Transient spectroscopic method and apparatus for in-process analysis of molten metal
First Claim
1. A method for spectroscopic analysis of a molten metal, comprising:
- providing a probe including a casing having an open end adapted to be immersed in the molten metal, laser means disposed in said casing for irradiating the surface of the molten metal adjacent the open end with a laser beam of predetermined energy density and focal spot size, and spectroscopic detector means disposed in said casing for detecting spectral components of light emitted from a plasma produced by the laser means;
immersing the open end of the casing into the molten metal;
irradiating the molten metal with a laser beam from said laser means to produce a plasma representative of the composition of the molten metal, said irradiating being performed during immersion of the casing open end into the molten metal; and
detecting spectral components of radiation emitted by the plasma by means of the spectroscopic detector means in the casing and producing signals corresponding to the detected spectral components.
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Abstract
A method and apparatus for in-process transient spectroscopic analysis of a molten metal, wherein a probe containing a pulsed high-power laser producing a pulsed laser beam having a substantially triangular pulse waveshape is immersed in the molten metal and irradiates a representative quantity of the molten metal. The pulsed laser beam vaporizes a portion of the molten metal to produce a plasma plume having an elemental composition representative of the elemental composition of the molten metal. Before the plasma plume reaches thermal equilibrium shortly after termination of the laser pulse, a spectroscopic detector in the probe detects spectral line reversals, as caused by absorption of radiation emitted by the hotter inner portion of the plasma plume to relatively coller outer portions of the plasma plume, during a short first time window. Thereafter, when the afterglow plasma is in thermal equilibrium, a second spectroscopic detector also in the probe performs a second short time duration spectroscopic measurement. A rangefinder measures and controls the distance between the molten metal surface and the pulsed laser.
50 Citations
52 Claims
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1. A method for spectroscopic analysis of a molten metal, comprising:
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providing a probe including a casing having an open end adapted to be immersed in the molten metal, laser means disposed in said casing for irradiating the surface of the molten metal adjacent the open end with a laser beam of predetermined energy density and focal spot size, and spectroscopic detector means disposed in said casing for detecting spectral components of light emitted from a plasma produced by the laser means; immersing the open end of the casing into the molten metal; irradiating the molten metal with a laser beam from said laser means to produce a plasma representative of the composition of the molten metal, said irradiating being performed during immersion of the casing open end into the molten metal; and detecting spectral components of radiation emitted by the plasma by means of the spectroscopic detector means in the casing and producing signals corresponding to the detected spectral components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An apparatus for spectroscopic analysis of a molten metal, comprising:
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a probe comprising a casing having an open end adapted to be immersed in the molten metal; laser means disposed in said casing for irradiating the surface of the molten metal adjacent to the open end of the casing with a laser beam so as to produce a plasma having a composition representative of the composition of the molten metal; and spectroscopic detecting means disposed in said casing and optically coupled to the plasma for detecting spectral components of radiation emitted by the plasma and producing signals corresponding to the detected spectral components. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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Specification