This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 19289-2003 Methods of measurement of density, resistivity and stacking factor of electrical steel sheet and strip. The main changes of this standard with respect to GB/T 19289-2003 are as follows:
——The gas pyknometer method is introduced, and the liquid immersion method and the calculation method based on the chemical composition are quoted (see 5.3);
——An example of the apparatus for determination of the resistivity using a rectangular sheet, which was previously part of the main body of the text, is moved to constitute informative Annex A (see Annex A; 3.4.3 of 2003 edition);
——An example of the determination of the density by using the gas pyknometer method is added as an informative Annex B (see Annex B);
——An example of the determination of density based on the calculation of silicon and aluminium contents is added as an informative Annex C. (see Annex C).
This standard, by means of translation, is identical to IEC 60404-13: 2018 Magnetic materials - Part 13: Methods of measurement of resistivity, density and stacking factor of electrical steel strip and sheet.
The Chinese documents consistent and corresponding with the normative international documents in this standard are as follows:
——GB/T 1033.3-2010 Plastics - Methods for determining the density of non-cellular plastics - Part 3: Gas pyknometer method (ISO 1183-3: 1999, IDT)
——GB/T 2900.60-2002 Electrotechnical terminology - Electromagnetism [eqv IEC 60050 (121): 1998]
——GB/T 3655-2008 Methods of measurement of the magnetic properties of electrical steel sheet and strip by means of an epstein frame (IEC 60404-2: 1996, IDT)
——GB/T 9637 Electrotechnical terminology - Magnetic materials and components [eqv IEC 60050 (221): 1990]
——GB/T 13789-2008 Methods of measurement of the magnetic properties of magnetic sheet and strip by means of a single sheet tester (IEC 60404-3: 2002, IDT)
The following editorial changes have been made in this standard:
——the name of this standard is modified;
This standard was proposed by China Iron and Steel Industry Association.
This standard is under the jurisdiction of SAC/TC 183 National Technical Committee on Iron and Steel of Standardization Administration of China.
The previous editions of this standard are as follows:
——GB/T 2522-1988;
——GB/T 3655-1992;
——GB/T 19289-2003.
Methods of measurement of resistivity, density and stacking factor of electrical steel strip and sheet
1 Scope
This standard specifies the methods used for determining the resistivity, density and stacking factor of grain-oriented and non-oriented electrical steel strip and sheet. These quantities are necessary to establish the physical characteristics of the material. Moreover, the density is necessary to allow specified values of the magnetic polarization, resistivity and stacking factor to be determined.
Since these properties are functions of temperature, the measurements will be made at an ambient temperature of 23℃±5℃ except when specified in this document.
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.
ISO 1183-3 Plastics - Methods for determining the density of non-cellular plastics - Part 3: Gas pyknometer method
IEC 60050-121 International electrotechnical vocabulary - Part 121: Electromagnetism
IEC 60050-221 International electrotechnical vo-cabulary - Part 221: Magnetic materials and components
IEC 60404-2 Magnetic materials - Part 2: Methods of measurement of the magnetic properties of electrical steel strip and sheet by means of an Epstein flame
IEC 60404-3 Magnetic materials - Part 3：Methods of measurement of the magnetic properties of electrical steel strip and sheet by means of a single sheet tester
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121, IEC 60050-221 and ISO 1183-3 apply.
4 Determination of the resistivity
4.1 General
Two methods for the determination of the resistivity of a test specimen are described in this clause; Method R1 using an Epstein strip specimen, and Method R2 using a rectangular sheet specimen.
Note: Method R2 is based on the van-der-Pauw (VDP) method [1] which is based on the theory of conformal mapping of two-dimensional fields. For a body of uniform thickness and arbitrary shape, an exact mathematical formula exists for the resistivity determined from the voltage to current ratio obtained using four contacts. The formula is simplified when specimens and contact positions are highly symmetrical. Method R2 is particularly appropriate for rectangular sheet specimens.
The method of determination of the resistivity ρ, based on the measurement of the geometric dimensions of the test specimen including the thickness, can be applied to all types of material specimens. However, the method for further use to determine the density ρm in accordance with 5.2 is restricted to the materials as specified in 5.1.
