Aluminum die forgines, due to a mix of heavy and thin cross sections, have non-uniform quenching residual stresses. Theses stresses lead to warpage and distortion during machining. To overcome these problems usually requires additional operations, resulting in added cost and flow times. Forgings can be purchased from the suppliers, non-heat treated, rough or finish machined, heat treated and ten finish machined. This adds to the cost of machining (twice); it also adds to the flow time due to the heat-treat operations. Even then some machined parts have to be scrapped, because the amount of warpage/distortion is beyond correction. Three parts of aluminum alloy 7050 of different sizes, configurations, cross sections and heat treatment callouts were machined after stress relieve. Machning steps and idstortion data will be discussed. Reasons for selecting a particular stress relieve application will be presented.
展开▼
