SU549759A1 - Method for determining magnetic aging of magnets from an alloy based on - Google Patents

Description

The invention relates to the production of permanent magnets. A known method for determining the magnetic aging of magnets from RCo-based alloys is based on measuring the decrease in magnetic induction in a short period of time and extrapolating the measured value for any period before the start of structural aging 1. According to this method, a series of magnets of a certain size and brand are selected. expose them to operating temperature for a time sufficient to allow the entire volume of the sample to reach this temperature. After that, the magnets are magnetized at this temperature, turn off the field and measure the decrease in magnetic induction from time t to t after switching on the field. The disadvantage of this method is the large error of the measurement technique. The purpose of the invention is to improve the accuracy and simplify the process of determining the magnetic aging of magnets. The proposed method is characterized in that the sample is magnetized to saturation at room temperature and the magnetic induction is measured, then the magnetized sample is heated to a temperature in the range of 150 to 300 ° C, and immediately cooled to room temperature, after which the magnetic induction is measured again . The following is a procedural description of the method. 1) Having selected the reference batch of data magnets of the brand and size, they magnetize them to saturation. 2) - With any magnetic induction tester, the field is measured at a characteristic point of the sample at room temperature. 3) The samples are heated to 15 ° -310 ° C (the heating temperature is higher, the smaller the demagnetizing factor), maintained at this temperature for 10-20 minutes and cooled to room temperature. 4) Again measuring the field at the characteristic point of the sample using the same magnetic induction meter as in n. 2, they determine the relative decrease in induction.

5) Samples are heated to operating temperature and maintained for any time determined, for example, by the duration of operation of the device in which the magnets are intended to be used. However, the exposure time should be such that no structural changes are initiated in the sample.

6) Samples, the reversible change in the magnetic induction of which as a result of prolonged exposure to temperature does not exceed the permissible limits, for example, the class of instrument for which they are intended to be used, are considered suitable

7) All other samples of the data of the size and brand are magnetized to saturation and make operations with them on

pp 2, 3, 4.

8) Magnets, the relative decrease in induction of which, measured in accordance with clause 4, is less than the relative decrease in the induction of the reference batch magnets, recognized as or equal to it, are also recognized as valid.

The example below illustrates the greater accuracy and reliability of the proposed method compared to the known.

Example.

They selected 12 magnets from the powder of an alloy of SmCo 5 with a relative density of 95-98%, which are cylinders with a diameter of 7.6 mm and a height of 3.8 mm, which, during exposure for 1000 hours at 150 ° C, would have aged no more than on 2%

1) Selected magnets are magnetized to a height of 150 kZ in a pulsed field with a duration of 30 ms.

2) The field at the characteristic point of the sample in the center of the circle at the cylinder end is measured using a magnetic comparator of multi-time comparison using NMR equipment. The accuracy of determining induction is + 0.1%, with the legs of the decisiveness caused by inaccurate reproduction of coordinates being the most significant.

3) The samples were heated to 150 + 5 ° C, kept at this temperature for 15 minutes and cooled to room temperature.

4) Again measured the field at a characteristic point of the sample using the same magnetic induction meter and determined the relative decrease in induction. The relative decrease in induction, indicated by the symbol (5, is presented in the table).

5) Samples were heated to 150 + 5 ° C and held for 10OO (relative decrease in induction after such exposure).

VIA compared to induction after 15 minutes of exposure is indicated by the symbol in.

6) Samples, the reversible change in the induction of which as a result of prolonged exposure to temperature did not exceed 2%, were found to be suitable (in our case, samples No. 1-7).

7) All other specimens of the size and brand data are magnetized to saturation and operations have been performed with them.

on nn 2, 3, 4.

8) Magnets, the relative decrease in induction of which, measured in accordance with clause 4, is less than or equal to the absolute value of 2%, are considered suitable.

Claims (1)

In the table, the symbol § ,. the results of determining the relative decrease of induction by a known method 15 and 60 minutes after switching on the field are indicated. From the table it follows that with a given measurement accuracy by the known method it is impossible to unambiguously determine the suitability of the magnets. For example, in sample No. 3 (the rear is absolute in magnitude than sample No. 9, although magnetic aging in 1000 hours is greater in sample No. 9; in samples No. 6 and 12 (5z are the same, and 2 differs by almost three times). 5 The invention The method of determining magnetic magnet of an alloy based on an RCog, based on measuring the relative 5 reduction of the magnetic induction of a sample, characterized in that, in order to improve accuracy and simplify the process, the sample is magnetized to saturation at room temperature and the magnetic induction is measured, then us g- 54975 9 6 the draw sample is heated to a temperature in the range of 150 to 300 ° C and immediately cooled to room temperature, after which the magnetic induction is measured again. Sources of information taken into account during the examination: 1. Mitkevich A. In The stability of permanent magnets. Energie, L., 1971, pp. 55.