Effects of manufacturing technological conditions of brass water-locking devices on the quality of finished products

The effect of the main operations of manufacturing brass ball valves (smelting, continuous casting of cylindrical blocks, hot stamping, machining and subsequent surface nickel plating) on the quality of the finished valve is studied. After each of specified above operations the microstructure was studied by optical and scanning electron microscopy (JEOL JSM 7001F and Carl Zeiss Axio Observer D1m). The hardness of individual phases measured on a Futur Tech FM-800 microhardness tester. The presence or absence of macro and micro cracks and its hardness were evaluated. It has been established that there are no discontinuities in the material in the cast billet along its cross section and the length of the rod. However, inhomogeneities characteristic of the cast structure in shape, size and number of main structural components are noted. In some places along the α/β interfaces continuous chains of Pb particles determined. During the subsequent hot stamping of semi-finished products, microcracks were formed on the particles of lead and non-metallic precipitates, formed by impurity elements: iron and silicon. The strength (hardness) in different parts of the stamping is not the same due to the different values of hot work hardening due to differences in the degrees of deformation and subsequent recrystallization. In general, the hardness of deformed brass is higher than the hardness of brass in cast state. In the finished product the nuclei of microcracks are identified, but the technological stage when they were formed cannot be definitely indicated. They may be a consequence of stamping or cutting as a result of internal tensions.