Abstract
Cartridge brass is represented by deep-drawing brass marked as Ms70 (CuZn30 according to DIN standards). Classical brass cartridge manufacturing technology uses rolled brass sheets as input semiproduct. Continuous pressure on manufacturing costs caused technological change which has introduced the manufacture of brass cartridges from bars. Brass bars are manufactured by hot extrusion pressing and subsequent cold drawing. The hot extrusion pressing process resulted to be a problematic operation in the brass bars Ms70 manufacturing. Therefore, the assessment of hot formability properties on universal plastometer SETARAM-VITKOVICE was realized. To determine the strain rates possibilities in a required range, two sizes of sample bars were examined. Furthermore, analysis of relations for calculation of the deformation during torsion test and their comparison were performed. Four computational relations were compared. Preliminary torsion tests were performed on samples taken from bars of cartridge brass Ms70. Temperature of formability was 850 °C. Torsion tests were carried out on long as well as on short sample bars. Plastometer was connected to control personal computer. The values of time, torque, tension force, speed of torsion, number of twists till rupture, and formability temperature behavior were recorded during torsion tests. Input torsion tests on cartridge brass enabled to determine experimental plan for the real process of extrusion pressing. The first results from torsion tests proved that brass Ms70 has significant effect of dynamic recrystallization after some deformation. Temperature of forming and the strain rate from which the extrusion press rate is derived are dominant parameters.
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