1. Core hardness of self-drilling and self-tapping scre […]
1. Core hardness of self-drilling and self-tapping screws: standard value HRC28-38. The test is carried out on a section 1-2 times the nominal diameter from the tail. If the nominal length is too short, you can embed it first, and then measure the hardness.
2. Surface hardness: standard MINHV450.
3. Carburized layer: standard 4#-6#: 0.05-0.18mm, 8#-12#: 0.10-0.23mm, 14#: 0.13-0.28mm. The main purpose of carburization is to increase the surface hardness and ensure the strength of the teeth. If the decarburization is too deep and the carburization is insufficient, the strength of the teeth will not meet the requirements, that is, the teeth will be damaged during the screwing test.
4. Screw-in test: Screw the self-drilling self-tapping screw into a steel plate with a reserved test hole. The self-tapping screw should form a matching thread in the test plate, and the screw thread itself will not be deformed or damaged until The end taper thread completely passes through the test plate. The screw-in test is only applicable to self-drilling and self-tapping screws of AB, B, BP and other types. The IFI stipulates that the test plate shall be made of semi-hard low-carbon cold-rolled steel, and the hardness of the steel plate shall be 70-85HRB Rockwell.