A detection method based on direct current magnetization and residual magnetism measurement

Abstract

The application discloses a detection method based on direct current magnetization and residual magnetism measurement. The absolute difference value between the forward magnetization measurement result and the reverse magnetization measurement result is used to characterize the "hard magnetic" characteristics of inorganic nonmetallic materials. The fixed deviation caused by possible environmental magnetic noise or system zero drift can be effectively removed, the measurement accuracy is improved, and the magnetic hysteresis characteristics of the inorganic nonmetallic materials are more purely reflected.

Description

Technical Field

[0001] This invention relates to the field of magnetic evaluation of inorganic non-metallic materials (such as cement, ceramics, etc.), and specifically to a detection method based on DC magnetization and remanence measurement. Background Technology

[0002] In the field of materials science and engineering, accurately assessing the magnetic properties of inorganic non-metallic materials (such as cement, ceramics, glass, certain semiconductors, and magnetic oxides) is crucial, as it relates to their application potential in many high-tech fields. Remanence detection of inorganic non-metallic materials can quickly estimate their magnetic properties, and this detection can effectively guide the production and processing of these materials, thereby ensuring material quality. Currently, the mainstream methods for remanence detection of inorganic non-metallic materials in industrial production are the fluxmeter method and the Hall effect method. The fluxmeter method, based on Faraday's law of electromagnetic induction, involves placing a magnetized sample into a detection coil. Changes in magnetic flux induce a current in the coil, which the fluxmeter integrates over time. However, in practical applications, it cannot eliminate the theoretical error caused by the "demagnetizing field." Furthermore, if the measurement operation is not fast enough, drift can be added to the flux reading, leading to positive and negative errors. Differences in operator technique can also result in poor repeatability. The existing Hall effect method currently lacks standardized operation, and it is highly sensitive to magnetization saturation. Summary of the Invention

[0003] To address the shortcomings of the existing technologies, the purpose of this invention is to provide a detection method based on DC magnetization and remanence measurement. This detection method can be standardized, providing a key guarantee for obtaining meaningful and reproducible magnetic performance detection data.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a detection method based on DC magnetization and remanence measurement, characterized by being implemented through the following steps: Step 1: Sample preparation and loading The inorganic non-metallic material sample to be tested should be placed in a plastic container, ensuring that the filling is uniform and tight, and that the sample condition is consistent. Step 2: Apply a positive magnetic field A plastic container containing the sample is placed in the central region of a charging coil connected to a DC power supply. When the power is turned on, a positive DC magnetic field is generated inside the charging coil. Step 3: Environmental Transfer Immediately after magnetization, disconnect the DC power supply to the charging coil and quickly and smoothly transfer the plastic container containing the magnetized sample to the central area inside the magnetic shielding barrel. A magnetic sensor is pre-placed inside the magnetic shielding barrel to ensure that the distance between the plastic container containing the magnetized sample and the magnetic sensor probe is constant and ranges from 4 to 6 cm. The positive remanence is measured and recorded as a. Step 4: Apply a reverse magnetic field Place the sample back into the center area of ​​the charging coil, apply a magnetic field opposite to that in step 2, and then transfer it to the center area inside the magnetic shielding barrel. Ensure that the distance between the plastic container containing the magnetized sample and the magnetic sensor probe is constant and takes a value of 4-6 cm. Measure the reverse remanence and record it as b. Step 5: Result Calculation The absolute difference between the measurement results after the application of the positive and negative magnetic fields is calculated and denoted as |a - b|.

[0005] Preferably, after the material is filled in step 1, it is compacted using a standard vibratory compactor. The compaction is stopped when the material volume change is less than 0.2% after 50-80 consecutive compactions.

[0006] Preferably, the plastic containers used for filling in step 1 need to be demagnetized and cleaned beforehand.

