25CrMo4 – specification and applications
25HM steel, which is a Polish equivalent of 25CrMo4, is alternately classified as structural steel for heat improvement and as a boiler steel designed to work at elevated temperatures. It exhibits very good strength properties, high ductility, weldability and good hardenability. Compared to the 35HM and 34CrMo4 grades, after heat treatment it has slightly worse strengths, but it makes up for the lower properties with much better ductility.
25HM achieves best durability values at dimensions up to 65mm after hardening in water, while after hardening in oil at dimensions and thicknesses up to 40mm. It is most often found in a heat-treated or softened state – less commonly in the normalized state.
For use in high temperature applications – the power industry – this steel is used in the production of parts working at 450 – 530 ℃, which exhibit creep resistance: flanges and welds for pipes, covers, nuts, heavy-duty screws, turbine rotors, turbine blades, toothed shafts, cylinder rods, seamless tubes, control parts, and levers.