta composite metal is the-so-called explosive bonding method which makes use of the blast force of a detonating explosive. In this process, two metal plates to be bonded together are spaced parallel or somewhat inclined to each other and an explosive layer is provided on one or both of the outer surfaces. Initiation of the explosive drives both plates into high-speed mutual collision, with the result that the two metals are bonded to each other. This is said to be due to the fact that both metals are liquefied and fused together at the impact point or that a jet produced out of the oxidized surface layers of both metals activates the surface layers, whose atomic attraction serves for bonding of the plates.

In explosive bonding, placing an explosive in direct contact with a metal may cause explosion shock to damage the metal surface, so that a layer of buffer material such as rubber sheet or water is provided between the explosive and the metal.

An advantage of the explosive bonding process as mentioned above is to make it possible to obtain a clad metal which is stronger in bonding force and more difficult to separate than the metallic composites produced by conventional plating methods, rolling process, and so forth. Nevertheless, the prior explosive bonding process has such a disadvantage as the application of so thin a metal sheet as, for example, less than 100 microns and especially below 25 microns is not practical in the following respect:

Namely, for said explosive bonding of metals, it is necessary to provide some space between two metals, and the space must be kept by placing granular supports between b'oth metal sheets, or shaping a metal sheet itself to have a surface with small projections, or holding the surrounding border of the metal sheet by means of adequate supports. In case, however, the thickness of the metal layer with which a base metal is to be clad, or cladding metal layer, is thinner than said space necessary for the bonding, protrusions due to supports take place on the resulting clad system, impairing the quality of the product, and there may be even the cases in which cracks occur at the supported positions. Moreover, in any of said supporting manners, the stiffness of the cladding metal is utilized to maintain the space, while the stiffness is smaller the thinner the metal sheet, so that, as the metal thickness lessens, the number of supports must be increased accordingly, thus making it impossible to obtain practical composite articles. Besides, in the course of bonding, both metals are liquefied where they collide with each other, and the surfaces turn into a liquid stream; therefore a thin cladding metal sheet is blown off with the jet because of the small strength of the whole Sheet, with the frequent result that the metal sheet has no original shape left, and this fact also constitutes an obstacle to the practical application of said process with a very thin cladding metal.

The conventional methods for coating a metal surface with the thin layer of another metal are such as hot dip coating, osmotic plating, electroplating, vacuum plating, and metal spraying. However, in the case of employment of these processes for metal coating, it has been generally necessary to perform specially careful surface finishing and also to make the operation with care in order to obtain satisfactory results. In the case of some combinations of metals, however, any cautious pretreatment and deliberate operation fail to produce a coating having a strength necessary and sufficient for practical use. For example, a composite metal formed by plating a noble metal such as platinum, iridium, gold, or silver with an anticorrosion metal such as titanium, tantalum, or zirconium is easily separable. Because of this defect, the plated metal assembly, when left as it is, is not practical. Hence, it has been tried, for increase of its adherence, to alloy the bonding surface zone after the plating by heat treatment or the like, but even this is not sufiicient, and

the resulting composite cannot withstand bending and other machining works.

An object of this invention is to provide an effective process for bonding an extremely thin layer of cladding metal to a surface of a base metal, which bonding has so far been impossible to perform.

Another object of this invention is to provide a composite multilayered system by simultaneous bonding of two extremely thin layers onto both surfaces of a base metal.

A still further object of this invention is the provision of clad metal systems wherein the cladding layer is nonpervious, uniform, and adherent, by a method that is convenient and economical.

A still further object of the invention is to provide unique clad assemblies from metals which heretofore could not be bonded together.

As the result of extensive study, the inventors have now found that the above described objects are accomplished completely by such a method as comprises adhering a thin layer of cladding metal to a surface of a supporting plate, supporting the thin layer parallel or slightly slanting to a surface of a metal to be clad (a base metal), said thin layer being spaced from the surface of said base metal, placing on the surface of said supporting plate or outer surface of said base metal a suitable detonating explosive and thereafter initiating said explosive layer.

The process embodying the present invention is better than the conventional explosive bonding process in the respect that such an extremely thin layer of cladding metal as below 25 microns in thickness in the state of being backed up by a supporting plate is to be bonded onto a base metal, the bonding thus improved being free from the aforesaid defects which arise along with the thinning of the layer of cladding metal.

