High-toughness low-alloy constructional steel and producing method thereof

The invention relates the low-alloy high-tensile structural steel and preparing method. The components are as follows: C:0.05%-0.60%, Si: 0.05%-0.70%, Mn: 0.5%-2.5%, P: <= 0.04%, S: <=0.04%, Cr: 0-0.70%, Ni: 0-0.70%, molybdenum: 0-0.60%, Cu: 0-0.20%, vanadium: 0.01%-0.30%, Al 0-0.1%, niobium: 0.001%-0.10%, N: 0.004%-0.02%, and the left is Fe. The method comprises the following steps: using revolving furnace to smelt, and using LF furnace to refine. The yield strength as is above 460Mpa, the dynamic ductility Akv is above 27J at low temperature (-40Deg.C), endurance life is above 2 million times, and the finished steel can be used for train brake beam, engineering machinery and hydraulic support without heat treatment. After quenching and high tempering modified heat treatment, the strength for extension of the steel is above 750Mpa, the dynamic ductility Akv is above 150J at low temperature (-40Deg.C). After carbonization, the steel can be used for abrasion-proof driving mechanism elements and parts.