GB/T 34190-2017 English PDF (GBT34190-2017)

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GB/T 34190-2017: Surface coating weight (thickness) of electrical steel -- X-ray spectrometric method
GB/T 34190-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 21
Surface coating weight (thickness) of electrical steel -
X-ray spectrometric method
ISSUED ON. SEPTEMBER 07, 2017
IMPLEMENTED ON. JUNE 01, 2018
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration Committee.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Principle ... 5 
5 Measurement method ... 5 
6 Measuring device ... 10 
7 Influencing factor ... 10 
8 Measuring process ... 11 
9 Measurement result ... 12 
10 Measurement uncertainty ... 12 
11 Test report ... 12 
Annex A (informative) Production of coating weight standard sample ... 13 
Annex B (informative) Calibration of coating weight standard curve ... 15 
Surface coating weight (thickness) of electrical steel -
X-ray spectrometric method
1 Scope
This Standard specifies the method that uses X-ray spectrometric method to
test the surface coating weight (thickness) of electrical steel.
This Method is for measuring the coating weight per unit area of a sample at
room temperature. The measurement results can also be expressed by the
thickness of the coating.
This Standard is applicable to the electrical steel that contains stable,
undisturbed, X-ray fluorescence intensity characteristic elements in surface
coating. The measurement range of a given coating material depends primarily
on the available characteristic X-ray fluorescence intensity and acceptable
measurement uncertainty. And it varies depending on the instrument and
measurement method used.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 16921, Metallic coatings - Measurement of coating thickness - X-ray
spectrometric methods
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T
16921 as well as the followings apply.
3.1 substrate
a material coated with a coating on its surface
3.2 surface coating
material coated on an electrical steel substrate mainly for insulation protection,
produce high intensity X-ray fluorescence. This action produces secondary rays
that characterize the elements in the coating and substrate. These secondary
rays have discrete wavelengths or radioactivity. Generally, primary X-rays are
generated by high-pressure X-ray tubes.
5.1.2 Excitation
With sufficient energy and stable environment for the X-ray tube, it shall
produce primary X-rays. The application voltage of most thickness measuring
equipment is 25kV ~ 50kV. However, low atomic number coating materials may
drop to 10kV. In general, a primary filter is added between the X-ray tube and
the sample to reduce the potential deviation of the measurement.
The main features of this type of stimulation are as follows.
a) produce parallel, high-energy beams on very small measurement areas;
b) easy to meet personal safety protection requirements;
c) obtain energy-stable scattered rays by electronic technology.
5.2 X-ray dispersion
5.2.1 General
X-ray fluorescence scattered on the surface of the coating usually contains
many components in coating thickness measurement. Generally, separate the
required ray components by wavelength or energy dispersion.
5.2.2 Wavelength dispersion
Screen characteristic wavelength ray of a coating or substrate with crystal
spectrometer.
5.2.3 Energy dispersion
X-rays are usually determined by wavelength or equivalent energy. The
relationship between wavelength λ and energy E is as shown in formula (1).
Where,
λ - X-ray wavelength, in nanometers (nm);
E - X-ray photon energy, in thousand electron volts (keV).
5.3 X-ray detection
The detector for the wavelength dispersion system can be a proportional
counter or a scintillation counter.
Detectors for energy dispersive systems that are suitable for receiving
fluorescent photons are generally selected by the manufacturer based on the
application of the device. In the range of energy from 1.5keV ~ 100keV, it is
generally measured under atmospheric conditions. It does not require vacuum
or helium environment.
After the fluorescent ray with different energy characteristics enters the energy
dispersive detector, the multi-channel analyzer shall detect the characteristic
line.
5.4 Coating weight (thickness) measurement
5.4.1 Scattering method
When using the scattering method, select a suitable line from the multiple
characteristic lines of the coating element, for example, Cr-Kα line in chromate
coating. Detect its fluorescence intensity with a detection system.
In general, a characteristic element refers to an element with a large content in
the coating, a large atomic number, and no or negligible in the substrate. The
zero point of the coating weight is the intensity of the scattered line produced
only when the uncoated sample is measured, known as background. The
maximum point of coating weight is the intensity of the scattered lines produced
when measuring an "infinite" thick sample. Generally it is 1.5 or 2.0 times the
usual measurement range.
In general, the intensity of scattered X-ray fluorescence depends mainly on the
excitation energy, the atomic number of the characteristic elements of the
coating, the irradiation area of the primary ray of the sample, and the coating
weight per unit area. If other influencing factors are constant, the X-ray
fluorescence intensity is a function of the weight per unit area or thickness of
the coating.
When measuring the characteristic ray intensity of an electrical steel coating,
the thickness of the coating shall increase to a saturation thickness. The
intensity of the fluorescent ray is continuously increased, as shown in Figure
1a).
5.4.2 Absorption method
When using the absorption method, select a suitable line from a plurality of
characteristic lines of the substrate element. Detect its fluorescence intensity
with a detection system. X-ray fluorescence intensity reaches a maximum when
the substrate is uncoated. As the weight of the coating increases, the intensity
selected as much as possible.
Since the coating may contain multiple dopants, other alloying elements are
present in the substrate. It is easy to produce interference spectrum lines that
are close to or the same as the characteristic line, which shall be eliminated as
much as possible in the measurement.
Since the actual coating density may differ from the standard sample density,
the measured value shall generally be multiplied by the density correction factor
as shown in formula (2).
Where,
C - coating weight per unit area, in grams per square meter or micron (g/m2 or
μm);
Cm - actual measured coating weight per unit area, in grams per square meter
or micron (g/m2 or μm);
ρs - coating density of standard sample, in kilograms per cubic meter (kg/m3);
ρc - coating density of sample to be tested, in kilograms per cubic meter (kg/m3).
Oil stains, impurities and other contaminants appear on the surface of the
coating, which may cause deviations in measurement results. Therefore, the
surface treatment shall be performed for t...