In this invention, the means for adhering a thin layer of cladding metal to a supporting plate may be chosen static force can be utilized, or else plating is employable.

For the plating, various conventional methods are alternatively employable. No matter what plating method may be employed, it is important, when the process is to be applied to this invention, to provide a pretreatment for exfoliation to the surface of the base metal, except the case where the thin layer deposited by plating may be easily peeled off from the surface of the base metal; for example, where the base metal is titanium, tantalum, zirconium, or the like and the thin layer is a platinum group metal. As the pretreating method for peeling off the thin layer, any suitable one of various known processes may be employed.

In most cases, the supporting plate is torn off from the thin layer of cladding metal by the shock at the time of explosive bonding; however, in case the supporting plate does not come olf the thin layer after the end of explosion, and adequate means, such as dipping the laminate in a solvent that solves the binder used, or heat treatment, may be employed at will.

The supporting plate of this invention may be composed of one or more of the following materials: plates of metals such as any kind of steel (e.g., alloyed steel, special steel, mild steel, carbon steel, stainless steel), nonferrous metals (e.g., Cu, Al, Ni, Ti, Ta, Zr), and nonferrous alloys (e.g., Duralumin, brass, bronze); plates made of natural vegetable materials such as wood, veneer, ebonite, and fiberboard; and plates of synthetic fibers such as Bakelite, hard polyvinyl chloride, and acrylic resin. In short, any material will do in so far as it is more rigid than the thin layer of cladding metal, tough to some exexplosive to be consumed. It has been observed in the case of this invention that, with the separation below 0.5 mm., the metal layers are seldom bonded together. The maximum spacing allowable is about 5 mm. In case this value is exceeded, the thin metal layers may be broken at the time of detonation, with no smooth bond surface obtained. The practically optimum space is 0.8 to 2 mm.

The detonating explosive to be used may be almost any of common industrial explosives commercially available. And gelatine dynamites are to be used after being formed in plate so that the weight per unit area may meet the required value, while, as to powdery explosives such as ammonium nitrate dynamite and carlit, first the other materials needed for the bonding are arranged as specified, and then the explosive to be used is measured as much as required, mounted, and smoothed so as to be uniform in thickness and density, and thereafter initiated.

The explosives which contain nitroglycerin, such as dynamite, have a fault that the operator suffers from headache owing to the vapor; therefore, penthrite may also be used singly or mixed with ammonium nitrate. In this case, however, the content of penthrite should at least be 10% or more; otherwise, the explosive property is bad. The content ranging from 30% to 70% is practically suitable. Besides, for oxygen balancing, penthrite may be mixed with starch, wood meal or a similar combustible substance in addition to ammonium nitrate, with the result that the explosive force increases. Furthermore, the mixing of water by 1.5 to 3.5% of the whole weight lowers the density of the explosive, improving the explosive property and also facilitating the handling of the explosive.

Some examples of the compositions of industrial explosives which are applicable to this invention are shown tent, and safe from breakdown due to shock of detonain the following table.

COMPOSITION OF INDUSTRIAL EXPLOSIVE Starch,

wood Nitro Heavy Wood Designation of explosive N G NC KN 0 NH-iNOa meal NaCl compound NH4C1O4 oil FeSi meal No. 1 dynamite 48-52 N 0. 2 dynamite 34-36 No. 3 dynarn1te-... 29-31 N o. 4 dynam1te 33-37 N o. 5 dynamite 10-15 Ammonium nitrate dynamite 7-9 Ammonium nitrate explosive- Black Carlit;

N G Nitroglycerin. NC =Nitroeellulose.

N itro compound, dinitronaphthalene, dinltrotoluene, trlnitrotoluene, etc.

tion. However, highly elastic materials such as natural rubber and synthetic rubber, foamed substances like polyurethane foam and polystylene foam, and materials which are essentially britttle to physical shock, such as cement and gypsum board, are not suitable.

Of course, the supporting plate to be used in the present invention may be composed of one or more layers of one or more kinds of materials. It is also a matter of course that an adequate protecting layer like rubber plate may be provided between explosive layer and base metal in order to prevent the metal from being damaged by explosive shock.

