JB/T 6641-2017 in English

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This standard is developed in accordance with the rules given in GB/T 1.1-2009.

This standard replaces JB/T 6641-2007 Rolling Bearings - Residual Magnetism and its Assessment Method.

In addition to editorial changes, the following main technical changes have been made with respect to JB/T 6641-2007:

——parts of expressions of terms are modified (see 3.1; 3.1 of 2007 edition);

——the dimensional range of bearing residual magnetism limit is expanded (see Table 1; Table 1 of 2007 edition);

——the residual magnetism limit tables of rolling element are combined (see Table 2; Tables 2~6 of 2007 edition).

This standard was proposed by the China Machinery Industry Federation.

This standard is under the jurisdiction of the National Technical Committee on Rolling Bearing of Standardization Administration of China (SAC/TC 98).

The previous editions of this standard are as follows:

——JB/T 6641-1993, JB/T 6641-2007;

——JB/T 8196-1996.
Rolling Bearings - Residual Magnetism and its Assessment Method

1 Scope

This standard specifies the residual magnetism limits, measuring methods and inspection rules for rolling bearing (hereinafter referred to as "bearing") and commercial rolling element (hereinafter referred to as "rolling element").

This standard is applicable to inspection and acceptance by the manufacturer and the user on all types of residual magnetisms of bearings and rolling elements with general purposes.

2 Normative References

The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 6930-2002
Rolling Bearings - Vocabulary
GB/T 24608-2009 Inspection Rules for Rolling Bearings and Commercial Parts

3 Terms and Definitions

For the purposes of this document, the terms and definitions given in GB/T 6930-2002 and the following apply.

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 Value Unit and Residual Magnetism Limits

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 Measuring and Assessment Methods

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 (δ) 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.

Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Value Unit and Residual Magnetism Limits
5 Measuring and Assessment Methods
6 Inspection Rules