PM Process

The powder metallurgical (PM) fabrication process is one of the base processes in manufacturing, like forging or casting. Unlike forging or casting, the starting material is in powdered form. In our case, the powder is a mixture of iron and the alloying components required to make steel. The first stage of manufacture involves uniaxial pressing of the powder at ambient temperature (or with the temperature elevated slightly to around 140 °C) using intricate tools. The result is a work piece that is close to its final dimensions, but is still mechanically unstable. Consolidating the work piece into a solid steel part occurs during the next stage of manufacture: thermal treatment – better known as sintering.

 

 

During this stage the microstructure transforms to one similar to cast steel at temperatures between 1100 °C and 1300 °C. The result is a solid steel part with very accurate dimensions and a tensile strength similar to forged steels. An additional pressing step in an enclosed tool – known as calibrating or sizing – can increase the density of the component and/or improve the dimensional tolerances, depending on the specifications for the finished component. All secondary processes like machining, heat treatment, etc. can be carried out on sintered components in the same way as on standard steel parts. Such secondary processes might include milling, grinding, hardening, bluing, coating, galvanizing, etc. Components made from pm are usually manufactured in big numbers. Therefore the production normally takes place on highly automated and linked production facilities, which guarantee the production of series products in high and reproducible quality. The advantage here is that the dimensions of the sintered component are almost (or actually are) identical to the final dimensions (netshape or near netshape manufacturing process). This saves having to remount the work piece for additional machining. In addition, due to the fact that consolidation takes place at temperatures below the melting point of the alloying elements, sintering is the most energy- and resource-conserving, and environmentally friendly process available.