New phenomenological quality criteria for continuous casting of steel based on solidification and microstructure tool IDS

Abstract

Although the formation of defects in continuous casting has been studied for several decades, a deeper understanding and improved quality prediction concepts are needed to correlate the defects with the actual steel compositions, machine data and casting parameters. The aim of this work was to derive new quality criteria based on steel composition and cooling pattern for continuous casting and for the subsequent cooling and reheating processes. The criteria were devised based on the outputs of multiphysics simulation tools for online casting applications. The developed criteria were found to be good predictors of whether a steel grade combined with a given cooling pattern is prone to a specific defect. The criteria useful in providing a theoretical justification as to why certain defects form or would form, and can be used for devising practical solutions to avoid them. In practice, the final determination of whether a defect will form depends on the cumulative impact of various single quality criteria combined with the models/data describing the mechanical and thermal stresses forming. The criteria proposed are applicable as part of online quality prediction systems in casting machines. In this paper, new quality criteria were proposed for different kind of cracking-related and gas defects along with case examples. In further work, the criteria will be used to develop rule-based online control systems, in which cumulative effects of individual quality criteria are combined with data from mechanical and thermal stress calculations.

Thermodynamic, Kinetic, and Microstructure Data for Modeling Solidification of Fe-Al-Mn-Si-C Alloys

“…Recently, several quality indices were developed to describe this sensitivity in solidifying steels. [80] For example, we made calculations for two of these indices, QI STR and QI SHE , which are associated with the disturbed strengthening above the solidus (QI STR ) and the disturbed shell growth below it (QI SHE ). Both events originate in the contraction related to the phase transformation from ferrite to austenite.…”

“…If the amount of the forming austenite is high,steel is highly sensitive to defects like longitudinal surface cracking (facial and corner), transverse corner cracking, hot cracking, and bleeding. The indices QI STR and QI SHE are described as [80] QI STR ¼ 65ðf a;Z max À f a SOL Þ ½ 14…”

Assessing the Effects of Steel Composition on Surface Cracks in Continuous Casting with Solidification Simulations and Phenomenological Quality Criteria for Quality Prediction Applications

“…Tempsimu is a software tool used for the steady-state simulation of heat transfer with 3D models for the mold and strand of a continuous casting machine. [29,30,[35][36][37][38] Tempsimu calculates not only the strand and mold temperatures but also other relevant information, such as the shell thickness and the total mold heat flux. As basic input information, Tempsimu requires the mold material properties, the secondary cooling configuration including the types and locations of the spray nozzles and rolls, the dimensions of the strand, the material properties of the steel grade, the spray cooling water flow rates, the amount of superheat, and the steady-state casting speed.…”

“…The validation of the online version of the coupled solidification and heat transfer tool at an industrial plant has already been conducted. [35] In this study, the steady-state version of the heat transfer model is applied by first collecting the required data describing the properties of the casting machine in question and the secondary cooling parameters which include the steady-state cooling water flows during casting. Further information regarding the fundamentals, assumptions, and validation of Tempsimu and CastManager for continuous casting is available in refs.…”

“…Further information regarding the fundamentals, assumptions, and validation of Tempsimu and CastManager for continuous casting is available in refs. [29,30,[35][36][37][38]…”