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An on-site experimental heat flux study and its interpretation in a FEMLAB finite element simulation of continuous casting of copper in the South-Wire process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-8318-1251
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
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2005 (English)In: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 58, no 4, 509-515 p.Article in journal (Refereed) Published
Abstract [en]

The South-Wire process, a development of the Properzi process, to continuously cast copper has been studied both experimentally and by finite element computer simulation. The experimental work has been performed on site to get temperature data as a function of time at several locations within the mould. These experimental data have been used to evaluate boundary conditions for the heat transfer from the strand-mould interface and through the mould. A simulation model of the casting process has been developed in the program FEMLAB. In this program temperature varying material data and time varying boundary conditions have been used. The simulation model has been verified by comparing with an analytical solution, and then applied to the real physical process.

Place, publisher, year, edition, pages
2005. Vol. 58, no 4, 509-515 p.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-10034ISI: 000232332700003Scopus ID: 2-s2.0-33644697046OAI: oai:DiVA.org:kth-10034DiVA: diva2:201543
Note
QC 20100803Available from: 2009-03-05 Created: 2009-03-05 Last updated: 2010-08-30Bibliographically approved
In thesis
1. On Peritectic Reactions and Transformations and Hot Forming of Cast Structures
Open this publication in new window or tab >>On Peritectic Reactions and Transformations and Hot Forming of Cast Structures
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with peritectic reactions and transformations that occur during the solidification of many alloys. Peritectics are believed to be a major cause of crack-formation in many steels, thus, good knowledge of the mechanisms by which these phenomena occur is essential for preventing such defects. The thesis also handles the behaviour of metals, in particular cast structures, during hot forming. Grain size and microstructure are of most importance in determining the strength, toughness and performance of a steel. For achieving enhanced mechanical and microstructural properties, good understanding of the phenomena occurring during hot forming is required.

Peritectic reactions and transformations were studied in Fe-base and steel alloys through differential thermal analysis (DTA) experiments and micrographic investigation of quenched DTA samples. The effect of the ferrite/austenite interface strain during the peritectic reaction on equilibrium conditions was thermodynamically analysed, and the results were related to temperature observations from DTA experiments conducted on Fe-base alloys and low-alloy steels. Massive transformations from ferrite to austenite were observed in the micrographs of a number of quenched low-alloy steel samples and it was proposed that these transformations are uncontrolled by diffusion, and occur in the solid state as a visco-plastic stress relief process. DTA study of an austenitic stainless steel indicated that the alloy can exhibit primary precipitations to either ferrite or austenite. A continuously-cast breakout shell of the steel was analyzed and it was suggested that the observed irregularities in growth were due to alternating precipitations of ferrite and austenite; parts of the shell with higher ratios of primary-precipitated ferrite shrink in volume at the peritectic temperature and experience reduced growths.

An experimental method for studying the behaviour of metals during hot forming developed, and hot compression tests were conducted on cast copper and ball-bearing steel samples. Flow stress curves were obtained at varying temperatures and strain rates, and the results showed good agreement with earlier observations reported in literature. Micrographic analysis of quenched samples revealed variations in grain size and a model was fitted to describe the grain size as a function of deformation temperature and strain.

Solidification growth during continuous casting of stainless steel and copper was numerically modelled. A varying heat transfer coefficient was proposed to approximate the experimentally measured growth irregularities in the continuously-cast stainless steel breakout shell. Solidification growth of pure copper was also modelled in the Southwire continuous casting process. Temperature measurements from the chill mould were used to approximate the temperature gradient and the heat extraction from the solidifying strand, and the results were used in a two-dimensional model of solidification.

 

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 34 p.
Series
Trita-MG, ISSN 1104-7127 ; 2009:02
Keyword
peritectic reactions, massive transformations, thermal analysis, Fe-base alloys, steels, growth irregularities, hot forming, compression testing, flow stress, grain size.
National Category
Metallurgy and Metallic Materials Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-10006 (URN)978-91-7415-242-5 (ISBN)
Public defence
2009-03-27, F3, Lindstedtsvägen 26, KTH, 13:00 (English)
Opponent
Supervisors
Note
QC 20100803Available from: 2009-03-04 Created: 2009-03-02 Last updated: 2010-08-03Bibliographically approved
2. On the Experimental Determination of Damping of Metals and Calculation of Thermal Stresses in Solidifying Shells
Open this publication in new window or tab >>On the Experimental Determination of Damping of Metals and Calculation of Thermal Stresses in Solidifying Shells
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis explores experimentally and theoretically two different aspects of the properties and behaviour of metals: their ability to damp noise and their susceptibility to crack when solidifying.

The first part concerns intrinsic material damping, and is motivated by increased demands from society for reductions in noise emissions. It is a material’s inherent ability to reduce its vibration level, and hence noise emission, and transform its kinetic energy into a temperature increase. To design new materials with increased intrinsic material damping, we need to be able to measure it. In this thesis, different methods for measurement of the intrinsic damping have been considered: one using Fourier analysis has been experimentally evaluated, and another using a specimen in uniaxial tension to measure the phase-lag between stress and strain has been improved. Finally, after discarding these methods, a new method has been developed. The new method measures the damping properties during compression using differential calorimetry. A specimen is subjected to a cyclic uniaxial stress to give a prescribed energy input. The difference in temperature between a specimen under stress and a non-stressed reference sample is measured. The experiments are performed in an insulated vacuum container to reduce convective losses. The rate of temperature change, together with the energy input, is used as a measure of the intrinsic material damping in the specimen. The results show a difference in intrinsic material damping, and the way in which it is influenced by the internal structure is discussed.

The second part of the thesis examines hot cracks in solidifying shells. Most metals have a brittle region starting in the two-phase temperature range during solidification and for some alloys this region extends as far as hundreds of degrees below the solidus temperature. To calculate the risk of hot cracking, one needs, besides knowledge of the solidifying material’s ability to withstand stress, knowledge of the casting process to be able to calculate the thermal history of the solidification, and from this calculate the stress. In this work, experimental methods to measure and evaluate the energy transfer from the solidifying melt have been developed. The evaluated data has been used as a boundary condition to numerically calculate the solidification process and the evolving stress in the solidifying shell. A solidification model has been implemented using a fixed-domain methodology in a commercial finite element code, Comsol Multiphysics. A new solidification model using an arbitrary Lagrange Eulerian (ALE) formulation has also been implemented to solve the solidification problem for pure metals. This new model explicitly tracks the movement of the liquid/solid interface and is much more effective than the first model.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xii, 41 p.
Series
Trita-MG, ISSN 1104-7127 ; 2006:03
Keyword
material damping, measurement methods, calorimetric methods, optical strain gauge measurements, hot cracking, stress in solid shells, ALE
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-4038 (URN)91-7178-377-6 (ISBN)
Public defence
2006-06-15, M3, Brinellvägen 68, 100 44 Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100929Available from: 2006-06-02 Created: 2006-06-02 Last updated: 2010-09-29Bibliographically approved

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