GB/T 3655-2000 Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings
Some standard content:
GB/T3655-2000
This standard adopts the International Electrotechnical Commission standard IEC404-2:1996 "Method for measuring the magnetic properties of electrical steel sheets (strips) using Epstein square rings" in a non-equivalent manner. The text of this standard is basically the same as IEC404-2:1996, with the addition of Chapter 8 "Calibration of measuring equipment", Appendix A "Method of cutting samples", Appendix B "Correction of waveform factors" and Appendix C "Average density of electrical steel sheets and strips". This revision of this standard has modified the following provisions: - The original Chapter 3 Accuracy and Repeatability was cancelled. - The original Chapter 6 in the sample cutting method was placed in Appendix A. - The original 7.7 (now 4.5), the repeatability of the measurement results was changed to 1.5%. The original 7.6.3.2 waveform factor correction was placed in Appendix B. The original Chapter 7 Tables 1 and 2 are placed in Appendix C. From the date of implementation of this standard, it will replace Replaces the magnetic properties part of GB/T3655-1992 "Measurement methods for magnetic, electrical and physical properties of electrical steel sheets (strips)".
Appendix A, Appendix B and Appendix C of this standard are all appendices to the standard. This standard was proposed by the State Bureau of Metallurgical Industry. This standard is under the jurisdiction of the National Technical Committee for Steel Standardization. The drafting units of this standard: China Institute of Metrology, Taiyuan Iron and Steel Company, Metallurgical Industry Information Standards Institute. The main drafters of this standard: Qu Qingchang, Li Xintian, Liu Zeyan, Wang Jingping, Li. This standard was first issued in May 1983 and revised for the first time in November 1992. 60
GB/T 3655--2000
IEC Foreword
IEC (International Electrotechnical Commission) is a worldwide organization for standardization work composed of all national electrotechnical committees (IEC National Committees) in the world. Its goal is to promote international cooperation on all issues related to standardization in the electrical and electronic fields. To this end, IEC, in addition to other activities, also publishes and publishes international standards. The preparation of these standards is entrusted to a number of specialized technical committees. Any IEC National Committee interested in the issues involved can participate in the preparatory work. International, governmental and non-governmental organizations that have ties to IEC can participate in the preparatory work. IEC works closely with the International Organization for Standardization (ISO), and the conditions for recognition between the two organizations are mutually consistent.
Because each technical committee has representatives from all interested parties, it is also possible to participate in the preparation of the standards. IEC has representatives of interested national committees, so the formal decisions or approvals of IEC on technical content represent, as far as possible, international consensus on the relevant issues. The proposed text has an internationally accepted recommended format and is published in the form of standards, technical reports or guidelines (guidelines) and accepted by various national committees.
In order to promote international unification, each IEC National Committee ensures that IEC International Standards are applied to the greatest extent possible in its national and regional standards. Some differences between IEC standards and corresponding national or regional standards should be clearly pointed out at the end. IEC has established a non-marking procedure to indicate its approval, and it cannot be used to declare (declare) that some equipment conforms to one of its standards. It is worth noting that some components of this standard may be the subject of patent rights. IEC will not be responsible for marking some or all of these patent rights.
1 Scope
National Standard of the People's Republic of China
Methods of measurement of the magnetic properties of electrical steel sheet and strip by means of an Epstein frameGB/T3655—2000
neqIEC404-2:1996
Replaces GB/T3655—1992
Magnetic properties part
This standard specifies the general principles of AC measurement of magnetic properties of electrical steel sheet and strip by means of an Epstein frame, the measurement method of specific total loss, the determination methods of peak value of magnetic polarization intensity, effective value of magnetic field intensity, peak value of magnetic field intensity and specific apparent power, the general principles of DC measurement, the DC measurement method of magnetic polarization intensity, the calibration of measuring equipment and the test report. This standard applies to the measurement of DC magnetic properties of grain-oriented and grain-non-oriented electrical steel sheets (strips) and the measurement of AC magnetic properties with an upper frequency limit of 400Hz. It is applicable to test specimens obtained from electrical steel sheets (strips) of any grade. The specimens should be demagnetized before measurement, and the measurement should be carried out at an ambient temperature of (23 ± 5) °C and a relative humidity of less than 80%. Measurements at higher frequencies should be carried out in accordance with GB/T10129.
