E-Thesis 254 views 255 downloads
Optimisation of High Yield Steel Coil Processing Characteristics / BENJAMIN VALENTINE
Swansea University Author: BENJAMIN VALENTINE
Abstract
Ribbed steel for the reinforcement of concrete has a characteristic high yield strength of at least 500 N/mm2, bonds well to concrete, and is ductile. Reinforcing steel is produced at Celsa Steel UK in coils approximately 1.5 km in length, which are post processed by customers to create reinforcemen...
| Published: |
Swansea University, Wales, UK
2023
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| Institution: | Swansea University |
| Degree level: | Master of Research |
| Degree name: | MSc by Research |
| Supervisor: | Coleman, M., Sackett, E., Thomas, S., and Hagg, C. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa69345 |
| Abstract: |
Ribbed steel for the reinforcement of concrete has a characteristic high yield strength of at least 500 N/mm2, bonds well to concrete, and is ductile. Reinforcing steel is produced at Celsa Steel UK in coils approximately 1.5 km in length, which are post processed by customers to create reinforcement structures used in construction projects. Post processing involves straightening and bending to make complex shapes, so consistent steel properties are required for high rates of production. Variations in the properties of a two-tonne coil can be caused during the manufacturing process and effect post processing as customers’ machines need frequent adjustments to shape the steel into the correct dimensions. When the coil needs too much adjustment, the coil is scrapped. This thesis identifies and evaluates the key properties effecting reinforcing steel post processing, then discusses the manufacturing processes that could be improved to better control the consistency of these properties.Through analysis of Celsa Steel UK’s historical data on yield strength in coils, it was found that sections of steel on the external layers of coils have up to 95 MPa greater yield strength than steel in the core of the coil. Increased cooling rate on the outside of the coil, compared to the core, is suggested to cause this variation.Scanning electron microscopy techniques were used to compare grain size, microstructure, composition, and texture between steel samples collected from customers of Celsa Steel UK. Samples that were rejected by customers were compared with samples that behaved consistently. Microstructure and composition were relatively consistent between all samples while grain size varied between 3 µm and 5 µm. This grain size variation is likely to be related to varying cooling rates. Texture was relatively randomised in all samples, and many showed a slight preference in the <110> orientation, indicating a weak rolling texture.As there were no significant differences in the above microstructural properties, an FEA Ansys model was constructed to investigate the effect of cross-sectional consistency on the bending behaviour during customer post processing. Simulations of bending a 12mm reinforcing steel bar with 0.8mm variation in perpendicular cross-sectional diameters showed 1.46 mm out of plane deflection, 100 mm from bend. For a 500 mm by 500 mm square, this out of plane behaviour would deform the shape by 73 mm perpendicular to the intended plane, similar to that seen by customers. |
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| Keywords: |
Steel, Metallurgy, Microscopy, Quenching, Bending |
| College: |
Faculty of Science and Engineering |
| Funders: |
Celsa Steel UK Group, European Social Fund |