Bolster and side frame are important running parts on the bogie of rail freight car. They bear the gravity of freight car and the alternating stress of wheels, which has a great impact on the safety of freight car operation. At present, the bolster and side frame are mainly formed by casting. They are made of low-carbon alloy steel and have complex structure. They belong to box porous structural parts. Their casting processes mainly include CO2 sodium silicate sand process, ester hardened sodium silicate sand process, resin sand process, V method and clay green sand process.
In recent years, there are many manufacturers using ester hardened sodium silicate sand process to produce bolster and side frame, such as Qiqihar Vehicle Co., Ltd., Jinxi Equipment Manufacturing Co., Ltd., China Ordnance First Machinery Group, etc; The main manufacturers using clay green sand process are Zhuzhou Siwei company and Tongling Vehicle Co., Ltd.
The reuse rate of old sand in clay green molding sand process can reach more than 95%, which has little environmental pollution. It has many advantages, such as high production efficiency, good collapsibility, good forming effect, easy repair, low production cost, and is conducive to the realization of automatic and mechanized production. However, the surface of sand mold cavity is very brittle and weak, and it is very easy to deform and damage under the action of external force; Under the scouring and extrusion of high-temperature liquid steel, the sand mold surface is easy to arch and produce casting defects such as sand inclusion scar, expansion box, sand sticking and sand hole.
These casting defects will not only reduce the appearance quality of steel castings, increase the subsequent cleaning workload and flaw detection difficulty of steel castings, but also reduce the service properties such as stiffness and strength of steel castings and affect the driving reliability.
The research mainly aims at the problem of sand inclusion and sand sticking defects in the process of green sand casting of bolster and side frame, analyzes the causes, and takes corresponding improvement measures, so as to achieve better production results.