Process for determining, by optical emission spectrometry, the content in a steel of an element such as aluminum, in the dissolved state and in the precipitated state

A process for determining, by optical emission spectrometry, the content in a steel of an element such as aluminium, in the dissolved state and in the precipitated state, said process comprising the steps of:

• subjecting a sample of the steel to be analyzed to spark discharging by causing an excitation circuit to generate sparks by successive elementary discharges;
• directing the optical emission of the sparks onto a diffraction grating so as to separate a light emission corresponding to the element to be metered;
• charging an integration capacitor with a current representative of the intensity of the light emission in response to each of said elementary discharges;
• converting the value of the charge of said capacitor to digital data;
• registering said digital data so as to store the various digital data representative of the respective light emission intensities responsive to said successive elementary discharges constituting a spark discharging cycle;
• determining among said stored digital data the number of intensities having a value comprised in each of a plurality of contiguous channels in order to set up a frequency diagram as a function of the light emission intensity;
• smoothing a curve representative of said frequency diagram, said smooth curve showing a part of substantially gaussian course on the low intensity side;
• determining the content of dissolved element as a linear function of the intensity value corresponding to the maximum peak of said gaussian part of the smooth curve;
• and
• determining the content of precipitated element by summing products n.sub.i, C.sub.i for all the channels located beyond the gaussian part, on the high intensity side of said frequency diagram, where n.sub.i is the number of intensities in channel i and C.sub.i is the middle intensity value of the same channel i.