"IF YOU CAN DRAW IT, WE CAN MAKE IT!"TECHNOLOGY FOR THE 21ST CENTURY
Heat treatment of foundry Stainless Steel Casting Parts
The requirements for heat treatment of foundry and die steel castings vary with their composition and conditions of use. For example, for casting tool steel castings, the general section size is small and the shape is complex. The heat treatment process should be selected to ensure strength, hot hardness and prevent deformation and cracking; while Stainless Steel Casting Parts are mostly large-sized slabs. Or inlays, the heat treatment process to ensure high strength and good toughness.
Since the composition of the foundry and the die steel is close to that of the same type of forging and die steel, the heat treatment specification is in principle based on the latter process.The commonly used heat treatments are pre-treatment (annealing) and final treatment (quenching, tempering and surface chemical treatment). For small casters and molds cast from metal or dry sand, in addition to normal annealing and quenching, they should be annealed immediately after casting to eliminate casting stress and avoid cracking.
The annealing of the foundry and the die steel is aimed at reducing the hardness for cutting and providing the best original structure for quenching. The annealing temperature selected is 30 to 70 higher than that of the same grade forged steel. C. Tables 11 to 30 show the annealing process of foundry and die steel. The casting and mold steel annealing may be performed by full annealing or spheroidizing annealing in order to obtain a spheroidal structure of fine spherical pearlite.
The specifications for the quenching process of foundry and die steel are listed in Table ll-31. The quenching temperature should generally be the lower limit of the same grade forged steel. In order to reduce quenching stress, prevent quenching cracks and shorten the residence time of foundry and die steel at high temperature quenching temperature, preheating is generally required, and the preheating temperature is 800-850.
The purpose of tempering of the foundry and die steel is to eliminate the quenching stress and complete the transformation of retained austenite. It is characterized by secondary hardening effect of steel during tempering. Figure ll-61 shows the tempering characteristic curve of ZG4CrSMoSiVl (HIS) steel. Table ll-33 is the specification of tempering process for foundry and die steel.