Hard alloy miniature product coercive force detection system and method

Abstract

The invention discloses a hard alloy miniature product coercive force detection system and method, and the system comprises a magnetizing and demagnetizing module which comprises a magnetizing coil and a demagnetizing coil, the magnetizing coil is arranged at the inner side of the demagnetizing coil, and the magnetizing coil and the demagnetizing coil are coaxially arranged; the positioning module comprises a sample vehicle, a sample placing groove, a conveying belt, a stepping motor, an infrared transmitting module and an infrared receiving module; the stepping motor is in transmission connection with the transmission belt, and the transmission belt penetrates through the two ends of a solenoid of the magnetizing coil / demagnetizing coil; the sample trolley is fixedly arranged on the conveying belt, the sample containing groove is fixedly formed in the sample trolley, and the sample containing groove coincides with the central axis of the magnetizing coil and the central axis of the demagnetizing coil. The infrared transmitting module and the infrared receiving module are symmetrically arranged on the two sides of the conveying belt and located on the outer side of the demagnetizing coil, and through cooperation of the infrared transmitting module, the infrared receiving module and the sample vehicle, whether the sample to be detected in the sample containing groove moves to a preset detection position or not is detected; the residual magnetism detection sensor is mounted in a solenoid of the magnetizing coil / demagnetizing coil, is close to the sample to be detected and is used for detecting the magnetic induction intensity of the sample to be detected on a horizontal component; the temperature control module comprises a temperature sensor and a cooling module which are arranged around the demagnetizing coil; the temperature sensor detects the temperature of the demagnetizing coil in real time.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide magnetic property parameter testing, specifically relating to a coercive magnetic force testing system and method for cemented carbide micro products. Background Technology

[0002] Cemented carbide, a material with high hardness, high wear resistance, and good toughness, has wide and important applications in many fields such as machining, mining, and the electronics industry. Coercivity, as a key magnetic property parameter of cemented carbide, directly reflects the uniformity of its internal microstructure and composition, playing a crucial role in the quality control and performance evaluation of cemented carbide products. Therefore, accurate, stable, and reliable detection of the coercivity of cemented carbide is of significant practical importance.

[0003] However, traditional coercive magnetic testing techniques for cemented carbide products face numerous challenges in their application to micro-products. On one hand, due to the tiny size of micro-cemented carbide samples, the magnetic signals they generate are extremely weak. Traditional testing methods struggle to effectively capture these weak signals, resulting in low signal intensity, inaccurate values, and an inability to provide a reliable basis for product quality assessment.

[0004] On the other hand, the testing process is highly susceptible to interference from external factors. Temperature fluctuations can significantly affect the performance of magnetic materials, thereby interfering with the coercivity test results. Traditional testing systems lack effective temperature control methods, making it difficult to ensure the temperature stability of the testing environment. Furthermore, traditional methods have low precision in sample positioning, making it difficult to ensure that the sample accurately reaches the designated testing location. This not only reduces the accuracy of the test but also results in poor repeatability of the test results, potentially leading to significant differences in test data obtained from different batches or by different operators.

[0005] Furthermore, during demagnetization, external disturbances such as noise and temperature can severely affect the determination of the zero-crossing point of remanence. Traditional detection methods lack effective anti-interference measures and cannot accurately determine the zero-crossing point of remanence in complex environments, resulting in large calculation errors of coercive force, which is difficult to meet the high-precision requirements of modern industrial production for the quality inspection of cemented carbide products.

[0006] In summary, traditional cemented carbide testing technologies suffer from problems such as inaccurate signal detection, susceptibility to external interference, and poor detection accuracy and repeatability in the coercive magnetic force testing of micro-products. There is an urgent need for a new testing system and method to solve these problems. Summary of the Invention

[0007] The purpose of this invention is to provide a coercive magnetic force detection system and method for cemented carbide micro products, which solves the problems of "weak magnetic signals of micro products are difficult to capture, detection is easily affected by external interference such as temperature, inaccurate sample positioning, and easy error in judging the zero-crossing point of residual magnetism during demagnetization" in the coercive magnetic force detection process of cemented carbide micro products, so as to improve the accuracy, stability and reliability of coercive magnetic force detection of cemented carbide micro products.

[0008] To achieve the above objectives, the present invention employs the following technical solution: a coercive magnetic force detection system for cemented carbide micro-products, comprising:

[0009] A magnetization / demagnetization module includes a magnetization coil and a demagnetization coil, wherein the magnetization coil is located inside the demagnetization coil and the magnetization coil and the demagnetization coil are coaxially arranged.

[0010] The positioning module includes a sample carriage, a sample placement slot, a conveyor belt, a stepper motor, an infrared emitting module, and an infrared receiving module. The stepper motor is connected to the conveyor belt, which passes through both ends of the solenoid of the magnetizing / demagnetizing coil. The sample carriage is fixed on the conveyor belt, and the sample placement slot is fixed on the sample carriage, with the central axis of the sample placement slot coinciding with that of the magnetizing and demagnetizing coils. The infrared emitting module and the infrared receiving module are symmetrically arranged on both sides of the conveyor belt and located outside the demagnetizing coil. Through the cooperation of the infrared emitting module, the infrared receiving module, and the sample carriage, the module detects whether the sample to be tested in the sample placement slot has moved to the predetermined detection position.

[0011] The residual magnetism detection sensor is installed inside the solenoid of the magnetizing / demagnetizing coil and close to the sample to be tested, and is used to detect the magnetic induction intensity on the horizontal component of the sample to be tested.

[0012] The temperature control module includes a temperature sensor and a cooling module disposed around the demagnetizing coil; the temperature sensor detects the temperature of the demagnetizing coil in real time.

