QC/T 597.2-2017Specifications for threaded fasteners with pre-applied adhesive coatings - Part 2: Polyamide locking coatings (English PDF)

3.1 Locking coating

Polyamide adhesive layer to prevent bolts from loosening. The adhesive layer can be applied all over the place (R) or partially (F), such as a strip or dot coating.

3.2 Screw-in torque

Torque measured when a bolt is tightened into a test nut.

3.3 TA tightening torque

Torque applied to the head of a nut or bolt when tightening.

3.4 Loosening torque

After the connection is loose, the maximum torque value measured when the adhesive layer bolt is screwed out.

4.1 General requirements

4.1.1 When the bolt with adhesive layer is screwed into the nut or screw hole, the nut and screw hole should be chamfered.

4.1.2 The adhesive layer prevents the part from completely disengaging from the mating part.

4.1.3 The bolt with adhesive layer can be reused 3 times when it meets the torque requirements specified in Table 2. When used for installation and adjustment, it can be used many times.

4.1.4 Under normal storage conditions, the bolts with adhesive layer shall ensure that the performance requirements do not change for at least 4 years.

4.2 Pre-coated parts and length

4.2.1 Basic requirements

4.2.1.1 It shall be ensured that the screwed part of the bolt and the test nut is within the length of the adhesive layer.

4.2.1.2 The residue of the adhesive layer shall not affect the screwing of the bolt.

4.2.2 Standard pre-coating

The standard pre-painted part of the bolt and the length of the adhesive layer are as specified in Figure 1. There should be no adhesion layer in the size a range.

4.2.3 Special pre-coating

The special pre-painted parts of the bolt and the length of the adhesive layer are as specified in Figure 2.

5.1 Basic requirements

5.1.1 During the test, the bolts with adhesive layer shall be stopped for at least 15s after tightening.

5.1.2 The test nut should not be reused.

5.2 Test pieces and equipment

5.2.1 During the arbitration test, the test bolts shall be M10 × 40, 8.8 grade, galvanized and passivated hexagon head screws in accordance with GB/T 5783. Other lengths are also available.

5.2.2 The test nut shall meet the M10, not less than 8 grade, galvanized and passivated hexagon nuts specified in GB/T 6170. The test nut must not be stained with lubricating materials such as oil and grease.

5.2.3 The test washer shall meet the requirements of GB/T 97.1. The test washer must not be stained with oil, grease, etc.

5.2.4 Test plate hardness > 35 HRC. The hole diameter should meet the intermediate assembly regulations of GB/T 5277.

5.2.5 The outer diameter of the test sleeve is the nominal diameter of the thread. Hardness > 35 HRC. Aperture should comply with the regulations of GB/T 5277.

5.2.6 The relative error of the torque indication value of the torque wrench or torque test equipment is ± 2%. The measurement range of the equipment used in the arbitration test is 50% ~ 100% of the upper measurement limit.

5.2.7 The difference between the holding temperature of the heating box and the heating target temperature should be less than ±2 °C.

5.3 Torque test

The torque test method is as specified in Figure 3, Figure 4, and Table 3.