The Bed-Type Demagnetizer is a specialized equipment used to degauss the residual magnetism in workpieces after machining or magnetic particle inspection. It employs the remote method for demagnetization. It is suitable for users with high demagnetization requirements and large batches of workpieces. The equipment features simple operation, wide application range, high work efficiency, and safety reliability. It is applicable for large-scale demagnetization of various metal materials (non-magnetic materials), causing metals originally with magnetic properties to lose their magnetism. It boasts high efficiency, excellent demagnetization results, and minimal residual magnetism, and is widely used in industries such as mechanical manufacturing, bearing production, hardware tool manufacturing, and mold making.
I. Technical Specifications:
1.1. Power: Three-phase 380V±10% 50Hz
1.2. Power: 20 Kw
1.3. Inner Diameter of Circle: Approximately Φ400 mm × 400 mm
1.4. Demagnetization Effect: ≤0.3 mT
1.5. Method of Transportation: Belt Conveyor Demagnetization, Trolley Demagnetization
Dimensions: Approximately 600×400×1200mm
Total weight: Approximately 200KG.
II. Working Principle:
Bed demagnetizer, place the workpiece on the conveyor belt tray when using the demagnetizer. As the demagnetizing coil is powered on, the motor and chain drive the workpiece on the conveyor belt into the demagnetizer, gradually moving away. A strong axial magnetic field is generated within the coil, which changes with distance, achieving the demagnetization purpose.
Section 3: Equipment Composition:
3.1 The workpiece is passed through a conveyor belt into the degaussing coil for demagnetization, then moved away from the workpiece. It can be combined with an inspection machine to form an inspection production line.
3.2 The demagnetizing coil is a major component of the equipment. The demagnetization purpose is achieved as the workpiece gradually moves away from the coil.
3.3 The control circuit consists of a demagnetization switch, contactor, power indicator, etc., controlling the operation of the entire demagnetization equipment.
IV. Importance of Demagnetization Processing:
After degaussing treatment, the workpiece is completely free of magnetism, does not attract other ferromagnetic materials, and is easy to clean; it reduces residual stress, extending the lifespan and enhancing the surface finish of the workpiece. The wear resistance, durability, and fatigue resistance of the magnetized workpiece are significantly improved.
Demagnetization treatment technology is a novel non-thermal processing technique for metal materials, which utilizes magnetic pulse processing to reduce the residual stress within steel workpieces, alter their dislocation structure and defect configuration, thereby enhancing the overall comprehensive mechanical properties of the workpieces. This demagnetization technique encompasses electronics, ferromagnetism, and metal materials science, boasting a high level of technological content.
Demagnetizers are generally used for degaussing permanent magnet materials (ALNICO, ferrite) and low coercivity materials (hardware, mold steel, etc.).
Magnetic degaussers and demagnetizers available in the market come in various models and specifications, with different objects to demagnetize yielding varied results.
V. Demagnetizer's Demagnetization Principle:
Demagnetization involves placing the workpiece in an alternating magnetic field, which generates hysteresis loops. As the amplitude of the alternating magnetic field gradually decreases, the trace of the hysteresis loops also becomes smaller. When the magnetic field strength reaches zero, the residual magnetism Br remaining in the workpiece is reduced to nearly zero. During demagnetization, the direction and magnitude changes of the current and the magnetic field must be "reversed and decayed simultaneously."
Demagnetization methods and demagnetization equipment:
1. Demagnetization Communication
AC Demagnetization Method
For batch degaussing of small and medium-sized workpieces, it is best to place the workpieces on a degaussing machine with tracks and trolleys. During degaussing, position the workpieces on the trolley, 30 cm in front of the coil. When the coil is powered on, slowly move the workpieces along the track through and away from the coil, at least 1 meter beyond, before turning off the power. For heavy or large workpieces that cannot be degaussed on a machine, you can also place the coil over the workpiece. Slowly move the coil through and away from the workpiece while powered, and turn off the power at least 1 meter beyond.
B Decrement Method
Due to the alternating direction of alternating current, the demagnetization can be gradually achieved by using an automatic decay demagnetizer or a voltage regulator to reduce the current to zero. This can be done by placing the workpiece inside the coil, between the two magnetization clamps of the flaw detector, or by using a rod contact to touch the workpiece and then decreasing the current to zero for demagnetization.
For welds on large pressure-bearing equipment, an alternating current electromagnetic yoke demagnetizer can also be used. Connect the two poles of the electromagnetic yoke across the sides of the weld, turn on the power, and allow the electromagnetic yoke to slowly move along the weld. Disconnect the power when it is 1 meter away from the weld, and then perform demagnetization.
2. DC Demagnetization
Direct current magnetized workpieces can be demagnetized using direct current reversing decay or ultra-low frequency current automatic demagnetization.
A DC Reversal Demagnetization
By continuously reversing the direction of direct current (including three-phase full-wave rectified current) and gradually reducing the current through the workpiece to zero, demagnetization is achieved. The number of current decay cycles should be as numerous as possible (typically requiring over 30 cycles), with each decay's current amplitude being as small as possible. If the decay amplitude is too large, the demagnetization goal will not be reached.
Super Low Frequency Current Automatic Demagnetization
Ultra-low frequency typically refers to frequencies ranging from 0.5 to 10 Hz, suitable for demagnetizing workpieces that have been electromagnetized with three-phase full-wave rectification.
3. Heat Treatment to Demagnetize Workpiece
Heating the workpiece to above the Curie point is the most effective method of degaussing, but it is neither economical nor practical.