OPTYPE – pressure-control system gives iron a lift

Global demand for cast iron products is increasing. How can Swedish foundries maintain and improve their competitiveness? Swerea has developed an energy-saving pressure-control system for countergravity casting.

In iron casting, molten metal is poured into a sand mould and allowed to solidify. A disadvantage is that surplus metal has to be remelted or discarded. Countergravity casting, an alternative method, has been used for more than 30 years for aluminium or brass castings. 

Iron countergravity casting

Now, the method is being tested with iron. Instead of ladling the 1 200-degree molten metal into the mould, it is cast from underneath by pressurizing the furnace with nitrogen. The vacuum created in the furnace allows the metal to rise through a fill pipe up into the mould. This simplifies casting, yields better material properties and a  etterquality finished product. 

In the OPTYPE project (Optimized yield casting process), Swerea has developed a unique, automated nitrogen pressure-control system.
A pressure sensor inside the furnace controls the nitrogen inflow; the operator only needs to set the desired pressure.

Method minimize material surplus

Less material surplus means more finished product and less raw-material consumption. Countergravity casting with a 10 kg melt yields 8 kg of finished product. The conventional process yields only half; 5 kg of finished product from a 10 kg melt. The new method results in improved competitiveness for foundries, energy savings and environmental gains. 

The project demonstrated a reduction in remelted material of about 10–15 percent. Potentially, this could be as much as 30 percent. There is a direct relation between reduced remelting, increased production capacity and climate-friendly sustainability.