China fasteners generally need to undergo surface tre […]
China fasteners generally need to undergo surface treatment. There are many types of fastener surface treatments. Generally, electroplating, oxidation, phosphating, and non-electrolytic zinc flake coating are commonly used. However, electroplated fasteners occupy a large proportion of the actual use of fasteners. It is especially widely used in industries and fields such as automobiles, tractors, home appliances, instrumentation, aerospace, and communications. However, for threaded fasteners, not only a certain anti-corrosion ability is required in use, but also the interchangeability of threads must be guaranteed, which can also be referred to as screwability here. To simultaneously meet the dual-use performance of "anti-corrosion" and "interchangeability" required by threaded fasteners in use, it is very necessary to formulate special plating standards.
High-strength threaded fastener product process
The production process of high-strength threaded fasteners is raw material reformation → cold heading forming → thread processing (thread rolling or thread rolling) → heat treatment → surface treatment → sorting and packaging. Generally, the thread rolling process after heat treatment is used above 10.9.
Automotive fastener materials
The commonly used steel grades for high-strength bolts are 35 steel, 45 steal, and ML35 steel for grade 8.8 bolts; 35CrMo; 40Cr for grade 10.9 bolts; 35CrMo, 42CrMo, and SCM435 for grade 12.9 bolts.
The raw materials for domestic fasteners are hot-rolled, while the steel for fasteners produced in countries such as Japan can be directly cold-headed. Users do not need pretreatment, which can reduce costs in terms of links.
The common failure modes of fastener failure include assembly elongation, fatigue fracture, and delayed fracture.
1. Requirements for fastener materials in terms of mechanical properties, especially strength;
2. The requirements of working conditions on the corrosion resistance of materials;
3. The working temperature requires the material's heat resistance (high-temperature strength, oxidation resistance);
4. Requirements for material processing performance in terms of production technology;