RU2419905C1 - Demagnetisation method of thin-wall annular parts of large diametre from ferromagnetic steels - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: according to demagnetisation method the remaining magnetisation of the part is measured diametrically in every 200 mm and the section of the highest magnetisation is determined. Then, 2-6 coils of cable with section of not less than 150 mm² and distance between coils of not less than 100 mm are wound on the section of part with highest magnetisation; thus, demagnetisation solenoid coil is formed; at that, number of coils is chosen inversely proportional to magnetisation degree. After that, rectified full-wave current with force of not less than 3000 A and frequency of 50 Hz is supplied during not less than 3 sec, and during next 20-30 sec the pulse remagnetisation of part is performed owing to smooth current force decrease to 0 A with change of current polarity in every 1.5 sec. If remaining magnetisation is more than 5 A/cm, the above demagnetisation cycle is repeated.

EFFECT: reducing energy consumption and time of demagnetisation of large-size ferromagnetic items.

2 cl

Description

The invention relates to the demagnetization of ferromagnetic thin-walled ring parts of large diameters (more than 1500 mm) with 3-10 poles and a degree of magnetization of 8-140 A / cm

In the manufacture of thin-walled ring parts of large diameters with large diameters, most of them have magnetization, which is local in nature, i.e. 1-3 sections appear to be magnetized by arcs from 10 ° to 120 °.

Magnetic fields of magnetized parts can cause undesirable consequences: malfunctioning of devices, in the gaps between parts, ferromagnetic products of wear of parts can accumulate and cause them to jam, which is unacceptable.

A known method of demagnetization of a ferromagnetic product, which consists in heating the product to a Curie temperature at which the magnetization disappears (Non-Destructive Testing and Diagnostics. Handbook edited by V.V. Klyuev, M., Mechanical Engineering, 1995, p.243-244).

The disadvantage of this method is a change in the mechanical properties of the material of the product as a result of heating and in some cases is unacceptable.

A known method of demagnetization of large-sized products, in which the product is exposed to an alternating magnetic field with an amplitude decreasing from a certain maximum value to zero, and a frequency depending on the magnetic permeability and thickness of the product, in which the product is simultaneously exposed to an alternating magnetic field, the frequency of which coincides with natural fundamental frequency of the mechanical resonance of this product, created by increasing the steepness of the rising and falling edges of the pulse due to t connecting the processing winding to the battery (RF patent No. 2157014, IPC 7 H01F 13/00, published September 27, 2000).

The method described in the patent also does not solve the problem of reducing the energy intensity and demagnetization time of the ring ferromagnetic products.

The demagnetization methods described above are significantly different from the claimed method.

The objective of the invention is to reduce the energy intensity and time of demagnetization of thin-walled ring parts of large diameter from ferromagnetic steels with 3-10 poles and a degree of magnetization to 140 A / cm large-sized ferromagnetic products.

The task is achieved by the fact that in the method of demagnetization of thin-walled ring parts of large diameter from ferromagnetic steels with 3-10 poles and a degree of magnetization of up to 140 A / cm, the residual magnetization of the component is measured in diameter every 200 mm; and determine the area of maximum magnetization; then, on the part with the highest magnetization, winding is made of 2-6 turns of cable with a cross section of at least 150 mm ² and a distance between the turns of at least 100 mm, forming a solenoid demagnetization coil, while the number of turns is selected inversely with the degree of magnetization, after which a rectified two-half-current with a force of at least 3000 A and a frequency of 50 Hz for at least 3 seconds; and over the next 20-30 seconds, the part is magnetically pulsed by magnetization reversal due to a gradual decrease in current strength to 0 A with a change in current polarity every 1.5 seconds; when the value of the residual magnetization is more than 5 A / cm, the specified demagnetization cycle is repeated.

It is advisable to demagnetize a part with a diameter of 1800-2300 mm, a cross-sectional area of 0.35 m ² to 1.35 m ² , with 3-10 poles and a degree of magnetization of up to 140 A / cm.

Demagnetization is as follows.

The proposed demagnetization method has been tested on ring parts made of ferromagnetic steels with a diameter of 1800-2300 mm, a cross-sectional area from 0.35 m ² to 1.35 m ² , with 3-10 poles and a degree of magnetization up to 140 A / cm.

As a power device, an experimental demagnetization unit OUR-1 was used, the developer and manufacturer of which is Scientific and Technical Center "Defectoscopy", with the following technical characteristics: maximum rectified current - 6000 A; current frequency 50 Hz; type of demagnetization current - rectified half-wave; operating mode of demagnetization by rectified current: current duration 2 s, pause duration 1.5 s; current regulation smooth from 0 to maximum value.

Preliminarily, for example, the IMP-6 device is measured with the remanent magnetization of parts by diameter every 200 mm and the maximum magnetization section is determined.

Then, a cable with a cross section of at least 150 mm ² with a distance between the turns of at least 100 mm and the number of turns 2-6 is wound onto the part of the part with the highest magnetization, forming a solenoid demagnetization coil, the ends of the cable are connected to the power device and a rectified biannual current with a force of at least 3000 A and a frequency of 50 Hz for at least 3 seconds.

Over the next 20-30 seconds, the component is magnetically pulsed magnetically reversed due to a smooth decrease in current from 3000 A to 0 A with a change in current polarity every 1.5 seconds.

When the value of the residual magnetization is more than 5 A / cm, the indicated demagnetization cycle is repeated.

The number of turns of the cable is chosen inversely with the degree of magnetization. The turns may relate to the part.

As a demagnetizing device, a power device is used that provides a rectified two-half-current supply of at least 3000 A and a frequency of 50 Hz.

These modes are selected experimentally.

Claims (2)

1. The method of demagnetization of thin-walled ring parts of large diameter of ferromagnetic steels, in which the residual magnetization of the part is preliminarily measured by diameter every 200 mm and the area of maximum magnetization is determined; then, on the part with the maximum magnetization, winding is made of 2-6 turns of cable with a cross section of at least 150 mm ² and a distance between the turns of at least 100 mm, forming a solenoidal demagnetization coil, while the number of turns is chosen inversely proportional to the degree of magnetization, after which a rectified half-wave a current of at least 3000 A and a frequency of 50 Hz for at least 3 s and for the next 20-30 s carry out a pulsed magnetization reversal of the part due to a smooth decrease in current from 3000 A to 0 A with a change lower current polarity every 1.5 s; when the value of the residual magnetization is more than 5 A / cm, the specified demagnetization cycle is repeated. 2. The demagnetization method according to claim 1, characterized in that the component with a diameter of 1800-2300 mm, a cross-sectional area of 0.35 to 1.35 m ² , with 3-10 poles and a degree of magnetization of up to 140 A / cm is subjected to demagnetization.