The effects of heat treatments on the hardness and microstructure of a hypoeutectic white iron, which is compost by 2.52% C, 1.51% Si, 0.20% Mn, 0.01% S y 0.02% P, was studied in the physical metallurgy laboratory. White iron square bars 12 mm x 12 mm x 200 mm long was used, supplied by nodular iron SA (FUMASA), which were heated to austenitizing temperature of 950 ° C for 2 hours under these conditions and heat treatment of annealing, quenching, tempering and Austempering were performed. The experimental results showed that with the annealing heat treatment was get it a malleable cast iron ferritic structure which consists of irregular nodules of graphite and ferrite (matrix). With the heat treatment of quenching, a high level of hardness is obtained (605.30 HB), due to because the microstructure is formed by plates acicular cementite and martensite. With decreases tempering hardness (...