LOW-ALLOYED, BORON-CONTAINING STEEL FOR FACE-HARDENED PARTS

摘要

The invention is related to metallurgy, in particular, to structural steels having improved mechanical properties and specified hardenability, and can be used in manufacture of gears for energy-intense machines. The invention provides a low-alloyed, boron-containing steel for face-hardened parts containing carbon, silicon, manganese, chromium, nickel, molybdenum, aluminium, calcium, boron, iron and impurities, characterized in that the steel further contains niobium with the following proportion of the components, wt.%: carbon 0.18-0.23, manganese 0.40-0.70, silicon 0.17-0.37, chromium 0.40-0.70, nickel 0.40-0.70, molybdenum 0.15-0.25, aluminium 0.02-0.05, calcium 0.0004-0.0050, boron 0.008-0.015, niobium 0.03-0.045, the balance being iron and inevitable impurities, wherein the total manganese, chromium, nickel and molybdenum content is within 1.35-2.35 wt.%, and the ratio of molybdenum to boron is within 10:1 to 30:1. As impurities, the steel contains phosphorus ≤0.025 wt.%, sulphur ≤0.025% and copper ≤0.15%. Hardenability (hardness of a specimen after end quenching) is, at a distance from the specimen end of 3 mm - from 44 to 47 HRC; at a distance of 11.0 mm - from 33 to 47 HRC; at a distance of 20.0 mm - from 20 to 44 HRC; at a distance of 40.0 mm - from 13 to 33 HRC. The claimed steel has specified hardenability, higher yield strength, impact strength and fatigue strength values.