The optical emission spectrometer requires a certain pre-ignition time for the excitation of the sample before analysis and sample preparation. So what is pre-ignition? What is the role of pre-ignition? The following editors will discuss with you with questions.
The sample is excited in a spark chamber filled with argon, and most of the air is driven away. Therefore, the effect of selective oxidation and the effect of oxidative absorption of ultraviolet light in the excitation discharge are relatively small, but there are still complex physical and chemical processes. Such as evaporation and diffusion processes. Therefore, the optical emission spectrometer must pass a certain time to reach a stable discharge, that is, the absolute intensity and relative intensity of the spectral lines of each element tend to stabilize. This process is called the pre-ignition stage.
The pre-combustion process is shorter than in the air, and the pre-combustion curves of different elements are different for different steel types. The optical emission spectrometer's choice of pre-burn time can be determined by trace method and integration method. The tracing method is to make the pre-ignition curve of each element, taking into account the time when each element reaches stability, and determining the common pre-ignition time. The integration method is to repeatedly excite the sample under different pre-ignition times and observe the reproducibility of the analysis results of each element, so as to select an appropriate pre-ignition time.
In general, the pre-ignition time for medium and low alloy steel can be 4-6 seconds; the pre-ignition time for high-alloy steel can be 5-8 seconds; and the pre-ignition time of free-cutting steel can be 10-30 seconds. However, the length of the pre-ignition time is also related to the performance of the light source. If the energy is large, the pre-ignition time will be shorter. With less energy, the pre-burn time will be longer. Pre-ignition in advance allows the equipment to analyze samples more accurately, while protecting the instrument and prolonging its service life.