[0013] Preferably, the cooling module includes a semiconductor refrigeration block, a cooling fan, and a cooling fan. The cooling fan is disposed on the surface of the semiconductor refrigeration block, and the semiconductor refrigeration block is used to provide a cold source for the cooling fan. The cooling fan is installed on the housing of the detection system and is used to dissipate heat from the detection system.

[0014] More preferably, the number of air conditioning fans is two.

[0015] Preferably, the circuit of the magnetizing coil includes a transformer TR1, a diode D1, a resistor R1, a storage capacitor C1, a relay RL1, a reverse working diode D2, and a magnetizing coil.

[0016] The 220V AC mains power is stepped up by transformer TR1, rectified by diode D1, and current-limited by resistor R1 before charging the storage capacitor C1. Relay RL1 is driven by a control signal, and its contacts control the switching of the magnetizing coil and the branch of the reverse working diode D2, thereby discharging the magnetizing coil.

[0017] Preferably, the circuit of the demagnetizing coil includes a digital-to-analog converter (DAC), an operational amplifier (U1), a reverse diode (D3), a sampling resistor (R2), a high-power Darlington transistor (Q1), and a demagnetizing coil.

[0018] The digital-to-analog converter (DAC) receives digital signals and outputs a voltage signal Vctl to the non-inverting input of operational amplifier U1. Operational amplifier U1 uses negative feedback to make the voltage across sampling resistor R2 equal to Vctl, thereby controlling the current flowing through sampling resistor R2 and the demagnetizing coil. High-power Darlington transistor Q1 amplifies the current and drives the demagnetizing coil. Reverse diode D3 provides a freewheeling circuit for the demagnetizing coil to protect the circuit.

[0019] This invention also provides a method for detecting the coercivity of cemented carbide micro-products, comprising the following steps:

[0020] Step 1: After the detection system is working normally, the temperature sensor monitors the temperature around the demagnetizing coil in real time. If the temperature is higher than the set threshold, the cooling module starts working; if the temperature is lower than the set threshold, the cooling module stops working.

[0021] Step 2: Start the system for automatic zeroing. At this time, no sample is placed in the sample placement slot. Apply a stable current Is0 to the demagnetizing coil. The residual magnetism detection sensor detects the magnetic induction intensity Bs0 on the horizontal component and records the voltage value corresponding to the magnetic induction intensity Bs0 at this time. Complete the zeroing process;

[0022] Step 3: After zeroing is completed, the stepper motor drives the conveyor belt to move the sample carriage out to the outside of the demagnetizing coil. The infrared light emitted by the infrared emitting module is blocked by the sample carriage, and the infrared receiving module cannot receive the infrared light. The infrared receiving module outputs a low-level signal. Then, the hard alloy miniature product to be tested is placed in the sample placement slot. The stepper motor drives the conveyor belt to move the sample carriage towards the inside of the magnetizing coil. During the movement, the end of the sample carriage moves forward continuously until the end of the sample carriage can no longer block the infrared light emitted by the infrared emitting module. At this time, the infrared receiving module will receive the infrared light again and output a high-level signal. At this time, the stepper motor performs a braking operation to achieve precise stopping and positioning of the sample placement slot.

[0023] Step 4: After the cemented carbide miniature product in the sample placement slot reaches the magnetizing coil and is accurately positioned, discharge the magnetizing coil to complete the magnetizing operation of the cemented carbide miniature product.

[0024] Step 5: After magnetization is completed, the demagnetizing coil performs demagnetization. The magnetic induction intensity on the horizontal component is detected by the residual magnetism detection sensor. The surface residual magnetism of the cemented carbide sample is calculated by combining the magnetic induction intensity Bs0 and the current Is0 when zeroing. If the surface residual magnetism is greater than zero, the demagnetizing current is increased until the residual magnetism intensity on the cemented carbide surface is detected to be zero. The magnitude of the applied demagnetizing current Is is recorded, and the coercivity value of the cemented carbide is calculated by the cemented carbide coercivity test value conversion algorithm.

[0025] Furthermore, the magnetization operation in step four is specifically as follows:

[0026] 4.1) The transformer steps up the 220V AC power to Vh. The AC power Vh charges the storage capacitor C1 through the normally closed contact of the single conducting diode D1 and the relay RL1. The maximum charging voltage is Vmax = 1.414 * Vh.

[0027] 4.2) Under normal circumstances, the circuit operates in the state of charging the storage capacitor C1; when the magnetizing coil needs to be discharged, a low level 0 is input to the CTR1 pin of the relay RL1 to make the relay RL1 conduct. At this time, the contacts of the relay close, disconnecting the capacitor charging circuit on the left and conducting the discharge magnetizing circuit on the right to discharge to the magnetizing coil.

[0028] 4.3) After the discharge is completed, a high level 1 is input to the CTR1 pin of relay RL1 to make relay RL1 non-conducting, the relay contacts are released, the circuit charges the storage capacitor C1, and waits for the next discharge operation.

[0029] Furthermore, the demagnetization operation in step five is specifically as follows:

[0030] The digital-to-analog converter (DAC) receives digital signals and converts them into a voltage signal Vctl, which is then input to pin 3 of operational amplifier U1. Based on the virtual short and virtual open principles of op-amp negative feedback, the voltage across resistor R2 is equal to the voltage Vctl, and the current flowing through R2 is the same as the current flowing through the demagnetizing coil. Specifically:

[0031]

[0032] The magnitude of the demagnetizing current on the demagnetizing coil can be controlled by controlling the output voltage of the digital-to-analog converter (DAC).

