Doctoral Thesis
DOI
10.11606/T.55.2018.tde-12112018-162119
Document
Author
Full name
Marcos Zambrano Fernandez
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2018
Supervisor
Committee
Cuminato, José Alberto (President)
Sobral, Yuri Dumaresq
Sousa, Fabrício Simeoni de
Tibiriçá, Cristiano Bigonha
Title in English
Mathematical modeling of ripple- and oscillation-mark formation in the casting of steel
Keywords in English
Asymptotic methods
Casting of steel
Mathematical modeling
Abstract in English
Ripple marks and oscillation marks are undesirable defects which occur on the surface of solidified steel produced industrially in the ingot and the continuous casting processes, respectively; these defects are characterized by more or less evenly spaced indentations on the metal surface. Although the mechanisms for their formation are thought to be qualitatively understood, there is still considerable scope for improvement as regards quantitative mathematical modeling. In this thesis, models for the two processes are developed. For the case of ripple marks, transient twodimensional (2D) momentum and heat transfer in ingot casting is considered, and a criterion is derived, in terms of the process parameters, that can help to inform how to avoid such marks. For the case of oscillation marks in continuous casting, a novel numerical formulation for a transient 2D model is developed with the aim of tracking the spatial location of the first point of molten steel to solidify, since this determines the profile of the final oscillation mark. In both cases, the models are nondimensionalized, and the sizes of the dimensionless parameters that appear are used to derive asymptotically reduced models, with a view to not only clarifying the qualitative behavior, but also as a means to reducing the computational expense; both finite-difference and finite-element methods are used to solve the resulting model equations. One of the conclusions is that, although experimentalists and metallurgists have, in the past, treated the two cases as being linked, the present modeling approach shows quite clearly, and perhaps for the first time, how they quantitatively differ.
Title in Portuguese
Modelagem matemática da formação de marcas ondulantes e oscilantes em lingotamento de aço
Keywords in Portuguese
Lingotamento do aço
Métodos assintóticos
Modelagem matemática
Abstract in Portuguese