The thickness of the supporting plate has only to have a value that ensures a rigidity necessary and sufiicient for keeping the cladding layer to be supported in the form of a flat plate, and accordingly varies depending upon the material of the supporting plate employed. However, in any of usual cases, a thickness of about 0.5 to 10 mm. is used, and especially a thickness of 1 to 3 mm. is practically optimum.

In the present invention, the metal layers must be spaced at least 0.5 mm. and supported parallel to each other. But the metal layers facing to each other at an intersectional angle of about one degree or less are permissible. The narrower the space, the harder the bonding usually, and accordingly the more is the quantity of the For more complete understanding of the invention, reference is now made to the attached drawings which represent cross-sectional views of assemblies which may be used to practice the invention;

FIGURE 1 shows a side elevational view partly in cross section of an assembly in which a thin metal layer is to be explosively bonded to a base metal.

FIGURE 2 is a side elevational view partly in cross section showing an assembly in which a thin metal layer plated on a metal plate is to be explosively bonded to a base metal.

FIGURE 3 is a side elevational view partly in cross section showing an assembly in which either surface of a base metal is to be clad with a thin metal layer at the same time.

FIGURE 4 is a side elevational view partly in cross section of an assembly in which two base metals are to be simultaneously clad, on one surface of each with a thin metal layer.

Like reference numerals designate corresponding parts in all the figures of the drawings.

In FIGURE 1, numeral 1 indicates a thin metal layer (hereunder referred to mainly as cladding layer), to which a base metal 2 is to be clad. 3 denotes a binder to adhere the cladding layer 1 to a supporting plate 4. 5 represents supports to provide a space between cladding layer 1 and base metal 2. 6 is a detonating explosive. 7 is a detonator. 8 indicates a foundation made of, e.g., steel plate. After all of them have been arranged as shown in the figure, the detonating explosive is initiated for explosive bonding of cladding layer 1 to base metal 2. Thus, the cladding layer is shifted from the surface of the supporting plate to the surface of the base metal.

FIGURE 2 shows a process for shifting a cladding layer to a base metal from a supporting plate which is plated with the cladding layer. The bonding force by plating is weak, permitting easy exfoliation, while the bonding force by explosive bonding is very strong. Hence, a cladding layer 1 is first deposited, by a conventional plating method, onto a proper supporting plate 4 which may be a metallic or nonmetallic plate, and then, together with the supporting plate 4, explosively attached to a base metal 2, the resulting assembly being a trilayered composite plate having the deposited cladding layer in the middle. This sandwiched layer is more strongly bonded to the base metal '2 than to the supporting plate 4, so that, by tearing off the assembly, the intermediate cladding layer leaves the supporting plate, and thus the base metal 2 is clad with the thin metal layer 1, that is, the intended product is obtained. In this figure, supporting plate 4 plated with claddinglayer 1 is placed on a base block 8, and base metal 2 is supported above the cladding layer 1 deposited on supporting plate 4 by means of supports 5. A detonating explosive 6 is located on base metal 2 and to be initiated by an electric detonator for the bonding intended.

FIGURE 3 represents an assembly in which both surfaces of a base metal are about to be simultaneously clad with a thin metal layer each. The assembly will be hereunder explained more in detail. In the figure, 1 and 1 indicate layers, and 2 is a base metal to be clad with thin metal layers 1 and 1. 4 and 4 denote supporting plates plated with cladding layers 1 and 1'. 5 and 5 represent supports which provide adequate spaces d and d between base metal 2 and deposited cladding layers 1 and 1. Numerals 5, 6, 7, and 7' refer to a detonating explosive, an electric detonator, a lead-in wire, and a foundation block, respectively. After the whole assembly has been set as shown, explosive bonding is carried out by initiating the explosive.

The resulting composite is a S-Iayered assembly of base metal 2, cladding layers 1 and 1, and supporting plate 4 and -4', with the base metal sandwiched by the cladding layers. Since the bonding force by plating is not stronger than that by explosive bonding, the cladding layers are more strongly attached to base metal 2 than to supporting plates 4 and 4. Therefore, by ripping the supporting plates 4 and 4 off from the base metal 2, the cladding layers are separated from the supporting plates 4 and 4-, and base metal 2 clad with thin metal layers 1 and 1 are produced as intended.