[0033] Furthermore, in step five, the surface remanence calculation process for the cemented carbide sample is as follows:

[0034] (1) During the demagnetization process, the digital quantity is output to the input terminal of the digital-to-analog converter (DAC) starting from 0 and increasing in increments of 1. The output voltage Vctl of the DAC is as follows:

[0035]

[0036] in, Indicates digital input. A bit representing a digital-to-analog converter (DAC). Represents the magnitude of the reference voltage;

[0037] (2) Each increase of 1 unit in the digital quantity results in... ,at this time The resulting change is:

[0038] The change in the magnitude of the demagnetizing current on the demagnetizing coil is:

[0039]

[0040] The magnitude of the demagnetizing current on the demagnetizing coil is:

[0041]

[0042] The magnetic flux density on the horizontal component is detected by a remanence detection sensor, and the surface remanence of the cemented carbide sample is calculated by combining the magnetic flux density Bs0 and the current Is0 when it is zeroed.

[0043] (3) Remanence on the surface of cemented carbide The calculation method is as follows:

[0044] s0

[0045] in, It is the magnetic flux density on the current horizontal component detected by the residual magnetism detection sensor;

[0046] (4) When detected When the value is zero, no new digital input is added to the digital-to-analog converter (DAC). The final digital input is... The magnitude of the current at this time is:

[0047] .

[0049] Furthermore, in step five, it is determined that the remanence of the cemented carbide surface is zero, specifically as follows:

[0050] 1) During the coercive charging and demagnetizing process of cemented carbide, the working current is generally large, and there is a large amount of heat generation in the charging coil and demagnetizing coil. The current in the demagnetizing coil is subject to certain interference and fluctuations. Therefore, the magnitude of the magnetic induction intensity detected by the residual magnetism detection sensor will be disturbed by external factors such as noise and temperature. Especially when the residual magnetism on the surface of cemented carbide is close to zero, the influence of interference will directly affect when to stop adding new digital quantity to the digital-to-analog converter DAC, i.e., the zero-crossing detection of the residual magnetism of cemented carbide.

[0051] 2) A digital filtering method is used to accurately detect the zero-crossing of residual magnetism. A digital-to-analog converter (DAC) is used to sample frequencies of... The analog voltage signal of the remanence of the cemented carbide miniature product within the acquisition time T. ( ),total The value of each point;

[0052] Combined with the voltage value corresponding to the magnetic induction intensity when zeroing The voltage corresponding to the surface remanence of the cemented carbide sample is calculated using the current Is0. :

[0053] ( )

[0054] Due to the current magnitude of the residual magnetic field on the surface of the cemented carbide Therefore, surface remanence zero-crossing detection is equivalent to directly detecting... Zero-crossing determination of voltage;

[0055] 3) To A second-order Butterworth low-pass digital filter is applied to the remanent magnetization values ​​of a cemented carbide surface.

[0056]

[0057] in This represents the voltage signal at the nth point after filtering, with coefficients... From the cutoff frequency and sampling frequency Decide;

[0058] 4) Traversal Find adjacent points of sign change:

[0059] ;

[0060] 5) Set minimum amplitude threshold Only when Only then is it considered a valid zero crossing.

[0061] Furthermore, in step five, the algorithm for converting the coercivity test value of cemented carbide is as follows:

[0062] (1) According to Ampere's circuital law, when the coil is long enough, the average magnetic field strength H generated at the center of the solenoid is:

[0063]

[0064] in Indicates the number of layers in the solenoid winding. The diameter of the wound copper wire is given. Therefore, the coercivity of the cemented carbide coil is positively correlated with the number of turns of the demagnetizing coil and the diameter of the wound copper wire, with a correlation coefficient of . ;

[0065] (2) By giving a known coercivity as The hard alloy sample was magnetized and demagnetized. During the demagnetization process, when the residual magnetic induction intensity on its surface was detected to be zero, the magnitude of the applied current was... The correlation coefficient at this time is for:

[0066]

[0067] (3) Calibrate the correlation coefficient Afterwards, the cemented carbide sample is tested. If, during the demagnetization process, the final demagnetization current is... Then its corresponding coercivity value should be:

[0068] .

[0069] This invention introduces a cooling module that intelligently adjusts the semiconductor cooling block and fan based on real-time temperature, creating a stable and reliable testing environment and effectively avoiding interference from temperature fluctuations on the test data. The system's automatic zeroing function precisely eliminates inherent magnetic interference, using the magnetic induction intensity without a sample as a benchmark to ensure consistent starting conditions for each test. Precise sample positioning during testing is achieved through a stepper motor, conveyor belt, infrared emitting module, and infrared receiving module, ensuring the sample accurately reaches the designated testing position and improving accuracy and repeatability. The magnetization module magnetizes the sample, and the demagnetization module demagnetizes it. A residual magnetism detection sensor detects the magnetic induction intensity on the horizontal component of the sample, calculates the residual magnetism on the hard alloy surface, and continuously increases the demagnetizing current until the residual magnetism on the sample surface reaches zero. The demagnetizing current is recorded, and the coercivity value is calculated.

[0070] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0071] This invention achieves multi-dimensional breakthroughs and optimizations in the detection of coercive magnetic force in cemented carbide micro-products. By installing a remanent magnetization detection sensor inside a solenoid and bringing it infinitely close to the sample, it successfully overcomes the problem of weak magnetic signals and low signal-to-noise ratio in micro-products. It can accurately capture previously imperceptible weak magnetic signals, laying a solid foundation for the accuracy of detection results.

[0072] The digital filtering method used in the demagnetization process of this invention effectively overcomes the disturbances of external factors such as noise and temperature by filtering and normalizing the collected data, and can accurately determine the zero-crossing point of residual magnetism.

[0073] This invention solves the problems of traditional methods being unable to effectively detect cemented carbide micro-products, such as low signal, inaccurate values, susceptibility to external interference, and poor detection accuracy and repeatability. It effectively improves the accuracy, stability, and reliability of coercivity detection for cemented carbide micro-products. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the structure of the present invention;

[0075] Figure 2 This is a circuit diagram of the magnetization module according to an embodiment of the present invention;

[0076] Figure 3 This is a circuit diagram of the demagnetizing module according to an embodiment of the present invention;

[0077] Figure 4 This is a schematic diagram of the residual magnetic signal on the sample surface during the demagnetization process according to an embodiment of the present invention.

