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Michel EUDIER: Engineer from École Centrale de Paris
INTRODUCTION
(Update of the text by René MEYER (Péchiney Ugine Kuhlmann) published in the present treaty)
Unlike conventional metallurgical processes, which always involve the solidification of a molten metal, powder metallurgy starts with a metal powder and uses a consolidation process known as sintering. This can be defined as a reaction between particles of a powder mass, resulting in the formation of a coherent continuous solid.
Sintering is not specific to powder metallurgy; it has been used since time immemorial by ceramists, who largely preceded metallurgists.
In the manufacturing processes that are the most important in terms of tonnage, the chain comprises three essential operations:
production of compressible metal powders; the powders may be pure metals or alloys, they may be mixed with each other or with other powders, non-metals or metal compounds such as oxides or carbides; the mixture further comprises a small proportion of a solid lubricant powder;
Cold pressing of the powder in tools to produce an agglomerated, manageable part of precise shape and dimensions; the uniaxial pressure is between 200 and 800 MPa;
sintering, which involves heating the tablets to a high temperature, but well below the melting point of the pure metal or alloy obtained; in most cases, a controlled, reducing atmosphere is required.
In this process, the shape and dimensions of the parts vary very little, and the final material therefore has significant residual porosity. In exceptional cases, dimensional shrinkage during sintering can lead to zero porosity.
Remember that :
1 µg/g is equivalent to 1 ppm by mass,
1 MPa = 10 6 Pa = 10 6 N/m 2 = 1 N/ mm 2 = 10 bar = 0.1 hbar = 0.102 kgf / mm 2 .
1 Torr = 1 mmHg = 133.33 Pa.
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Bibliographical index
Directories
Reviews
France
Bulletin de la Construction Mécanique (irr) (Fiches CETIM), (Section: 826 Métallurgie des poudres).
Bulletin Signalétique du CNRS (m) (Section 740: Metals and metallurgy).
Materials and Techniques (m).
Revue Internationale des Hautes Températures et des Réfractaires (formerly Revue des Hautes Températures et des Réfractaires) (tri)....
Standardization
The particular characteristics of the raw materials and products used in powder metallurgy have made it necessary to create standards for testing methods and specifications, specially adapted to this field of metallurgy. The first standards were published by the Metal Powder Industries Federation (MPIF) in the USA some thirty years ago. Most of them were adopted by the American Society for Testing and Materials (ASTM),...
Manufacturers. Suppliers
Metal powders for sintering
Aluminium Péchiney.
Baudier Poudmet SA.
CIME Bocuze.
Comptoir Lyon-Alemand Louyot (CLAL).
Étain (Cie Française de l').
Eurotungsten.
Imphy SA.
Le Nickel (Sté).
Métafram (Sté)....
Organizations
Non-exhaustive list
France
Association Française de Normalisation AFNOR Powder metallurgy commissions.
Chambre Syndicale des Fabricants de Pièces et d'Outils en Carbures Métalliques Durs.
Chambre Syndicale des Métaux et Produits Spéciaux Division: powders and sintered metals.
Société Française de Métallurgie SFM Commission:...
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