X-ray or gamma ray systems or devices – Specific application – Fluorescence
Patent
1986-04-24
1988-08-16
Church, Craig E.
X-ray or gamma ray systems or devices
Specific application
Fluorescence
378 44, 378 71, G01B 1502, G01N 23223
Patent
active
047649453
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of measuring a layer thickness and composition of an alloy plating, and more particularly to a method of measuring the layer thickness and the composition of an alloy plating including a metal identical with a substrate metal. This method is suitable for use in the analysis of a Zn--Fe group alloy-plated steel plate of one or two layers.
BACKGROUND ART
Various plated steel plates having excellent anticorrosion properties, workability, coating properties, weldability and the like have been developed for use in motor vehicle bodies, electrical household appliances and building materials, and are widely used. In order to stabilize the production quality of these plated steel plates, it is essential to analyze the thickness (deposit value) and the composition (content) of the plating to carry out the process control.
For a steel plate having a plating composed of a content other than Fe, such as a Zn plated steel plate and a Zn--Ni alloy-plated steel plate, the thickness and the composition of the plating can be comparatively easily analyzed using fluorescent X-rays, and apparatus for this type of analysis has been put to practice.
However, analysis of a Zn-Fe group alloy-plated steel plate, the outstanding characteristic feature of which has been noted recently, has been impossible by the ordinary method of fluorescent X-rays because the intesity of the Zn fluorescent X-rays is varied due to the content of Zn or Fe in the plating and the thickness of the plating. In addition, for Fe, a large quantity of Fe fluorescent X-rays are generated from a substrate steel plate, and these fluorescent X-rays cannot be discriminated from the Fe fluorescent X-rays in the plating.
For this reason, the following methods of analyzing the Zn--Fe group one layer alloy-plated steel plate have heretofore been proposed. One method is proposed in Japanese Patent Laid-Open No. 24680/1980, wherein, using a Zn plated steel plate which has been subjected to the Zn--Fe alloying process, a fluorescent X-ray intensity of a metal other than Fe, i.e. that of Zn, is measured by two measuring angles differing from each other. Using predetermined simultaneous equations on the basis of both measured values, the thickness of the plating on the plated steel plate and the degree of alloying (Fe content) are obtained. According to this method, Zn fluorescent X-ray intensities of a sufficiently thick pure Zn sample are previously measured by two measuring angles, and subsequently, a Zn fluorescent X-ray intensity of a Zn alloy-plated steel plate is measured by the same X-ray spectroscope. Analysis is made of the ratio with the pure Zn fluorescent X-ray intensity obtained previously at the respective measuring angles. The fluorescent X-ray quantitative method wherein the measuring angles are varied has been the basic theory of the method of analyzing the fluorescent X-rays published in textbooks from old times and is well known to everyone.
A second method is proposed in Japanese Patent Laid-Open No. 223047/1983, wherein an Fe content in the plating of a Zn--Fe alloy-plated steel plate is obtained from an Fe fluorescent X-ray intensity by a first excitation ray incident angle and the fluorescent X-ray measuring angle, both of which Fe fluorescent X-rays from the substrate steel plate are not substantially detected. The thickness of the plating is obtained from an Fe fluorescent X-ray intensity by a second excitation ray incident angle and a fluorescent X-ray measuring angle, both of which Fe fluorescent X-rays from the substrate steel plate can be detected.
However, since a plated steel plate flows at a speed as high as 100 meter/min, for example on a production line, the plated steel plate is bound to flutter more or less. The influence of this fluttering is received only by the steel plate, so that, according to the former method proposed in Patent Laid-Open No. 24680/1980, the analyzing accuracy is necessarily deteriorated.
In general, the thickness of the plating of the alloy-plated steel pla
REFERENCES:
patent: 2711480 (1955-06-01), Friedman
patent: 3903414 (1975-09-01), Herbstein et al.
patent: 3925678 (1975-12-01), Eberspaecher et al.
patent: 4169228 (1979-09-01), Briska et al.
Church Craig E.
Freeman John C.
Kawasaki Steel Corp.
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