[0078] In the diagram: 1. Computer host; 2. Monitor; 3. Visual detection software; 4. Control module; 5. Data acquisition module; 6. Residual magnetism detection sensor motherboard; 7. Residual magnetism detection sensor; 8. Power supply module; 9. Magnetizing module; 10. Demagnetizing module; 11. Magnetizing coil; 12. Demagnetizing coil; 13-1. First cable connector; 13-2. Second cable connector; 14. Sample carriage; 15. Sample placement slot; 16. Conveyor belt; 17. Stepper motor; 18. Infrared emitting module; 19. Infrared receiving module; 20. Motor controller; 21. Semiconductor cooling block; 22. Cooling fan; 23-1. First cooling fan; 23-2. Second cooling fan; 24. Temperature sensor. Detailed Implementation

[0079] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0080] Example 1

[0081] like Figure 1As shown, a coercive magnetic force testing system for cemented carbide miniature products includes a computer module, a data acquisition and control module, a charging and demagnetizing module, a cable connection module, a sample carriage precision positioning module, and a temperature control module.

[0082] The computer module includes: computer host 1, monitor 2, and visual detection software 3;

[0083] The data acquisition and control module includes: control module 4, data acquisition module 5, residual magnetism detection sensor motherboard 6, residual magnetism detection sensor 7, and power module 8; control module 4 is connected to data acquisition module 5, residual magnetism detection sensor motherboard 6 is connected to residual magnetism detection sensor 7, and power module 8 provides power to the entire detection system; residual magnetism detection sensor 7 is installed inside the solenoid of magnetizing / demagnetizing coil and close to the sample to be tested, and is used to detect the magnetic induction intensity on the horizontal component of the sample to be tested;

[0084] The magnetization and demagnetization module includes: a magnetization module 9, a demagnetization module 10, a magnetization coil 11, and a demagnetization coil 12. The magnetization module 9 is connected to the magnetization coil 11, and the demagnetization module 10 is connected to the demagnetization coil 12. The magnetization coil 11 is located inside the demagnetization coil 12, and the magnetization coil 11 and the demagnetization coil 12 are coaxially arranged.

[0085] The cable connection module includes: a first cable connector 13-1 and a second cable connector 13-2;

[0086] The sample carriage precision positioning module includes: a sample carriage 14, a sample placement slot 15, a conveyor belt 16, a stepper motor 17, an infrared emitting module 18, an infrared receiving module 19, and a motor controller 20; the stepper motor 17 is connected to the conveyor belt 16, which passes through both ends of the solenoid of the magnetizing / demagnetizing coil; the sample carriage 14 is fixed on the conveyor belt 16, the sample placement slot 15 is fixed on the sample carriage 14, and the sample placement slot 15 coincides with the central axis of the magnetizing coil 11 and the demagnetizing coil 12; the infrared emitting module 18 and the infrared receiving module 19 are symmetrically arranged on both sides of the conveyor belt 16 and are located outside the demagnetizing coil 12. Through the cooperation of the infrared emitting module 18, the infrared receiving module 19, and the sample carriage 14, the module detects whether the sample to be tested in the sample placement slot 15 has moved to the predetermined detection position.

[0087] The temperature control module includes: a semiconductor cooling block 21, a cooling fan 22, a first cooling fan 23-1, a second cooling fan 23-2, and a temperature sensor 24 disposed around the demagnetizing coil 12; the cooling fan is disposed on the surface of the semiconductor cooling block 21, and the semiconductor cooling block 21 is used to provide a cold source for the cooling fan; the cooling fan 22 is mounted on the housing of the detection system and is used to dissipate heat from the detection system.

[0088] In one specific embodiment, the magnetization module 9 includes a transformer TR1, a diode D1, a resistor R1, a storage capacitor C1, a relay RL1, a reverse-working diode D2, and a magnetization coil 11, such as... Figure 2 As shown;

[0089] The 220V AC mains power is boosted by transformer TR1, rectified by diode D1, and current-limited by resistor R1 before charging the storage capacitor C1. Relay RL1 is driven by a control signal, and its contacts control the switching of the magnetizing coil 11 and the branch of the reverse working diode D2, thereby discharging the magnetizing coil 11.

[0090] In one specific embodiment, the demagnetizing module 10 includes a digital-to-analog converter (DAC), an operational amplifier U1, a reverse diode D3, a sampling resistor R2, a high-power Darlington transistor Q1, and a demagnetizing coil 12, such as Figure 3 As shown;

[0091] The digital-to-analog converter (DAC) receives digital signals and outputs a voltage signal Vctl to the non-inverting input of operational amplifier U1. Operational amplifier U1 uses negative feedback to make the voltage across sampling resistor R2 equal to Vctl, thereby controlling the current flowing through sampling resistor R2 and demagnetizing coil 12. High-power Darlington transistor Q1 amplifies the current and drives demagnetizing coil 12. Reverse diode D3 provides a freewheeling circuit for demagnetizing coil 12 to protect the circuit.

[0092] Example 2

[0093] A method for detecting the coercivity of cemented carbide micro-products includes the following steps:

[0094] Step 1: Connect the first cable connector 13-1 and the second cable connector 13-2 using cables to supply power from the system power module 8 to the motor controller 20, the sample carriage precision positioning module, and the temperature control module. Connect the magnetization module 9 and the demagnetization module 10 to the magnetization coil 11 and the demagnetization coil 12 respectively, and connect the residual magnetism detection sensor 7 to the residual magnetism detection sensor motherboard 6. Because the interference of metallic magnetic materials on the hard alloy sample should be minimized during the magnetic detection process, the magnetization coil 11 and the demagnetization coil 12 are assembled separately from parts 1-10 and kept at a certain distance. After the system power module 8 starts working normally, the temperature control module starts, and the temperature sensor 24 detects the temperature around the demagnetization coil 12 in real time. If it is higher than the set threshold, the semiconductor cooling block 21 is powered on to make it work, and the cooling fan 22 starts synchronously. The first cooling fan 23-1 and the second cooling fan 23-2 start working. If the temperature is lower than the set threshold, the semiconductor cooling block 21 and the fans will stop working. The comparison of test data with and without the cooling system is shown in Table 1.

