Quality Of Castings

- Aug 20, 2018-

Mainly includes the appearance quality, the intrinsic quality and the use quality. Appearance quality refers to the surface roughness of castings, surface defect, size deviation, shape deviation, weight deviation; Internal quality mainly refers to the chemical composition of castings, physical properties, mechanical properties, metallographic structure, as well as holes, cracks, inclusions and segregation in castings, etc. use quality refers to the working durability of castings under different conditions,

including abrasion resistance, corrosion resistance, cold shock, fatigue, shock absorption and other properties as well as cutting, solderability and other technological performance. Casting quality has a great influence on the performance of mechanical products. For example, the wear resistance and dimensional stability of machine tool castings directly affect the precision of machine tool to maintain life; all kinds of pump impeller, shell and hydraulic parts of the internal cavity size, the accuracy of the profile and surface roughness, directly affect the pump and hydraulic system efficiency, energy consumption and corrosion development, and so on; internal combustion engine cylinder, cylinder head, cylinder liner, piston ring,

The strength and the heat resistance of the castings, such as exhaust pipes, directly affect the working life of the engine. There are many factors affecting casting quality, the first is the design process of castings. Design, in addition to the working conditions and metal properties to determine the geometric shape of castings, size, it is also necessary to consider the rationality of the design from the angle of casting alloy and casting process characteristics, that is, the obvious size effect and solidification, shrinkage, stress and so on, in order to avoid or reduce the component segregation of castings, deformation, Cracking and other defects. The second is to have a reasonable casting process. That is, according to the casting structure, weight and size, casting alloy characteristics and production conditions, the selection of suitable classification surface and molding, core-making method, reasonable set up casting tendons, chill, riser and gating system. To ensure the acquisition of high-quality castings. The third is the quality of raw materials used for foundry. Metal charge, refractory material, fuel, flux, modifier and casting sand, molding sand binder, paint and other materials of substandard quality, will make the casting hole, pinhole, slag, sticky sand and other defects, affecting the casting appearance quality and internal quality, serious will make the casting scrap.

Four is the process operation, must make the reasonable craft operation procedure, enhances the worker's technical level, causes the craft procedure to obtain the correct implementation. In casting production, the quality of castings should be controlled and inspected. The first step is to develop a process code and technical requirements for the control and inspection of raw materials, auxiliary materials and each specific product. Each process is strictly according to the process Code and technical conditions for control and inspection. Finally, the finished castings are inspected for quality. should be equipped with reasonable detection methods and the appropriate testing personnel. Generally, the appearance quality of castings can be used to judge the surface roughness of castings, and the fine cracks of the surface can be examined by coloring method and magnetic powder method. The internal quality of castings can be examined and judged by means of audio, ultrasonic, Eddy Current, X-rays and gamma rays.