2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard by being referenced in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest version of the following standards. GB/T2521-1996 Cold-rolled grain-oriented and non-oriented magnetic steel strip (sheet) GB/T5212-1985 Hot-rolled silicon steel sheet for electrical use GB/T10129-1988 Method for measuring medium-frequency magnetic properties of electrical steel sheet (strip) 3 General principle of AC measurement
3.1 Principle of the 25cm Epstein square ring method The 25cm Epstein square ring consists of a primary coil, a secondary coil and a sample as the core. It forms an unloaded transformer, and its characteristics are measured according to the methods described in the following chapters. 3.2 Samples
The samples are assembled into a square with double lap joints (see Figure 1) to form four bundles of equal length and equal cross-sectional area. Figure 1 Double lap joints
Steel strips should be sampled according to the corresponding product standards, and the cutting method is shown in Appendix A (Appendix to the standard). Approved by the State Administration of Quality and Technical Supervision on October 25, 2000 62
2001~09-01 Implementation
GB/T 3655-—2000
The cutting of the specimens requires neat and flat cutting, good right angles, and no obvious burrs on the edges. If heat treatment is required, it should be carried out in accordance with the corresponding product standards. The strips should have the following dimensions: width b = 30mm±0.2mm;
length 280mm≤L≤320mm.
The strip length tolerance is ±0.5mm.
When cutting strips parallel or perpendicular to the rolling direction, the long side of the parent steel sheet should be used as the reference direction. For the angle between the specified and actual shearing directions, the following tolerances apply: ±1° for grain-oriented electrical steel sheets; ±5° for grain-free steel sheets. The measurement should be carried out without additional insulation. The number of strips constituting the test specimen shall be a multiple of 4 and shall comply with the provisions in the product standard. The effective mass of the test specimen [see formula (1)] shall be at least 240 g. The recommended specimen length is 300 mm and the mass is approximately 1 kg: 3.325 cm Epstein square ring
The 25 cm Epstein square ring (hereinafter referred to as the square ring) shall consist of 4 coils into which the strips constituting the test specimen are inserted (see Figure 2). 250 mm
Lm =0. 94 n
Figure 225 cm Epstein square ring
The square ring includes a mutual inductor for air flux compensation. The winding frame supporting the coil is made of a hard insulating material, such as phenolic resin. The winding frame has a rectangular cross-section with an internal width of 32 mm. The recommended approximate height is 10 mm. The coil shall be fixed on an insulating, non-magnetic base plate (see Figure 2). The side length of the square formed by the inside of the sample strip should be 220mmtmm (see Figure 2).
Each of the four coils should have two sets of windings:
set of primary windings, on the outside (magnetizing windings);
set of secondary windings, on the inside (voltage windings). Note: An electrostatic screen may be added between these windings. The windings should be evenly distributed over a minimum length of 190mm, and the number of turns of each coil should be one quarter of the total number of turns. The primary windings of the four coils should be connected in series, and the secondary groups should also be connected in series. The number of primary and secondary turns can be selected to suit the special conditions of power supply, measuring instrumentation and frequency.
Note: The total number of turns usually recommended is 700 or 1000. In order to minimize the influence of winding impedance, the following requirements should be met: R,
≤1.25×1060
≤2.5×10-H
where Ri, R2——
are the resistance of the primary and secondary windings, 2; LiLa—
are the inductance of the primary and secondary windings, H: ≤5×10-*0
≤2.5×10-9H
GB/T3655-2000
Ni, N are the total number of turns of the primary and secondary windings, respectively. Note: For example: If these windings have the following characteristics, these requirements are met: Total number of turns: N 700,N,=700t
Primary (outer) winding: Each of the four coils is wound with a double-strand copper wire with a nominal cross-sectional area of about 1.8mm2, three layers in parallel, a total of 175 turns; Secondary winding: Each of the four coils is wound with a single-strand copper wire with a nominal cross-sectional area of 0.8mm2, one layer, a total of 175 turns. The effective magnetic path length Lm is specified to be 0.94m. Therefore, the effective mass ma, that is, the magnetic effective mass of the sample, is calculated according to formula (1): n
Where: L—length of the sample strip, m;
Lm—effective magnetic path length, m (Lm=0.94 m); m——total mass of the sample, kg;
m.—effective mass of the sample, kg.