[0095] Step 2: Click the zeroing button in the visualization detection software 3 to start the system's automatic zeroing. At this time, do not place any sample in the sample placement slot 14. After receiving the instruction, the control module 4 controls the magnetization module 9 to apply a stable current Is0=5A to the demagnetizing coil 12. The residual magnetism detection sensor 7 detects the magnetic induction intensity Bs0 on the horizontal component and records the voltage value corresponding to the magnetic induction intensity Bs0 at this time. At this point, the zeroing record work is completed;

[0096] Step 3: After zeroing is completed, the motor controller 20 will control the stepper motor 17 to rotate the conveyor belt 16, moving the sample carriage 14 out of the demagnetizing coil 12. At this time, the infrared light emitted by the infrared emitting module 18 is blocked by the sample carriage 14, and the infrared receiving module 19 cannot receive the infrared light. The infrared receiving module 19 outputs a low-level signal. Then, the hard alloy micro product to be tested is placed in the sample placement slot 15. After clicking the test button on the visualization detection software 3, the motor controller 20 will control the stepper motor 17 to rotate the conveyor belt 16, driving the sample carriage 14 towards the magnetizing coil 11. During the movement, the end of the sample carriage 14 moves forward continuously until the end of the sample carriage can no longer block the infrared light emitted by the infrared emitting module 17. At this time, the infrared receiving module 18 will receive the infrared light again and output a high-level signal. At this time, the motor controller 19 immediately controls the stepper motor to perform a braking operation, realizing the precise stopping and positioning of the sample carriage. The comparison of test data between manually positioned and automatically positioned sample carriages is shown in Table 2.

[0097] Step 4: After the sample carriage 14 arrives at the magnetizing coil 11 and is precisely positioned with the sensor, the control module 4 controls the magnetizing module to discharge the magnetizing coil, thus completing the magnetizing operation of the cemented carbide sample.

[0098] Step 5: After the magnetization module 9 completes its operation, the control module 4 controls the demagnetization module to perform the demagnetization operation. At the same time, the residual magnetism detection sensor motherboard 6 detects the magnetic induction intensity on the horizontal component through the residual magnetism detection sensor 7, and calculates the surface residual magnetism of the cemented carbide sample by combining the magnetic induction intensity Bs0 and the current Is0 when zeroing. If the surface residual magnetism is greater than zero, the demagnetization module is controlled to continuously increase the demagnetization current until the residual magnetism intensity on the surface of the cemented carbide is detected to be zero. At this time, the magnitude of the applied demagnetization current Is is recorded, and the coercivity value of the cemented carbide is calculated by the cemented carbide coercivity test value conversion algorithm, and the result is displayed on the display 2.

[0099] In step four, the magnetization operation is specifically as follows:

[0100] (1) The magnetization circuit includes: transformer TR1, diode D1, current limiting resistor R1=1 ohm, energy storage capacitor C1=10000uF, relay RL1, reverse working diode D2 and magnetization coil 11. The magnetization coil 11 is designed with 3 layers, internal resistance of 1 ohm and wire diameter of 0.002m.

[0101] (2) The transformer steps up the 220V AC power to Vh=260V. This AC power Vh charges the storage capacitor C1 through the normally closed contact of the single conducting diode D1 and the relay RL1. The maximum charging voltage is Vmax=1.414×260V≈368V.

[0102] (3) Under normal circumstances, the circuit is in the state of charging the storage capacitor C1. When the magnetizing coil 11 is to be discharged, the control module 4 inputs a low level 0 to the CTR1 pin of the relay RL1, so that the relay RL1 is turned on. At this time, the contacts of the relay are closed, the capacitor charging circuit on the left is disconnected, and the discharge magnetizing circuit on the right is turned on to discharge the magnetizing coil 11.

[0103] The maximum discharge current is 368 volts / 1 ohm = 368 A, and the average charging magnetic field strength is approximately: ;

[0104] (4) After the discharge is completed, the control module 4 inputs a high level 1 to the CTR1 pin of the relay RL1, so that the relay RL1 is in a non-conducting state, the relay contacts are released, the circuit charges the storage capacitor C1, and waits for the next discharge operation.

[0105] Step five, the demagnetization operation, specifically involves:

[0106] (1) The demagnetizing circuit includes: digital-to-analog converter DAC, operational amplifier U1, reverse diode D3, sampling resistor R2, high-power Darlington transistor Q1 and demagnetizing coil 12;

[0107] (2) The control module 4 inputs a digital signal to the DAC digital-to-analog converter. The DAC converts the digital signal into a voltage signal Vctl and inputs it to pin 3 of the operational amplifier U1. According to the virtual short and virtual open principle of the operational amplifier negative feedback, the voltage across resistor R2 is equal to the voltage Vctl. At this time, the current flowing through the sampling resistor R2 (R2=0.2 ohms) is the same as the current flowing through the demagnetizing coil 12, which is:

[0108]

[0109] Therefore, by controlling the output voltage of the DA converter, the control module 4 can directly control the demagnetizing current on the demagnetizing coil 12.

