Hunan Forever Elegance Technology Co.,Ltd under the guidance of Professor Chen Duxing from the Autonomous University of Barcelona, ​​conducted open-circuit samples of soft magnetic materials for about two years. The research of magnetic property testing equipment has successfully verified the FE-2100SD soft magnetic DC solenoid cylinder sample demagnetization correction method, FE-2100SD3 soft magnetic material class B permeance method and FE-2100HC after the assessment of thousands of test data. Coercive force tester for soft magnetic materials, and applied for invention patents (application number: 201810169642.2) for the determination method of ferromagnetic cylindrical DC magnetic performance standard sample and the correction method of magnetometer. Hunan Forever Elegance Technology Co.,Ltd is currently the only manufacturer of DC magnetic performance equipment that unifies the three test methods.

In the process of completing this project, we found that the measurement of the coercive force Hc of the material in the measurement of soft magnetic open circuit samples is not so simple. Refer to GB/T 3656-83" Electrical pure ferromagnetic properties measurement method", GB/T 13888-92 "Method for measuring the coercivity of magnetic materials in open circuit samples" (basically refer to IEC 404-7) and GB/T 3656-2008 "Coercivity of soft magnetic materials" There is a big problem in the method of force displacement measurement, that is, the coercive force measurement of soft magnetic material open circuit samples using standard specifications may have a large negative deviation, and the deviation will decrease with the increase of the material’s aspect ratio. , As the coercivity of the material increases, the aspect ratio requirement decreases.

According to the latest GB/T 3656-2008 "Method for Measuring the Coercivity of Soft Magnetic Materials", the following two points are worthy of scrutiny:

1. Sample preparation: The sample should be a long strip with a length-to-width (or diameter) ratio less than 10mm. The recommended size of the thin-plate sample is: long (200±0.3) mm, width (20±0.2)mm, thickness 1mm~4mm, the recommended size of rod sample is: sample length 200±0.2mm, diameter 10±0.2mm (that is, aspect ratioγ=20), the sample is flat Straight, uniform cross-sectional area, no obvious holes, burrs, corrosion and other defects.

2, the result shows: the effective number of digits of the measurement result should be determined according to the evaluation result of uncertainty. If the measurement meets the requirements of this standard, the reproducibility of the measurement result of the coercivity Hc is expressed as a relative standard deviation of 3%.

We select two ferromagnetic cylindrical rods with relatively large differences in coercivity for correlation analysis.

Sample One, Q235 steel, diameter 10mm

Sample 2, Germany 4015IL (Cr steel), diameter 8mm

It can be found that the test of cylindrical rod-shaped ferromagnetic materials has exceeded the standard requirements. Refer to GB/T 13888-92 (or IEC 404-7) for a test accuracy of 5%, 4015IL materials will also exceed. In addition, the annex of GB/T 13888-92 mentions: “For samples with high coercivity, the length ratio is often less than 5:1. In this case, use several segments of the same material against the two ends of the sample during magnetization to lengthen the sample, which is conducive to the magnetization to saturation. ” Actually, this method should be considered for samples with lower coercivity.

Uses a standard B-type permeance meter to test the rod-shaped open circuit samples, the coercivity is a positive deviation, and the deviation is related to the pole shoe material. There will be a difference between the use of DT4 pure iron and 1J50 . By calibrating the permeance meter, the accurate measurement of open-circuit samples can be met. These three methods complement each other and can be mutually verified.

In recent years, there have been more and more requirements for device testing Hc, mainly involving enterprise users such as the relay industry, solenoid valves and fuel nozzles. The Coercimeter-03 of Italian LE company and the K-HC1000 of Japan's Riken are products recognized worldwide. The Cr3 of LE company refers to IEC 404-07 standard and adopts Hall sensor to test saturation magnetization, and then reverse demagnetization until the stray magnetic field drops to zero. Read the current at this time to calculate the coercivity; K-HC1000 of Riken, Japan The coercive force is calculated by applying different demagnetization magnetic fields to the saturated magnetized sample, and constantly throwing the test induction coil (or sample), and testing the corresponding current when the magnetic flux is zero to calculate the coercive force. Both methods It is feasible. Under the condition that the resolution of the Hall sensor is satisfied, the former has better test continuity and more accurate data. Therefore, our FE-2100HC also adopts this method to manufacture. The fluxmeter method is completed by FE-2100SD, that is, the simulated impact method is used to test the hysteresis loop of the open circuit sample, which is fully computer-controlled automatically to reduce man-made or mechanical operation errors. Domestic counterparts may not know much about the GB/T 13888-92 (or IEC404-07) standard, so they basically use the GB/T 3656 magnetic flux method for measurement. Therefore, it is necessary for us to compare these two methods (sample length is 100mm, diameter is 8mm):

After more than a year of research on three test methods, the phased conclusions are:

1. The FE-2100SD solenoid demagnetization correction method is adopted, which can meet the accurate measurement of ferromagnetic cylindrical long samples, and the coercive force Hc accuracy can be controlled in the range of -1.0% Inside, it can meet the precise measurement of magnetization curve and hysteresis loop, including maximum permeability um, remanence Br, and saturation magnetic induction Bs.

2, FE-2100SD3 is used to configure a Class B permeance meter, which can meet the measurement of open-circuit samples of ferromagnetic materials with a length greater than 100mm, a diameter less than 30mm, and a coercivity greater than 100A/m , The accuracy of coercive force Hc can be controlled within +3.0%, and at the same time, it can meet the precise measurement of hysteresis loop and including remanence Br and saturation magnetic induction Bs.

3. The use of FE-2100HC can meet the requirements of accurate measurement of ferromagnetic cylindrical long samples, and the accuracy of coercive force Hc can be controlled within -1.0%, because only testing Hc value, no demagnetization correction.

4. For the coercivity Hc measurement of special-shaped devices, basically the above three methods are difficult to achieve, unless the coercivity of the material has exceeded thousands of A/m, such as Cemented carbide materials, but this is precisely the equipment urgently needed by the majority of enterprises. How to solve it is the most critical issue.

Hunan Forever Elegance Technology Co.,Ltd has processed some non-standard permeance meters in communication with many users and continuous experiments. To test the coercivity of special-shaped devices, current users include: Suzhou Juchang Precision Hardware Machinery Co., Ltd., Xinhui ABB, Ningbo Wanbao Electric Co., Ltd., Ningbo Tianlong Co., Ltd., Schneider Electric (Shanghai) Co., Ltd., Shanghai University Materials College and Changzhou Zhongjing Electrical Appliance Factory. Won the praise of users, basically solved the user's acceptance inspection of processed devices, as well as the inspection of their own annealing process.

2019.1.9 (user test samples are summarized according to the requirements)

The test results of your company’s samples using FE-2100HC and FE-2100SD configuration solenoids are as follows:

Extended reading: