Chromium powder as a reference material for the quality control of particle-size measurement by laser diffraction

Chromium is an important alloying element for aluminium melts. During aluminium cast house practice, chromium is mainly added to melts of aluminium in the holding furnace as tablets or minitablets (compressed compacts of chromium and aluminium powders). Particle-size analyses of chromium powder used as raw material can routinely be carried out by laser diffraction to assure correct packing. Factors affecting the laser diffraction analysis were studied by means of designed experiments in order to improve and control the quality of such particle-size measurements. Moreover, a laboratory reference material based on chromium powder was produced to assure the quality control of particle-size measurements. The material was carefully handled (collection, pre-treatment and preservation) and its homogeneity and term stability were verified. Laser diffraction analyses were validated against sieve-type measurements for the same material.