Method and device for spectral analysis of a chemical composition of molten metals
The invention relates to the field of spectral analysis of the chemical composition of ferrous and non-ferrous metals and can be used in metallurgical factories to monitor the ongoing production of molten (liquid) electrically conductive materials directly in the melting units. A method for optical emission spectral analysis of the chemical composition of an electrically conductive metal melt includes the following steps: immersion of a refractory probe with a sampler into a container with a metal melt at an angle to its surface, ingress of the metal melt into the sampler due to the ferrostatic pressure and stabilization of its level due to an inert gas flow, excitation of plasma torch using electric spark from an electrode located inside the sampler, transfer of the plasma glow through the optical channel to the input of the spectrometer, receiving a spectrum of the chemical elements in the metal, processing this spectrum in the computer to evaluate composition and the mass fraction of the chemical elements in the melt, wherein when measuring the level of the liquid sample in the sampler is stabilized and maintained at the level of the lateral opening in the wall of the sampler due to the flow of inert gas, which is continuously fed into the probe and comes out as bubbles through the hole directly into the melt medium. The technical effect: increase in sensitivity and accuracy of spectral analysis of electrically conductive melts, increase in reliability and simplification of the device for plasma excitation.
1. A method for optical emission spectral analysis of the chemical composition of an electrically conductive melt, including immersing a refractory probe with a sampler into the metal melt, forming a molten metal sample therein due to the ferrostatic pressure; exciting a plasma torch on its surface, transmitting the plasma glow through an optical channel to the spectrometer's input, obtaining a spectrum of chemical elements of the molten metal therein, processing the resulting spectrum in a computer to assess the composition and mass fraction of the chemical elements in the melt, characterized in that in order to increase the sensitivity and accuracy of the optical emission spectral analysis, an electric spark method is used for excitation of plasma on the liquid metal sample in an inert gas stream medium using a spark generator electrode located in the sampler tube at a distance of the discharge analytic gap above the surface of the molten metal sample present in the tube, which is electrically connected through the medium of the metal melt with a counter electrode of the spark generator, wherein a stable level of liquid metal sample in the sampler tube is maintained at the level of the lateral opening in the middle part of its wall due to compensation of the ferrostatic pressure of the metal melt by the dynamic pressure of the inert gas stream, which continuously passes into the sampler tube from the immersion probe and exits through this lateral opening directly into the melt medium.
2. The method of claim 1 , characterized in that the stabilization of the level of the liquid metal flowing into the sampler tube through the bottom opening is provided at the level of the lateral opening in the tube wall due to the excess liquid metal overflowing through it into a hollow refractory chamber surrounding the tube and the cavity of which is isolated from the melt medium and is in communication with the atmosphere.
3. The method of claim 1 , characterized in that in the process of measuring the spectrum, a refractory probe with a sampler is immersed with a rod into the molten metal inclined to its surface at a certain angle, wherein the optical axis of the light guide lens passes at the same angle through the lateral side of the plasma torch excited by the electrode on the surface of the liquid metal sample in the sampler, and the electrode of the spark generator is offset from the axis of the sampler tube to the upper segment of its wall.
4. A device for spectral analysis of a molten metal in a melting tank, comprising: an immersion refractory probe with a sampler, a device for supplying inert gas to the sampler, an optical system with a light guide, a spectrometer and a computer, characterized in that the device comprises an electric spark generator with a discharger and electrodes connected to its outputs, while the refractory sampler is made in the form of a quartz or ceramic tube with its top end opening connected to the immersion probe with an integrated optical system and an inert gas supply device, the sampler tube itself has at least one opening in the middle part of the side wall for the inert gas to exit, and also has at least one opening in the lower part for the liquid metal to flow in, further, the immersion probe contains two refractory electrodes, one of which is installed in the sampler tube at a distance of the discharge gap above the lateral opening in the middle part of the tube and is offset from the tube's center to its wall, and the second electrode is located on the outside of the probe.
5. The device of claim 4 , characterized in that a part of the sampler tube of the immersion probe with at least one lateral opening in its wall and an integrated electrode is located inside the hollow refractory chamber, and the lower part of the sampler tube with an opening for the liquid metal inflow is outside of the hollow chamber, moreover, the cavity of the refractory chamber is isolated from the melt medium and is in communication with the atmosphere through a special opening in the immersion probe.
6. The device of claim 5 , characterized in that the lower central end opening of the sampler tube is closed or sealed, and at least one opening for the liquid metal inflow is located in the lower part of its side wall, while the size of this opening determines the rate of liquid metal inflow into the sampler tube.