Published on 21 January 2013
When an American company needed to determine the chemical composition of some pipeline fittings for which the supplier was unable to provide adequate documentation, TWI's analysis service was able to help.
In cases like this, it is desirable to use a minimum quantity of material for analysis, as removal of a sample from a completed structure involves repair and is therefore costly. Also, such repairs may require lengthy downtime.
The ability to analyse small samples is equally important where limited amounts of material are available, for example in a failure investigation. One of several suitable methods available at TWI involves argon arc remelting to produce a sample for optical emission spectrometry (OES) calibrations.
A unique feature of the TWI designed and built remelter is that the air is evacuated before filling with argon, rather than just purging and is followed by remelting the sample with a 300A DC arc initiated by an HF start. Elimination of any air, and addition of zirconium deoxidant, virtually eliminate elemental losses. In addition, analysis of remelted samples on calibrations produced using remelted certified reference materials and incorporating extensive inter element interference corrections, ensures that accurate results are obtained for a wide range of alloy types.
The process can be used to prepare synthetic standards by remelting a mixture of carefully weighed proportions of two or more certified reference materials, usually millings.
For information about TWI's capabilities please contact us.