In traditional pouring systems, molten steel flowing through a sand mold easily undergoes sand washing, which leads to sand inclusions, surface water marks and other defects when the liquid material is unstable. In traditional exhaust systems, floating sand easily forms in the airway after the air hole is drilled, resulting in sand inclusion in the casting. When cutting the air hole of the casting body, it is easy to cut the casting to form a lack material defect. To continuously improve the internal and external quality of knuckle castings for railway freight cars, a number of measures, such as adopting double-pass double-injection pouring cups, improving pouring methods, designing integrated splicing refractory runners, testing grid exhaust valves, testing multiple types of sand, and optimizing special sand box tooling, significantly improves the quality of the knuckle, increasing the qualified rate from 82% to over 96%.