A Positive material inspection on steel work-pieces is in most cases due to the determination of the material identity using a spectrometer. Used for this are both stationary and portable operating spectrometers, in which the air-emission spectrum of the taken off work-piece on the untreated surface is compared with the spectrum of a reference sample.
The chemical Ist-analysis of the about 100 mm long reference piece is usually either wet-chemically or in the laboratory by means of a vacuum-emission spectrometer determined. The carbon content of the work-piece is very poorly or not at all determined due to spectroscopy, so that another method for determination of carbon is required. Usually, the visual grinding spark test is thus being used.
This method is not entirely meaningful, since the grinding spark test is a subjective test and the error rate for materials with only minor differences in carbon content due to the limited ability of perceive by the human eye, is still very high.