Inspection of stress relief heat treatment effect on residual stress at cold drawned alpha-beta brass

In this study, the residual stress after cold deformation in CuZn39Pb3 free cutting brass alloy which is shaped by cold drawing method, a plastic deformation process which is widely used for alpha-beta double phase brass rod production is investigated experimentally with Mercury (I) Nitrate test. In the case of brass parts with residual stress, stress corrosion crack is observed under corrosive conditions (like moist, ammonia, mercury). In the Mercury (I) nitrate test, the residues under load are kept in the mercury solution for 30 minutes in a highly corrosive environment. In this way, the corrosion mechanism is accelerated. At the end of the experiment, deep cracks are seen in parts with critical residual stress. CuZn39Pb3 rod parts with the cold drawing after hot extrusion provided by PIREKS BAKIR ALASIMLARI A.S, reduction of 5.24% on section was achieved. Considering this deformation rate, stress relief annealing was applied to the pieces at 150 ° C and 250 ° C for 30 minutes to remove the residual stress. The mechanical properties of the parts grouped according to stress removal conditions were determined by brinell hardness method and tensile test. Accordingly, no significant change was observed in the hardness and tensile strength of materials by stress relief. Mercury (I) Nitrate test prepared by TS EN ISO 196 standard was applied to the parts prepared after different stress removal conditions. The parts obtained at the end of the experiment and the samples cut from these parts were examined under an optical microscope. As a result of the experiment, deep cracks were observed in the parts which were not annealed after cold drawing and cracks were detected on the surfaces of the annealed parts at 150 ° C, 30 min. No cracks were detected at 250 ° C,30 min. annealed parts.