The EPSRC Prosperity project in Rapid Product Development is a partnership between Tata Steel, Swansea University and Warwick University. Its aim is to develop faster methods for the development of new strip steel grades. Tata steel produces many grades of steel which differ in their chemical compositions (the proportions of different elements added to the steel), their processing in the steel plant (how much are they deformed, how quickly and at what temperatures) and their final properties (strength, ductility etc.). Different grades may also be required to maintain properties over their service lifetime (e.g. corrosion resistance) or they may be required to be processed in secondary manufacturing steps (e.g. welded or pressed into different shapes). The ability to accelerate the development of new steel grades would provide a significant economic advantage for Tata Steel.
So, what is the problem?
Strip steel is produced in the form of a long strip of steel which is about 1 metre wide and 1000 metres long and weighs several tonnes. After rolling and heat treatment, the steel strip is coiled into a large cylinder for transport. Hundreds of tonnes of molten steel are required to begin the process of coil manufacture. Clearly such a system is not very flexible if one wanted to look at some different alloy compositions or processing steps to identify new grades. Besides this, such an approach would be expensive, slow and carries the possibility of inadvertently damaging the production line which is in almost constant production.
One way to get around this problem is to look at much smaller amounts of material in a laboratory and use smaller rolling mills and furnaces to simulate what would happen in a full-size coil. The partners in this project possess a very wide range of characterisation equipment (to check alloy composition and to study the microstructures formed in the steel), many different mechanical testing machines (to measure strength, ductility etc.) and importantly three different small-scale rolling mills in which small blocks of material can be rolled flat into ‘steel strip’. In the MACH1 labs at Swansea a new lab scale rolling mill has just been commissioned. This mill compliments a larger rolling mill at Warwick University and an even larger one at SAMI in Swansea University. Between them, these three mills can roll material weighing a few hundred grams up to tens of kgs. So, the idea is to create small amounts of potential new steel alloys, process them using the miniaturised testing facilities, study their microstructures and properties and thus predict potential new and improved grades for Tata Steel. All of this being done with reduced cost, reduced usage of material and without interfering with the production lines at Tata Steel.
But, and there is always a ‘but’.
Although creating a small amount of material with a certain chemical composition is possible (although great care is needed) it is much more challenging to recreate the processing conditions a real coil would experience by using small-scale laboratory equipment. The forces applied to the steel, the rates at which they are applied, and the often complex and varying temperatures required at different stages all conspire together to affect the final microstructure and properties of the final product. As an example (and there are many other examples), the amount of material used in the real rolling procedure is much greater than the small amount used in a laboratory rolling procedure. The smaller amount of material loses heat much more quickly during processing which makes it very difficult to recreate real-life temperature variations. This could lead to unwanted differences in microstructures and properties between laboratory and production material. And there are other technical challenges. Smaller amounts of laboratory produced steel means that only smaller specimens can be machined out of them for testing mechanical properties. The size and geometry of small test specimens can affect what is measured by testing machines which is another factor that must be understood and quantified.
Watch Hot Rolling Mill Test Trial:
By all partners working as a team, sharing knowledge and data and using advanced computer modelling techniques, the Prosperity Project aims to quantify and understand these factors and others so that Tata Steel can use the small-scale and miniaturized methods confidently to accelerate the development of new steel grades for the UK steel industry.
