Because Q355NH weathering steel contains 0.20 ~ 0.50% copper, and the copper content of the steel is more than 0.20%, surface cracks are easily formed on the surface of the billet, and surface cracks are easy to occur when heating. After adding the copper element, overcoming the surface cracks and hot rolling cracks of the shaped billet has become a key issue in the production of weathering H-beams.
Resolution measures are formulated as follows:(1) Adjust the
Q355NH steel composition: If a certain amount of nickel is added to the steel (Ni: Cu = 1: 3 ~ 1: 2), the copper-enriched layer on the surface of the steel can become a copper-nickel enrichment with a melting point exceeding 1 200 ° C (2) Adopt LF ladle refining technology to improve the purity of molten steel and reduce inclusions in molten steel; (3) Control the heating and rolling process of Q355NH weathering steel slab. Adopt weak reducing atmosphere heating; adopt high temperature, fast firing, fast rolling process rolling; use high-pressure water descaling technology; (4) adjust the appropriate continuous casting process parameters to reduce the occurrence of billet cracks.
