The coarse grain size of the casting refers to the defect that the grain structure is excessively large and unsuitable for application after mechanical inspection or fracture inspection. The coarse grain structure may be spread over the whole casting or may occur in the casting. Partial. In essence, coarse grain defects are a metallurgical defect. Based on years of production practice and reference to relevant materials, the author talks about the causes and preventive measures of coarse defects in castings.