Inspection content of fasteners

Fasteners, also known as standard parts in the market, are a general term for a type of mechanical parts used to securely connect two or more parts (or components) into a whole. They are called “industrial meters” and have wide applications in fields such as machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, instruments, and supplies.

The performance inspection items of fasteners include: size, chemical composition, non-destructive testing, mechanical properties including bolt connection coefficient of torsion, tightening axial force, tensile (yield strength, tensile strength), hardness, and mechanical properties testing of steel structure fasteners

The performance grades of bolts for steel structural join are 4.6, 4.8, 6.8, 8.8, 10.9, 12.9, etc. The bolts of grade 8.8 and above are supported by low-carbon alloy steel or medium carbon steel and heat treated, which are generally called high-strength bolts, and the rest are commonly called ordinary bolts

Inspection content of fasteners

1. Appearance dimensions: thread go/no go gauge, surface roughness, various dimensions such as major diameter, pitch diameter, minor diameter, profile angle, pitch, etc.

2. Mechanical performance testing: tensile test, holding test, hardness test, re tempering test, impact test, wedge load test, shear test, fatigue test, locking performance, torque coefficient, tightening axial force, friction coefficient, anti slip coefficient, screwability test, gasket elasticity, toughness test, hydrogen embrittlement test, etc.

3. Chemical composition analysis: fastener chemical composition analysis, fastener metal material grade identification, etc.

4. Metallographic analysis: microstructure, depth of decarburization layer, depth of carburization layer, grain size rating, inclusion content, macrostructure, etc.

5. Failure analysis: crack analysis, fracture analysis, fracture analysis, etc.

6. Corrosion resistance test: neutral salt spray test (NSS), acetate spray test (AASS), copper accelerated acetate spray test (CASS)