Frequently asked questions by future Galvalibs 2.0 users

Laser Induced Breakdown Spectroscopy (LIBS) is a laser-based compositional analysis method of solids or liquid matter.  In its basic principle, a high-energy laser pulse heats a small volume of the target to plasma level. The light emitted by this plasma is then collected and analyzed by an optical spectrometer. Since each individual element, such as Al, Fe and Zn, only emits light at specific optical wavelengths, or colours called optical spectral lines, isolating and measuring the intensity of selected spectral lines can detect the presence and concentration of elements in the plasma. The method makes it easy to measure Al and Fe concentrations in a galvanizing bath.

With standard methods of bath chemistry monitoring, a bath sample is taken at a specific location in the bath at a given time and then analyzed in a laboratory. Between sampling, the operators have no information about the concentrations and the ensuing actions to take. Since the Galvalibs continuously monitors the molten metal flowing under the probe, operators benefit from comprehensive volumetric information about the bath chemistry. The Galvalibs measurement directly conveys the concentration of dissolved elements, so there’s no need to correct the recorded values for temperature, eliminating error due to inaccurate temperature readings.

The Galvalibs LIBS signal is recorded in a controlled, inert environment: a high-quality Argon bubble. No external contamination can skew the measurement. In addition, continuous recordings, as many as 1,000, are combined to reject outliers and reduce noise. This results in higher-accuracy spectral line intensities and, in turn, the concentration values of each element analyzed.

Studies have shown that bath chemistry is fairly well distributed in a standard galvanizing bath, except near where ingots and steel coils are inserted in the bath (dross formation). As a result, the Galvalibs can be inserted at any location in the bath, except downstream, in the flow of molten metal from the feed ingot. With robotic drossing, care must be taken with the robot’s path.  However, the unit is typically inserted in the bath next to the side of the snout away from the robot path.

In its standard operation, the Galvalibs probe beam focusses on a small spot inside a bubble of inert Argon gas, deep within the volume of the molten bath. This microsampling of the bubble wall vaporizes the liquid phase. The small beam spot limits the possible presence of solid particles (dross) in the probed volume, yielding a measurement of the dissolved phase only. If a dross particle is detected in the microsample, a higher-than-normal signal intensity for intermetallic elements is recorded. With its shot-per-shot signal processing, the Galvalibs can sort the data and produce reliable, independent measurements of solid and dissolved content.

In its standard operation, the Galvalibs probe beam focusses on a small spot inside a bubble of inert argon gas, deep within the volume of the molten bath. This microsampling of the bubble wall vaporizes the liquid phase. The small beam spot limits the possible presence of solid particles (dross) in the probed volume, yielding a measurement of the dissolved phase only. If a dross particle is detected in the microsample, a higher-than-normal signal intensity for intermetallic elements is recorded. With its shot-per-shot signal processing, the Galvalibs can sort the data and produce reliable, independent measurements of solid and dissolved content.

Most ICP systems directly measure each element’s total amount of concentration, but the Galvalibs uses effective (dissolved only) concentration amounts for proper calibration. In ICP, solubility curves must be used to convert total amounts measured into effective concentration amounts. Since solubility is a function of the temperature of the melt in the bath, an accurate temperature measurement is needed to get an accurate value of the effective concentrations.  The GCU, based on high-quality Certified Reference Materials, provides accurate concentration values of the dissolved elements of a bath sample. There’s no need for temperature information or temperature correction.

When the GCU is mounted on the Galvalibs, the laser probe beam is focussed to a small spot size on the surface of the solid sample in an environment of a continuous flow of inert gas, Argon. The small size of the beam spot limits the possible presence of solid particles (dross) embedded in the probed volume, yielding a measurement of the dissolved phase only. If a dross particle is present within the microsample, a higher than normal intensity of the signal for intermetallic elements is recorded. With its shot-per-shot signal processing, the unit is able to sort the data and produce reliable independent measurements of solid and dissolved content.