Residual stresses in 7050 aluminum alloy restruck forged block

Unacceptable levels of residual stresses in restruck (compression stress relieved) forged block (hand forgings) lead to very high scrap, rejections and rework (hand straightening). This is due to machining distortion, bow, twist and oil canning of parts aggressively machined from aluminum alloy 7050 restruck forged block. Industry practices to manufacture restruck forged block vary considerably among the manufacturers, and hence, influence the final product delivered to the customers. Manufacturing parameters that have influence on stress levels in compression stress relieved forged block will be discussed. Case histories of production parts machined from desirable test materials will be presented. Layer removal technique (machining deflection) for determining comparative residual stress levels in forged block as well as plate will be discussed. Correlation between ion, residual stress level materials, determined by layer removal techniques, and machining distortion of production parts will be presented. A combination of parameters influence the levels of residual stresses in restruck forged block - the combination being unique to each manufacturer. Some of tile manufacturers are limited in their capability to produce blocks with consistently uniform/low residual stress levels, due to limitations of their processes and equipment.