GB/T 2522-2026 Methods of measurement of the coating insulation resistance and coating adhesion of electrical steel strip and sheet English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS
CCS
National Standard of the People's Republic of China
GB/T 2522-2026
Methods of measurement of the coating insulation resistance and coating adhesion of electrical steel strip and sheet
电工钢带(片)涂层绝缘电阻和附着性测试方法
Issue date: 2026-04-30 Implementation date: 2026-10-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Test Method for Coating Insulation Resistance
5 Test Method for Coating Adhesion
Test methods for coating insulation resistance and adhesion of electrical steel strip (sheet)
1 Scope
This document specifies test methods for the coating insulation resistance and adhesion of electrical steel strip (sheet).
This document applies to the testing of surface insulation resistance and interlamination resistance of non oriented and grain oriented electrical steel strip (sheet), as well as to the testing of the adhesion of insulating coatings on non oriented and grain oriented electrical steel strip (sheet).
2 Normative References
The following document is essential for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 8170 Rules of rounding off for numerical values and expression and judgement of limiting values
3 Terms and Definitions
No terms and definitions are defined in this document.
4 Test Method for Coating Insulation Resistance
4.1 Principle of measurement
The Franklin method, which allows only single coating measurement, is used.
A schematic diagram of the measuring device for the surface insulating coating resistance is shown in Figure 1. Under a specified voltage and pressure, 10 metal contacts of fixed area are pressed onto one coated surface of an electrical steel strip (sheet) specimen. The performance of the surface insulating coating is evaluated by measuring the total current flowing through the 10 contacts.
Two spiral drills are used to make contact with the metal substrate of the specimen, thus completing the current circuit.
The arrangement of the test apparatus and the voltage stabilising circuit is shown in Figure 2. A 5 Ω × (1 ± 1 %) resistor is connected in series with each contact. The voltage between the series resistors of the contacts and the spiral drills is stabilised at 500 mV × (1 ± 0.5 %) by a DC power supply. The total current measurement through all contacts is controlled within the range of 0 A to 1 A.
In schematic arrangement A of the circuit, the two spiral drills act as current return contacts to the metal substrate [see Figure 2a)].
In schematic arrangement B of the circuit, the two spiral drills perform different functions [see Figure 2b)]. One spiral drill provides the current return connection to the metal substrate. The other spiral drill provides voltage feedback control. This feedback control eliminates the influence of the contact resistance between the spiral drills and the metal substrate.
Generally, schematic arrangement A is used. When measuring a relatively low surface insulation resistance, where contact resistance has a significant influence on the measurement value, schematic arrangement B may also be used.
4.2 Test specimen
Each test specimen shall consist of a single piece or a single length of strip. The length and width of the specimen shall be greater than the length and width of the contact head assembly described in 4.3.1, respectively.
To obtain representative results, the test specimen shall be cut uniformly from the full width of the electrical steel strip (sheet). The surface of the specimen shall be clean, flat, free from stains and scratches.
This measurement is destructive, and the specimen can be used only once.
4.3 Test equipment
4.3.1 Contact head assembly
The specimen is pressed between a flat base plate and a contact head assembly. The contact head assembly consists of 10 vertically mounted metal rods that move axially under spring compression within a fixed housing. The 10 contacts are usually arranged in two rows, but may be arranged in a single row for convenience. The end of each metal rod is fitted with a contact pole shoe made of bronze or other suitable material (such as stainless steel), insulated from the frame.
Two spiral drills are positioned at the ends of the contact row, on the same side of the specimen.
NOTE 1: Pole shoes with a universal joint can compensate for small angular deviations of the contacts, improving electrical contact.
The area of each of the 10 contacts shall be either 64.5 mm² or 100 mm². Correspondingly, the total area of the 10 contacts is either 645 mm² or 1000 mm². The permissible deviation for the area of an individual contact or the total area of the 10 contacts is ±1 %. A total contact area of 645 mm² is normally selected.
NOTE 2: Only a total contact area of 645 mm² is used internationally. The test results obtained with the two different total areas are generally not comparable.
