Development of high-performance cast steel crankshafts

<p>To produce cast steel crankshafts, risering and gating systems are developed. Filling and solidification simulations of the steel crankshaft rigging are carried out to confirm that the rigging developed will produce a low porosity casting. A sand mold is created with Computer-aided design software, based on the developed crankshaft and rigging. Two prototype crankshafts are cast from the sand molds, and analyzed for porosity. The porosity analysis results are compared directly to the simulated porosity, and found to be in good agreement. From the analysis of the prototype crankshaft, rigging systems for a two-on and single-throw crankshaft are developed.</p> <p>A new casting method for steel is developed. The counter-gravity with pressurization during solidification casting method utilizes vacuum pressure of 7.3 psia to draw liquid steel into a mold, where it is held until the inlet has solidified. Once the inlet has solidified, the vacuum pressure is released, and the pressure of the entire system is raised to 45 psia. Exothermic hot topping keeps the top of the riser liquid while the rest of the casting forms a solid shell. Therefore, the pressure only acts on the liquid metal at the top of the riser, forcing the liquid metal to feed farther into the casting. The new method is tested with simple bar castings. Analysis of cast bars shows that centerline porosity is fed by the riser when pressurized, while the gravity-filled control casting is not.</p>