TECHNOLOGY NEWS:
Simulating success for production speed and quality
How fast a continuous process can run while maintaining a quality product is a key concern for any process engineer. When Jonas Fjellstedt of Outokumpu Copper Research and Development in Sweden wanted to determine how to improve efficiency in a plant producing metal rods he turned to FEMLAB® multiphysics modelling software. Based on the simulation results, he was not only able to suggest changes in the process that have increased the production rate by 40%, but also to propose a new inlet design that improves product quality.
The process in question transports liquid metal from a holding furnace, through a refractory inlet, to a water-cooled graphite-lined copper mould. When the rod has cooled sufficiently, a flying saw cuts the strand into manageable pieces. If the rod moves slowly, it has plenty of time to cool off before being sliced. But because only the rod’s exterior needs to be solid when it exits the mould, internal cooling can take place after exit, thereby allowing the rod to move at a higher speed through the process. If it moves too fast though, the sawed-off rod still has a liquid or ‘mushy’ consistency in its centre, which is unacceptable. The engineers also want to avoid reheating the solid shell as long as melt remains in the centre, to avoid porosity.
To determine exactly how far and quickly the rod can move before being cut, Fjellstedt developed a multiphysics model in FEMLAB. The cooling rate dictates where solidification starts, and the cooling rate and flow together determine the position and shape of the molten region in the steady state. Thus Fjellstedt's model uses FEMLAB’s Non-Isothermal Flow application mode for the flow with a phase transition along with the Heat Transfer application mode, which handles latent heat in the rod. With a viable model in hand, Fjellstedt wanted to evaluate how much he could improve the process rate by adding a secondary cooling stage once the rod exits the furnace. He was able to determine that it is safe to increase the velocity by 40% compared to the previous nominal rate, yet suffer no process changes.
A final issue was that of surface quality. The initial configuration of the die and mould assembly led to a recirculation zone in the laminar flow of the molten metal, something engineers believe explains occasional surface defects. With the help of FEMLAB, Fjellstedt was able to propose a different design of the inlet region to eliminate this recirculation backstep, and thus achieve better quality in the final product.
FEMLAB® is a registered trademark of Comsol AB – Sweden
Fax: +46 8 412 9510 • Website: www.comsol.com
Company: |
Outokumpu Copper AB |
Country: |
Sweden |
Fax: |
+46 21 198113 |
Email: |
|
Website: |
www.outokumpu.com |