Comparisons of extruded magnesium rods by hyperbolic curve die and parabolic curve die

Abstract

In order to predict defects of extrusion especially the surface cracks caused by hyperbolic curve die and parabolic curve die in direct extrusion process, three dimensional (3D) thermo mechanically coupled finite element simulations of extruding AZ31 alloy into small rod at certain ram speeds have been performed using DEFORM TM 3D. A half of the geometries including billet and dies with hyperbolic curve die and par abolic curve die have been designed and meshed due to symmetry. Simulation parameters including work piece characteristics and process conditions (e.g., billet temperature, extrusion ratio, and ram speed) have been taken into consideration. The simulation results have been verified in extrusion experiments under iden tical conditions as simulation conditions. It can be found that hyperbolic curve die could improve homoge neity of the metal flow, avoid the formation of the dead zone, decrease additional tensile stresses and increase uniformity comparing with parabolic curve die. The parabolic curve die may cause continuous cracks on the surface of the extruded rod. Theoretical results obtained by the simulations agree well with the experiments data. The obtained results provide the fundamentals and practical guidelines for the choice and design of die structures to produce magnesium rods with finish surface.

Experimental Analysis for Lubricant and Punch Selection in Shear Extrusion of Aa-6063

“…The use of shear die in the extrusion of complex shapes leads to a complicated problem of metal flow imbalance that often results in shape defects and to obtain a straight and true product in size, the design of the location of the die orifice and the specification of the die land length is of paramount importance [11][12][13]. Other die process parameters which may affect the quality of the extrudate are the shape ratio of the billet, extrusion ratio and the capacity of the extrusion press [14].…”

“…Hu performed a coupled thermomechanical finite element simulation on the defect of extrusion and submitted that the use of hyperbolic curve die leads to improved homogeneity of metal flow, increased uniformity and less chance of formation of dead zone whereas parabolic curve may cause continuous cracks on the surface of the extruded rods [11]. The use of shear die in the extrusion of complex shapes leads to a complicated problem of metal flow imbalance that often results in shape defects and to obtain a straight and true product in size, the design of the location of the die orifice and the specification of the die land length is of paramount importance [11][12][13].…”