Energy saving in the Foundry Industry by Novel Single Shot Melting Process

This project aims to compare the energy used in traditional foundry processes and a novel single shot foundry technology, CRIMSON, and to develop a model of the processes that encapsulates the energy content at each stage. This model can then be used to persuade casting designers to use more energy-efficient processes which consider casting quality as well as design flexibility. The UK retains a globally recognised casting expertise, in copper, aluminium and new light-metal alloys that underpins many competitive, technology-based industries vital to keep the UK's aerospace and automotive base ahead of the competition. These industries draw on advanced R&D work carried out by Birmingham's high-profile Casting Research Group.The University of Birmingham has been at the leading edge of casting R&D for many years. Today, it is internationally acknowledged as a front runner, and the CRIMSON technique - Constrained Rapid Induction Melting Single Shot method - is one such technology which is helping the casting industry make a step-change in product quality, manufacturing responsiveness and energy use.A typical light-metal foundry will tend to work in the following way: from 100 kg to several tonnes of metal is melted in a first furnace, held at about 700 oC in a second, transferred into a ladle and finally poured into the casting mould. It can take a shift (8 hours) to use all the melt in a typical batch and any leftover unused melt is poured off to be used again, or becomes scrap. Quality issues also arise, which must be mitigated: during the time for which the melt is held at temperature, atmospheric water is reduced to hydrogen and oxygen. The hydrogen is highly soluble in the metal at this temperature, but as the casting cools and solidifies, the gas is ejected into bubbles. The bubbles become porosity in the solid casting and have a detrimental effect on performance, therefore, as much gas must be removed as possible from the melt. The oxygen forms a thin layer of oxide on the melt surface, which is then inevitably entrained in the liquid metal when it is transferred between the different furnaces and when the metal is finally poured. The oxide layer (or bi-film) is now an inclusion which, again, has a detrimental effect on the material properties. The longer the metal is held liquid, the more hydrogen is absorbed and the thicker the oxide becomes on the surface.At each stage of the process there are energy losses due to oxidation and furnace inefficiencies, casting yields and eventually scrap. So from an initial theoretical 1.1 GJ/tonne required tomelt aluminium it is possible to estimate that each tonne of aluminium castings shipped will actually use about 182 GJ/tonne.Instead of going through this batch process, the CRIMSON method uses a high-powered furnace to melt just enough metal to fill a single mould, in one go, in a closed crucible. It transfers the crucible into an up-casting station for highly computer-controlled filling of the mould, against gravity, for an optimum filling and solidification regime. The CRIMSON method therefore only holds the liquid aluminium for a minimum of time thus drastically reducing the energy losses attributed to hold the metal at temperature. With the rapid melting times achieved, of the order of minutes, there isn't a long time at temperature for hydrogen to be absorbed or for thick layers of oxide to form. The metal is never allowed to fall under gravity and therefore any oxide formed is not entrained within the liquid. Thus higher quality castings are produced, leading to a reduction in scrap rate and therefore reduced overall energy losses.The first challenge in the project is to measure accurately the energy used at each stage in each of the processes investigated and to calculate the energy losses from oxidation and scrap. The second challenge is to incorporate this information into a model that can be used by casting designers and foundry engineers.