[0007] Preferably, in steps 2 and 4, the charging coil needs to be calibrated periodically. Specifically, the charging coil is placed in the charging head, and a gaussmeter or teslameter is used in conjunction with a Hall probe to detect whether the peak magnetic field strength at the center point of the coil meets the standard.

[0008] Preferably, the magnetizing magnetic field strength and time in steps 2 and 4 are set to ensure that the magnetization inside the material reaches a saturated state.

[0009] Preferably, the transfer time in step 3 is 5-10 seconds.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. The method of the present invention is simple to operate, cost-controllable, and can effectively obtain the remanent magnetic characteristic value of inorganic non-metallic materials, and can be widely used in material research and development and quality control; 2. This invention uses the absolute difference between the forward magnetization measurement results and the reverse magnetization measurement results to characterize the "hard magnetic" properties of inorganic non-metallic materials. This can effectively eliminate the fixed deviations caused by possible environmental magnetic noise or system zero-point drift, improve the accuracy of the measurement, and more purely reflect the hysteresis properties of the inorganic non-metallic materials themselves. Detailed Implementation

[0011] The present invention will now be further described with reference to specific embodiments. Any parts not detailed below are based on existing techniques in the art.

[0012] Example 1 1. Magnetization stage: Exciting magnetism Sample preparation and loading: The inorganic non-metallic material sample to be tested (usually powder or small pieces) is carefully loaded into a standard-sized (e.g., 14cm × 9cm × 11cm) square plastic container. The choice of plastic material is crucial, as it has no significant magnetism, thus avoiding interference with test results. The loading should be as uniform and compact as possible to minimize gaps and ensure consistency in sample condition. For the same material, the greater the weight or the denser the loading, the greater the absolute value of the measured remanent magnetism. Therefore, standardized container size and loading condition (loading density) are fundamental to ensuring comparability of results. The chemical composition, crystal structure, grain size, and phase distribution of the material sample itself are the root causes determining its fundamental magnetic properties.

[0013] 2. Application of a positive magnetic field: Carefully place the plastic container containing the sample into the central region of a specially designed charging (magnetizing) coil connected to an existing precision DC power supply. By precisely adjusting the current and voltage of the power supply (usually monitored and calibrated in real time using a gaussmeter), a uniform DC magnetic field with controllable intensity and a clear direction (positive) is generated inside the charging coil (e.g., set to a target value of 8 mT). Under the influence of this magnetic field, the magnetic domains in the sample (if the material is magnetic) will align in a direction along the external field, and the material as a whole will be magnetized. 8 mT is a typical value for the magnetic field strength; the specific strength needs to be adjusted according to the expected performance of the material and the testing standards. The specific magnetization time and intensity must ultimately ensure that the magnetization inside the sample reaches saturation or a stable state (the relaxation process is essentially complete).

[0014] 3. Environmental transfer: Eliminating interference After the set magnetization time (e.g., 5 seconds) ends, immediately cut off the power to the charging coil, and the external magnetic field will disappear instantly; The plastic container containing the magnetized sample is quickly and smoothly transferred to the center of a magnetically shielded barrel. This magnetically shielded barrel is made of a high-permeability material (such as permalloy), and its core function is to shield stray magnetic field interference from the external environment to a great extent, providing a "pure" environment with near-zero magnetic field for subsequent high-precision remanence measurements.

[0015] 4. Remanence Measurement: Quantitative Performance Inside the magnetically shielded container, a highly sensitive magnetic sensor (such as a sensor based on the Hall effect, fluxgate, or SQUID technology) is pre-placed. The position of the magnetic sensor probe is at a strictly defined distance (e.g., set to 5 cm) relative to the surface of the plastic container holding the sample (such as the upper or lower surface, which needs to be consistent in repeatability tests). This distance must be precisely constant because the magnetic field strength decreases significantly with distance. In the quiet environment of a magnetically shielded container, a magnetic sensor precisely measures the residual magnetic field strength retained by the sample inside the container. This measurement (usually denoted as 'a', representing the remanence after positive magnetization) directly reflects the material's ability to maintain its magnetization state after the external field is removed, and is a key indicator for evaluating its magnetic properties (such as remanence Br).

