Method of laser emission spectroscopic analysis of steel and apparatus therefor

Claim 1

A method of laser emission spectroscopic analysis of steel, wherein a light emitted when a laser beam irradiates the surface of the steel is spectrally separated and elements contained in the steel are quantitatively analyzed, comprising the steps of: irradiating a sample with an infrared pulse laser beam to turn a part of said sample into plasma such that an energy density on the surface of the sample is 2.0×10 9 W/mm 2 or more; receiving a light emitted from the surface of the sample by a light introducing system at a solid angle of 16 degrees or more through a path held under an atmosphere of inert gas blown into said path at a flow rate of at least 50 l/min, and thereafter forming an image on an inlet slit of a spectroscope with said light; and quantitatively analyzing said light, such that a firstly emitted portion of said light generating white noise is excluded, and a subsequently emitted portion of said light is analyzed, and an analyzed value is obtained from a spectral line intensity of an element to be measured only when an intensity of a preset spectral line or an intensity ratio between a pair of preset spectral lines is within a preset range.

Claim 2

A method of laser emission spectroscopic analysis of steel, wherein a light emitted when a laser beam irradiates the surface of the steel is spectrally separated and elements contained in the steel are quantitatively analyzed, comprising the steps of: irradiating a sample with an infrared pulse laser beam to turn a part of said sample into plasma such that an energy density on the surface of the sample is 2.0×10 9 W/mm 2 or more; receiving a light emitted from the surface of the sample by a light introducing system at a solid angle of 16 degrees or more through a path held under an atmosphere of inert gas blown into said path at a flow rate of at least 50 l/min, and thereafter forming an image on an inlet slit of a spectroscope with said light; and quantitatively analyzing said light, such that a firstly emitted portion of said light generating white noise is excluded, and a subsequently emitted portion of said light is analyzed, and an analyzed value is obtained from a spectral line intensity of an element to be measured only when an intensity of a preset spectral line or an intensity ratio between a pair of preset spectral lines is within a preset range.

Claim 8

An apparatus for laser emission spectroscopic analysis of steel, wherein a light emitted when a laser beam irradiates the surface of the steel is spectrally separated and elements contained in the steel are quantitatively analyzed, comprising: laser oscillating means assembled thereinto with a mode lock mechanism, for emitting an infrared pulse laser beam having an energy density of 2.0×10 9 W/mm 2 or more on the surface of a sample to turn a part of said sample to plasma; a focusing mirror for focusing a light emitted from the surface of the sample at a focusing solid angle of 16 degrees or more; a casing and means for introducing inert gas through an inert gas introducing port in said casing at a flow rate of at least 50 l/min for holding a path of said light emitted from the sample under an atmosphere of the inert gas in said casing; spectroscopic means wherein said light emitted from the sample whose image is formed at an inlet slit of the spectroscopic means by said focusing mirror is spectrally separated into spectral lines by a diffraction means; detecting means including a group of photoelectric signal transducing elements wherein preset spectral lines of target elements are converted into electric signals; a spectrum intensity monitor for monitoring an intensity of a preset spectral line or an intensity ratio between a pair of preset spectral lines; gate means to be opened during a period from 1.5 microsecond after the start of the irradiation by the laser beam up to 16 microseconds and when the intensity of the preset spectral line or the intensity ratio between the pair of preset spectral lines is within the preset range, so that an output from said spectroscopic means can be adopted in the analysis; and signal processing means for obtaining an analyzed value in response to a signal inputted from said spectroscopic means when said gate means is opened.

Claim 9

An apparatus for laser emission spectroscopic analysis of steel, wherein a light emitted when a laser beam irradiates the surface of the steel is spectrally separated and elements contained in the steel are quantitatively analyzed, comprising: laser oscillating means assembled thereinto with a mode lock mechanism, for emitting an infrared pulse laser beam having an energy density of 2.0×10 9 W/mm 2 or more on the surface of a sample to turn a part of said sample to plasma; a focusing mirror for focusing a light emitted from the surface of the sample at a focusing solid angle of 16 degrees or more; a casing and means for introducing inert gas through an inert gas introducing port in said casing at a flow rate of at least 50 l/min for holding a path of said light emitted from the sample under an atmosphere of the inert gas in said casing; spectroscopic means wherein said light emitted from the sample whose image is formed at an inlet slit of the spectroscopic means by said focusing mirror is spectrally separated into spectral lines by a diffraction means; detecting means including a group of photoelectric signal transducing elements wherein preset spectral lines of target elements are converted into electric signals; a spectrum intensity monitor for monitoring an intensity of a preset spectral line or an intensity ratio between a pair of preset spectral lines; gate means to be opened during a period from 1.5 microsecond after the start of the irradiation by the laser beam up to 16 microseconds and when the intensity of the preset spectral line or the intensity ratio between the pair of preset spectral lines is within the preset range, so that an output from said spectroscopic means can be adopted in the analysis; and signal processing means for obtaining an analyzed value in response to a signal inputted from said spectroscopic means when said gate means is opened.