[0110] In step five, the method for detecting residual magnetism on the surface of the cemented carbide sample during demagnetization is as follows:

[0111] (1) During the demagnetization process, the control module 4 outputs a digital quantity to the input terminal of the DAC digital-to-analog converter starting from 0, and increments by 1. The output voltage Vctl of the DAC digital-to-analog converter is as follows:

[0112]

[0113] in, This indicates the digital input of control module 4. This indicates that the DAC (Digital-to-Analog Converter) has 12-bit precision. Represents the magnitude of the reference voltage;

[0114] (2) Each increase of 1 unit in the digital quantity results in... ,at this time The resulting change is:

[0115] The change in the magnitude of the demagnetizing current on the demagnetizing coil 12 is:

[0116]

[0117] The magnitude of the demagnetizing current on magnetic coil 12 is:

[0118]

[0119] At this time, the magnetic induction intensity on the horizontal component is detected by the remanence detection sensor 7, and the surface remanence of the cemented carbide sample is calculated by combining the magnetic induction intensity Bs0 and the current Is0 when it is zeroed.

[0120] (3) The calculation method for the remanence of cemented carbide surface is as follows:

[0121] s0

[0122] in, It is the magnetic flux density on the current horizontal component detected by the residual magnetism detection sensor 7;

[0123] (4) When detected When the value is zero, control module 4 stops adding new digital input to the DAC digital-to-analog converter, and the final digital input is... The magnitude of the current at this time is:

[0124]

[0125] (5) During the coercive charging and demagnetizing process of cemented carbide, the working current is generally large. The demagnetizing module 10 and the charging coil 11 and demagnetizing coil 12 have a large heat generation phenomenon. The current on the demagnetizing coil has certain interference and fluctuation. Therefore, the magnitude of the magnetic induction intensity detected by the residual magnetism detection sensor 7 will be disturbed by external factors such as noise and temperature. Especially when the residual magnetism on the surface of cemented carbide is close to zero, the influence of interference will directly affect the accurate time when the control module 4 stops adding digital quantity to the DAC digital-to-analog converter, that is, the zero-crossing detection of the residual magnetism of cemented carbide.

[0126] (6) A digital filtering method is used to accurately detect the zero-crossing of residual magnetism. First, the digital-to-analog converter (DAC) in the data acquisition module 5 is used to acquire data at a frequency of [frequency value missing]. The analog voltage signal corresponding to the remanence of the cemented carbide sample within time T on the sensor motherboard 6 is acquired. ( ),total The values ​​at each point, combined with the voltage value corresponding to the magnetic induction intensity at zero adjustment. The voltage value corresponding to the surface remanence of the cemented carbide sample is calculated using the current Is0:

[0127]

[0128] ( )

[0129] Due to the current magnitude of the residual magnetic field on the surface of the cemented carbide Therefore, surface remanence zero-crossing detection is equivalent to directly detecting... Zero-crossing determination of voltage;

[0130] (7) A second-order Butterworth low-pass digital filter is applied to the remanent magnetization values ​​of a cemented carbide surface.

[0131]

[0132] in This represents the voltage signal at the nth point after filtering, with coefficients... From the cutoff frequency and sampling rate It was decided that the design would be carried out using the bilinear transformation method, resulting in b0 = 0.000944, b1 = 0.001888, b2 = 0.000944, a1 = -1.911197, and a2 = 0.915025.

[0133] The original and filtered remanent magnetization signals of the sample surface during the demagnetization process are as follows: Figure 4As shown in Table 3, the test results of samples with and without the filtering module are as follows: the repeatability of the test results of the samples with the filtering module is better than that of the samples without the filtering module.

[0134] (8) Traversal Find adjacent points of sign change:

[0135]

[0136] (9) Set minimum amplitude threshold Only when Only then is it considered a valid zero crossing.

[0137] The algorithm for converting the coercivity test value of cemented carbide is as follows:

[0138] (1) According to Ampere's circuital law, when the coil is long enough, the average magnetic field strength H generated at the center of the solenoid is:

[0139]

[0140] in Indicates the number of layers in the solenoid winding. The diameter of the wound copper wire is given. Therefore, the coercivity of the cemented carbide coil is positively correlated with the number of turns of the demagnetizing coil and the diameter of the wound copper wire, with a correlation coefficient of . ;

[0141] (2) By giving a known coercivity as The hard alloy sample was magnetized and demagnetized. During the demagnetization process, when the residual magnetic induction intensity on its surface was detected to be zero, the magnitude of the applied current was... The correlation coefficient at this time is for:

[0142]

[0143] (3) Calibrate the correlation coefficient Afterwards, the cemented carbide sample is tested. If, during the demagnetization process, the final demagnetization current is... Then its corresponding coercivity value should be:

[0144]

[0145] Table 1 Comparison of test data with and without cooling system on.

[0146] Standard value of coercivity of standard sample (KA / m) Test after power-on (KA / m) Test again after 30 minutes of continuous operation without cooling (KA / m). Tested after 30 minutes of continuous operation with the cooling system on (KA / m). 5.2 5.26 5.35 5.30 12.5 12.46 12.58 12.51 22.0 22.05 22.21 22.12 36.0 36.15 36.40 36.23

[0147] Table 2 Comparison of test data between manually positioned and automatically positioned sample carriages

[0148] Coercivity of standard sample (KA / m) Manual positioning 1 (KA / m) Manual positioning 2 (KA / m) Automatic positioning 1 (KA / m) Automatic positioning 2 (KA / m) 5.2 5.3 5.18 5.26 5.23 12.5 12.42 12.58 12.46 12.48 22.0 21.90 22.16 22.05 22.10 36.0 36.30 35.80 36.15 36.18

[0149] Table 3 Comparison of test data for normal zero-crossing detection with and without filtering of residual magnetism.