3.4 Air Flux Compensation
(1)
The mutual inductor for air flux compensation is placed at the center of the space enclosed by the four coils, with its axis perpendicular to the plane formed by the axes of these coils. The primary winding of the mutual inductor should be connected in series with the primary winding of the square circle, and the secondary winding of the mutual inductor should be connected in series with the secondary winding of the square circle in reverse connection (see Figure 3).
The mutual inductance value should be adjusted in such a way that when there is no specimen in the device, an alternating current is passed through the primary winding so that the voltage measured between the non-common ends of the secondary windings is not greater than 0.1% of the voltage appearing between the secondary windings of the test device itself. In this way, the average value of the induced voltage in the total secondary winding is proportional to the peak value of the magnetic polarization intensity in the specimen. A
Figure 3 Circuit of the Wattmeter Method
3.5 Power Supply
The power supply should have low output impedance and high voltage and frequency stability. During the measurement, the output voltage stability is required to be 0.1%, and the set frequency accuracy is required to be 0.1%.
For the measurement of the effective value of the specific total loss, the specific apparent power and the magnetic field strength, the secondary voltage waveform factor should be 1.111±1%. Note: This can be done by some methods, such as using an electronically controlled power supply or a negative feedback power amplifier. The secondary voltage waveform factor is the ratio of the effective value of the secondary voltage to the average value of the secondary voltage.
To determine the waveform factor, two voltmeters can be used: one is an effective value response voltmeter; the other is an average value response voltmeter. Note: The waveform of the secondary induced voltage should be checked with an oscilloscope to ensure that only the fundamental component exists. 3.6 Voltage measurement
The secondary voltage of the square circle should be measured with a voltmeter with an input impedance of not less than 1000Q2/V. 3.6.1 Average value voltmeter
A voltmeter with an average value response accuracy of ±0.2% or better should be used. Note: The preferred instrument is a digital voltmeter. 3.6.2 Effective value voltmeter
A voltmeter with an effective value response accuracy of ±0.2% or better should be used. Note: The preferred instrument is a digital voltmeter. 64
3.6.3 Peak value voltmeter
GB/T3655-2000
A voltmeter with an accuracy of ±0.5% or better that is sensitive to peak value should be used. 3.7 Frequency measurement
A frequency meter with an accuracy of ±0.1% or better should be used. 3.8 Power measurement
A wattmeter with an accuracy of ±0.5% or better under actual power factor and waveform factor conditions should be used to measure power. The resistance of the wattmeter voltage loop should be at least 5000 times its reactance unless the wattmeter is compensated for its resistance. If a current measuring instrument is included in the circuit, it should be short-circuited when adjusting the secondary voltage and measuring losses. 4 Method of measuring specific total loss
4.1 Preparation for measurement
The square ring and the measuring equipment shall be connected as shown in Figure 3. Weigh the specimen and determine its mass within ±0.1%. After weighing, the strips shall be stacked in the coil of the Epstein square ring and overlapped at the corners with double overlap joints, with the same number of strips in each branch of the square ring so that the inner side length of the square formed is 220 mm +. mm. When half of the strips are sheared parallel to the rolling direction and half are sheared perpendicular to the rolling direction, the strips sheared in the rolling direction shall be inserted into the two opposite branches of the square ring, and those sheared perpendicular to the rolling direction shall be inserted into the other two branches. It is important to ensure that the air gap between the strips in the overlapping part is as small as possible. It is allowed to apply a force of about 1 N to each corner perpendicular to the plane of the overlapping strips.
The specimen shall be demagnetized before measurement. The initial amplitude of the demagnetization field should be higher than the test point, and then the magnetic polarization intensity should be slowly reduced to zero in small increments.
4.2 Power supply adjustment
Observe the ammeter of the primary circuit and slowly increase the output of the power supply to ensure that the wattmeter current circuit is not overloaded until the average value of the secondary voltage U of the Epstein square reaches the required value. This value is calculated according to the required magnetic polarization intensity value in formula (2). (02) = 4fN2 R +R.
