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Seeing is believing - our exciting new way to visualize metal flow during hot working  

Hot working plays a major role in improving the properties of steel. But to refine the process it would be great if we could see how the metal actually flows inside the workpiece. That is now possible thanks to an innovative approach to visualization developed by the Ovako R&D team. And the even better news is that these practical investigations show an almost perfect correlation with our computer simulations.

In addition to changing the shape of a steel workpiece, a hot working process such as forging improves its properties by breaking down its cast structure, closing porosity and redistributing segregated elements. The result is enhanced strength, fatigue life and impact resistance. To achieve the optimum benefit, it is important to achieve the correct flow of the steel grain.

The flow visualization process starts by taking a series of workpieces, such as the 100Cr6 (Ovako grade 803) sample shown here as the starting point for ring rolling, and then drilling a number of holes right through them. We then insert into these holes rods made of a dissimilar steel, in this case C9D, that will act as “markers”.

In parallel with this practical method, the R&D team has also been developing computer simulations of metal flow using our FORGE finite element method (FEM) software. These simulations show an almost perfect correlation with the real-life industrial trials as seen below.

In addition to ring rolling, we have also applied the same practical approach to forging and rolling processes. The next step would be to apply the technique to tube rolling.

While there are many external checks that can be made on the quality of a hot-worked product, such as temperature, surface finish and dimensional accuracy, they do not tell us what has happened inside it. This situation has changed with the development of our elegant new approach that enables us to gain a deeper understanding of how metal flows under hot working. It will play a vital role in refining our processes to deliver the highest quality products to our customers. Furthermore, because this new visualization method shows such good correlation with our FORGE FEM simulations it gives us greater confidence in using FEM for process optimization.