Fasteners are a general term for a type of mechanical parts used when two or more parts (or components) are fastened and connected into a whole.Fasteners are characterized by a wide variety of specifications, different performances and uses, and a high degree of standardization, serialization, and generalization. Therefore, some people call the existing standard type of fasteners standard fasteners, or simply standard Pieces.Others are called non-standard parts.But their important role is the same.Today, I will introduce the process flow of fasteners and material processing.
1. Product process of high-strength threaded fasteners
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 for the above 10.9 level.
2. Automotive fastener materials
高强度螺栓常用的钢材牌号为8.8级螺栓用35钢、45钢、ML35钢；10.9级螺栓用35CrMo；40Cr；12.9级螺栓用35CrMo,42CrMo、SCM435。
The raw materials for domestic fasteners are basically hot-rolled, while the steel for fasteners produced in Japan and other countries can basically 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.
3. Cold heading forming and thread processing (thread rolling or thread rolling, tapping)
In addition to the quality of threaded fasteners, forming equipment, thread processing equipment and molds (production technology and equipment) are key factors to ensure their quality.Especially in the supply of large quantities of multiple varieties, how to ensure the consistency of the product and the prevention of defects for automotive fasteners that require high processing accuracy is one of the problems faced by the fastener production.
4. Heat treatment
The heat treatment quenching and tempering is to improve the comprehensive mechanical properties of fasteners and meet the specified tensile strength value and yield ratio of the product.The quenching and tempering heat treatment process has strict requirements on raw materials, furnace temperature control, furnace atmosphere control, and quenching medium.The main control defects include carbon segregation in the core of the material, surface decarburization during the material and annealing process, cold heading cracks, quenching cracking and deformation during quenching and tempering.
Heat treatment process: feeding→cleaning→heating→quenching→cleaning→tempering→coloring→off-line.
5. Surface treatment
The surface treatment of automobile fasteners mainly includes the following methods. a. The non-electrolytic plating layer is hot dip plating, penetration plating, mechanical plating, Dacromet sintered film, etc. b. The electrolytic coating is galvanized, zinc-nickel alloy, zinc-iron alloy, etc. c. Phosphating treatment. d. Blackening treatment, etc.