Investigation of the causes of cracking on the housings of brass ball valves

In order to determine the cause of cracks on the housings of finished brass ball valves, samples cut from cracked cranes produced from June to September 2023 were studied, moreover, with the help of these samples, it was possible to study the fracture surface and the microstructure of the section bordering the fracture, including the element composition of individual structural components. A detailed study of the microstructure of the material of these products was performed using a scanning microscope “JEOL JSM-7001F”, which has an attachment - the Oxford energy dispersion analyzer “INCA X-max 80”, which allows for micro X-ray spectral analysis of individual parts of the brass microstructure. The study revealed a large difference in the concentration of lead in the slot and on the surface of the fracture bordering it, which is typical for almost all destroyed cranes. In this regard, the influence of the onset of crystallization and the rate of extraction of brass rods from the furnace on the distribution of lead and embrittling impurities in the volume of experimental cast samples, and then in forgings made from these cast blanks, was studied. It is shown that cracks formed on the surface of a part of the samples (Nos. 1, 2, 4) after hot deformation. Moreover, the probability of their formation during the stamping of the crane body decreases when using more homogeneous cast cylindrical blanks, which can be obtained, as the study showed, by increasing the degree of supercooling of the liquid phase and the crystallization rate. The results obtained provide useful information in the analysis of technological operations for the production of lead brass products LS59-1B.