Siemens Aktiengesellschaft

Bernhard Rothkegel

Horst Schreiner

Wolfgang Haufe

Rudolf Scherbaum

Contact materials based on AgSnO.sub.2 and having Bi.sub.2 O.sub.3 and CuO as further metal oxide additives were previously disclosed. In these materials the total content of all metal oxides was supposed to be between 10 and 25% by volume with the SnO.sub.2 share equal to or greater than 70% by volume of the total amount of oxide. According to this invention the quantity of SnO.sub.2 is kept smaller than 70% by volume; specifically at about 65%, but in any case equal to or greater than 50%. The SnO.sub.2 weight content is to be in the 4% to 8% range and the weight percentage ratio of SnO.sub.2 to CuO is to be between 8:1 and 12:1. In the associated production process, either Bi.sub.2 O.sub.3 powder is purposely admixed to an internally oxidized alloy powder (IOAP) in an additional operation, a grain restructuring with locally different Bi.sub.2 O.sub.3 concentrations occurring in the structure after sintering and compacting. Alternatively, higher bismuth percentages in the alloy powder can be worked with directly, which is again internally oxidized to an IOAP. From these starting materials two-layer sintered contact elements with a solderable silver layer can be efficiently produced.

Method for the production of sintered electrical contact material for

Sintered electrical contact material for low voltage power switching

Electrical contact materials based on AgCdO with CdO as the main active component have proven to be particularly advantageous for low voltage switchgear in the power industry. However, when switching AgCdO contact materials, CdO, which is classified as toxic, can escape into the environment through burn-off. It is important, therefore, to keep the CdO content as low as possible in the contact material, or to exclude it completely. The contact material according to the invention is a sintered contact material consisting of AgSnO.sub.2 with at least two other metal oxide additives; namely, Bi.sub.2 O.sub.3, CuO and optionally CdO. Relative to SnO.sub.2, these additives Bi.sub.2 O.sub.3, CuO optionally CdO, amount quantitatively to a total maximum of 25 percent by volume of the total amount of oxide.

Sintered, electrical contact material for low voltage power switching

The composite according to the invention is prepared by milling an atomized silver, two metal oxide alloy powder dry or wet in a mill in order to reduce its particle size and deform its particle shape. Subsequently an internal oxidation of the powder is carried out in two stages, at a first temperature range between 673.degree. K. and 773.degree. K. for two to six hours and in a second temperature range between 873.degree. K. and 1073.degree. K. for 0.5 to 2 hours. The internally oxidized powder is pressed into molded parts and these are densified by sintering in a temperature range between 973.degree. K. and 1173.degree. K. in air or a neutral atmosphere and by coining.

Cadmium-free silver and metal oxide composite useful for electrical

In a method for molding formed parts in automatic multiposition presses, using powdered materials having a flowability characterized by a flow time exceeding 60 seconds per 100 g of powder flowing from a 60.degree. standard funnel with a nozzle aperture of 4 mm and a nozzle length of 4 mm, the powdered material having in the mold a filling height to diameter ratio larger than two, the powder is conveyed into the mold by means of filling devices located at a plurality of separate charging stations, pressed at a separate pressing station and ejected at yet another separate station. The filling heights in each mold is subdivided into at least two individual filling heights so that the filling of the mold to these individual filling heights can be carried out at different charging stations.

Method for the dry molding of formed parts

In the manufacture of molded single layer bodies in an automatic press, the press output is substantially increased by providing, on a circular table, at least two work positions at a predetermined distance from each other. At each work position, a pressing process for pressing the powder and an ejecting process for ejecting the finished molded body take place. Filling devices are arranged between the work positions in such a manner that the filling vessel of each filling device covers a wide angular range of the circular table. Pressing and ejecting take place during standstill of the press table, and the filling of the die takes place during the transport of the press table from the one to the other work position.

Automatic press

In order to generate a graphite free, solderable surface on a contact piece for electric contacts, which consists of silver with graphite particles up to about 5% by weight finely and uniformly distributed therein, the contact piece is subjected to a wet scouring treatment, simultanouesly using scouring stones.

Method for generating a solderable surface on a contact piece of silver

An impregnated sintered material for making electrical contact members which have a low fusing force and little burning in which a powder mixture of W, Ag and/or Cu, a wetting promoting metal, and 2 to 5 percent by weight graphite is granulated thermically, and another 1 to 6 percent by weight graphite admixed to the granules, after which the mixture is compacted to form a skeleton and impregnated with Ag and/or Cu. The carbon contained in the finished material is partly in bound form as WC and partly free carbon in a 1:5 to 5:1 ratio.

Impregnated sintered material for electrical contacts and method for its

A contact member for high electrical loads has a plurality of component parts. One of these parts is made of a non-welding material resistant to burn-off and another part is made of a solderable material having electrically conductive properties. The material of each of the parts is configured as a porous skeleton structure. The parts are disposed next to each other and an impregnating metal impregnates both of the parts to preclude the occurrence of a boundary layer at the interface of the parts.

Contact member and method of manufacture

To make an electric contact material, a molten alloy of silver and a non-noble metal is atomized into spheroidal particles having a particle size ranging up to almost 1 mm, and the fraction of these particles having a particle size ranging between 0.2 and 1 mm is separated, a small remainder of smaller particle size being treated as a reflux. This fraction is heated in an oxidizing atmosphere to oxidize the non-noble metal internally within the particles and the latter are then mechanically broken, as by suitable milling or pulverizing, into fragments having a particle size no greater than about 0.3 mm. The fragmented particles are then compressed, as by pressure molding, extrusion, etc., and sintered to provide a sintered silver-metal oxide electric contact material.

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Nuremberg, Germany

Bernhard Rothkegel