JB/T 6641-2017Rolling bearings - Residual magnetism and its assessment method (English PDF)

3.1 residual magnetism of bearings

in the case that bearing is magnetized, the residual magnetism after demagnetization

3.2 residual magnetism of rolling elements

in the case that rolling element is magnetized, the residual magnetism after demagnetization

4.1 Value unit

The residual magnetism is expressed by magnetic induction intensity and its unit is millitex (mT).

4.2 Residual magnetism limits

4.2.1

The residual magnetism limits of bearings shall be in accordance with those specified in Table 1.

Table 1 The residual Magnetism Limits of Bearings

Nominal outside diameter of bearing mm Maximum residual magnetism value mT

> <=

- 30 0.4

30 50 0.5

50 120 0.6

120 250 0.8

250 500 1.0

500 1 000 1.3

1 000 - 1.5 4.2.2 The residual magnetism limits of rolling elements shall be in accordance with those specified in Table 2.

Table 2 The Residual Magnetism Limits of Rolling Elements

Type of rolling element Nominal diameter mm Maximum residual magnetism value mT

> <=

Steel ball 0.5 5 0.1

5 50 0.25

50 - 0.3

Needle roller - 1 0.1

1 3 0.15

3 5 0.20

5 - 0.25

Cylindrical roller - 10 0.15

10 18 0.2

18 30 0.25

30 50 0.3

50 - 0.4

Tapered roller - 18 0.2

18 30 0.25

30 50 0.3

50 - 0.4

Spherical roller - 10 0.2

10 30 0.3

30 50 0.4

50 - 0.5

5.1 Measuring instruments

The measurement of residual magnetism shall be conducted in accordance with the theory of Hall effect, and for measuring instrument, the maximum range shall at least be 2mT, the resolution shall be less than or equal to 0.1mT and the measurement accuracy shall be ±3%. The specifications of Hall elements equipped on instruments are: 4mm×2mm×0.2mm, and the distance (delta) from the plane of Hall element to probe face is 1mm±0.05mm (as shown in Figure 1). The measuring instruments of residual magnetism shall be periodically calibrated by qualified units to ensure its validity.