total of 13 domestic automotive fastener companies were interviewed and investigated in this survey, and all the companies under investigation have passed the TS16949 system certification. An average car has about 1500 fasteners, and the total bolt assembly time for each car is about 2.5~3.2h. It can be seen that the variety and quality of fasteners have an important impact on the level of the main engine and the quality of the vehicle. This article analyzes the localization of high-strength threaded fasteners and the management of supply quality from the perspective of the production process of high-strength threaded fasteners. Product flow of high-strength threaded fasteners The production process of high-strength threaded fasteners is raw material transformation → cold heading forming → thread processing (thread rolling or thread rolling) → heat treatment → surface treatment → sorting and packaging, generally used above grade 10.9 Thread rolling process after heat treatment. The steel grades commonly used for high-strength bolts of automotive fastener materials are 35 steel, 45 steel, and ML35 steel for grade 8.8 bolts; 35CrMo for grade 10.9 bolts; 40Cr; 35CrMo, 42CrMo, and SCM435 for grade 12.9 bolts. The raw materials for domestic fasteners are basically in the hot-rolled state, while the steel for fasteners produced in Japan and other countries is basically in the state of direct cold heading. Users do not need pretreatment, which can reduce costs from the link. Common failure modes of fastener failure are assembly elongation, fatigue fracture, and delayed fracture. In addition to the material, the quality of cold heading forming and thread processing (thread rolling or thread rolling, tapping) threaded fasteners, forming equipment and thread processing equipment and molds (production process and equipment) are the key factors to ensure their quality. Especially in the state of large-scale and multi-variety supply, automotive fasteners that require high machining accuracy, how to ensure product consistency and defect prevention is one of the problems faced by fastener production. For the cold heading equipment and thread processing equipment of the investigated companies, domestic equipment accounts for about 40%, Taiwan equipment accounts for 50%, and imported (Europe, America, Japan) equipment accounts for about 10%; Partial folding, thread streamline upsetting, tooth wrinkles and cracks, etc. Domestic fastener factories are limited by capital or other reasons, and most of them use domestic equipment and Taiwan equipment to produce fasteners for automobiles. To ensure the dimensional tolerance and geometric tolerance of large-scale production of high-end fastener products, online monitoring should be increased. Means and mold making level. Eliminate unqualified products in production, so as to ensure the assembly quality of OEMs and OEMs.  About 80% of the surveyed fastener enterprises have heat treatment equipment, and most of them use Taiwan heat treatment process lines; the process line equipment is a continuous mesh belt furnace with atmosphere protection, and the atmosphere, temperature and process parameters are controlled by a computer. The high-strength fastener industry is a relatively competitive industry. If we want to have a thorough and objective analysis of the technology and market of the high-strength fastener industry, we need to start from the following aspects: domestic high-strength fasteners Industry and Enterprise Competition Pattern High-strength Fastener Industry Industrial Policy High-strength Fastener Product Technical Standards and Regulations my country's High-strength Fastener Product Technology Competition Pattern Dynamics Regarding these six aspects, many domestic research institutions have conducted in-depth research and research, and many institutions have long been engaged in research and research in this industry.
Comparing the physical properties of stainless steel and carbon steel, the density of carbon steel is slightly higher than that of ferritic and martensitic stainless steel, but slightly lower than that of austenitic stainless steel; the resistivity is based on carbon steel, ferritic, martensitic and The order of austenitic stainless steel is increasing; the order of linear expansion coefficient is similar, austenitic stainless steel is the highest and carbon steel is the smallest; carbon steel, ferritic and martensitic stainless steel are magnetic, austenitic stainless steel is non-magnetic, But its cold work hardening will generate magnetism when it is transformed into intensite, and heat treatment method can be used to eliminate this martensitic structure and restore its non-magnetic properties. Compared with carbon steel, austenitic stainless steel has the following characteristics: 1) High electronegative rate, which is about 5 times that of carbon steel. 2) The large coefficient of linear expansion is 40% larger than that of carbon steel, and with the increase of temperature, the value of the coefficient of linear expansion of stainless steel screws increases accordingly. 3) Low thermal conductivity, about 1/3 of carbon steel.
When using, after installing the nut and the bolt in place, insert the locking strip from the groove of the bolt, and make the V-shaped locking teeth of the locking strip snap into one of the V-shaped tooth grooves, and push the locking strip into the groove as a whole. The V-shaped locking teeth are stuck in the nut, and the locking strip body is stuck in the groove of the bolt, thereby restricting the relative rotation of the nut and the bolt, and there are threads between the nut and the bolt to restrict their relative sliding, so it can prevent the nut from loosening, even from The bolt falls off; when the nut needs to be disassembled, it is only necessary to pull out the locking strip from the groove, and the nut can be disassembled normally.
As a standard part, it should have its own general specifications. For hexagonal nuts, the commonly used standards are: GB52, GB6170, GB6172 and DIN934. The main differences between them are: GB6170 is thicker than GB52, GB6172 and DIN934. Thick from DIN934, commonly known as thick nut. The other is the difference between the opposite sides, the opposite sides of DIN934, GB6170 and GB6172 in the M8 nut series are 13MM smaller than the opposite side 14MM of GB52, and the opposite sides of M10 nuts, DIN934 and GB52 are 17MM. The opposite side of GB6170 and GB6172 should be 1MM larger, M12 nut, DIN934, GB52's opposite side is 19MM larger than GB6170 and GB6172's opposite side 18MM is 1MM larger. For M14 nuts, the opposite side of DIN934 and GB52 is 22MM, which is 1MM larger than the opposite side of GB6170 and GB6172, which is 21MM. The other is the M22 nut. The opposite side of DIN934 and GB52 is 32MM, which is 2MM smaller than the opposite side of GB6170 and GB6172, which is 34MM. (Besides the thickness of GB6170 and GB6172 are the same, the width of the opposite side is exactly the same) The rest of the specifications can be used in general without considering the thickness.
Yueluo Company adopts the following technical solutions: fasteners for preventing nuts from falling off, including bolts and nuts, the nuts are provided with screw holes, the screw holes are provided with internal threads, the bolts are provided with M grooves along its axial direction, M ≥1; There is an arc-shaped notch on the screw hole of the nut, and there are N V-shaped tooth grooves along the axial direction of the nut in the arc-shaped notch, N≥2; a locking strip is placed in the groove, and the locking The bar includes a locking bar body and a V-shaped locking tooth, the width of the locking bar body is the same as the width of the groove, the V-shaped locking tooth is located on one side of the locking bar body, and the V-shaped locking tooth is engaged with the V-shaped locking tooth.
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