Industrial Metallographic Microscopes for Characteristic Identification of Casting Materials
The properties of casting materials (mechanical, physical and chemical properties such as strength, toughness, magnetic performance and corrosion resistance) are generally determined by their internal microstructure, including atomic bonding in crystal lattices, molecular structure, microconstituents, grain shape and grain size. These properties determine the service functions of castings, such as high‑strength castings, free‑machining castings, corrosion‑resistant castings, heat‑resistant castings and wear‑resistant castings. To manufacture and apply castings properly, it is necessary to understand their microstructure. Casting materials need to be tailored for specific applications to meet design specifications. Material properties can be improved by appropriately modifying the internal microstructure; any change to the microstructure via processing will correspondingly alter material properties. During production, modifying the internal microstructure of castings changes their material properties and service performance. Heat treatment is a typical application of this principle.
Based on the above, heat treatment of castings can be defined as follows: Heat treatment is a controlled process involving heating, holding and cooling of castings to modify their internal microstructure, so as to improve mechanical properties or achieve special service purposes. The desired casting properties can be obtained by controlling the heating rate, holding temperature, holding time and cooling rate in the heat treatment process. The foundation of any heat treatment process consists of four basic factors:
① Heating rate
② Selection of appropriate holding temperature
③ Holding duration at the set temperature
④ Cooling rate