Where: IU,1-average value of the induced voltage in the secondary winding, V; A-cross-sectional area of a sample, m;
f-frequency, Hz;
j--—peak value of magnetic polarization intensity, T;
N2-—total number of turns of the secondary winding;
R;-total resistance of the instrument in the secondary circuit, 2; R,——series resistance of the secondary winding and the transformer, a. The cross-sectional area of the sample is calculated according to formula (3):
Where: A-cross-sectional area of the sample, m\: total mass of the sample, kg;
L-length of the sample strip, m;
...( 2)
·(3)
Pm——density of the sample, kg/m.
Note: The density value of the sample can be deduced from the product standard, or measured according to the corresponding standard, or obtained by looking up the table of silicon and aluminum content of the product [see Appendix C (Appendix of the standard, etc.]. 4.3 Power measurement
Short-circuit the ammeter of the primary circuit and, if necessary, readjust the secondary voltage. Determine the waveform factor of the secondary voltage according to the provisions of 3.5 and then record the reading of the wattmeter.
4.4 Determination of total loss
GB/T 3655—2000
The power Pm measured by the wattmeter includes the power consumed by the instrument in the secondary circuit. Therefore, the total loss P of the sample is calculated according to formula (4):
Where: P.
The total loss of the sample calculated, W:
Total number of turns of the primary winding;
Total number of turns of the secondary winding;
The power measured by the wattmeter, W;
R;——Total resistance of the instrument in the secondary circuit, Q;[U
——Average value of the induced voltage in the secondary winding, V. The measured specific total loss P is calculated according to formula (5): (1. 1110,1)2
Where: P
Specific total loss of the sample, W/kg;
Length of the sample strip, m;
Lm—effective magnetic path length, m (Lm=0.94m); m——total mass of the sample, kg;
me—effective mass of the sample, kg;
P.——calculated total loss of the sample, W.
4.5 Repeatability of specific total loss measurement
（4）
The repeatability of the measurement results obtained by the method described in this chapter is expressed as a relative standard deviation, which is 1.5% for measurements on grain-oriented materials when the magnetic polarization intensity is not greater than 1.7 T and for measurements on grain-non-oriented materials when the magnetic polarization intensity is not greater than 1.5 T. For measurements at higher magnetic polarization intensities, the relative standard deviation is expected to increase. 5 Magnetic polarization Methods for determining peak intensity, effective value of magnetic field intensity, peak magnetic field intensity and specific apparent power This chapter describes the determination methods for the following characteristics: peak magnetic polarization intensity ";
- effective value of magnetic field intensity H;
- peak magnetic field intensity H;
specific apparent power S.
5.1 Sample
The sample shall comply with the provisions of 3.2.
5.2 Measurement principle
5.2.1 Peak value of magnetic polarization intensity
The peak magnetic polarization intensity shall be calculated by the average value of the secondary voltage measured by the method described in Chapter 4, and then by formula (2). Note: After the peak value of magnetic polarization intensity is measured, add the product of the peak magnetic field intensity H and the corresponding point to obtain the peak magnetic induction intensity B(T) at that point, where μo is the magnetic constant, and its value is 4 yuan × 10-7 H/m. 5.2.2 Effective value of magnetic field strength
The effective value of magnetic field strength should be calculated from the effective value of current measured by the ammeter in the circuit of Figure 4. Another method is to connect a precision resistor with an accuracy of 0.1% (its typical value is in the range of 0.1Q to 1) to the circuit to replace the ammeter, and then follow 3.6, use an effective value response voltmeter to measure the voltage generated on this resistor. The frequency should be adjusted to the required value. The peak value of the magnetic polarization intensity should be adjusted to the required value calculated by formula (2) by adjusting the secondary voltage of the Epstein square ring. Then measure and record the effective value of the current. The effective value of the magnetic field strength is calculated according to formula (6):
Where: A-
—effective value of magnetic field strength, A/m;
I,--—effective value of magnetizing current, A;
GB/T3655--2000
Lm---effective magnetic path length, m (Lm=0.94m), N,-—total number of turns of the primary winding.
