2007-04-03 Pressing & Sintering

PM Steel Components with the Strength of Wrought Steel

The utilization of PM steel components in automotive has increased steadily during the last decades. Further growth is forecast based on new applications primarily in the engine and transmission systems. The designer of components for these automotive systems has to decide what type of material to use. The most common and established materials are wrought steels such as steel bar, forgings or castings. The steel bar has the advantage of reliable and well documented mechanical performance and the possibility to achieve almost any shape. The disadvantages on the other hand are often high machining cost and large material loss in the form of turnings. Both forgings and castings have since long been established materials for automotive applications requiring medium to high strength. Both technologies have the advantage of near-net shape and machining can be limited to just a few parts of the components. These manufacturing technologies, however, create an anisotropic material and therefore the mechanical performance of components made by forging and casting is strongly dependent on the specific processing steps used by the manufacturer of the components. A fourth alternative material for the designer is PM steel. In this case net shape is achievable and machining can be completely excluded or limited. This, in turn, reduces the manufacturing cost of the component. Due to the unique forming method of powder compaction the design of the components can often involve multiple functions or be designed to reduce size or weight. The decision by the designer, however, is also based on experience, track-record, availability of reliable material performance data, existence of material standards and supply opportunities. Due to the longer experience of machining, forging and casting and the more widespread use of these technologies as compared to powder metallurgy much effort is needed to serve the designer with such information to choose PM steel for a component. This paper discusses the situation today regarding potential new applications for PM steels and the opportunities to fulfil the designers’ demands for these with PM materials, component manufacturing knowledge and available data of the mechanical performance.