Abstract
Equations have been derived previously to predict coldextrusion pressures from material constants and parameters representative of the extrusion process. To test the validity of these equations over a wide range of conditions, data from backwardextrusion and compression tests obtained on pure lead, aluminum, copper, pure iron, an iron-manganese alloy, and six steels are presented here. The data were obtained over a range of extrusion ratios (l.28 to 2.72) and extrusion speeds (0.005 to 1020 inches/ minute). The results confirm the validity of the equations, establishing the fact that the deformation energy, taken as the area under the true-stress—true-strain curve, is the parameter that determines cold-extrusion pressures.
The strain factor parameters used to characterize the extrusion process were significantly different for low speed (≤ 2 in./ min) and high speed (960 in./min) extrusion. This reflects a change in the deformation pattern with extrusion speed and is shown to result from heating effects associated with high-strain-rate deformation. Transmission electron microscopy of irons and steels extruded at high speeds show evidence of considerable heating—in the case of pure iron extruded at 986 in./min, the substructure was completely recovered. Predictions of extrusion pressures from theories that neglect this adiabatic heating effect, such as slipline solutions, may thus be in considerable error.
formerly with United States Steel Corporation
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Kashar, L.J., Dunlap, R.W., O’Connell, T.E. (1971). Deformation Criteria for Predicting the Cold-Extrusion Pressures of Metals. In: Hoffmanner, A.L. (eds) Metal Forming: Interrelation Between Theory and Practice. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-1757-3_6
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DOI: https://doi.org/10.1007/978-1-4615-1757-3_6
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