Figure 4 Circuit for measuring the effective value of magnetizing current
5.2.3 Peak value of magnetic field intensity
The peak value of magnetic field intensity shall be obtained from the peak value of magnetizing current 1, and 1. is obtained by measuring the voltage drop across a known precision resistor R with an accuracy of 0.1% using the peak voltmeter shown in Figure 5. For this measurement, the waveform factor of the secondary voltage is allowed to exceed the specified value (see 3.5). The peak value of magnetic field intensity is calculated according to formula (7):
Where: H-peak value of magnetic field intensity, A/m,
1,-peak value of magnetizing current 1,-
Lm-effective magnetic path length, m (Lm=0.94m); Ni-total number of turns of the primary of Epstein square coil. 6
Figure 5 Measurement of the peak magnetic field strength using a peak voltmeter (7)
Alternatively, the peak magnetizing current 1 can be obtained by measuring the average voltage across the secondary winding of a transformer Mn with an accuracy of 0.5%, the primary of the mutual inductance being connected in series with the primary of the square. In this method it must be ensured (for example by viewing the waveform on an oscilloscope) that the waveform of the mutual inductance secondary voltage does not cross zero more than twice per cycle. The circuit is shown in Figure 6. The voltmeter can be the same instrument used to measure the average value of the square secondary voltage. In this method, the peak magnetic field strength should be calculated according to formula (8): R+Rm×U.
Where: Mp is the mutual inductance coefficient in the circuit of Figure 6, H; Rm is the resistance of the secondary winding of the transformer Mp, α; an internal resistance of the average voltmeter, α;
Um is the average value of the secondary induced voltage of the transformer Mp, V. R
5.2.4 Determination of specific apparent power
GB/T 3655—2000
Figure 6 Circuit for measuring peak magnetic field intensity using mutual inductor M. Given the magnetic polarization intensity and frequency, the specific apparent power of the sample can be obtained by measuring the corresponding effective value of the magnetizing current (see 5.2.2) and the effective value of the secondary voltage of the square ring. The effective value of the voltage should be measured at both ends of the secondary winding of the Epstein square ring using a voltmeter that meets the requirements of 3.6.
The specific apparent power is calculated according to formula (9):
where: S,--
=10, N4L
(9)
Specific apparent power, VA/kg;
1,-effective value of magnetizing current, A,
-effective magnetic path length, mLm=0.94m); L
length of the sample strip, m;
total mass of the sample, kg;
m. —-effective mass of the sample, kg;
N,-total number of turns of a square primary winding; N—total number of turns of a square secondary winding;
U,-effective value of the induced voltage of the secondary winding, V. 5.3 Repeatability
The repeatability of the measurement results obtained by the method described in this clause depends essentially on the accuracy of the measuring instruments used and close attention to the physical details of the test. When the accuracy of the instrument used is ±0.5% or better, in the saturation region of the basic magnetization curve (grain-oriented electrical steel sheet H500A/m, grain-non-oriented electrical steel sheet H≥1000A/m), the repeatability of the peak magnetic polarization intensity measurement result corresponding to the given magnetic field intensity peak of the sample is 1% of the standard deviation; the repeatability of the apparent power is 2% of the standard deviation (for magnetic polarization intensity values below the knee point of the magnetization curve) to 7% (for magnetic polarization intensity values close to saturation); the repeatability of the measurement results of other parameters is 2% of the standard deviation. 6 General principles of DC measurement
6.125cm Epstein square ring method principle
25cm Epstein square ring consists of a primary winding, a secondary winding and a test sample as the core. It forms an unloaded transformer, and its DC characteristics are measured using the methods described in the following chapters. 6.2 Test specimens
The test specimens shall be in accordance with the provisions of 3.2.
6.325cm Epstein Square
The 25cm Epstein Square shall be constructed in accordance with 3.3. 6.4 Air Flux Compensation
The effects of air flux shall be compensated by the mutual inductance described in 3.4. 68
6.5 Power Supply
GB/T 36552000
The power supply shall have a rated current sufficient to produce the required maximum magnetic field strength. The ripple shall be less than 1% and the current stability shall be such that the total relative flux variation is not greater than 0.2%.