Two spring loaded spiral drills, approximately 3 mm in diameter, are rotated to penetrate the insulating coating of the specimen, making electrical contact with the metal substrate.
4.3.2 Power supply
A DC regulated power supply with a maximum load current of 1.0 A shall be used to ensure that the voltage between the two electrodes is stabilised at 500 mV.
4.3.3 Current measurement
The total current flowing through the insulating coating between the 10 contacts and the parallel metal substrate (see Figure 2) shall be measured with a measurement uncertainty of ±2 % or less.
The total current value may be determined by measuring the voltage drop across a current sensing resistor Rₛ connected in series with the current circuit, or may be measured directly with an ammeter. The current sensing resistor shall not be included in the voltage stabilising circuit. Individual contact currents may be analysed by measuring the voltage drop across each resistor.
4.3.4 Measurement of applied force
The total force applied to the test specimen by all the contacts shall be measured with a measurement uncertainty of ±5 % or less.
4.4 Equipment verification
The equipment shall be verified using at least one of the following methods:
a) Apply the contacts and drills to a clean copper plate at the rated test pressure. The total current through the 10 contacts shall be controlled within the range of 0.97 A to 1.03 A. If this is not achieved, check the cleanliness of the contacts, the sharpness of the drills and the contact resistance, and then verify again.
b) Under the rated test pressure, press the contacts onto a sheet of carbon paper overlying a sheet of white paper. The impression on the white paper shall be uniform, with no evidence of force concentration. A pressure measuring plate that indicates pressure distribution by colour density change may be used instead of the carbon paper and white paper.
c) Connect standard resistors of 0.1 Ω, 1 Ω, 10 Ω and 100 Ω, in sequence, between the drill and the contact pole shoe. The displayed value shall be stable and reach the required current level.
Standard
GB/T 2522-2026 Methods of measurement of the coating insulation resistance and coating adhesion of electrical steel strip and sheet (English Version)
Standard No.
GB/T 2522-2026
Status
to be valid
Language
English
File Format
PDF
Word Count
7000 words
Price(USD)
210.0
Implemented on
2026-11-1
Delivery
via email in 1~3 business day
Detail of GB/T 2522-2026
Standard No.
GB/T 2522-2026
English Name
Methods of measurement of the coating insulation resistance and coating adhesion of electrical steel strip and sheet
GB/T 2522-2026 Methods of measurement of the coating insulation resistance and coating adhesion of electrical steel strip and sheet English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS
CCS
National Standard of the People's Republic of China
GB/T 2522-2026
Methods of measurement of the coating insulation resistance and coating adhesion of electrical steel strip and sheet
电工钢带(片)涂层绝缘电阻和附着性测试方法
Issue date: 2026-04-30 Implementation date: 2026-10-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Test Method for Coating Insulation Resistance
5 Test Method for Coating Adhesion
Test methods for coating insulation resistance and adhesion of electrical steel strip (sheet)
1 Scope
This document specifies test methods for the coating insulation resistance and adhesion of electrical steel strip (sheet).
This document applies to the testing of surface insulation resistance and interlamination resistance of non oriented and grain oriented electrical steel strip (sheet), as well as to the testing of the adhesion of insulating coatings on non oriented and grain oriented electrical steel strip (sheet).
2 Normative References
The following document is essential for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 8170 Rules of rounding off for numerical values and expression and judgement of limiting values
3 Terms and Definitions
No terms and definitions are defined in this document.
4 Test Method for Coating Insulation Resistance
4.1 Principle of measurement
The Franklin method, which allows only single coating measurement, is used.
A schematic diagram of the measuring device for the surface insulating coating resistance is shown in Figure 1. Under a specified voltage and pressure, 10 metal contacts of fixed area are pressed onto one coated surface of an electrical steel strip (sheet) specimen. The performance of the surface insulating coating is evaluated by measuring the total current flowing through the 10 contacts.
Two spiral drills are used to make contact with the metal substrate of the specimen, thus completing the current circuit.