FIGURE 4 illustrates a system for manufacturing in one bonding operation two composite plates each having one surface clad with a thin metal layer. Numerals 1 and 1' denote cladding layer, and 2 and 2' represent base metals to be coated with metal layers 1 and 1. 4 indicates a supporting plate both surfaces of which are plated with cladding layers 1 and 1. Supports 5 and 5' provide adequate separations d and d. 6, 7, 7' and 8 indicate respectively a detonating explosive, an electric detonator, a lead-in wire, and a foundation. After the system has been set up as shown in the figure, the detonating explosive is initiated for explosive bonding.

The resulting composite plate is an assembly of supporting plate 4, cladding layers 1 and 1' and base metals 2 and 2', the supporting plate being interposed between cladding layers 1 and 1'. Since the bonding force by plating is weaker than that by explosive bonding, the cladding layers are more firmly bonded to the base metals than to the supporting plate. Hence, by trying to separate base metals 2 and 2 from supporting plate 4,

6 the plate 4 is stripped of cladding layers 1 and 1, and thus two base metals each clad with a thin metal layer are simultaneously produced as intended.

In this invention, a thin metal layer is firmly attached to a rigid supporting plate to form an apparently stiff. sheet. Consequently, not only the thin metal layer is easy to handle, but also, when supports are in use for maintaining a space, the number of the supports can be lessened; besides, without supports provided between cladding layer and base material, the cladding layer can be subjected to explosive bonding just as a rigid cladding metal layer. Furthermore, the thin metal layer, reinforced by the supporting plate, may withstand a jetting arising at the time of explosive bonding.

The process embodying the present invention further makes it possible to plate, for example, titanium with platinum firmly, so that economically ideal electrode materials such as the electrode of titanium coated with platinum are obtainable, and thus the process has a great industrial value.

EXAMPLE 1 This example was performed in accordance with the process shown in FIGURE 1.

A molybdenum sheet 1, 0.2 mm, thick, mm. wide and 300 mm. long, was stuck to a plate of mild steel (supporting plate) 4, 2.3 mm. thick, mm. wide and 350 mm. long, in substantially concentric relationship to each other by means of an epoxide resin paste 3. On the other hand, a mild steel plate 2, 5 mm. thick, 100 mm. wide and 300 mm. long was placed on a base block 8, Supports 5 mounted on the base 8 were used to bear mild steel plate 4 at the four corners so that the upper surface of mild steel plate 2 and the lower surface of molybdenum sheet 1 were spaced in parallel with each other by a distance of 1 mm. Almost all the outer surface of the supporting plate of mild steel 4 was covered with a dynamite 6 formed into a 10 mm. thick plate, which was subsequently initiated by means of an electric detonator 7 attached to one side of the rectangular dynamite plate.

After detonation of the dynamite, molybdenum plate 1 and mild steel plate 2 were found to be firmly bonded together into a flat and smooth composite metal plate of 5.2 mm. thickness. In addition, the supporting plate of mild steel 4 was separated after the bonding, and the resin left on the composite metal plate was removed by heating the whole composite assembly at 300 C.

EXAMPLE 2 The process shown in FIGURE 1 was applied to this example.

A IO-micron-thick platinum foil was stuck to a supporting plate of hard polyvinyl chloride, 3, mm. thick, 300 mm. wide and 600 mm. long, with epoxy resin, and the assembly was mounted, platinum-side up, on a foundation slab made of mild steel.

Above the surface of the platinum foil was placed almost concentrically a titanium plate (K850), 1 mm. thick and 350 mm. by 650 mm. in such a way as the titanium plate form an angle of one degree to the platinum foil with a space distance d of 1 mm. at the closest side. The titanium plate was supported at the four corners by support positioned on the foundation.

Then, almost all the upper surface of the titanium plate was covered with an 8 mm. thick dynamite No. 3 plate, which was subsequently initiated by an electric detonator attached to the side of the dynamite plate which was closest to the base slab.

Following the detonation of the dynamite plate, only the platinum foil was completely bonded to the titanium plate in concentrical relationship to the latter, to form a composite plate.

An electrode was made of this composite plate and tested on the same electrolytic conditions as an electrode made by the conventional process for coating titanium with platinum under the best conditions of the prior process. Even after the lapse of twice the time having passed till the occurrence of platinum separation to the electrode made by the conventional process, no exfoliation occurred to the electrode of this composite, which still kept a good electrolysis.

