USE OF DRI AND HBI FOR NITROGEN CONTROL OF STEEL PRODUCTS

摘要

Due to the increasing production of flat products and other high-end steel products via the EAF steelmaking route, the requirement for strict N_2 control is becoming ever greater. A variety of options are available to control N_2 including improved operating practices and use of virgin iron units. It has been demonstrated that use of DRI or HBI assists in N_2 control by diluting the N_2 content of the source iron units, generating a slag early in the melting stage in order to shield the metal from the atmosphere, helping generate a foamy slag, and producing a CO boil within the steel bath to flush out N_2. It also has been demonstrated that by reducing the N_2 content of steel products, DRI and HBI can promote improvement in the mechanical properties of those products. In particular, increased use of HBI leads to improved strength, toughness, and ductility, which promote better formability. Also there is also evidence that use of HBI reduces susceptibility to cracking during rolling. Further, many steel producers' measurements show that use of DRI/HBI consistently results in lower N_2 content compared to 100% scrap use. DRI/HBI not only reduces residual content but also ensures greater consistency in chemical composition and, therefore, steel properties. Hence, the steel producer can be confident of meeting product requirements and minimizing downgraded product and unnecessary inventory.