CH658214A5 - COPPER-BASED REACTION LOT. - Google Patents

Description

The present invention relates to a reaction solder based on copper. Copper solders and copper alloy solders have long been known as hard solders. In addition to the use of solder material consisting exclusively of copper, copper alloy solders are known, for example, which contain between about 40 and 60 percent by weight copper, small amounts, e.g. 0.2 percent by weight, silicon, the rest of zinc or optionally nickel. To produce the solders, the metal or alloy is melted, poured into molds and then subjected to conventional

Measures such as drawing, pressing, rolling into wires, profiles, sheets or powder are produced by grinding. Fluxes can be added or melted.

Copper and copper alloy solders have the ability to react with the cast iron, steel, hard metal etc. to be soldered to form solid solutions and / or stoichiometrically defined connections. Solders of this type are therefore briefly referred to as reaction solders. For economic and technical reasons, they are used on a large scale, in particular for brazing steel, cast iron and hard metals, on a large scale in the construction of machine parts, apparatus, devices, tools, electric motors and the like. This is often done, especially when brazing steel and hard metals, at relatively high temperatures, for example above 1100 ° C, in a vacuum or under protective gas. Hard metals are understood to mean, in particular, tungsten carbide-cobalt alloys, usually with low, balanced carbon contents, whereby the cobalt binding metal can also be replaced by other metals (such as nickel). This also includes titanium and tantalum carbides, which usually also contain cobalt and possibly other metals as binders.

It has now been shown that when using the known copper-based solders, for example when soldering steel with hard metal, the results achieved are not fully satisfactory. For example, signs of dissolution were observed along the grain boundary of the steel. This results in a corresponding reduction in the static and, above all, dynamic strength. The toughness of the steel in particular is markedly reduced in this area. In contrast, in the case of hard metal, embrittlement of the edge zone through diffusion, formation of intermetallic phases and the Kirkendall effect with formation of a “rotten” zone was frequently observed. Furthermore, the formation of an n-like layer was sometimes observed, especially when brazing steel with the carbide, as a result of a certain depletion of carbon on the carbide side. These serious diffusion-related effects lead to unbearably poor results, especially when subjected to impact.

Surprisingly, it has now been found that these disadvantages can be avoided by a reaction solder based on copper which contains 0.5 to 20 percent by weight cobalt and in which copper and cobalt are at least partially present in the heterogeneous phase. These constituents are preferably completely in a heterogeneous phase. In addition to the predominant proportion of copper and the specified amount of cobalt, other conventional alloy components such as silicon, e.g. in amounts of 0.1 to 0.4 percent by weight and / or carbon, in particular in an amount of up to 0.8 percent by weight (ie 0-0.8 percent by weight). Furthermore, common solder components, such as fluxes, binders volatile at the soldering temperature, e.g. In the case of powdered solder, powder moldings or layered structure of the solder, organic compounds donating carbon under soldering conditions, in particular instead of or in addition to another carbon component, strength-increasing substances which may can also participate in the reaction, metals, non-metals, organic substances and the like, substances known per se, can be added.

A reaction solder with 88-97 percent by weight of copper, 1-12 percent by weight of cobalt, 0-0.6, in particular 0.05-0.5 percent by weight of carbon has proven particularly useful, with any remaining component from conventional solder components, as mentioned at the outset , can exist and at least copper and / or cobalt

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partially, preferably completely in the heterogeneous phase. A reaction solder which is present in the aforementioned manner in a heterogeneous phase and which contains at least 91% by weight of copper, 2-8% by weight of cobalt and up to 0.4% by weight of carbon has proven particularly successful. In a particularly preferred embodiment, the heterogeneous reaction solder consists of 94-97 percent by weight copper, 3-6 percent by weight cobalt and up to 0.6 percent by weight carbon. In general, it is particularly preferred if the cobalt content is between 1 percent by weight and the maximum amount of cobalt that is soluble at the soldering temperature.

