Chromite sand AFS45-55 is a commonly used model in sand casting. Its particle size meets the requirements of AFS Foundry Association. However, in practical applications, the ratio of fine powder under a 100 mesh sieve has a significant impact on the performance of casting sand. In the quality control process of casting grade chromite sand, 4-5 mesh screens are usually used for particle size distribution testing. The particles screened below 100 mesh and above 140 mesh are not further sorted. Recently, a customer has special requirements for the particle size of AFS45-55. Our lab conducted further tests on the particles under 140 mesh, 200 mesh, and 270 mesh sieves. The following are the test results: