Effect of Boron on the Structure and Properties of Cast Iron Castings.

Cast iron castings have been obtained in sand and metal molds. Owing to the accelerated crystallization of cast iron in shell molds, the graphite inclusions are crushed, and the structure of the metal matrix becomes pearlitic, instead of ferritic-pearlitic, as in sand molds. The structure changes notably when the cast iron is alloyed with boron. Carboborides of type Fe//3(C,B), which are very hard and wear-resistant, are formed in the metal matrix. The hardness of microalloyed cast iron increases to 223-228 HB in comparison with 137-179 HB in unalloyed cast irons. The wear resistance of cast iron alloyed with boron is 1. 42 to 1. 80 times greater than that of unalloyed cast iron.