EXAMPLE 3 The example was accomplished by the method illustrated in FIGURE 2. A stainless plate (SUS 27) 4, 1 mm. thick and 300 mm. by 600 mm. was electrically plated, on one surface, with a S-micron-thick platinum layer 1, by employing the stainless plate as the cathode and platinum as the anode with a liquid containing platinum diaminonitrite, Pt(NH (NO of 16.5 grams per liter, ammonium nitrate of 100 grams per liter, sodium nitrate of 10 grams per liter, and 28% ammonia water of 50 grams per liter, and by feeding electric current for 30 minutes under the conditions of the liquid temperature being 98% C. and the current density 2.5 amperes per square decimeter.

As shown in FIGURE 2, the above-mentioned stainless plate 4 was placed, with the electrically deposited platinum layer 1 facing upward, on a foundation of mild steeel plate 8. Above the platinum layer and spaced therefrom a distance d of 1 mm. was positioned a titanium plate (K850) 2, 2 mm. thick and 320 mm. by 620 mm., in parallel with each other by supports 5. An explosive 6 (dynamite No. 3) formed into an 8 mm. thick plate was placed almost all over the surface of the titanium plate 2, and initiated at one side by an electric detonator 7. The result was that the platinum layer 1 was separated from the stainless plate 4 and bonded to the titanium plate 2, thus forming with the latter a composite metal plate.

EXAMPLE 4 The process employed for this example was that shown in FIGURE 3.

Two titanium plates 4 and 4', each being 1 mm. in thickness, 150 mm. in width and 250 mm. in length, were electrically plated with platinum layers 1 and 1, each being about 5 microns thick, by employing each of the titanium plates as the cathode and platinum as the anode with a liquid containing platinum diaminonitrite,

of 16.5 grams per liter, ammonium nitrate of 100 grams per liter, sodium nitrate of grams per liter, and 28% ammonium water of 50 grams per liter, and by supplying electric current for 30 minutes under the conditions of the liquid temperature of 98 C. and the current density of 2.5 amperes per square decimeter. Then, the mm. wide surrounding portion of either of the platinum layers 1 and 1' deposited on the titanium plates 4 and 4' was peeled off with a knife so that the remaining platinum layer was surrounded by the exposed titanium margin.

The titanium plates plated with platinum layers and thus exposed were positioned, with spaces d and d, respectively, 1 mm. apart from a zirconium plate 2, 1 mm. thick and 150 mm. by 250 mm, in parallel with one another and with the platinum layers facing to the zirconium plate. The spaces d and d were maintained by supports 5 and 5', which were in contact with the exposed titanium margins surrounding the platinum layer. The whole assembly was set on a fiberboard base block 8. The topmost titanium plate 4 was covered, almost all over the surface, with an explosive 6 (dynamite No. 3) formed into an 8 mm. thick plate, which was subsequently initiated by means of an electric detonator 7 attached to one side of the dynamite plate.

After detonation of the dynamite, the platinum layers 1 and 1' were separated from the surface of the titanium plates 4 and 4', and the zirconium plate 2 clad on both surfaces with the platinum layers was obtained,

8 EXAMPLE 5 A 0.5 mm. and 50 mm. by 50 mm. titanium plate electroplated with a S-micron-thick platinum layer by the same process as Example 3 was placed, platinum-side up, on a 5 mm. thick and 250 mm. by 250 mm. fiberboard in the center. Besides, a 1 mm. thick and 200 mm. by 200 mm. titanium plate was stuck, by means of a doubleside adhesive tape, to the central portion of a surface of a 6 mm. thick and 250 mm. by 250 mm. fiberboard made by pasting together two 3 mm. thick fiberboards. Next, the fiberboard was supported, titanium-side down, just above and parallel to the platinum layer with the standoff distance of one millimeter, by supports at the four corners of the upper and lower fiberboards which were in complete dimensional alignment.

All over the upper surface of the top fiberboard was loaded an explosive powder composed of 40% ammonium nitrate and 60% PETN, at a weight distribution of 40 grams per square decimeter, and the explosive was initiated at one side by means of an electric detonator. In addition, cardboard was used to frame the powdery explosive along each side of the fiberboard so that the powder might not spill.

