Overview of demagnetization methods for demagnetized galvanized steel pipes

The strength of the residual magnetic field of demagnetized galvanized steel pipes is related to the following factors:

①Magnetic properties of materials;

②Recent magnetization history of materials;

③Applied magnetic field strength;

④Magnetization direction (longitudinal or circumferential);

⑤Geometric shape of the specimen, etc.

Generally, there are three commonly used demagnetization methods for demagnetized galvanized steel pipes: conventional demagnetization methods include thermal demagnetization and electromagnetic demagnetization, among which electromagnetic demagnetization methods include AC demagnetization, DC demagnetization, and yoke demagnetization.

First, the demagnetized galvanized steel pipe is required to have a sufficiently high magnetic field strength. In order to overcome the coercive force corresponding to the residual magnetism in the workpiece, the direction of the residual magnetic field is reversed. In other words, a high-intensity magnetizing current is used for periodic transformation to achieve the purpose of demagnetization; secondly, the demagnetized galvanized steel pipe is required to gradually reduce the magnetic field strength in each magnetization cycle to adapt to the change of coercive force.

First, the concept of demagnetization

Phenomenon: When the steel pipe is processed, iron filings are adsorbed around, indicating that the steel pipe is magnetic. (Concept and characteristics of magnetic field)

Cause analysis: Eliminate contact with magnetic materials during production and circulation; magnetic test, friction (fast, directional); VS material difference, scope definition, condition analogy.

Second, the demagnetization method of demagnetizing galvanized steel pipe:

1. Beating method, that is, strong vibration demagnetization: (generally cannot meet the requirements of complete demagnetization);

2. Demagnetizer, reverse magnetization demagnetization: (commonly used at the entrance of shopping malls);

3. High temperature demagnetization: (high temperature is the accelerated movement of molecules in the magnet, thereby changing the direction of its original molecular current, and then changing the magnetism of the demagnetized galvanized steel pipe, and weakening it to disappearance), Curie temperature. Not less than 770℃.