Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1986-04-22
1988-03-01
Lechert, Jr., Stephen J.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75230, 419 10, 419 32, 419 33, 419 36, 419 37, 419 39, 419 54, 21914623, C22C 2900
Patent
active
047283629
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention relates to high voltage electrodes in accordance with the type of the main claim. A device for the ignition voltage distribution in ignition system designed for internal combustion engines is described in the DE-OS No. 31 36 745, wherein electrodes are used which have calcium and silicon as main components. However, it is disadvantageous that this material in sintered condition does not have the hardness or toughness required for a high service life. A further disadvantage of such electrodes is that it is hard to contact them, since this material is hard to solder and hard to weld.
ADVANTAGES OF THE INVENTION
In contrast thereto the inventive high voltage electrodes which in addition to calcium and silicon contain iron have the advantage that they have a sufficient hardness for a long life span in the sintered condition and that they can be more easily soldered and welded and can be more easily contacted with a carbon brush than the aforementioned material. The method in accordance with claim 6 is advantageous in that demixing of the two components is eliminated, which otherwise can easily occur, since the CaSi has a density of about 2.5 g/cm.sup.3, and iron has a density of about 7.8 g/cm.sup.3.
Further embodiments and improvements of the high voltage electrodes stated in the main claim are made possible by the measures stated in the subclaims. For an optimum contacting it is particularly advantageous when the actual high voltage electrode has a tipstretched contact area which consist solely of iron.
DRAWING
One exemplified embodiment of the invention is illustrated in the drawing and is explained in more detail in the subsequent description. The FIGURE illustrates schematically a section of a mold provided with a separating wall for making a high voltage electrode with a tipstretched contact area.
DESCRIPTION OF THE EXEMPLIFIED EMBODIMENT
For making a high voltage electrode 70% by weight iron powder with a granular size of <0.2 mm, 29% by weight calcium silicide powder in the screen fraction of <0.2 mm as well as 1.0% by weight calcium wolframate CaWO.sub.4 or sodium molybdate Na.sub.2 MoO.sub.4 are thoroughly mixed. A nonalloyed iron powder is used as an iron powder, the calcium silicide powder substantially consists of CaSi.sub.2 with small components of Ca.sub.2 Si and CaSi. The adding of calcium wolframate or sodium molybdate serves for the reduction of the burning voltage, whereby the interference in the ignition distributor in which the electrode is used is improved. After adding 1% by weight of a solid organic binder substance like, for example, ethyl cellulose which had been dissolved in a diluting oil, the powder mixture is granulated by the fluid bed method until a size of the granulate from 0.2 to 0.4 mm is obtained. This preparation of the powder to be processed by means of a granulating process, although unusual when processing metal powders, is necessary in order to improve poor fluidity of the powder as well as poor hardness and edge durability of molded elements made from such powders, and, in the first place to prevent a demixing of iron and calcium silicide. One has to take into consideration that iron has a density of about 7.8 g/cm.sup.3, while the calcium silicide density is only at about 2.5 g/cm.sup.3, so that an untreated powder mixture has the tendency that the iron powder gradually settles downwardly. Due to the granulating process this danger of demixing id completely eliminated, moreover round granulate particles are formed and have a good fluidity after the evaporation of the thinning oil that increased temperature and can therefore be very well processed in the following operating steps.
The finished granulate to which a slight amount of a customary organic lubricant had been added, for example, zinc stearate is filled into a press mold, as schematically illustrated in the drawing. The mold consists of wall 1 and two movably disposed lower plungers or dies 2 forming together with the wall a hollow chamber 3 corresponding to the
REFERENCES:
patent: 1972463 (1934-09-01), Ludwigshafen
patent: 2116399 (1938-05-01), Marth
patent: 3256699 (1966-06-01), Henderson
patent: 4282420 (1987-08-01), Banks
Grunwald Werner
Koch Hans-Peter
Leuze Gundmar
Neu Hans
Lechert Jr. Stephen J.
Robert & Bosch GmbH
Striker Michael J.
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