The carbon which may be present in the heterogeneous reaction solder according to the invention can e.g. are present as a constituent of the mixture, in particular in the case of a powdery structure, as an optionally saturated CoC alloy or as an organic substance which forms a corresponding amount of carbon. Such organic carbon compounds which form carbon by decomposition are generally known (Römpps Chemie Lexikon, 7th edition, esp.

1811).

The components of the reaction solder, preferably copper and / or cobalt, can be present, at least in part, in a finely divided, preferably powdery state. This can be powder mixtures, e.g. Shaped bodies produced by powder metallurgy, optionally with a content of further additives, act with or without a carrier. The heterogeneous reaction solders can, for example, also be contained in solid or pasty carriers which are preferably inert or else reactive, such as carbon-forming carbon compounds, metals, etc.

A multilayer, e.g. Sandwich-like structure of the reaction solder, the layers having different compositions, specifically such that copper and cobalt, at least some of them, are arranged in different layers. In this case, layers can be provided that only copper or carbon

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balt, in addition to other constituents, or also layers with mutually different copper / cobalt concentrations. Those heterogeneous reaction solders which have essentially or 5 layers consisting predominantly of copper or cobalt are particularly preferred, in particular if such a copper layer is arranged between two cobalt layers. Common soldering aids, binders, carbon-forming agents and the like may e.g. be arranged between the layers angelo.

In addition to the soldering of steel and cast iron, the copper alloy solders according to the invention have proven particularly useful for soldering steel with hard metals, in particular tungsten carbide-cobalt hard metals, which regularly contain WC, 15 Co and C in balanced proportions.

Also the use for brazing steel with hard metals based on titanium or tantalum carbide, the cobalt or other metals, such as Containing nickel as a binder is possible. Above all, the arrangement of the Ko-20 baltschicht on the steel side results in a sealing-like effect while largely preventing iron diffusion.

example 1

In the case of a copper-based reaction solder, there is one, e.g. electroplated cobalt layer of 8 n arranged. When used for brazing steel with hard metal, preferably in such a way that the cobalt layer faces the steel, a substantial increase in the impact strength of the brazing is achieved.

Example 2

In the case of a copper-based reaction solder, a cobalt layer of 5 (x e.g. galvanic) is applied to both sides of a 35 copper foil of 0.15 mm. Significant increases in strength are achieved when soldering steel with hard metal.

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Claims (10)

658 214 1. Reaction solder, based on copper, characterized in that it Contains 0.5-20% by weight cobalt and the components copper and cobalt are present, at least in part, in the heterogeneous phase. 2. reaction solder according to claim 1, characterized in that it 88-97% by weight copper 1-12% by weight cobalt 0-0.6, in particular 0.05-0.5% by weight of carbon remainder contains other solder components and copper and cobalt are present, at least in part, preferably completely, in the heterogeneous phase. 2nd PATENT CLAIMS 3. Reaction solder according to claim 1 or 2, characterized in that it contains at least 91 wt .-% copper 2-8 wt .-% cobalt and up to 0.4 wt .-% carbon. 4. reaction solder according to one of the preceding claims, characterized in that it consists of 94-97% by weight of copper contains 3-6% by weight of cobalt and up to 0.6% by weight of carbon. 5. Reaction solder according to one of the preceding claims, characterized in that the carbon is contained as a mixture component, in the form of a cobalt-carbon alloy, preferably up to the saturation of the cobalt and / or in the form of a substance providing the corresponding amount of carbon under soldering conditions . 6. Reaction solder according to one of the preceding claims, characterized in that the constituents, preferably copper and / or cobalt, are present, at least partially, in a finely divided, preferably powdery state. 7. reaction solder according to one of the preceding claims, characterized in that the components are contained in a, preferably inert, solid or pasty carrier. 8. Reaction solder according to one of the preceding claims, characterized in that it is multi-layered and the components copper and cobalt are at least partially arranged in different layers. 9. reaction solder according to claim 8, characterized by a layer consisting at least predominantly, preferably solely of copper, and a layer consisting predominantly, preferably solely of cobalt, optionally containing small amounts of carbon, or by such a copper layer between two such cobalt layers. 10. Use of the reaction solder according to one of the preceding claims for the production of soldering steel with hard metal.