GB/T 37591-2019Cold-rolled non-grain oriented electrical steel strip specialized for large generators with power of 700MW or higher (English PDF)

5.3 Delivery conditions

The steel strip shall be coated with insulation coating on both sides. The type of insulation coating is determined by the supplier. When the purchaser has special requirements, it shall be determined through consultation between the supplier and the purchaser.

5.4 Surface quality

5.4.1 The surface of the steel strip shall be smooth, without oil stains and rusts.

If it is within the thickness tolerance range and does not hinder the normal use of the steel strip, it is allowed to have scattered distribution defects, such as scratches, bubbles, etc.

5.4.2 The color of the insulation coating on the surface of the steel strip shall be uniform and firmly adhered, so that it shall not fall off during cutting or stamping operation.

5.5 Shear adaptability

The steel strip shall be easy to cut or stamp. It shall be able to cut the steel strip into its usual shape at any position. Ensure that the steel strip can be processed accurately with the appropriate cutting or punching tools. If the purchaser has special requirements for cutting or stamping, it shall be determined by the supplier and the purchaser through consultation.

6.1 Magnetic properties

6.1.1 The magnetic properties of the steel strip shall meet the requirements of Table 2.

6.1.2 After the aging test, the magnetic properties of the steel strip shall meet the requirements of Table 2. If the supplier can guarantee, it may not carry out the test.

6.1.3 Because the thickness of the coating shall affect the measurement of magnetic properties, the magnitude of the impact or the correction value is determined through consultation between the supplier and the purchaser.

7.2 Sampling

7.2.1 General requirements

7.2.1.1 Test specimen shall be taken from each acceptance lot.

7.2.1.2 The specimen for magnetic properties shall be taken from the beginning and end of each coil.

7.2.1.3 The inner and outer rings of steel coils shall be considered as packaging materials. The specimen shall not be taken from this part. During re-inspection, the specimen shall be cut from the outer ring of the steel coil no less than 3m.

The specimen to be taken shall meet the requirements of GB/T 3655 and shall avoid the splicing area.

7.2.1.4 By properly arranging the test sequence, the same specimen can be used to test multiple characteristics.

7.2.2 Magnetic properties

7.2.2.1 The test specimen for magnetic properties is taken in the longitudinal and transverse directions of the steel strip respectively. The specific requirements are as follows:

a) When using a 25cm Epstein circle to test, a pair of specimens consists of 4 times the sample pieces. The recommended weight is about 0.50kg.

The sampling method, size and allowable deviation of the specimen shall meet the requirements of GB/T 3655;

b) When using a monolithic tester to test, it generally takes two specimens.

If the specimen is square, only one specimen is required. The sampling method, size and allowable deviation of the specimen shall meet the requirements of GB/T 13789.

7.2.2.2 When testing the specific total loss of the steel strip aging specimen, the aging specimen shall be insulated at (225±5)°C for 24h. Then cool in the air to the ambient temperature.

7.2.3 Geometrical characteristics and deviations

7.2.3.1 The specimen to test the thickness, width, unevenness and sickle

For each characteristic specified, each acceptance lot shall be tested. Unless otherwise specified, the test shall be carried out at a temperature of (23±5)°C.

7.3.2 Magnetic properties

7.3.2.1 Magnetic polarization and specific loss

The test method for the magnetic properties of steel strips is conducted in accordance with GB/T 3655 or GB/T 13789.

7.3.2.2 Anisotropy of specific total loss

The test method for the magnetic properties of steel strips is conducted in accordance with GB/T 3655 or GB/T 13789. Use a full-transverse specimen to measure specific total loss P1. Use a longitudinal specimen to measure specific total loss P2. Calculate according to formula (1).

7.3.3 Geometrical characteristics and deviations

7.3.3.1 Thickness

The thickness of the steel strip is tested at a distance of not less than 25mm from the edge of the steel strip. The thickness shall be tested by using a micrometer with an accuracy of 0.001mm.

7.3.3.2 Width

Test along the longitudinal axis of the vertical steel strip.

7.3.3.3 Sickle bend

The sickle bend of steel strip shall be tested according to YB/T 4292.

7.3.3.4 Unevenness

The unevenness of steel strip shall be tested according to YB/T 4292.

7.3.3.5 Residual curvature

The residual curvature of steel strip shall be tested according to YB/T 4292.

7.3.3.6 Burr height

The burr height of steel strip shall be tested according to YB/T 4292.

7.3.4 Technical characteristics

7.3.4.1 Stacking factor

The stacking factor of steel strip shall be tested according to GB/T 19289.

7.3.4.2 Bending times

The bending times of steel strip shall be tested according to GB/T 2521.1.

7.3.4.3 Deviation of shear edges due to internal stress

The deviation of shear edges of steel strip caused by the internal stress shall be tested according to YB/T 4292.

7.3.4.4 Surface insulation coating resistance

The surface insulation coating resistance of steel strip shall be tested according to GB/T 2522.

7.3.4.5 Tensile strength and elongation at break

The tensile strength and elongation at break of steel strip shall be tested according to GB/T 228.1-2010.

7.3.4.6 Hardness

The hardness of steel strip shall be tested according to GB/T 4340.1.