Process for fixing a graphite-rich material onto a metallic body

A process for fixing a graphite-rich material onto a metallic body by mixing graphite powder with a plastic material to obtain a graphite-rich material, pressing the graphite-rich material onto a layer of a metal-rich material, in a single step, forming thereby a green pressing formed of a graphite-rich component and a metal-rich layer, aligning the green pressing with the metallic body to which it is to be fixed, and subjecting the aligned metallic body and green pressing to a heat treatment to bond the metal-rich layer to the metallic body.

BACKGROUND OF THE INVENTION 
The invention concerns a process for fixing a graphite-rich material onto a 
metallic body. 
In many graphite applications, it is advantageous, and sometimes necessary, 
to fix the graphite onto a metallic body in such a manner as to give good 
heat- and/or electricity-conductivity. This is so in the case of sliding 
bow current collectors, grounding contacts, graphite linings in fusion 
reactors and in electrical contacts in general. 
According to the present state of technology, such fixings or bondings are 
produced by soldering, in which the graphite surface requires elaborate 
preparation in order to achieve an anchorage of the solder in the graphite 
material. 
SUMMARY OF THE INVENTION 
The invention is based on the task of simplifying the fixing process and 
yet still achieving reliable fixing. 
To achieve this and other objects, the invention is directed to a method 
for fixing a graphite-rich material onto a metallic body, comprising the 
steps of: 
mixing graphite powder with a plastic material to obtain a graphite-rich 
material; 
pressing the graphite-rich material onto a layer of a metal-rich material, 
in a single step, forming thereby a green pressing comprising a 
graphite-rich component and a metal-rich layer; 
aligning the green pressing with the metallic body to which it is to be 
fixed; and 
subjecting the aligned metallic body and green pressing to a heat treatment 
to bond the metal-rich layer to the metallic body.

DETAILED DESCRIPTION OF THE INVENTION 
According to the invention, the prior processes are simplified in that a 
metal-rich layer, especially a solder layer, and a graphite-rich layer, 
comprising graphite and a smaller amount of plastic, may be pressed 
together in a single process step, and are then sintered onto a metallic 
body, during which the graphite-rich layer simultaneously hardens. The 
green pressing resulting from the pressing of the metal-rich layer and 
graphite-rich layer is aligned with the metallic body, i.e. a formed 
shape, and subjected to heat treatment, with or without a protective gas, 
so that the formed object comprising graphite and plastic additive hardens 
in the case of a thermosetting resin, or is cemented in the case of a 
thermoplastic material, and the metal-rich layer, i.e. the solder, forms a 
lasting bond by fusion with the metallic object. This dispenses with the 
intermediate steps necessary in the prior art, and a more cost-favorable 
manufacture is achieved. 
In the present specification, the term "green pressing" is understood to 
mean an unsintered pressing, a "metal-rich" material is understood to mean 
a material with a graphite content of at least 50% by weight and a 
graphite-rich material is least 50% by weight and a graphite-rich material 
is understood to mean a material with a graphite content of at least 50% 
by weight. 
The plastic materials used to form the graphite-rich materials are 
thermosetting resins, including those materials known in the art as 
"duroplasts." Thermosetting resins are generally present in the 
graphite-rich material in an amount of 8 to 25% by weight. The plastic 
material may also be a thermoplastic, which is generally present in the 
graphite-rich material in an amount of 3 to 15% by weight. 
The metal-rich layer of the invention is preferably tin or a tin-lead 
alloy, and the metallic body can be a copper body. 
SUMMARY 
In a simplified process for the fixing of a graphite-rich material onto a 
metallic body and which gives reliable bondings, the graphite-rich 
material contains a hardenable duroplast. This is pressed together with a 
metal-rich layer in one pressing process to form an unsintered pressing 
which contains a graphite-rich component. The pressing is then aligned 
with the metallic body and, in one process step, then subjected to a 
temperature treatment during which not only the duroplast in the 
graphite-rich material hardens but the metal-rich layer also forms a close 
bond with the metallic body.