6.6 Instrument Accuracy
The accuracy of the measuring instrument shall be as follows:
6.6.1 Flux Integrator
A flux integrator with an accuracy of ±0.3% or better shall be used. 6.6.2 Amperemeter
An amperemeter with an accuracy of ±0.2% or better shall be used. 7 DC measurement method for magnetic polarization intensity
7.1 Preparation for measurement
The Epstein ring and the measuring device should be connected as shown in Figure ?. Weigh the sample and place it in the Epstein ring as described in 4.1. The sample is then demagnetized by reducing the alternating magnetic field or by gradually reducing and reversing (the frequency of reversal is about twice per second) the DC current in the primary winding of the Epstein ring. The initial value of the magnetic field intensity generated by the demagnetization current should be higher than the magnetic field intensity used in the previous measurement. The cross-sectional area A of the sample should be calculated according to formula (3). Figure ? DC test circuit for measuring discontinuous values of magnetic polarization intensity 7.2 Determination of magnetic polarization intensity
Using the circuit shown in Figure 7, discontinuous magnetic polarization intensity values can be determined for corresponding magnetic field intensity values, or the basic magnetization curve can be obtained from a series of discontinuous values. On the other hand, the continuous recording method can be used to connect a calibrated four-terminal resistor in series with the magnetizing winding of the square ring, as shown in Figure 8, and the voltage terminal is connected to the X input terminal of an XY recorder, and the output terminal of the flux integrator is connected to the Y input terminal of the XY recorder. A plotter or computer interface can be used instead of the XY recorder. w.
Figure 8 DC test circuit of continuous recording method The magnetic field strength is measured by measuring the magnetizing current in the primary winding of the square ring, and then calculated according to formula (10): N,
Where: H-
Magnetic field strength, A/m;
XY recorder
（10）
-Magnetizing current, A;
GB/T3655-2000
Lm-Effective magnetic path length, m (Lm-0.94m); Ni-Total number of turns of the primary winding of the square ring. wwW.bzxz.Net
In order to obtain discontinuous magnetic polarization intensity values, first adjust the flux integrator to zero, and then increase the current flowing through the primary winding until the required magnetic field intensity value is reached.
The changes in magnetizing current and flux meter readings should be recorded. The magnetic polarization intensity value should be calculated according to the change in flux meter readings and the calibration constant of the flux integrator according to formula (11):
Where: J-
Measured magnetic polarization intensity change, T;
A-cross-sectional area of the sample, m\;
αi-reading of the flux integrator;
Kj-calibration constant of the flux integrator, VS; N,-total number of turns of the secondary of the Epstein square ring. 7.3 Determination of hysteresis loop
(11)
According to the wiring method in Figure 8, when the current in the magnetizing coil scans one cycle, a hysteresis loop can be obtained on the XY recorder. 7.4 Repeatability of magnetic polarization intensity measurement
The repeatability of the measurement results obtained by the method described in this chapter is 1.0% of the standard deviation. 8 Calibration of measuring device
In order to ensure the consistency of the measurement results of the magnetic parameters of electrical steel sheets (strips) in domestic and foreign comparisons, it is necessary to have a reliable measurement guarantee while implementing this standard.
8.1 The 25cm Epstein square circle used in the device is the main standard measuring tool of this device. It should be calibrated by the metrology department and can only be used in formal measurements with the calibration certificate issued by the department. 8.2 Other instruments, meters and measuring tools used in the device should also be calibrated regularly by the metrology department to confirm that they have the accuracy level specified in this standard.
8.3 The metrology department shall be responsible for issuing standard samples of several materials as working standards for the calibration device. 9 Test report
The test report shall include the following contents:
a) Model and mark of the sample;
b) Density of the material (customary or measured);
c) Length of the sample strip:
d) Number of strips;
e) Ambient temperature during measurement;
f) Measurement frequency;
g) Magnetic polarization intensity value or magnetic field intensity;
h) Measurement results.
GB/T3655—2000
Appendix A
(Difficult Appendix)
Method of cutting samples
The cutting of electrical steel sheets (strips) shall make the sample taken as representative of the steel sheets (strips) as possible. The recommended cutting and discarding positions are shown in Figures A1 and A2. Take any one of the two pairs of samples a and b in Figure A1, and cut off the discarded part of the sample. Figure A1.1 is applicable to products with specifications of 900mm×1800mm and 1000mm×2000mm, while Figure A1.2 is applicable to products of various specifications. When a pair of samples obtained according to Figure A1.2 weighs less than 1kg, a pair of samples can be formed by taking a, b, and c (i.e. taking two pieces and discarding one piece) or not discarding one piece. Figure A2 shows the cutting method of grain-oriented electrical steel sheets (strips). Al.1
Figure A1 Cutting method of hot-rolled and cold-rolled non-oriented electrical steel sheets 71
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.