After the detonation of the explosive, the 1 mm. thick and 200 mm. by 200 mm. titanium plate was found to be firmly clad, on the central area of one surface, with the S-micron-thick and 50 mm. by 50 mm. platinum layer, while the 0.5 mm. thick and 50 mm. by 50 mm. titanium plate which had been electroplated with the platinum layer was left alone.

EXAMPLE 6 The method shown in FIGURE 4 was employed.

A titanium plate 4, 0.5 mm. thick, 150 mm. wide, and 250 mm. long, was electrically plated, on both surfaces, with platinum layers 1 and 1, each being about 5 microns in thickness. The titanium was used as the cathode, and platinum as the anode, and a liquid composition of platinum diaminonitrite, Pt(NH (NO of 16.5 grams per liter, ammonium nitrate of grams per liter, sodium nitrite of 10 grams per liter, and 28% ammonium water of 50 grams per liter was employed. Electricity was supplied for 30 minutes with the liquid temperature of 98 degrees centigrade and. the current density of 2.5 amperes per square decimeter.

As shown in the figure, above and below the platinumplated titanium plate 4 and spaced therefrom a distance d and a" of 1 millimeter were positioned zirconium plates 2 and 2, one mm. thick and mm. by 250 mm., parallel to one another, by means of supports 5 and 5, which were located at the four corners of the plate assembly as outside as possible. The whole assembly was mounted on a fiberboard base 8.

The whole surface of the upper zirconium plate 2' was covered with an explosive 6 (dynamite No. 3) shaped into an 8 mm. thick plate, which was then initiated by means of an electric detonator 7 attached to one side of the dynamite plate.

After the detonation, the platinum layers were separated from both surfaces of the titanium plate 4, and two zirconium plates 2 and 2' clad respectively with the platinum plates 1 and 1' could be obtained.

EXAMPLE 7 The platinum-plated stainless plate prepared by the process described in Example 3 was positioned horizontally with the plated side facing upward. Along the surrounding border of the surface of the deposited platinum layer was formed an enclosure of 5 mm. height by using silicon strip putty, and epoxide resin mixed with a hardening catalyzer was poured into the enclosure to the full and left until hardened. After the hardening, the putty was removed, and the portion of the deposited platinum layer which lay under the putty was cut away with a knife. Then, the epoxide resin was forced to separate with the result that the platinum layer under the resin parted from the surface to the stainless steel plate, attached firmly to the surface of the resin. Thus, the resin plate clad with the -micron-thick platinum layer was obtained.

The same procedure as Example 2 was then followed except the use of the above described platinum-coated resin plate in place of the platinum-coated hard polyvinyl chloride plate, and the 5-micron-thick platinum layer could be explosively bonded firmly to the titanium plate.

EXAMPLE 8 A titanium plate (KS50), one mm. thick, 300 mm. Wide and 600 mm. long, was electroplated with a 4-micron nickel layer on one surface. The titanium plate was used as the cathode, and the anode was pure nickel. The solution employed for the plating contained nickel sulfate (NiSO -7H O) of 250 grams per 1iter,.nickel chloride (NiCl -6H O) of 50 grams per liter, and boric acid (H BO of 30 grams per liter, and electric current was made to run for 20 minutes with the current density 'of l ampere per square decimeter.

The nickel-plated titanium plate was placed on a 6 mm. thick foundation of rubber plate, with the nickel layer facing upward. Above the nickel layer was positioned a stainless steel plate (SUS27), 1 mm. thick and 350 mm. by 650 mm., in parallel and substantially concentric relationship to each other, with a standoff distance of l millimeter, which was provided by means of supports-interposed between the stainless plate and the foundation rubber plate and located at the four corners. A rubber plate of the same thickness and quality as the foundation rubber plate was stuck on the whole upper surface of the stainless steel plate, and all over the upper surface of the rubber plate was uniformly spread a powder dynamite as thick as'10 mm., and the dynamite was initiated at one side by means of an electric detonator.- Being powdery, the dynamite was enclosed with a cardboard frame so as not to spill.

Following the detonation of the dynamite, only the nickel layer electrically deposited on the surface of the titanium layer was firmly bonded to the under surface of the upside stainless steel plate, and the'stainless steel plate clad in the middle with the inckel layer was prepared.

