A Die Assembly for Hydrodynamic Drawing of Nichrome Strips

Abstract

The available die assembly designs for hydrodynamic drawing cannot be used to produce difficult-to-form nichrome strips, which are employed as heating elements in commercial resistance furnaces. Due to intensive cold work hardening, the σ_u of nichrome reaches 1300 MPa. Nichrome also demonstrates high adhesion to the drawing channel of carbide dies (despite the use of top coating lubricant and effective lubrication), which also contributes to the heating of the die. This hampers achieving even semifluid friction conditions, required surface condition, and satisfactory tool durability. To prevent the failure of the hard-alloy inserts and to provide the fluid friction conditions, use is made of die assemblies consisting of a steel holder and hard-alloy inserts. The difference between the thermal expansion coefficients of hard alloy and steel ensures the appropriate tensile stresses, tight contact between the die components, and confinement of the lubricant