[0016] 5. Reverse magnetization and perform residual magnetism measurement. To further accurately isolate potential background or systematic errors and better characterize the "hard magnetic" properties (coercivity-related) of the material, a reverse magnetization measurement is usually performed: the sample, along with the plastic container, is placed back into the central region of the charging coil, and a magnetic field in the opposite direction (with the same intensity and time, such as reverse magnetization of 8 mT for 5 seconds) is applied. The sample is then transferred to the magnetic shielding container again, and its remanence (denoted as b) is measured. The transfer speed is consistent with the previous forward magnetization measurement. Final Calculation: The net magnetic property characteristic value of the material is given by the absolute difference between the two measurements, |a - b|. This method effectively cancels out fixed deviations caused by environmental magnetic noise or system zero-point drift, and more purely reflects the hysteresis characteristics of the material itself.

[0017] If conditions permit, the detection method of this invention is recommended to be carried out under constant temperature conditions.

[0018] The following method, as described in Example 1, was used to perform residual magnetism testing on the following materials: iron powder, limestone, silica sand, fly ash, low-magnetic functional cement clinker, and low-magnetic functional cement. The specific results are shown in Table 1 below. .

Claims

1. A detection method based on direct current magnetization and remanence measurement, characterized in that, This can be achieved through the following steps: Step 1: Sample preparation and loading The inorganic non-metallic material sample to be tested should be placed in a plastic container, ensuring that the filling is uniform and tight, and that the sample condition is consistent. Step 2: Apply a positive magnetic field A plastic container containing the sample is placed in the central region of a charging coil connected to a DC power supply. When the power is turned on, a positive DC magnetic field is generated inside the charging coil. Step 3: Environmental Transfer Immediately after magnetization, disconnect the DC power supply to the charging coil and quickly and smoothly transfer the plastic container containing the magnetized sample to the center of the magnetic shielding barrel. A magnetic sensor is pre-placed inside the magnetic shielding barrel to ensure that the distance between the plastic container containing the magnetized sample and the magnetic sensor probe is constant. The positive remanence is measured and recorded as a. Step 4: Apply a reverse magnetic field The sample is placed back into the center area of ​​the charging coil, a magnetic field opposite to that in step 2 is applied, and then transferred to the center inside the magnetic shielding barrel. The distance between the plastic container containing the magnetized sample and the magnetic sensor probe is kept constant. The reverse remanence is measured and recorded as b. Step 5: Result Calculation The absolute difference between the measurement results after the application of the positive and negative magnetic fields is calculated and denoted as |a - b|.

2. The detection method based on DC magnetization and remanence measurement according to claim 1, characterized in that, After the material is loaded in step 1, it is compacted using a standard vibratory compactor. The process is stopped when the material volume change is less than 0.2% after 50-80 consecutive compactions.

3. The detection method based on DC magnetization and remanence measurements according to claim 2, characterized in that, The plastic containers used for filling in step 1 need to be demagnetized and cleaned beforehand.

4. The detection method based on DC magnetization and remanence measurement according to claim 1, 2, or 3, characterized in that, In steps 2 and 4, the charging coil needs to be calibrated periodically. The specific calibration method is to place the charging coil in the charging head and use a gaussmeter or teslameter in conjunction with a Hall probe to detect whether the peak magnetic field strength at the center point of the coil meets the standard.

5. The detection method based on DC magnetization and remanence measurement according to claim 4, characterized in that, In steps 2 and 4, the magnetization magnetic field strength and time are set to ensure that the material is magnetized to saturation.

6. The detection method based on DC magnetization and remanence measurement according to claim 1, characterized in that, The transfer time in step 3 is 5-10 seconds.