Fastener is a general term for a class of mechanical parts used when two or more parts (or components) are fastened together to form a whole. Fasteners are characterized by a wide variety of specifications, different performance and uses, and the degree of standardization, serialization and generalization is very high. Therefore, some people call a class of fasteners in the existing national standards as standard fasteners, or referred to as standard fasteners for short. Others are called non-standard parts. But their important role is the same. Today, we will introduce the process of fastener and material processing.

  1. Product flow of high strength thread fasteners

  The production process of high strength threaded fasteners is raw material modification cold heading forming threading processing (rolling or rubbing) heat treatment surface treatment sorting and packaging. The process of rolling after heat treatment is generally adopted for the fasteners above 10.9 grade.

  2. Automotive fastener materials

  The steel grades commonly used for high strength bolts are grade 8.8 35, 45, ML35, grade 10.9, 35CrMo, 40Cr, grade 12.9, 35CrMo, 42CrMo and SCM435.

  The raw materials for fasteners in China are basically hot-rolled, while steel for fasteners produced in Japan and other countries can be directly cold-headed. Users do not need pretreatment and can reduce costs from links.

  The common failure modes of fasteners are assembly elongation, fatigue fracture and delayed fracture.

  Cold heading forming and thread processing (rolling or rubbing, tapping)

  Except for material, forming equipment, thread processing equipment and die (production process and equipment) are the key factors to ensure the quality of thread fasteners. Especially under the condition of large-scale and multi-variety supply, how to ensure the consistency of products and the prevention of defects is one of the problems faced by fastener production.

  4. Heat treatment

  Heat treatment and tempering is to improve the comprehensive mechanical properties of fasteners and to meet the required tensile strength and yield strength ratio of products. Tempered and tempered heat treatment process has strict requirements on raw materials, furnace temperature control, furnace atmosphere control, quenching medium and so on. The main control defects are the carbon segregation in the center of the material, surface decarbonization during annealing, cold heading crack, quenching crack and deformation during quenching and tempering.

  Heat treatment process: feeding cleaning heating quenching cleaning tempering coloring off-line.

  5. Surface treatment

  Surface treatment of automobile fasteners mainly includes the following ways. A. Non-electrolytic coatings are hot dip, infiltration, mechanical plating, Dacromet sintered film, etc. B. Electrolytic coatings are galvanized, zinc-nickel alloy, zinc-iron alloy, etc. C. Phosphating treatment. D. Blackening treatment, etc.