A fastener is a general term of a type of mechanical […]
A fastener is a general term of a type of mechanical part that is used when two or more parts (or components) are fastened together into a single unit. Fasteners are characterized by a wide variety of specifications, performance purposes, and standardization, serialization, generalization is extremely high, so there are already national standards for a class of fasteners called standard fasteners, or simply as standard parts. And others are called non-standard pieces. But they serve the same important purpose. Today, we will follow the process of fasteners and material processing by Zhejiang Weigao Standard Parts Co.
1. High-strength threaded fastener product process
The process of production of high strength threaded fasteners is raw material reforming → cold heading → thread processing (rolling or rolling) → heat treatment → surface treatment → sorting and packaging, 10.9 levels above the general use of heat treatment after the rolling process.
2. Fastener material
The steel grades commonly used for high strength bolts are 35CrMo, 45CrMo, ML35 for 8.8 grade bolts; 35CrMo, 40Cr for 10.9 grade bolts; 35CrMo, 42CrMo, SCM435 for 12.9 grade bolts.
China fasteners with raw materials are basically hot-rolled states, and as Japan and other countries' production of fasteners with steel is a direct cold upsetting state, users do not need to pre-treat, can reduce costs of the link.
Common forms of failure of fasteners are assembly elongation, fatigue fracture, and delayed fracture.
3. Cold heading and threading (rolling or rolling, tapping)
The quality of threaded fasteners in addition to the material, forming and thread processing equipment and dies (the production process and its equipment) is key factors of ensuring their qualitties. Especially in the state of supply of large quantities of multiple varieties, the high requirements for processing accuracy of fasteners, how to ensure product consistency and defect prevention is one of the problems faced by fastener production.
4. Heat treatment
Heat treatment conditioning is used to improve the overall mechanical properties of fasteners to meet the specified tensile strength values and yield ratio of the product. The tempering heat treatment process has strict requirements for raw materials, furnace temperature control, furnace atmosphere control, quenching medium, etc. The main control deficiencies are carbon precipitation in the heart of the material, surface decarburization of the material and during annealing, cold upsetting cracks, quenching cracks, and deformation during tempering.
Heat treatment process: feeding → cleaning → heating → quenching → cleaning → tempering → coloring → down line.
5. Surface treatment
The fastener surface treatment is mainly in the following ways: a. The non-electrolytic plating layer is hot-dip plating, dipping plating, mechanical plating, Dacromet sintered film, etc. b. The electrolytic plating layer is galvanized, zinc-nickel alloy, zinc-iron alloy, etc. c. Phosphorization treatment. d. Blackening treatment, etc.