Specialized metallurgical processes – compositions for use therei – Compositions – Loose particulate mixture containing metal particles
Patent
1998-05-27
2000-10-03
Mai, Ngoclan
Specialized metallurgical processes, compositions for use therei
Compositions
Loose particulate mixture containing metal particles
75352, 75354, 75369, 75243, 75246, 75247, B22F 100
Patent
active
061267120
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a metal powder granulate comprising one or more of the metals Co, Cu, Ni, W and Mo, a process for its preparation and its use.
Granulates of the metals Co, Cu, Ni, W and Mo have many applications as sintered materials. For example copper metal granulates are suitable for preparing copper sliding contacts for motors, tungsten granulates can be used to prepare W/Cu infiltration contacts, Ni and Mo granulates may be used for corresponding semi-finished applications. Cobalt metal powder granulates are used as binder components in composite sintered items, e.g. hard metals and diamond tools.
DE-A 43 43 594 discloses that free-flowing metal powder granulates can be prepared by pulverising and screening out a suitable range of particle sizes. However, these granulates are not suitable for producing diamond tools.
EP-A-399 375 describes the preparation of a free-flowing tungsten carbide/cobalt metal powder granulate. As starting components, the fine powders are agglomerated, together with a binder and a solvent. In a further process step the binder is then removed thermally and the agglomerate is after-treated at 2500.degree. C. in a plasma in order to obtain the desired free-flowing property. Fine cobalt metal powder, however, cannot be granulated using this process because similar processing problems occur at temperatures above the melting point as those encountered during the processing of very fine powders.
DE-A 44 31 723 discloses that pastes of oxide compounds can be obtained if water-dilutable, non-ionogenic rheological additives are added. These additives may be thermally removed, resulting in compact layers on substrates. However, the objective of this process is to coat the substrate with finely divided, completely agglomerate-free particles.
EP-A 0 659 508 describes the preparation of metal powder granulates of the general formula RFeB and RCo, wherein R represents rare-earth metals or compounds, B represents boron and Fe represents iron. Here, an alloy of the components is first prepared and this is reduced to the desired fineness by milling. Then binder and solvent are added and the slurry is dried in a spray drier. The disadvantage of this process, in particular for preparing diamond tools, is that the metals are first alloyed and the fine cobalt powders lose their characteristic properties due to the melting procedure, as described in DE-A 43 43 594. The prior art for producing cobalt metal powder granulates is therefore to add binders or organic solvents to fine cobalt metal powder and to produce corresponding granulates in suitable granulating devices, as can be deduced e.g. from the brochures relating to the granulating machine G10 from the Dr. Fritsch KG Co., Fellbach in Germany and for the solids processor from the PK-Niro Co. in Soeberg, Denmark. The solvents are carefully removed after granulation by an evaporation procedure, but the binder remains in the granulates and has a significant effect on the properties.
The granular particles obtained in this way have a rounded shape. The surface is relatively compact without large pores or openings for the escape of gases. The bulk density determined in accordance with ASTM B 329 is relatively high, 2.0 to 2.4 g/cm.sup.3 (Table 2). FIG. 1 shows the scanning electron (SEM) photograph of a commercially available granulate from the Eurotungstene Co., Grenoble, France, and FIG. 2 shows a commercially available granular material from the Hoboken Co., Overpelt, Belgium. Although the rounded shape of the particles and the high bulk densities lead to the desired improved flow properties for cobalt, processing problems are still not inconsiderable in practice.
For example, relatively high compression forces have to applied during cold compression in order to obtain preforms with sufficient strength and edge stability. The reason for this is that the production of firmly interlocking compounds, i.e. expressed more simply, the hooking together of the individual particles, which is important for pro
REFERENCES:
patent: 3975217 (1976-08-01), Kunda et al.
patent: 5102452 (1992-04-01), Taskinen et al.
patent: 5185030 (1993-02-01), Miller et al.
patent: 5482530 (1996-01-01), Hohne
patent: 5575830 (1996-11-01), Yamashita et al.
patent: 5662943 (1997-09-01), Yamashita et al.
patent: 5713982 (1998-02-01), Clark et al.
patent: 5723535 (1998-03-01), Krismer et al.
Gries Benno
Hohne Matthias
Cohen Jerry
H. C. Starck GmbH & Co. KG
Mai Ngoclan
LandOfFree
Metal powder granulates, method for their production and use of does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metal powder granulates, method for their production and use of , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metal powder granulates, method for their production and use of will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-190742