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Working smarter to “yield” improvements in energy consumption

Keeping energy consumption to a minimum is not only fundamental in running a foundry but also in protecting the environment and doing all that is possible to halt climate change, says foundry consultant Per Rolf Roland.

Speaking exclusively to Foundry Trade Journal, Roland - who has many years of experience running foundries around the world and now offers detailed technical advice to the industry - said that focus must be on the metallurgy, the moulding practice and the gating design.
In his previous position at Vestas and his more recent work as a foundry consultant, Roland has spent a great deal of time working with foundrymen, particularly in grey iron and ductile iron foundries, to tackle the “thorny” issue of reducing energy consumption, thus saving money and contributing to an improved world.
He said: “As most of the energy consumption in the foundry is used for melting. How much you have to melt to produce a net casting is mostly presented as the yield. The yield can vary between 40 to 90 per cent. If yield is 50 per cent, you have to melt two ton of iron to get one ton of net castings.
“I know many foundrymen regard the yield of the melting to be a law of nature and their facilities are often are at the 50 per cent level or even lower. However, in the case of ductile as well as grey cast iron, the yield should be at least 80 per cent. My experience as a foundry manager and as a consultant is that it is possible to meet the lower figure if you follow certain rules in metallurgy, moulding practice and gating practice.
“As an example, if you produce 10,000t net castings per year at 50 per cent yield you have to re-melt 5,000t. If you can improve to 80 per cent yield, you only have to re-melt 2,000t. The savings are 3,000t metal per year at an electricity consumption of 700kWh/h equal to 2,100,000 kWh/year. That represents a lot of money (in the UK more than £200,000 per year) and offers savings for the environment.”

WASTED ENERGY
Much of Roland’s work has been focused on increasing the yield from 50 per cent to closer to 90 per cent by reducing or eliminating risers and pouring cups. The energy and cost savings are significant. This is made possible implementing some basic steps in the foundry as follows:
• Optimum metallurgy i.e. carbon content sufficient for compensating shrinkage and at the same time fulfilling mechanical requirements.
• Optimum solidification i.e. inoculation that enables the graphitisation at the critical stage and time.
• Hard moulds that enable resistance to wall pressure(1).
• Ingates that solidify before the graphitisation in the casting takes place.
“The energy consumption to melt (re-melt) the materials used for risers and pouring cups is wasted energy,” he said. “Additionally there is a great productivity increase if you can avoid cutting and grinding all risers and handle all the return material. The cost of prefabricated risers is also an important factor in the cost picture.”
Roland says that although the above are all known technologies, few have really taken full benefit of it. “I have introduced these procedures in several foundries worldwide - and shown that it works,” he tells us. “Cost has been reduced, energy has been saved and quality improved. 
Roland is currently working with IK4-Azterlan, the world-renowned metallurgical research centre in Durango, near Bilbao, on the subject with special attention being paid to extend the principle to smaller castings. “For large castings this is proven technology in the foundries that have learned to do the right things, but savings are available for everyone.”
For more information on the research currently being undertaken contact IK4-Azterland, www.azterlan.es

REFERENCE
1. Izaga Julian, ‘Optimization of chemically bonded sand moulds’, presented at the World Foundry Congress 2012, Monterrey, Mexico. www.thewfo.com