High-strength steel for forging

摘要

In the present invention, there is disclosed a Forged steel composition containing 0.3 to 0.5 percent by weight of carbon, 0.1 to 0.4 percent by weight of silicon, 0.7 to 1.5 percent by weight of manganese, 1.2 to 3.5 percent by weight of chromium, 0.1 to 0.6 percent by weight of molybdenum, up to 0.7 percent by weight of nickel, at least one element being selected from the group consisting of vanadium. Niobium and tantalum in the total amount 0.03 to 0.35 percent by weight, and 30 to 250 ppm of nitrogen, the balance being iron and undesired impurities. The invented Forged steel forms a microstructure consisting of bainite and martensite and contains nitrogen in solid solution with vanadium, niobium and tantalum in such en amount that (total weight percentage of vanadium, niobium and tantalum + 0.001 x /N (ppm) in solid solution) is more than or equal to 0.068. A preferred feature of the invented forges steel is small amount of expensive alloying ingredients (particularly nickel) at maintenance of the steel high strength. The steel is particularly suitable for manufacture of big crankshafts intended for ships.