HOT-ROLLED THICK H-BEAM WITH YIELD STRENGTH GRADE OF 500 MPA AND PREPARATION METHOD THEREFOR

摘要

A hot-rolled thick H-beam with a yield strength grade of 500 MPa and a preparation method therefor. The chemical composition of the hot-rolled H-beam is, in percentage by weight: C: 0.10% to 0.20%, Si: 0.15% to 0.30%, Mn: 0.8% to 1.30%, Nb: 0.02% to 0.05%, V: 0.10% to 0.16%, Ni: 0.40% to 1.0%, P: ≤ 0.015%, S: ≤ 0.01%, Mo: 0.15% to 0.35%, Al: ≤ 0.05%, O: ≤ 0.004%, and N: 0.01% to 0.02%, the balance being Fe and unavoidable impurities. The H-beam adopts a composite micro-alloy composition with a medium carbon content combined with high nickel and vanadium contents suitable for normalizing rolling, thereby obtaining a stably controlled high-strength hot-rolled H-beam of a 500 MPa grade or higher for maritime use. The final structure of the H-beam is mainly refined pearlite and pro-eutectoid ferrite, containing a small amount of a bainite structure. By means of structural refinement, phase transformation strengthening, and precipitation strengthening, the H-beam can be provided with an impact toughness of greater than 100 J at a temperature of -40°C under high strength and large thickness requirements.