[0150] Coercivity of standard sample (KA / m) Unfiltered test 1 (KA / m) Unfiltered test 2 (KA / m) Filtering test 1 (KA / m) Filtering test 2 (KA / m) 5.2 5.35 5.3 5.26 5.23 12.5 12.72 12.68 12.46 12.48 22.0 21.8 22.15 22.05 22.10 36.0 36.35 36.4 36.15 36.18

[0151] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A coercive magnetic force detection system for cemented carbide miniature products, characterized in that, include: The magnetization and demagnetization module includes a magnetization coil (11) and a demagnetization coil (12), wherein the magnetization coil (11) is located inside the demagnetization coil (12), and the magnetization coil (11) and the demagnetization coil (12) are coaxially arranged. The positioning module includes a sample carriage (14), a sample placement slot (15), a conveyor belt (16), a stepper motor (17), an infrared emitting module (18), and an infrared receiving module (19). The stepper motor (17) is connected to the conveyor belt (16) for transmission, and the conveyor belt (16) passes through both ends of the solenoid of the magnetizing coil / demagnetizing coil. The sample carriage (14) is fixed on the conveyor belt (16), and the sample placement slot (15) is fixed on the sample carriage (14), and the sample placement slot (15) coincides with the central axis of the magnetizing coil (11) and the demagnetizing coil (12). The infrared emitting module (18) and the infrared receiving module (19) are symmetrically arranged on both sides of the conveyor belt (16) and are located outside the demagnetizing coil (12). Through the cooperation of the infrared emitting module (18), the infrared receiving module (19), and the sample carriage (14), the module detects whether the sample to be tested in the sample placement slot (15) has moved to the predetermined detection position. The residual magnetism detection sensor (7) is installed inside the solenoid of the magnetizing / demagnetizing coil and close to the sample to be tested, and is used to detect the magnetic induction intensity on the horizontal component of the sample to be tested. The temperature control module includes a temperature sensor (24) disposed around the demagnetizing coil (12) and a cooling module; the temperature sensor (24) detects the temperature of the demagnetizing coil (12) in real time.

2. The coercivity detection system for cemented carbide miniature products according to claim 1, characterized in that, The cooling module includes a semiconductor cooling block (21), a cooling fan (22), and a cooling fan. The cooling fan is disposed on the surface of the semiconductor cooling block (21), and the semiconductor cooling block (21) is used to provide a cold source for the cooling fan. The cooling fan (22) is installed on the outer shell of the detection system and is used to dissipate heat from the detection system.

3. The coercivity detection system for cemented carbide miniature products according to claim 1, characterized in that, The circuit of the magnetizing coil includes a transformer TR1, a diode D1, a resistor R1, a storage capacitor C1, a relay RL1, a reverse working diode D2, and a magnetizing coil (11). The 220V mains power is stepped up by transformer TR1, rectified by diode D1 and current limited by resistor R1, and then charges the storage capacitor C1. Relay RL1 is driven by control signal, and its contacts control the opening and closing of the magnetizing coil (11) and the reverse working diode D2 branch, so as to discharge to the magnetizing coil (11).

4. The coercivity detection system for cemented carbide miniature products according to claim 1, characterized in that, The circuit of the demagnetizing coil includes a digital-to-analog converter (DAC), an operational amplifier (U1), a reverse diode (D3), a sampling resistor (R2), a high-power Darlington transistor (Q1), and a demagnetizing coil (12). The digital-to-analog converter (DAC) receives digital signals and outputs a voltage signal Vctl to the non-inverting input of the operational amplifier U1. The operational amplifier U1 uses the principle of negative feedback to make the voltage of the sampling resistor R2 equal to Vctl, thereby controlling the current flowing through the sampling resistor R2 and the demagnetizing coil (12). The high-power Darlington transistor Q1 is used to amplify the current and drive the demagnetizing coil (12). The reverse diode D3 provides a freewheeling circuit for the demagnetizing coil (12) to protect the circuit.

5. A method for detecting the coercivity of cemented carbide micro-products, characterized in that, Includes the following steps: Step 1: After the detection system is working normally, the temperature sensor (24) detects the temperature around the demagnetizing coil (12) in real time. If the temperature is higher than the set threshold, the cooling module starts working; if the temperature is lower than the set threshold, the cooling module stops working. Step 2: Start the system to automatically zero. At this time, no sample is placed in the sample placement slot (15). A stable current Is0 is applied to the demagnetizing coil (12). The residual magnetism detection sensor (7) detects the magnetic induction intensity Bs0 on the horizontal component and records the voltage value corresponding to the magnetic induction intensity Bs0 at this time. Complete the zeroing process; Step 3: After zeroing is completed, the stepper motor (17) drives the conveyor belt (16) to move, and the sample carriage (14) is moved to the outside of the demagnetizing coil (12). The infrared light emitted by the infrared emitting module (18) is blocked by the sample carriage (14), and the infrared receiving module (19) cannot receive the infrared light. The infrared receiving module (19) outputs a low-level signal. Then, the hard alloy micro product to be tested is placed in the sample placement slot (15). The stepper motor (17) drives the conveyor belt (16) to move the sample carriage (14) towards the inside of the magnetizing coil (11). During the movement, the end of the sample carriage (14) moves forward continuously until the end of the sample carriage (14) can no longer block the infrared light emitted by the infrared emitting module (17). At this time, the infrared receiving module (18) will receive the infrared light again and output a high-level signal. At this time, the stepper motor (17) performs a braking operation to achieve precise stopping and positioning of the sample placement slot (15). Step 4: After the cemented carbide micro product in the sample placement slot (15) reaches the magnetizing coil (11) and is accurately positioned, the magnetizing coil (11) is discharged to complete the magnetizing operation of the cemented carbide micro product. Step 5: After magnetization is completed, the demagnetizing coil (12) performs demagnetization operation. The magnetic induction intensity on the horizontal component is detected by the residual magnetism detection sensor (7). The surface residual magnetism of the cemented carbide sample is calculated by combining the magnetic induction intensity Bs0 and the current Is0 when zeroing. If the surface remanence is greater than zero, increase the demagnetizing current until the remanence intensity of the cemented carbide surface is detected to be zero. Record the magnitude of the applied demagnetizing current Is, and calculate the coercivity value of the cemented carbide using the cemented carbide coercivity test value conversion algorithm.