4.2 Principles of measurement
4.2.1 Method of determining ρ for an Epstein strip specimen (Method R1)
The circuit for the measurement of the resistance of an Epstein strip specimen shall be connected as shown in Figure 1. Two electrical contacts A and B shall be arranged on either end of the shorter sides of the test specimen to supply a homogeneous current through the test specimen in the longitudinal direction. Two electrical contacts, C and D, located inside the contacts A and B shall be arranged on a longer side edge of the test specimen to measure the voltage over the length le. It is not necessary to remove the oxide layer or other insulating coatings because the contacts are made at the cut edges of the specimen.
Key:
A，B，C，D——electrical contact;
A1——DC ammeter;
V1——DC voltmeter;
le——distance between C and D;
IAB——current flowing between A and B;
S——switch for current reversal;
UCD——voltage between C and D.
Figure 1 Circuit for the measurement of resistance of an Epstein strip specimen (Method R1)
If a current flows homogeneously through the test specimen, the resistance R of the material over the length le of the Epstein strip specimen shall be calculated using Formula (1):
(1)
where,
R——the resistance of the material over the length le between the contacts C and D, Ω;
UCD——the voltage between the contacts C and D, V;
IAB——the current flowing between the contacts A and B, A;
The resistivity ρ shall be calculated using Formula (2):
(2)
where,
ρ——the resistivity of the material of the test specimen, Ω·m;
b——the width of the test specimen, m;
d——the thickness of the test specimen without an insulation layer, m.
le——the distance between the contacts C and D, m.
4.2.2 Method of determining ρ for a rectangular sheet specimen (Method R2) with supplementary remarks for strip specimen
The circuit for the measurement of the resistance of a square-shaped or rectangular sheet specimen shall be connected as shown in Figure 2. Four electrical contacts A, B, C and D shall be arranged symmetrically at the centre of each edge of the test specimen. The contacts A, B, C and D shall be as small as possible. With a current flowing through the contacts A and B, the voltage between the contacts C and D shall be measured. It is not necessary to remove the oxide layer or other insulating coatings because the contacts are made at the cut edges of the specimen.
The resistance RAB,CD shall be calculated using Formula (3):
(3)
where,
RAB,CD——the resistance measured between the contacts C and D, Ω;
UCD——the voltage between the contacts C and D, V;
IAB——the current flowing between the contacts A and B, A;
Key:
A, B, C, D——electrical contact;
A1——DC ammeter;
V1——DC voltmeter;
IAB——switch for current reversal;
S——reverse current switch;
UCD——voltage between C and D.
Figure 2 Circuit for the measurement of resistance of a rectangular sheet specimen (Method R2)
Correspondingly, the resistance RAB,CD shall be obtained from the voltage between the contacts D and A and the current flowing through the contacts B and C.
On the basis of the theory of conformal mapping of two-dimensional fields [1], for a body of uniform thickness and arbitrary shape, the following formula holds:
(4)
where,
ρ——the resistivity of the material of the test specimen, Ω·m;
d——the thickness of the test specimen without an insulation layer, m.
Fρ——a function of the ratio only.
If the ratio is close to 1, the function Fρ becomes 1, so that it can be omitted [1]. To ensure that this ratio is close to 1, the contacts shall be arranged symmetrically at the centres of the edges of the rectangular sheet specimen as shown in Figure 2.
Method R2 can also be applied to Epstein strip specimen, in this case, to obtain a reliable result of the measurement, a certain number (e.g. >10) of Epstein strip specimens should be tested, and the average should be taken as the result.
Note: It has been shown that Method R2 (van der Pauw method [1]) is equivalent to Method R1, within limits which are lower than the dispersion between individual strip specimens of one grade of material [2]. The Method R2 has the advantages of versatility of specimen shape [3].
4.2.3 Determination of thickness d
4.2.3.1 General
The thickness of the test specimen d used in Formulae (2) and (4) shall be determined as specified in 4.2.3.2.
