There are four important methods for testing non-standard screw fasteners:
1、 Appearance quality request
The appearance examination of non-standard screws is conducted from various aspects such as appearance, plating layer, etc.
2、 Examination of screw coating thickness
1. Measuring method: The amount used includes micrometers, vernier calipers, plug gauges, etc.
2. Magnetic method: The magnetic method is used to measure the thickness of a coating layer, which is a non-destructive measurement of a non-magnetic coating layer on a magnetic substrate using a magnetic thickness gauge. Screw customization, such as size inspection items, specifies the thread gauge, thread stop gauge, thread small diameter, opposite edge width, diagonal dimension, nut height, and the perpendicularity of the nut support surface to the thread axis for hex nuts; The specifications for flat washers include inner diameter, outer diameter, thickness, coaxiality of the outer circle to the inner hole, and flatness. The mechanical performance inspection items for hexagonal nuts are specified as hardness and tensile strength; And only the hardness is specified for flat washers.
3. Microscopy method: Microscopy method, also known as metallographic method, involves magnifying etched fasteners on a metallographic microscope with a micrometer eyepiece to measure the thickness of the coating on the cross-section. Non standard screw customization inspection method: The inspection method for standard fasteners is specified in the technical specifications of the product. And professional standards have been established for the testing methods of fasteners (size and geometric accuracy).
4. Timed flow method
The timed flow method is to inject a solution that can dissolve the coating onto the local surface of the coating, and calculate the thickness of the coating based on the time required for the local coating to dissolve. There are also plating drop method, anodic dissolution Coulomb method, etc.
3、 Test for adhesion strength of screw coating
There are many methods to evaluate the adhesion between coating and substrate metal, usually including the following. Fastway
1. Friction polishing experiment;
2. Filing method experiment;
3. Scratch method;
4. Tortuous experiment;
5. Thermal shock experiment;
6. Squeezing method.
4、 Examination on corrosion resistance of non-standard screw coatings
The methods for testing the corrosion resistance of coatings include: atmospheric exposure test; Neutral salt spray experiment (NSS experiment); Acetate salt spray experiment (ASS experiment), copper accelerated acetate salt spray experiment (CASS experiment); And the Corrosive Cream Corrosive Experiment (CORR Experiment) and the Solution Drip Corrosive Experiment; Immersion experiment, intermediate immersion corrosion experiment, etc. Non standard screw customization inspection method: The inspection method for standard fasteners is specified in the technical specifications of the product. And professional standards have been established for the testing methods of fasteners (size and geometric accuracy). Fastway
