Shrinkage Defects Essay

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4.1 Shrinkage Defect: 4.1.1 Definition • Shrinkage defects occur when standard feed metal is not available to compensate for shrinkage as the thick metal solidifies. • The shrinkage defect usually forms at the top of the hot spots. They require a nucleation point, so impurities and dissolved gas can induce closed shrinkage defects. • Solidification leads to volumetric contraction which must be compensated by feeding. If this compensation is inadequate either surface shrinkage or internal shrinkage defects are produced making the casting weaker. • While the material is changing from liquid to solid Contraction takes place at varying rates, which causes irregularly shaped shrinkage cavities depressions. • This defect occurs in all castings but more frequently in heavy sections in all alloys with along solidification range. This is different from hot tears and creaks. Figure – 4.1.1 Identification of Shrinkage defect. 4.1.2 Causes of Shrinkage Defect The various causes for shrinkage defect are given below.  Failure to obtain direction solidification of the casting, because of low pouring temperature or incorrect gating system.  Inadequate risers for heavy section.  Unsatisfactory casting design.  Excessive or inadequate pouring temperature.  Due to improper design of gate and riser. 4.1.3 Remedies of shrinkage defect 1. Ensure directional progressive solidification. For solidification in a casting component for proper way is shown in fig. Figure 4.1.2 Solidification rate diagram 2.... ... middle of paper ... ...l casting component.  That’s why this pouring temperature range (1390◦c to 1420ºc) is selected during the pour of molten metal in the mould. CONCLUSION: • From this project we have solved the casting defects such as Blow hole and Shrinkage. • The Blow Hole solution is done by some remedies in pump part (Upper housing and Lower housing) • The Shrinkage defect is solved by simulation process in Automobile part (Steering joint). • The simulation process is done in softCAST software. • In final, the shrinkage defect is solved by some of changes in pouring temperature (1370◦c to 1470◦c). • From this pouring temperature shrinkage defect is generated in spure and riser. • After all spure and riser is cut in fettling shop and casting component is defect free.

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