Meaning
Analytical technique used to determine the chemical composition of a metal sample by measuring the light emitted or absorbed by its atoms. Foundries and scrap yards use a spectrographic assay to verify the purity of incoming materials and ensure that final products meet customer specifications. This method provides a fast and highly accurate breakdown of every element present in the alloy, from the primary metal to trace contaminants.
It is a fundamental tool for quality control in the modern metals industry.
Analytical Precision
Modern instruments can detect elements at the parts per million level in just a few seconds. The spectrographic assay works by exciting the atoms in a sample using an electric spark or a laser and then analyzing the resulting light spectrum. Each element produces a unique set of spectral lines that the computer uses to calculate the exact percentage of the material.
This precision allows manufacturers to create alloys with very tight tolerances for aerospace or automotive applications.
Quality Control
Every batch of molten metal is tested before it is poured into molds to ensure it matches the required recipe. If the spectrographic assay shows that the mixture is low on a specific element, the operator can add more of that alloy to the furnace. This real-time feedback loop prevents the production of entire batches of defective parts.
Handheld devices also allow scrap sorters to identify and categorize different grades of metal on the warehouse floor.
Sampling Boundary
Accuracy depends on the sample being clean and representative of the entire lot of material. The spectrographic assay only measures the very surface of the metal disc or the specific point targeted by the laser. If the sample is contaminated with oil, paint or oxidation, the results will be incorrect.
Proper grinding and cleaning of the sample surface are required steps to ensure that the light spectrum reflects the true internal chemistry of the metal.
