Pan American Materials Congress: Steels: Steelmaking & Solidification
Sponsored by: Third Pan American Materials Congress Organizing Committee
Program Organizers: Omar Garcia-Rincon, TERNIUM Mexico SA de CV; Andre Costa E Silva, EEIMVR - Universidade Federal Fluminense
Tuesday 3:40 PM
February 28, 2017
Room: Marina E
Location: Marriott Marquis Hotel
Session Chair: Martha Guerrero-Mata, Universidad Autonoma de Nuevo Leon
3:40 PM Invited
Jansto: New Generation Niobium Bearing Structural Steels for Future Infrastructure Demands: Steven Jansto1; 1CBMM-North America, Inc.
The new generation of value-added low carbon niobium (Nb) microalloyed beam, plate and rebar construction steels for both low and high yield strength and energy absorption applications are shifting designers to new lower cost materials. The civil engineering and end user community demand structural reinforcing bars, shapes, beams and plates with improved energy absorption and fatigue properties. The future market demands better fire and seismic resistance, yield-to-tensile ratio consistency, improved bendability and weldability. These attributes are difficult to obtain from steel producers today with their current higher carbon microalloyed steel approach. However, there is a global shift in motion to low C-Nb bearing construction steels displacing traditional materials. For example, in the construction beam sector and rebar sector improved properties result for 0.02 to 0.04%Nb in low carbon steel for S355 and S420 beams and for S500 and S600 low carbon reinforcing bars.
Controlling Mold Heat Transfer by Dispersed Metallic Particles in Slag Film during Continuous Casting of Steels: Jungwook Cho1; 1Pohang University of Science and Technology
The extinction coefficient of CaO-SiO2-CaF2-based commercial mold fluxes with additive of iron oxide has been investigated by using a FT-IR and a UV-visible spectrometer in order to clarify the thermal radiation behavior through mold flux film during continuous casting of steels. The iron oxide has been reduced to metallic iron droplets by reaction with graphite crucible during melting, which brings considerable increase of the extinction coefficient due to the scattering. The number of metallic particles is intensively proportional to boron contents due to the transition of molar structure, BO4 to BO3, with increasing boron oxide. It is found that calculated scattering coefficients based on Mie scattering theory are well agreed with measured ones. As the increased scattering coefficient of glassy film would not cause any serious side effects on casting operations, utilization of scattering effects is believed to be significantly essential for future design of commercial mold fluxes.
Modeling of Metal-Slag Mass and Momentum Exchanges in Gas-Stirred Ladles: Marco Ramírez-Argáez1; Carlos González-Rivera1; 1UNAM
Ladle refining plays a key role in achieving the quality of the steel. Specifically the metal-slag mass exchange is studied through a scaled water physical model in which thymol, a solute, is added to the water (steel) and silicon oil (slag) picks up the thymol, while the ladle is agitated with the central gas injection and samples of water were taken to track the thymol concentration with time with a UV-visible spectrophotometer. Also, a mathematical model was developed and solved with the CFD code Fluent Ansys to represent the fluid flow and the mass transfer phenomena through the solution of the continuity, the turbulent momentum conservation and species mass conservation equations. A good agreement between the measured and the computed results regarding the thymol concentration evolution in water was found so the model was validated and it may be used to study metal-slag exchanges in the steel ladle.
Dissolution of MgO Containing Additions in Steelmaking Slag and Its Impact on the Formation of Magnesiowustite: Antonio Augusto Martins1; Rafaela Batista1; Roberto Avillez2; Andre Costa E Silva3; 1CSN; 2PUC-RIO; 3EEIMVR
MgO containing additions are used in steelmaking processes to protect refractories. Solid MgO and FeO are fully miscible. Thus, formation of magnesiowustite is possible in oxidizing slags. In the EAF slags, magnesiowustite saturation is believed to play a critical role in foaming. In Converters, this phase is believed to affect slag splashing/coating processes. Previous work indicated that the dissolution of MgO containing additions may be hindered by the formation of solid layers on their surfaces. Thus, thermodynamics alone is not sufficient to support the assumption that magnesiowustite will be present. In this work the evolution of MgO containing phases was followed through sampling converter slags at different stages of the process. The samples were analyzed and the observed phases fractions were compared to equilibrium phase distribution calculated using computational thermodynamics. The results were analyzed considering dissolution mechanisms and barriers. The impact on magnesiowustite formation and steelmaking process is discussed.
Study on Adjustment and Optimization of LF Refining Slag of Spring Steel 55SiCrA: Chao Gu1; Yanping Bao1; Lu Lin1; Min Wang1; Lihua Zhao1; Zixuan Wu1; 1University of Science and Technology Beijing
The spring steel 55SiCrA produced in a domestic steel factory is deoxidized by Si with “100 t EAF-LF-VD-CC”. The fluoric content (CaF2 = 17.41-22.15%) and the binary basicity (R = 1.9-3.0) of applied LF refining slag are high. To avoid environmental pollution caused by fluorine, meanwhile guarantee the speed of melting slag and smelting effect on molten steel, the structure of refining slag was adjusted. A new fluorine-free slag system was obtained by changing slagging process, adjusting adding amounts of slag-making materials, such as lime, calcium carbide, silicon carbide and so on. This new fluorine-free slag was applied in industrial tests. The results showed that this new fluorine-free slag could meet smelting demands well. The average oxygen content of spring steel 55SiCrA billets could decreased from 1110-6 to 910-6 and the plasticity of inclusions also changed better. All observed inclusion in billets were within the 1400°C liquidus.
The Effect of Deoxidation Practice on Quality Characteristics of Converter Refined AISI 1006 Steel: Antonio Augusto Martins1; Rafaela Batista1; Andre Costa E Silva2; 1CSN; 2EEIMVR - Universidade Federal Fluminense
In converter steelmaking of 1006 steel, two tapping practices are used with respect to deoxidation: partial aluminum deoxidation during tapping (“rimming practice”) and aluminum killed tapping. There is a perception that the “rimming practice” may be more economical and result in the same quality as the fully killed on tapping practice. In this work the effects of the tapping practice on steel quality and cost variables were evaluated for AISI 1006 steel. Oxygen content, aluminum content and yield, the type of alumina inclusions formed, as well as the performance of the steel during tinfoil rolling were evaluated and compared. The higher quality of the steel produced via the fully killed practice is demonstrated. It is also shown that a complete cost evaluation favors this practice in the case of tinfoil production.