The invention discloses a high-strength and high-
toughness heat treatment method of medium-carbon
silicon-
manganese-
chromium-
nickel series low
alloy steel, relating to a high-strength and high-strength heat treatment method of low
alloy steel and aiming at solving the problem that the medium-carbon
silicon-
manganese-
chromium-
nickel series low
alloy steel treated by a traditional heat treatment process cannot simultaneously obtain excellent strength,
ductility and
toughness. The high-strength and high-
toughness heat treatment method comprises the following steps of: 1, carrying out austenitizing treatment on the medium-carbon
silicon-
manganese-
chromium-
nickel series low
alloy steel, and then carrying out isothermal
quenching to finish primary heat treatment; and 2, carrying out isothermal
quenching on the medium-carbon silicon-manganese-chromium-nickel series low
alloy steel subjected to the primary heat treatment in the step 1, and finally
quenching to
room temperature. The medium-carbon silicon-manganese-chromium-nickel series low
alloy steel treated by using the method disclosed by the invention has the tensile strength of 1580MPa-2000MPa, the yield strength of 1340MPa-1870MPa, the
ductility of 9.0-22.9 percent and the
percentage reduction of area of 16.0-43.2 percent. The high-strength and high-toughness heat treatment method can be used for heat treatment of the medium-carbon silicon-manganese-chromium-nickel series low alloy steel.