This part of the standard specifies the principle, instrument, test procedure, test result processing and content of the test report of the laser rapid determination method for refractory powder for investment casting. This method is suitable for the particle size determination of refractory powder with a particle size in the range of 0.02 μm to 2000 μm for investment casting. According to the principle, the Furanhofer diffraction and Mie scattering theory are adopted, and the laser is used to capture the size information of powder particles passing through the beam of light, and the signal is transmitted to the computer Control system through the sensing system. The signal is processed and analyzed by special software, and the relationship between particle size and content is obtained. The equipment required for the test includes the laser powder Particle size distribution tester and the corresponding special software for particle size testing. Mastersizer 2000 or GSL-101 laser powder Particle size distribution tester is recommended. The test steps include equipment inspection, opening equipment and software, adding dispersing medium, back bottom test, adjusting test parameters, adding samples, and three consecutive tests. If the test data match well, it is qualified. If it does not fit, the sexual repeability test and take corresponding measures.