The Relationship Between Mechanical Properties, Preferred Orientation and Press Forming Behaviour of Copper and 70/30 Brass

Abstract

A study has been made of the mechanical properties, press forming behaviour and preferred orientation of copper and 70/30 brass in a wide range of conditions produced by temper rolling and temper annealing. The mechanical properties and R values at 0°, 45°and 90° to the rolling direction were determined by tensile testing, while the stretch forming, deep drawing and redrawing properties were assessed using the respective Erichsen tests. An attempt was made to relate the earing characteristics of deep drawn cups to preferred orientation, which was assessed from pole figures, and to the planar variation in R value. The stretch formability of both materials was a maximum in the annealed condition, and there was little difference in performance between material temper rolled and temper annealed to the same hardness. The deep drawing capacity of copper was a maximum after small rolling reductions, while that of 70/30 brass was a maximum in the annealed condition. For both materials annealing to temper increased the deep drawing capacity compared with rolling to temper; for copper the increase was greatest when temper annealing created a recovered state. Thickness strain and hardness distributions were measured on sectioned cups to assist in the interpretation of the cup drawing results. The redrawing capacity of copper increased with increase in hardness of the initial strip, but 70/30 brass would not redraw in any condition. The ear height and position on cups drawn from both materials in all conditions was related to the proportionate variation in R value, and the variation in cup height appeared to be related to the planar variation in R value when considered in a radial direction.