Steel Powders for High Performance Automotive Parts 940423
Increased use of powder-forged connecting rods in the automotive industry prompted an investigation into the suitability of powders from different suppliers for this application. Specifications developed by North American users call for ultra clean powders to enhance machinability and fatigue life.
Powders from four manufacturers were each blended with graphite and lubricant, then pressed, sintered and forged to full density. Metallographic samples were prepared and evaluated for inclusion content. In addition, the powders were mixed to the composition of connecting rods, (C - 0.5%, Cu - 2% and MnS - 0.3%), and were similarly pressed, sintered and forged. Test bars were machined from the forged discs. Uniaxial fatigue tests were performed in the tension-compression mode and strain-life curves were developed.
It was determined that all powders examined were very clean and were comparable in their inclusion content. Fatigue test results have shown that all four materials had strain-life curves within a narrow scatterband. It was concluded that all four powders examined are suitable for forging high performance automotive parts. Thus, connecting rod manufacturers have freedom of choice in regards to sources of the base raw material for these highly stressed parts. There is also an adequate supply of powder for conversion of steel connecting rods to powder metal.