The surface defects of impeller castings are first inspected by visual observation, in which a 5x magnifying glass is also used. Visual inspection is often accompanied by many processes, such as boxing, shelling, preliminary inspection after molding, cutting pouring riser, removing sand core and inspection after heat treatment.
The inspection shows that there is no fire escape during the pouring process of impeller casting; After sand cleaning, there are no surface defects such as sand sticking, bulging, sand inclusion, cold shut and insufficient pouring on the casting surface; The impeller contour is clear, the molding is complete, the surface of the cast impeller and disc is smooth and smooth, and the transition between planes is smooth and excessive; After the pouring riser is removed, the residual amount is 5mm ~ 8mm, and the root tissue of the pouring riser is dense.
Although there are flash on the upper and lower end faces of cast impeller blades due to the existence of mold closing clearance, the flash problem can not be considered because the upper and lower end faces have machining allowance of 5mm and 3mm respectively. Through comprehensive judgment, the appearance quality of impeller casting meets the requirements of gb12231-89.