6. The method for detecting the coercivity of cemented carbide micro-products according to claim 5, characterized in that, In step four, the magnetization operation is specifically as follows: 4.1) The transformer steps up the 220V AC power to Vh. The AC power Vh charges the storage capacitor C1 through the normally closed contact of the single conducting diode D1 and the relay RL1. The maximum charging voltage is Vmax = 1.414 * Vh. 4.2) Under normal circumstances, the circuit works in the state of charging the storage capacitor C1; when the magnetizing coil (11) is to be discharged, a low level 0 is input to the CTR1 pin of the relay RL1, so that the relay RL1 is turned on and works. At this time, the contacts of the relay are closed, the capacitor charging circuit on the left is disconnected, and the discharge magnetizing circuit on the right is turned on to discharge the magnetizing coil (11). 4.3) After the discharge is completed, a high level 1 is input to the CTR1 pin of relay RL1 to make relay RL1 non-conducting, the relay contacts are released, the circuit charges the storage capacitor C1, and waits for the next discharge operation.

7. The method for detecting the coercivity of cemented carbide micro-products according to claim 5, characterized in that, Step five, the demagnetization operation, specifically involves: The digital-to-analog converter (DAC) receives digital signals and converts them into voltage signals Vctl, which are then input to pin 3 of the operational amplifier U1. Based on the virtual short and virtual open principle of the operational amplifier's negative feedback, the voltage across resistor R2 is equal to the voltage Vctl, and the current flowing through R2 is the same as the current flowing through the demagnetizing coil (12). Specifically: The magnitude of the demagnetizing current on the demagnetizing coil (12) can be controlled by controlling the output voltage of the digital-to-analog converter (DAC).

8. The method for detecting the coercivity of cemented carbide micro-products according to claim 5, characterized in that, In step five, the surface remanence calculation process for the cemented carbide sample is as follows: (1) During the demagnetization process, the digital quantity is output to the input terminal of the digital-to-analog converter (DAC) starting from 0 and increasing in increments of 1. The output voltage Vctl of the DAC is as follows: in, Indicates digital input. A bit representing a digital-to-analog converter (DAC). Represents the magnitude of the reference voltage; (2) Each increase of one unit in the digital quantity results in... ,at this time The resulting change is: The change in the magnitude of the demagnetizing current on the demagnetizing coil (12) is: The magnitude of the demagnetizing current on the demagnetizing coil (12) is: The magnetic induction intensity on the horizontal component is detected by the remanence detection sensor (7), and the surface remanence of the cemented carbide sample is calculated by combining the magnetic induction intensity Bs0 and the current Is0 when it is zeroed. (3) Remanence on the surface of cemented carbide The calculation method is as follows: s0 in, It is the magnetic flux density on the current horizontal component detected by the residual magnetism detection sensor (7); (4) When detected When the value is zero, no new digital input is added to the digital-to-analog converter (DAC). The final digital input is... The magnitude of the current at this time is: 。 9. The method for detecting the coercivity of cemented carbide micro-products according to claim 8, characterized in that, In step five, it is determined that the remanence of the cemented carbide surface is zero, specifically as follows: 1) During the coercive charging and demagnetizing process of cemented carbide, the working current is generally large, and there is a large heating phenomenon in the charging coil (11) and the demagnetizing coil (12). The current on the demagnetizing coil is subject to certain interference and fluctuation. Therefore, the magnitude of the magnetic induction intensity detected by the residual magnetism detection sensor (7) will be disturbed by external factors such as noise and temperature. Especially when the residual magnetism on the surface of cemented carbide is close to zero, the influence of interference will directly affect when to stop adding digital quantity to the digital-to-analog converter DAC, that is, the zero-crossing detection of the residual magnetism of cemented carbide. 2) A digital filtering method is used to accurately detect the zero-crossing of residual magnetism. A digital-to-analog converter (DAC) is used to sample frequencies of... The analog voltage signal of the remanence of the cemented carbide miniature product within the acquisition time T. ( ),total The value of each point; Combined with the voltage value corresponding to the magnetic induction intensity when zeroing The voltage corresponding to the surface remanence of the cemented carbide sample is calculated using the current Is0. : （ ） Due to the current magnitude of the residual magnetic field on the surface of the cemented carbide Therefore, surface remanence zero-crossing detection is equivalent to directly detecting... Zero-crossing determination of voltage; 3) To A second-order Butterworth low-pass digital filter is applied to the remanent magnetization values ​​of a cemented carbide surface. in This represents the voltage signal at the nth point after filtering, with coefficients... From the cutoff frequency and sampling frequency Decide; 4) Traversal Find adjacent points of sign change: ； 5) Set minimum amplitude threshold Only when Only then is it considered a valid zero crossing.

10. The method for detecting the coercivity of cemented carbide micro-products according to claim 5, characterized in that, In step five, the algorithm for converting the coercivity test value of cemented carbide is as follows: (1) According to Ampere's circuital law, when the coil is long enough, the average magnetic field strength H generated at the center of the solenoid is: in Indicates the number of layers in the solenoid winding. The diameter of the wound copper wire is given. Therefore, the coercivity of the cemented carbide coil is positively correlated with the number of turns of the demagnetizing coil and the diameter of the wound copper wire, with a correlation coefficient of . ; (2) By giving a known coercivity as The hard alloy sample was magnetized and demagnetized. During the demagnetization process, when the residual magnetic induction intensity on its surface was detected to be zero, the magnitude of the applied current was... The correlation coefficient at this time is for: (3) Calibrate the correlation coefficient Afterwards, the cemented carbide sample is tested. If, during the demagnetization process, the final demagnetization current is... Then its corresponding coercivity value should be: 。

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