EXAMPLE 9 A titanium plate (K850), one mm. thick, 300 mm. wide and 600 mm. long, was electroplated with a 6-micron thick gold layer'by using the titanium plate as the cathode, graphite as the anode, and a solution containing gold of 3.5 grams per liter (added as gold fulminate) and potassium cyanide (KCN), and 'by'feeding electric current for 60 minutes under the conditions that the solution temperature was 60 to 70 degrees centigrade and that the current density was 0.2 ampere per 'square deci meter. Then, an explosive bonding operation was carried out in the same manner as shown in Example 5, with the result that the stainless steel plate clad with gold layer was produced.

EXAMPLE 10 A titanium plate (K850), 1 mm. and 300 mm. by 600 mm., was electroplated with a lO-micron silver layer by employing the titanium plate as the cathode, silver as the anode, and a solution containing silver cyanide (AgCN) of 33.5 grams per liter, potassium cyanide (KCN) of 52.5 grams per liter and potassium carbonate (K CO of 37.5 grams per liter, and 'by supplying electricity for minutes with the current density of 1 ampere per square decimeter. Then, a bonding operation was performed by the same process as shown in Example 5, and the stainless plate clad with the silver layer was obtained.

10 EXAMPLE 11 A titanium plate, 1 mm. thick and 50 mm. by 100 mm., was electroplated with an abOut-Z-micron-thick rhodium layer by using the titanium plate as the cathode, platinum as the anode, and a solution containing rhodium of 10 grams per liter and sulfuric acid (H of 55 grams per liter and by passing electric current for 30 minutes with the solution temperature of 50 degrees centrigrade and the current density of 2 amperes per square decimeter. With a 0.5 mm. thick and mm. by mm. zirconium plate, the same procedure as described in Example 5 was employed, resulting in successful bonding of the rhodium layer to the zirconium plate.

EXAMPLE 12 A titanium plate, 1 mm. thick and 50 mm. by 100 mm., was electroplated with an about-2-micron palladium layer by employing the titanium plate as the cathode, platinum as the anode, and a plating liquor prepared by adding ammonia water to a solution having palladium diaminonitrite, Pd(NH (NO of 4 grams per liter, ammonium nitrate (NH NO of 100 grams per liter and sodium nitrite (NaN-O of 10 grams per liter so that the pH might be 7 or more, and by supplying electricity for one hour with the liquor temperature of 50 degrees Centigrade and the current density of 1 ampere per square decimeter. After the same method as Example 5, the zirconium plate clad with the palladium layer was obtained.

EXAMPLE 13 A titanium plate, 0.5 mm. thick and 50 mm. by 50 mm., was electroplated, by the same method as Example 3, with a S-micron platinum layer. This platinumplated titanium plate was placed on a 5 mm. thick and 200 mm. by 200 mm. fiberboard in the middle, with the platinum layer facing upward. Above the platinum layer and separated therefrom by a distance of one millimeter was supported a l-mm. thick and 200 mm. by 200 mm. titanium plate in parallel with the platinum layer, and further, parallel to and one millimeter above the titanium plate was held a 2 mm. thick copper plate dimensionally conforming to the titanium plate. The fiberboard, titanium plate and copper plate were in complete overlapping relationship, with the spacing provided by supports situated at the four corners. The upper surface of the copper mite, which was subsequently initiated at one side by means of an electric detonator.

, Following the detonation of the dynamite, the 200 mm. by 200 mm. copper and titanium plates were securely bonded together, and also the platinum layer was firmly applied to the central portion of the titanium plate bonded to the copper plate, while the 50 mm. by 50 mm. titanium plate so far electroplated with the platinum layer was left unbonded.

EXAMPLE 14 The titanium plate clad with the platinum layer in Example 5 was again placed, with the platinum layer facing downward, on a 5 mm. thick and 250 mm. by 250 mm. fiberboard. Besides, a copper plate, 2 mm. in thickness and 200 mm. by 200 mm., was stuck onto a 6 mm. thick and 250 mm. by 250 mm. fiberboard by the same technique as Example 13, and supported also in the same manner so that the lower surface of the copper plate and the upper surface of the titanium were parallel to each other with a space distance of one millimeter.

The whole upper surface of the topfiberboard was covered with a 10 mm. thick plate made of a dynamite. After the explosive bonding operation, a copper-titaniumplatinum trilayered plate was obtained.

