The spectrometer in aluminium sand casting

Published - 10th Nov 2015

In sand casting, the chemical composition of a casting alloy has a critical influence over its physical and mechanical properties and, ultimately, its performance.

Each metal pour can contain up to 25 different chemical constituents so it is vital that this balance is correct. If there is insufficient magnesium, for example, the casting will not cure properly when heat treated and it would not be fit for purpose.

Various elements can affect the chemical composition such as the percentage of raw ingot or recycled metal used.  At the foundry, we use a spectrometer to verify the chemical constituents of every metal melt before it is poured to ensure that it meets BSI standards.

First of all, a metal dab is produced using a sample of the molten material from the furnace. This is placed in a lathe where the surface is machined to ensure a smooth, flat finish. The metal dab is then placed in the spectrometer and it is vaporised with a testing probe.

Arc spark optical emission spectroscopy is used to analyse the chemical constituents of the sample. The atoms and ions in the atomic vapour are excited into the emission of radiation. The radiation emitted is passed to the spectrometer optics directly or via an optical fibre, where it is dispersed into its spectral components. The radiation intensity is proportional to the concentration of the various elements in the sample.

A breakdown of the chemical constituents, by percentage, is displayed on screen for our foundry engineers to analyse. The results appear using a colour-coded system. If any elements are outside normal ranges, our engineers can finely tune the chemical constituents of the metal melt accordingly.

Using data from this spectrographic testing, we are able to supply materials certificates to our customers to verify the results, if required.

If you would like any further information about our casting capabilities, please call us on +44 (0)1794 512685 or email us at sales@haworthcastings.co.uk