Post treatment of castings

Post treatment of castings
Post treatment of casting is a process of heat treatment,reshaping,rust prevention and rough finish for casting after cleaning up. Post treatment of casting is the last line process of casting production.
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Heat treatment: For some casting,heat treatment is required after casting cleaning in order to improve or change raw castings,remove innerstress,ensure the casting performance,prevent deformation and damage of the castings. Heat treatment of casting usually has hardening, annealing, normalizing,as-cast conditioning,precipitation heat treatment,stress relieving,soften and graphitization treatment, ect. For example,high manganese steel castings require high wear resistance and toughness enough and it’s internal organization shall be the austenite. So we need make quenching treatment for castings, making castings heat to austenite region and make complete austenitizing, then rapidly quench water chilling and make the austenite keep down.This process is also called water toughening treatment or solid solution treatment.
Reshaping: It is divided into three aspects of modification, repair and surface finishing. Some castings are out of shape,make the out-of-tolerance part size in the solidification ,cooling and heat treatment process and need to repair by a correct method. Repair is mainly proceeded using mechanical power at room temperature or temperature state.When the deformation is too large,it can also use the casting weight, or pressure for high temperature correction inside the furnace.External defects of castings mainly use welding method to repair. Leakage defects of castings requiring air, liquid can be solved by pushing the plugging agent. That the casting surface is rough and uneven hanging wheel and commonly use hanging wheeling and high speed to polish and finish.
Rough finish: Castings should be partly for rough machining according to the technical conditions before delivery. After rough machining, we can find defects timely and solve it, also can reduce weight and make the wastes and scraps to incorporate classification recycling.
rust prevention：For some castings and machine tool castings, we shoud do rust prevention to prevent from rust during transport and storage before delivery. General is to paint primer after final inspection.