1 1 EXAMPLE 1s A plate of hard polyvinyl chloride, 1 mm. thick and 100 mm. by 200 mm., after cleaned, was immersed in 10% stannous chloride solution for 5 minutes and washed for surface activation. There, a silver-mirror reaction solution was poured onto one surface for the plate, which was thus plated with silver by the silver-mirror reaction.

The silver-mirror reaction solution was prepared by the so-called Rochelle salt method, as follows:

First, silver nitrate of 5 grams was solved in water of 300 milliliters, and ammonia water was added to the solution until a precipitate once formed was again solved. The solution was then filtered and diluted with water to 500 milliliters.

Separately, silver nitrate of 1 gram was solved in water of 500 milliliters. The solution was boiled, and Rochelle salt of 0.83 gram solved in a small amount of water was added to the boiled solution. Then, the solution was kept boiling until a grey precipitate was formed, and thereafter filtered and diluted with water to 500 milliliters. Both of the resulting solutions of the same volume were mixed together into the silver-mirror reaction solution.

The thin silver layer thus deposited upon the polyvinyl chloride plate was explosively bonded onto a surface of a titanium plate, 1 mm. thick and 150 mm. by 250 mm., by the same process as each example.

What we claim and desire to secure by Letters Patent 1s:

1. A process for bonding a thin cladding metal layer on one face of a metal base comprising, removably adhering to a surface of a nonelastic support plate an entire major surface of a thin cladding metal layer, said thin cladding metal layer having a non-self-supporting thickness such that it would tend to sag at any portions thereof if unsupported throughout the overall area thereof, positioning said support plate with the thin metal cladding layer with every portion thereof supported on said support plate and spaced from, facing and in substantially parallel relationship to a face on a metal base, imparting relative movement between the support plate and the metal base by detonating an explosive on a surface of said support plate opposite to the cladding metal layer or on a surface of said metal base opposite said face thereof to impact the cladding metal layer and said face of said metal base in substantially parallel relationship at high velocit to permanently bond the cladding metal layer on said face of said metal base.

2. A process according to claim 1, in which the thickness of the cladding layer is less than 100 microns.

3. A process according to claim 1, in which the thickness of the cladding layer is less than 25 microns.

4. A process for bonding a respective thin cladding metal layer on each of two opposite faces of a metal base, comprising removably adhering to each of two nonelastic supporting plates a respective thin cladding metal layer, each thin cladding metal layer having a non-selfsupporting thickness such that it would tend to sag at any portions thereof if unsupported throughout the overall area thereof, between the two resulting composite plates interposing said base so that the thin cladding layers have every portion thereof spaced from, facing and in substantially parallel relationship tosaid opposite faces of said base, placing a detonating explosive on the exposed surface of one of the supporting plates, said exposed surface being opposite said surface to which said thin cladding layer is adhered, and initiating the explosive, thereby causing instant bonding of said thin cladding layers to said opposite faces of said base.

5. A process according to claim 4, in which the thickness of each of the cladding layers is no greater than microns.

6. A process according to claim 4, in which the thickness of each of the cladding layers is less than 25 microns.

7. A process for bonding a respective thin cladding metal layer on one face of each of two metal bases, comprising remov-ably adhering to each of two opposite faces of a nonelastic supporting plate a respective thin cladding metal layer, each thin cladding metal layer having a non-self-supporting thickness such that it would tend to sag at any portions thereof is unsupported throughoutthe overall area thereof, interposing the resulting composite plate between two metal bases so that each portion of the thin cladding layers is spaced from, facing and in substantially parallel relationship to a face of a respective one of said bases, placing a detonating explosive on the surface of one of said bases opposite the surface thereof facing the composite plate, and initiating said explosive, thereby causing instant bonding of said thin cladding layers to the face of each of said bases facing the composite plate.

8. A process according to claim 7, in which the thickness of each of the cladding layers is no greater than 100 microns.

9. A process according to claim 7, in which the thickness of each of the cladding layers is less than 25 microns.

References Cited UNITED STATES PATENTS 3,137,937 6/1964 CoWan et a1. 29486 3,261,088 7/1966 Holtzman 29-421 X 3,281,930 11/1966 Fordharn 29470.1

PAUL M. COHEN, Primary Examiner U.S. Cl. X.R. 29-199, 421 484, 497.5

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