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July
2006 |
Analysis of Transverse Corner Cracks on Slabs and Countermeasures
H.T. Tsai (left), principal research engineer, H. Yin (second from left), staff research engineer, and M. Lowry (second from right), staff research engineer, Mittal Steel USAResearch and Develop ment Center, East Chicago, Ind. (h.tsai@mittalsteel.com, hongbin.yin@mittalsteel.com, michael.lowry@mittalsteel.com); and S. Morales (right), superintendent — continuous casting, Mittal Steel Lázaro Cárdenas, Michoacan, Mexico (saul.morales@mittalsteel.com)
Transverse corner cracks on peritectic and HSLA grades were analyzed at Mittal Steel Lázaro Cárdenas. Countermeasures taken at the caster mold and
secondary cooling have led to significant improvements in transverse corner cracking. |
Advanced Alternative Coatings for Mold
Copper Liners
Jeffrey K. Brower (pictured), general manager of technology and quality assurance, Voest-Alpine Services & Technologies, Pittsburgh, Pa. (jeff.brower@siemens.com); Keith D. Rapp, general manager of operations, and Michael J. Powers, coatings and technologies manager, Sumitec Inc., Benton Harbor, Mich. (keith.rapp@vastcorp.com, mike.powers@vastcorp.com)
Using the foundation of nickel-boron-based alloys, alternative coatings with exceptional hardness were developed. The positive characteristics of these
coatings are described, as well as their ability to reduce cost while maintaining or improving slab quality. |
Analysis of Mold Friction
in a Continuous Casting Machine of Round Bars
Carlos Cicutti (top left), technological manager, and Constantino Capurro (top right), junior researcher, Tenaris Center for Industrial Research, Campana, Argentina (ccicutti@tenaris.com); Angel Carranza (bottom left), continuous casting manager, and Manuel Beirana (bottom right), steel plant technology, TenarisTamsa Steelmaking Division, Veracruz, Mexico (jcarranza@tamsa.com.mx); and Luis Ferro, steelmaking manager, TenarisDalmine, Dalmine, Italy
TenarisTamsa’s new, hydraulically driven mold oscillator is capable of continuously monitoring mold-strand
friction. The influence of process variables was
evaluated, and the relationship between mold signals and defects in the final product was also investigated. |
Improvement of Secondary Cooling Reliability for Dofasco’s No. 1 Continuous Caster
Dave Currey (left), senior research leader, ManhKha Trinh (center), steelmaking technology project coordinator, and Victor Goertz (right), caster machine repair team leader, Dofasco Inc., Hamilton, Ont., Canada (david_currey@dofasco.ca, manhkha_trinh@dofasco.ca, victor_goertz@dofasco.ca)
Dofasco initiated a project to improve secondary
cooling reliability. Following the implementation of several corrective actions, significant improvements in slab and coil quality resulted, and hot mill delays for bowed slabs were reduced. |
Audits of Secondary Cooling Systems in Existing Casters as a Method to Enhance Product Quality and Productivity
Ray Boyle (left), applications engineering manager, Lechler Ltd., Sheffield, England (rayboyle@lechler.com), and Jürgen W. Frick (right), Lechler GmbH, Metzingen, Germany (frju@lechler.de)
This article discusses the method and structure of a caster audit and shows typical examples. Also discussed is how the design of secondary cooling systems can allow the caster the flexibility to maintain optimum
casting parameters for each steel grade. |
Recent Vacuum Degassing Facility Designs and Results
J. Kevin Cotchen, senior process engineer — steelmaking, SMS Demag Inc., Pittsburgh, Pa. (kevin.cotchen@sms-demag.us)
This article describes the design considerations for a number of degasser projects from their initial concept through design. Comparisons are drawn between the requirements of various facilities and their actual design. Process results are also highlighted. |
Modeling of Continuous Casting Defects Related to Mold Fluid Flow
Brian G. Thomas, Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill. (bgthomas@uiuc.edu)
The quality of continuously cast steel is greatly influenced by fluid flow in the mold, particularly at the meniscus. Recent examples of computational model applications at the University of Illinois are presented to investigate the formation of several different types of defects related to flow phenomena. The amount of gas injection into the tundish nozzle to avoid air aspiration is quantified by modeling. Computational model calculations of superheat transport and surface-level fluctuations are presented. Meniscus defects, such as subsurface hooks and their associated inclusions, may form if the superheat contained in the steel is too low, or if top-surface-level fluctuations are too large. A thermal stress model has been used to compute the distortion of the meniscus during a level fluctuation. Gas bubbles and inclusion particles may enter the mold with the steel flowing through the submerged nozzle. In addition, mold slag may be entrained from the top surface. These particles may be removed safely into the slag layer, or may become entrapped into the solidifying shell, to form sliver or blister defects in the rolled product. Transient, turbulent flow models have been applied to simulate the transport and entrapment of particles from both of these sources. The insights gained by these modeling efforts aid greatly in the development of processing conditions to avoid the formation of these defects. |
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