The arrangement of the test apparatus and the voltage stabilising circuit is shown in Figure 2. A 5 Ω × (1 ± 1 %) resistor is connected in series with each contact. The voltage between the series resistors of the contacts and the spiral drills is stabilised at 500 mV × (1 ± 0.5 %) by a DC power supply. The total current measurement through all contacts is controlled within the range of 0 A to 1 A.
In schematic arrangement A of the circuit, the two spiral drills act as current return contacts to the metal substrate [see Figure 2a)].
In schematic arrangement B of the circuit, the two spiral drills perform different functions [see Figure 2b)]. One spiral drill provides the current return connection to the metal substrate. The other spiral drill provides voltage feedback control. This feedback control eliminates the influence of the contact resistance between the spiral drills and the metal substrate.
Generally, schematic arrangement A is used. When measuring a relatively low surface insulation resistance, where contact resistance has a significant influence on the measurement value, schematic arrangement B may also be used.
4.2 Test specimen
Each test specimen shall consist of a single piece or a single length of strip. The length and width of the specimen shall be greater than the length and width of the contact head assembly described in 4.3.1, respectively.
To obtain representative results, the test specimen shall be cut uniformly from the full width of the electrical steel strip (sheet). The surface of the specimen shall be clean, flat, free from stains and scratches.
This measurement is destructive, and the specimen can be used only once.
4.3 Test equipment
4.3.1 Contact head assembly
The specimen is pressed between a flat base plate and a contact head assembly. The contact head assembly consists of 10 vertically mounted metal rods that move axially under spring compression within a fixed housing. The 10 contacts are usually arranged in two rows, but may be arranged in a single row for convenience. The end of each metal rod is fitted with a contact pole shoe made of bronze or other suitable material (such as stainless steel), insulated from the frame.
Two spiral drills are positioned at the ends of the contact row, on the same side of the specimen.
NOTE 1: Pole shoes with a universal joint can compensate for small angular deviations of the contacts, improving electrical contact.
The area of each of the 10 contacts shall be either 64.5 mm² or 100 mm². Correspondingly, the total area of the 10 contacts is either 645 mm² or 1000 mm². The permissible deviation for the area of an individual contact or the total area of the 10 contacts is ±1 %. A total contact area of 645 mm² is normally selected.
NOTE 2: Only a total contact area of 645 mm² is used internationally. The test results obtained with the two different total areas are generally not comparable.
Two spring loaded spiral drills, approximately 3 mm in diameter, are rotated to penetrate the insulating coating of the specimen, making electrical contact with the metal substrate.
4.3.2 Power supply
A DC regulated power supply with a maximum load current of 1.0 A shall be used to ensure that the voltage between the two electrodes is stabilised at 500 mV.
4.3.3 Current measurement
The total current flowing through the insulating coating between the 10 contacts and the parallel metal substrate (see Figure 2) shall be measured with a measurement uncertainty of ±2 % or less.
The total current value may be determined by measuring the voltage drop across a current sensing resistor Rₛ connected in series with the current circuit, or may be measured directly with an ammeter. The current sensing resistor shall not be included in the voltage stabilising circuit. Individual contact currents may be analysed by measuring the voltage drop across each resistor.
4.3.4 Measurement of applied force
The total force applied to the test specimen by all the contacts shall be measured with a measurement uncertainty of ±5 % or less.
4.4 Equipment verification
The equipment shall be verified using at least one of the following methods:
a) Apply the contacts and drills to a clean copper plate at the rated test pressure. The total current through the 10 contacts shall be controlled within the range of 0.97 A to 1.03 A. If this is not achieved, check the cleanliness of the contacts, the sharpness of the drills and the contact resistance, and then verify again.
b) Under the rated test pressure, press the contacts onto a sheet of carbon paper overlying a sheet of white paper. The impression on the white paper shall be uniform, with no evidence of force concentration. A pressure measuring plate that indicates pressure distribution by colour density change may be used instead of the carbon paper and white paper.
c) Connect standard resistors of 0.1 Ω, 1 Ω, 10 Ω and 100 Ω, in sequence, between the drill and the contact pole shoe. The displayed value shall be stable and reach the required current level.
