How to magnetize a magnet

A magnetizing machine is needed to magnetize a magnet block which is not magnetized or demagnetized after magnetization. What are the magnetization directions of magnets? How is the magnet magnetized? What should be paid attention to during magnetization? This article will give a detailed description.

Magnetization direction of magnet

There are two kinds of magnetization directions: radial magnetization and axial magnetization, and some others, such as multipole magnetization, radial magnetization and inclined magnetization. Most magnetic materials can be magnetized to saturation in the same direction, which is called “magnetization direction” (orientation direction). A magnet without orientation (also called isotropic magnet) is much weaker than an oriented magnet (also called anisotropic magnet).

How to magnetize a magnet

At present, there are two kinds of magnetization methods: DC magnetization and pulse current magnetization
(1) The equipment used for DC magnetization is electromagnet magnetizer.

Its structure is shown in Figure 1. When the coil is working, DC power is supplied to the coil. The gap between the two iron cores can be adjusted by adjusting the nut. Before magnetization, clean the surface of the magnet with clean water, put the magnet into the gap between the iron core of the magnetizer and clamp it. Direct current is applied to the magnetizing coil to reach the maximum value, and the current is cut off for 3 to 4 seconds. The magnet has been magnetized. Because the residual magnetic induction of a single magnet is low after magnetization, and the residual magnetic induction of a magnetic stack combination magnetization is high, it is generally to magnetize a single magnet first, and then stack a composite magnetic stack for magnetization. The magnetization field intensity of the magnetizer should be 5-7 times of the coercivity of the magnet.

Figure: DC magnetizer
1 – movable iron core; 2 – exciting coil; 3 – yoke; 4 – nut
(2) Pulse current magnetization.

The equipment used is pulse current magnetizing device, which is mainly composed of pulse device and magnetizing coil. Its magnetization field intensity is very high, and it can magnetize the magnetic stack directly. When it works, the strong pulse current passes through the magnetizing coil, which generates a strong magnetic field instantly and magnetizes the magnetic stack in the magnetizing coil. DC electromagnet has low magnetizing ability, but it has simple structure and low equipment cost, so it is suitable for small and medium-sized magnetic separation plants. The pulse current magnetizing device is suitable for large-scale magnetic separation plants and magnetic separation equipment manufacturers because of its large magnetizing capacity, complex device and high cost.

The structure of the magnetizing machine is relatively simple. In fact, it is an electromagnet with extremely strong magnetic force. It is equipped with iron blocks of various shapes as additional magnetic poles, so as to form a closed magnetic circuit with the charged magnet. When magnetizing, the additional magnetic poles and the charged magnet can be set up. As long as the exciting current is added, the brushing can be completed instantly.

What should be paid attention to in magnetization?

When the length of the magnet is close to the magnetizing coil, the vertical center position of the magnet should coincide with the vertical center position of the magnetizing coil. Only in this way can the magnetic field strength at both ends of the magnet be equal and the symmetry of the magnetization be reduced. Due to the magnetization method, the magnetic field strength at both ends of the magnet is equal.
It is theoretically proved that the magnetic field strength at both ends of the magnetizing coil is 1/2 of the magnetic field strength at the central point of the coil. When the magnet is close to the length of the magnetizing coil, the products of series H and SH and above may not be saturated magnetized. When the magnetic field strength is not large enough, even the products of Series M and N cannot be saturated magnetized. In general, the length of the magnetizing magnet should be less than 2/3 of that of the magnetizing coil.
Judgment on the easy magnetization direction (orientation direction) of magnets: for square squares and vertical axially oriented cylinders, there is the problem of orientation (easy magnetization direction) identification. Magnetized products or borrowed instruments can be used for identification. The specific methods are as follows:

• 1. Identification with magnetized products: for square blocks, due to the anisotropy of the material, the magnetic chips are arranged in the orientation direction, so the orientation direction is easy to magnetize. After magnetization, the attraction of the opposite polarity is larger, but the attraction of the non orientation direction is smaller, so as to identify and determine the orientation direction The magnet should be a little larger, and it is not easy to distinguish the difference of the suction when passing through the magnet. Generally, the magnetized magnet can only be used to detect the cylinder oriented perpendicular to the axial direction: use the magnet to suck up the cylinder surface, and the direction perpendicular to the ground is the orientation magnetization direction;
• 2. A magnet can be drawn on a square material. The direction of the magnet is perpendicular to the flux coil. The side with relatively large flux value is the orientation plane, and the direction perpendicular to this plane is the orientation direction.

Source: China Permanent Magnet Manufacturer www.rizinia.com