The invention relates to the technical field of steel for
agricultural machinery, in particular to low-yield-strength
impact-resistant steel for a rotary blade of
agricultural machinery and a manufacturing method of the low-yield-strength
impact-resistant steel. Cr, Nb, B and Re are used for alloying, meanwhile, the technological parameters such as
casting blank heating, rough and finish rolling descaling pressure, the rolling temperature, the
reduction rate, the coiling temperature and the
cooling speed are controlled, and the prepared steel for the agricultural
machine rotary blade is low in yield strength and good in punch forming performance; the yield strength of the agricultural
machine rotary blade part produced by using the
composite material is 300-400MPa, the tensile strength is 700-800MPa, and the
ductility is greater than or equal to 18%; after heat treatment, the yield strength is 1400 MPa or above, the tensile strength is 1900 MPa or above, the
ductility is larger than or equal to 10%, the
impact energy AKv at the temperature of 20 DEG C is larger than or equal to 25 J, the
hardness is 53 HRC or above, the wear-resisting life is prolonged by two times or above, and the service life is obviously prolonged.