For this reason, closed, preferable hermetically sealed launder or transfer systems which minimise turbulence during transfer are preferable. Care should also be taken to ensure solutions chosen are adequately insulated and feature controllable heating to ensure melt temperature is maintained at a constant level. This eliminates any need for potential reheating which, in addition to wasting energy, can also result in further oxidation and reduction in usable yield.
Metal loss - the enemy of cost-efficiency
There are many ways in which aluminium foundries can reduce costs. Reducing energy consumption is certainly a significant opportunity for savings. This topic is covered in detail here with our special energy savings guide.
Another significant cost driver, especially considering the cost of non-ferrous raw materials and related logistics/handling, is metal loss. When considered over the service life of a melting furnace these two factors combined are responsible for up to 95 percent of the overall costs. Depending on aluminium alloy, a metal loss of just 1% of an annual melting output of 5,000 metric tons could equate to an average financial loss of 70,000 EUR.
Industry leaders agree - metal loss is the enemy of cost-efficiency and improving yield should be an important objective. This remains the single biggest opportunity for die casters to reduce waste and maximise return on investment (ROI).
To help seize this opportunity, here are some of the most common causes of metal loss together with tips and technologies that can help tackle them.
Avoiding aluminium oxidation: the path to real savings
Metal loss during melting, transfer and dosing is almost always linked to the oxidation of aluminium. Aluminium and aluminium alloys oxidise relatively quickly compared with other metals in both solid and molten states – though oxidation rate significantly increases with temperature, meaning molten aluminium is particularly susceptible.
Aluminium oxides form as a direct result of exposure to air and can be impacted by excess heat. Oxides also vary in type – some leading to greater levels of dross, while others are more likely to negatively impact general metal quality which will send scrap rates soaring.
This may sound a complicated puzzle to solve. However, it is important to remember that solutions exist that are specifically designed to minimize opportunity for oxidation, and also to limit any subsequent disturbance of oxides so that they do not mix into the melt and can be more easily removed – all of which helps increase your usable yield. This is why prevention and control starting with the furnace design is a logical place to start.
3 melting furnace features to maximize metal yield
Time to rethink metal transfer?
Metal transfer from melting furnace to holding/dosing solutions and die casting machines, is a foundry process prone to metal loss.
Open ladle systems with holding furnaces present the biggest threat to yield, not only due to greater risk of atmospheric exposure but also because of potential spills – a safety concern in its own right – and melt turbulence.
Less processes, less loss
Each individual process which takes place between melting and casting introduces a potential opportunity for metal loss.
For this reason, adopting ‘combination technologies’ which blend multiple functions can prove beneficial when seeking to increase yield. Many are also highly adaptable and can integrate with aluminium casting cells of different size and layout.
Dosing that won’t drain resources
Dosing furnaces – closed holding furnaces which support direct and timely delivery of molten aluminium to casting lines – are widely recognised for their favourable metal yield in comparison to traditional, stand-alone holding furnaces. In fact, figures from practical experience show they can reduce metal loss by as much as 80%.