The Harwell Imaging Partnership (HIP) has assisted Tata Steel, the second largest steel producer in Europe, in furthering understanding of the cracking mechanisms that can be active during hot rolling of free cutting steels.
Tata Steel provides steel products for a variety of high value, competitive sectors including construction, defence and security, shipbuilding, automotive and aerospace. The production of steel products includes a stage called ‘hot rolling’, in which hot metal reheated to a temperature up to 1200°C is deformed between rollers to increase its strength and toughness whilst producing the required shape. Free-cutting steels are well suited for high quality machining due to increased sulphur content, however this can cause the metal to initiate ductility break-ups and cracks during hot rolling. This induces high manufacturing costs and wastes resources as surface defects must be corrected.
The HIP has provided Tata Steel with access to the Diamond Light Source (funded by the Science and Technology Facilities Council and the Wellcome Trust) and their synchrotron X-ray micro tomography capability. This was used to collect tomographic images during tensile testing showing the development of micro-voids, which coalesce to macro-cracks in steel over time and deformation, up to the point at which the failure occurs. In situ measurements during hot deformation were compared with tensile specimen samples that had been interrupted at different stages of deformation, where slower measurements allowed smaller features to be resolved. The results showed that the development of damage takes place where plastic deformation becomes localised, particularly where there are clusters of MnS inclusions.
This project has provided Tata Steel with data to compare with computer simulations and other experimental results to gain a wider understanding of how the microstructure influences the various regimes of damage mechanisms and ultimately how the hot rolling process can be improved, without compromising the machinability of the steel. This will reduce the scrapped percentage of the product, significantly decreasing the company’s long term manufacturing costs.
As hot-rolling is used extensively and consumes considerable power, an improvement of as little as 1% per yield has the potential to save up to £1million over the course of a year, providing a substantial financial return for Tata Steel. The positive impact on the environment increases the company’s sustainability, whilst their superior manufacturing process allows Tata Steel to maintain a competitive advantage in demanding, high value global markets.
The Science and Technology Facilities Council (STFC) keeps the UK at the forefront of international science and tackles some of the most significant challenges facing society and industry.
We collaborate with industry, the research community and government to develop business opportunities arising from our world-leading science and technology.
The STFC Harwell Imaging Partnership connects businesses with imaging capabilities and technical expertise from the research community to stimulate innovation and business growth. Capabilities supplied include microscopy, tomography and ‘functional imaging’ using X-rays, neutrons and lasers.
For more information about how your business could benefit from working with the Harwell Imaging Partnership: