Composite alloys for special purposes, which include antifriction silicon-manganese brasses of types LMtsKNS and LMtsKA, should have a microscopically homogeneous structure and a microstructure with specific characteristics. The determining parameters for the structure of this class of brass are a uniform distribution and sizes of inclusions of lead and intermetallic compounds, which affect substantially their strength, wear resistance, processability, antifriction properties and other operational characteristics. In this connection, it is interesting to study the possibility of predicting the sizes of primary inclusions of intermetallic compounds and crystals of the base under different production conditions, including the use of nontraditional methods of heat treatment. The present paper considers the structure of antifriction brass LMtsKNS after cooling at different rates as a function of the crystallization temperature.