E-Thesis 136 views 253 downloads
Understanding Scale Growth on Carbon Steel Tubes During High Temperature Processing / MEGAN KENDALL
Swansea University Author: MEGAN KENDALL
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PDF | E-Thesis – open access
Copyright: the author, Megan Elizabeth Kendall, 2025
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DOI (Published version): 10.23889/SUThesis.71061
Abstract
Conveyance tube manufacturing is a high temperature process which promotes rapidsurface oxidation. During heat treatment, an oxide mill scale layer grows on tube surfaces.Inconsistent spalling of this layer from the outer tube surface contributes to yield loss, surface degradation, and tool wear. Ex...
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Swansea
2025
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | EngD |
| Supervisor: | Sackett, E. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa71061 |
| Abstract: |
Conveyance tube manufacturing is a high temperature process which promotes rapidsurface oxidation. During heat treatment, an oxide mill scale layer grows on tube surfaces.Inconsistent spalling of this layer from the outer tube surface contributes to yield loss, surface degradation, and tool wear. Experimental and theoretical studies of curved surface oxidation struggle to accurately recreate industrial processes. The computational thermochemistry software, Thermo-Calc©, was used to investigate external oxidation kinetics during conveyance tube manufacturing. A model was developed using the Stefan problem, tailored thermochemical databases, and a numerical solution to the diffusion equation. Particular attention was paid to geometric effects. There was strong agreement between oxide mass gain predictions by the model and equivalent thermogravimetric experiments. However, poor agreement between oxide thickness gain predictions by the model and industrial samples revealed scope for further work addressing transient heating, porosity, and thermomechanical manufacturing operations. Continuous oxide thickness data derived from the Thermo-Calc© model were used to evaluate thermal, growth, and manufacturing-related oxide stress. An Advanced Oxide Scale Failure Diagram (AOSFD),relating critical strain to instantaneous oxide thickness, was developed using these stress data. The AOSFD was used to demonstrate the impact of the transition to induction heating technology on oxide failure, namely improved electromagnetic control and changes to temperature control margins. Overall, this project demonstrates the use of computational techniques to predict geometry-specific oxide kinetics, and how the resulting data can be used to predict the mechanical state of the oxide. The continuous data presented are ideal for the development of an AOSFD which can predict how a given thickness of oxide will fail, if at all, depending on its strain state. The AOSFD is simple to use and therefore offers a practical tool for making informed decisions during conveyance tube manufacturing. |
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| Keywords: |
oxidation, modelling, steel, diffusion, heat treatment, geometric effects, failure assessment |
| College: |
Faculty of Science and Engineering |
| Funders: |
COATED M2A from the European Social Fund via the Welsh Government (c80816), the Engineering and Physical Sciences Research Council (Grant Ref: EP/S02252X/1), and Tata Steel UK Ltd |