La fractura de materiales de ingeniería es casi siempre un hecho indeseable por varias razones, tales como la seguridad de vidas humanas, pérdidas económicas y la interferencia con la disponibilidad de productos y servicios. La industria automotriz ha estado siempre a la vanguardia en investigación ya que el mercado cada vez es más competido y exige productos de confiabilidad y de bajo costo. Los fabricantes y usuarios de ballestas desean buen desempeño, durabilidad y una reducción en el peso ya que esto se refleja en el consumo de combustible, por lo cual es más competitivo fabricar ballestas que ofrezcan la mayor tolerancia al daño posible, y con una alta tenacidad de fractura se asegura una mayor vida útil de las ballestas ante la presencia de discontinuidades. / Abstract. This project evaluates the behavior of fracture toughness in specimens of AISISAE 5160H steel used in the manufacture of automotive leaf spring. Specimens from four suppliers were subjected to quenched and tempered from seven different temperatures. The specimens were precracking in fatigue machine and subject to fracture toughness test in SENB settings, creating fracture surfaces, which were classified and inspected macroscopically (to simple view and in stereoscopic) and microscopic (scanning electron microscope-SEM). The material was characterized by chemical analysis, hardness and metallography. Ruled in Standard E399-08 was selected the type of specimen, was determined the precracking assembly and the fracture toughness was calculated in terms of Jtotal and Jcritical. With the development of this project found that the tempered temperature influenced the fracture toughness and was evident that one of the providers had a strong performance at lower fracture toughness than the other three suppliers.