A unique powder metallurgy process is becoming increasingly recognized as one of the most effective ways of manufacturing complex shapes from high quality alloys. Using a technique perfected by its own research staff, Santasalo Powdermet can now manufacture components such as valve bodies and complex manifolds that meet the highest standards of metallurgical integrity.
Part of the Metso Corporation, the company is based in Surahammar, Sweden where it works with the world's largest Hot Isostatic Press (HIP). This makes it possible for the company to manufacture components up to 2.9 meters long and 1.15 m in diameter.
The company regularly manufactures valve bodies for the offshore industry as well as steam turbine rotors, reactor components all lend themselves to manufacture by the Powdermet process. It also proved to be the only option available for the designers of an atomiser for a marine diesel engine that was made from a special alloy that could be neither cast nor forged.
The first stage in the manufacturing process involves construction of a capsule out of 2 mm sheet carbon steel. Every detail of the work piece has to be shaped so that the capsule can serve as a mould for the finished item. It must be completely airtight and to allow for shrinkage, the capsule must be around 2% larger than the finished product.
The Powdermet process makes it possible to manufacture components in any type of metal. These are supplied as a high grade powder with grains of a uniform 750 microns. The capsule is filled with the powder and the air is evacuated before sealing. Once in the press, the capsule is subjected to temperatures ranging from 1,130-1,180 degrees C in an atmosphere of argon which is used to create pressures of up to 1,400 bar.
Metal matrix
The work piece is likely to be in the press for up to 12 hours and on removal it is subjected to an etching process that removes the carbon steel capsule and leaves the component ready for final finishing as required. When viewed under a microscope, the finished metal product will demonstrate a uniformly fine granular structure which is metallurgically superior to the longer and more inconsistent grains that result from a component being forged.
Most products made using the Powdermet process tend to be duplex steels although a new area is MMC (Metal Matrix Composites) which can be duplex with a large quantity of chromium carbides. This combination of ductile matrix and hard ceramic reinforcement gives a unique quality of ductility and wear resistance specific to a particular task.
Composite for Gullfaks
HIP can also be applied to manufacture components from composites of different metals. This enables the designer to address different problems of wear resistance that may be present in the same component and is a facility that was chosen for a mixer used on the Gullfaks platform.
Although 2.9 meters is the maximum dimension of components possible in the HIP, there are Powdermet products many times this size installed offshore having been delivered in pieces and welded together in-situ. The three components supplied for a manifold on Phillips' Jade platform in the UK North Sea were joined to create a unit more than 7 meters long and Powdermet believes that this facility makes its process a valuable option available to designers faced with complex tasks.
For more information contact Gôte Bjôrman, Sanatasalo Powdermet. Tel +46 220 348 80, Fax +46 220 334 90, Email: [email protected]
