Slag samples are typically collected at the end of the steelmaking process, and the slag compositions are then often used as a reference of process control and refractory compatibility. While these samples are important and essential, they don’t reflect the transient slags that were responsible for refining reactions such as dephosphorization, desulfurization and inclusion absorption during the process. This paper will focus on the role of these transient slags and how they can be engineered to benefit the basic oxygen furnace, electric arc furnace and ladle refining processes. This paper will also provide some insights on the physical-chemical aspects of slags in steelmaking.
Control and understanding of the slag evolution path is important for the optimal performance of the basic oxygen furnace (BOF) process. Variables such as scrap, flux additions, lance movement and O2 flow influence the slag evolution that controls the hot metal refining. At Tata Steel IJmuiden, a modified sublance probe was used to take slag and metal samples from a 330-metric-ton converter at different refining periods. The dynamic evolution of slag chemistry and mineralogy were estimated. The influence of the process variables on slag FeO evolution and its effect on hot metal P refining are discussed with the help of a dynamic BOF model.
Dynamic velocity control of the jet from a top-blowing lance is important because the preferable jet conditions for physical phenomena and metallurgical reactions change during blowing. This study investigated a new approach in which the jet velocity is controlled by applying actuation gas in 1/10-scale model experiments. The actuation gas paths were set in a plane vertical to the main nozzle, and the actuation gas flowrate was controlled independently from that of the main gas. Although the total flowrate was constant, the jet velocity from the nozzle increased with the actuation gas flowrate.
AK Steel–Middletown Works determined to change one of its two 225-ton basic oxygen furnace (BOF) vessels. The BOF vessel and trunnion ring were previously fabricated with a bracket support system. After a thorough technical analysis, AK Steel chose to revamp the vessel and trunnion ring to accommodate the Vaicon Link 2.0 suspension system. The vessel was installed in 2017. The paper describes the principles of the suspension system, the project execution and results from an inspection after 17 months of operation.
This paper reviews the design and operational decisions that were made in 2005 during the replacement of a double-width, double-inlet, 75-inch-diameter, 9,000 lb., dual-speed, centrifugal fan wheel for a Q-BOP blast furnace due to excessive cracking in the wheel. The original centrifugal fan showed excessive cracking after 10 years of speed cycling duty. The replacement fan has been operating for more than 10 years and shows no signs of fatigue cracking. However, decisions were made to change the blade type and wheel material due to the original finite element analysis (FEA) and plant experience. This paper reviews the original analysis by an Algor FEA package and decisions by the plant personnel, and evaluates the process against a present-day ANSYS FEA analysis and over a total operating experience of 25 years.