China Foundry (Nov 2008)
Reduced energy consumption by using streamlined gating systems
Abstract
In foundries a lot of effort is done to minimize energy consumption in the production to reduce costs and hence increase the competitiveness. At the same time the foundries must live up to the increased demands for high quality castings.Traditional gating systems are known for a straight tapered down runner, a well base and 90?bends in the runner system. Previous work has shown that the traditional way of designing gating systems creates high inconsistency in fl ow patterns during fi lling. In the streamlined gating systems there are no sharp changes in direction and a large effort is done to confi ne and control the fl ow of the molten metal during mould fi lling.The main objective in the work presented here is to use the principles of the streamlined gating systems to reduce the weight of the gating system relative to the traditional layouts. By reducing the weight of gating system and thereby improving yield, the amount of molten iron needed is also reduced, hence reducing the energy consumption for melting.Experiments in real production lines have proven that it is possible to achieve a reduction in the poured weight by using the streamlined gating systems. In a layout for casting of three valve housings in a vertically parted mould the weight of the gating system was reduced by 1.1 kg changing from the traditional layouts to the streamlined gating systems. This weight reduction corresponds in this case to a 20% weight reduction for the gating system.Using streamlined gating systems with fan gates to give a benefi cial heat distribution in the castings may be an effi cient tool to eliminate the need for heat treatment. In the experiments the change in gating system from the traditional layout to the streamlined layout removed the need for heat treatment. This obviously means a huge energy saving in the foundry. The energy consumption for heat treatment of iron has been found to be 0.489 kWh/kg. The valve housing in the experiments weighs 3 kg so when the need for heat treatment is removed, around 1.5 kWh is saved per casting. Along with the reduction in energy used the foundry also save the cost of handling the castings for the heat treatment and the production times is reduced considerably.When the moulds for the vertical layout is produced on a DISAMATIC that produces 350 moulds an hour the total energy saved per hour for both melting and heat treatment becomes 2,000 kWh and per eight hour work day 16,000 kWh. Seen in this perspective the potential for saving energy in the foundries is substantial.Furthermore the experiments where ductile iron valve housings was cast also proved that it is possible to lower the pouring temperature from 1,400篊 to 1,300篊 without the risk of cold runs. This is possible due to a high flow rate during mould fi lling in combination with low velocities due to the use of fan gates. All of this has also been investigated in experiments using glass plate fronted moulds.
