Basic oxygen furnace (BOF) lance life improvements were made at No. 3 Steel Producing (No. 3 SP) at ArcelorMittal Indiana Harbor after premature lance tip failures resulted in a failure mode investigation of lance B-5. This led to making improvements to the water baffle inspection, which improved water flows to the lance tip; increased post-combustion step height from 7.5 feet to 11 feet; and utilized a 4-hole composite tip design at 18,000/23,000 scfm O2 flowrate instead of the regular 4-hole tip with a 25,000 scfm design O2 flowrate, in order to accommodate the variable O2 flowrates used during the blow to contain slopping. As a result, the average lance life has increased from the initial 144 in 2012 to 326 heats as of October 2016. The slag FeO as a function of the lance life will be discussed. The lance costs have decreased by about 44%. This paper will discuss the above factors and the various lance operating procedures instituted to enhance BOF lance life.
At Ternium Brasil, formerly thyssenkrupp CSA, a positive heat balance at the BOF process is faced, mainly because of low utilization of scrap and plant design. A singular logistic concept for hot metal transport between the blast furnace and the steel plant was established to optimize transportation and energy balance. Up to 80 kg of iron ore pellets per ton of steel is necessary for a 340-t BOF heat balance. In order to accomplish this, a stable blowing process and intensive operational development have been executed: a slopping rate reduction of 80% was achieved without changing the blowing time. This paper describes the steps of this development and the results.
Primary steelmaking through basic oxygen furnace converters represents an important point in steel production. Against a challenging and competitive market, operational stability and innovations are necessary to reach quality and suitable costs. In order to study the combined blowing through a cold physical model, in similarity with Ternium Brasil’s 330-ton converter, visual inspection and colorimetry methods were used to define the jet penetration and the best tuyere configuration, respectively, on the metal bath behavior. A bath lance distance was found that decreases mix time with low slopping probability. After cold model results, parameters can be recalculated for industrial practice with good agreement.
A unique KOBM selective coating practice was successfully developed in ArcelorMittal Dofasco KOBM Steelmaking at the end of 2012. The practice includes developments of both proper slag chemistry and slag coating practice. Proper coating practice refers to the amount of retained slag, vessel rotation angle, coating time, gas flowrate, etc., which is dependent on not only locations of vessel wear, but also on the available time for coating. With the implementation of this practice, the refractory wear rate has greatly decreased in every section of the vessel. This brings significant gains for Dofasco steelmaking, such as improved KOBM productivity, reduced gunning material and refractory cost. In addition, the steelmaking working environment is also improved. In general, KOBM vessel life is no longer a big concern in Dofasco KOBM steelmaking.
The continuous demand by the agricultural and heavy transportation consumer industries for stronger, tougher, lighter and more cost-effective steel products represents a series of unique opportunities and challenges for the steel industry. Therefore, it is necessary to have a fundamental understanding of the intrinsic relationships between alloy design-thermomechanical processing (TMP)-transformation behavior-final microstructure and mechanical properties. This work presents an example from conception to validation. The validation stages were performed by laboratory studies and industrial trials. The fundamental concept was based on information from different thermodynamic software packages and mean flow stress models applied to the designed steel compositions, TMP and transformation behavior. The final microstructure was characterized using electron optics techniques. The steels exhibited an excellent package of strength-toughness properties. These properties were obtained by a combination of fine bainitic ferrite, fine TiNbV-carbide precipitation and acicular ferrite. The final microstructural features were the result of the proper microstructural conditioning of the austenite prior to the transformation and the cooling strategy on the runout table. The results of this study are presented and discussed.
The mechanical stirring method with an impeller has been widely applied to the hot metal desulfurization process in Japan. In order to optimize the composition of desulfurization flux, the effect of AlN on the hot metal desulfurization was examined using 300-kg-scale hot metal experiments. It was shown that AlN contributes to deoxidation reaction in the hot metal, and the desulfurization efficiency was improved due to a decrease in the CaO/Al2O3 ratio or increasing the metal temperature.