4.2.3.2 Calculating the thickness from the density ρm
The thickness of the test specimen d shall be calculated using the value of the density ρm determined as specified in 5.3, or supplied by the manufacturer. The thickness d shall be determined from the following formula:
(5)
where,
m——the mass of the test specimen, kg;
ρm——the density of the material of the test specimen, kg/m3;
b——the width of the test specimen, m;
l——the length of the test specimen, m.
4.3 Test specimen
4.3.1 Epstein strip specimen
The Epstein strip specimen used in Method R1 (according to 4.2.1), conforming with IEC 60404-2, shall have the following dimensions:
——width b = 30 mm ±0.2 mm;
——length 280 mm ≤ l ≤ 320 mm with a tolerance of ± 0.5 mm.
4.3.2 Rectangular sheet specimen
The dimensions of the square-shaped or rectangular sheet specimen used in Method R2 (according to 4.2.2), conforming with IEC 60404-3, shall be as follows:
——width 300 mm ≤ b ≤ 500 mm with a tolerance of ± 0.5 mm;
——length 500 mm ≤ l ≤ 610 mm with a tolerance of ± 0.5 mm.
4.4 Apparatus
4.4.1 Common requirements for Method R1 and Method R2
The following equipment is required:
——according to 4.2.3.2, a calibrated balance, capable of weighing the mass of the test specimen to within ± 0.1%;
——a power supply consisting of a stable low voltage DC current source capable of supplying a current of the order 1A to 10A (unless a four-terminal ohm meter is used, as specified in 4.5.2 and 4.5.3);
——a resistance measuring device (e.g. ammeter and voltmeter of accuracy ±0.1% or better, or a Kelvin bridge or a four-terminal ohm meter of corresponding accuracy) capable of measuring the resistance R of the test specimen to within ±1%;
——a jig for making contact with the test specimen (as specified in 4.4.2 and 4.4.3) and, between the contacts, a supporting flat plate smaller than the test specimen (on sides where contacts are arranged) but not by more than 5mm (10mm for rectangular sheet specimens) on each side. The thickness of the support shall allow the contacts to touch the specimen lying on the support.
4.4.2 Requirements for Method R1
The apparatus for making electrical contact with the strip specimen employs four contacts: two voltage contacts (tips) are mounted on a removable bridge and two current contacts are fixed to the base plate. The four contacts shall be arranged so that the two voltage contacts C and D lie on a longer edge of the strip between the current contacts A and B (see Figure 1). The current contacts shall be arranged symmetrically in the center of each of the shorter edges of the strip within ±0.5 mm. The two voltage contacts shall have a relatively sharp edge (e.g. with a radius of curvature of 1mm). The distance between the voltage contacts C and D shall exceed 200 mm. The minimum distance between the voltage contacts and the current contacts shall be not less than the width of the test specimen (the distance le between the tips shall be determined within ±0.5mm, see Figure 1).
4.4.3 Requirements for Method R2
Four contacts with a relatively sharp edge (e.g. with a radius of curvature of 1 mm) shall each be mounted on a holder which is fixed to the base plate. The contacts shall be arranged symmetrically in the center of each edge of the specimen, within ± 1mm (or ± 0.5 mm for an Epstein strip specimen) (see Figure 2).
Foreword i
1 Scope
2 Normative references
3 Terms and Definitions
4 Determination of the resistivity
4.1 General
4.2 Principles of measurement
4.3 Test specimen
4.4 Apparatus
4.5 Measuring procedure
4.6 Reproducibility
4.7 Test report
5 Determination of the density
5.1 General
5.2 Method based on the measurement of resistance (Method D1)
5.3 Gas pyknometer method (Method D2)
5.4 Test report
6 Determination of the stacking factor
6.1 General
6.2 Test specimen
6.3 Measuring procedure
6.4 Reproducibility
6.5 Test report
Annex A (Informative) An example of the apparatus for the measurement of the resistivity using a rectangular sheet specimen (Method R2)
Annex B (Informative) An example of the determination of density using the gas pyknometer method (Method D2)
Annex C (Informative) Calculation of density based on silicon and aluminium content (Method D4)
Bibliography
