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Fasteners commonly used in domestic and foreign material analysis
The vast majority of fasteners are made of steel. As a person working in the fasteners industry, it is necessary to understand the changes, distinctions and applications, and if it is a technician, you should have a better understanding. I understand the material I use, with reference to relevant information, and share this knowledge, for just engaged in the industry can be used as a guide for senior people, we can further explore the material we now commonly used standard parts There are: ISO (International) GB (China DIN (Germany) AISI / SAE (USA) JIS (Japan) bolts and other materials for external thread Some are not mechanical performance requirements or ISO Class 4.8 SAE Grade 1-2 and other low-carbon Steel fasteners, enough with Q235A SAE 1015 DIN C15, do not heat treatment at all, made by direct cold work, while the level of slightly higher fasteners such as: ISO Class 6.8 SAE Grade 3-4 is to use carbon content of 0.2 % Of the steel, such as C1020 C1022 Ml20 ML35, such screws do not need any heat treatment, cold processing strength can meet the requirements.In fact, the higher the carbon content, the more difficult cold forming, it is not necessary for the 6.8 level The screws are not used in special cases, but the most common ones are the screws of ISO Class 8.8 SAE Grade 5, generally used in medium carbon steel, ML35 SAE 1035 DIN 35 JI S SWRCH35K after heat treatment (quenching + tempering), you can also use SAE5140 40Cr, etc., alloying elements increase the hardenability of heat treatment is of great help, so the specifications of the screw can choose to use alloy steel, not with carbon Steel leads to the existence of the "quench impermeable" part of the center that we often say ISO Class 9.8 10.9 SAE Grade 8 is made of low to medium alloyed steel, heat-treated (quenched + tempered), alloyed in mechanical properties There is a very good combination, commonly used materials for the 40Cr 35CrMo SAE5140 SCM435 SAE4135 SAE4137 JIS SCr440 (H) DIN 41Cr4, etc., in fact 45 # can meet the required mechanical properties, but in the overall mechanical properties than the alloy slightly Inferior. ISO Class12.9 SATM A574 is a high strength bolts requiring high mechanical properties, then use medium carbon steel after heat treatment (quenching and tempering), such as SCM435 35CrMo SAE 4137 SAE4135 DIN 34CrMo4, such high If the strength of the bolt surface treatment to go through the pickling process, will produce hydrogen embrittlement, so be sure to dehydrogen this process (especially the existence of the tip Of the fastener), or else will die miserable. Nuts and other materials with no internal thread mechanical properties or ISO Class 5-6 SAE Grade 3-4 generally C1010 Q235A or C15, does not require heat treatment, cold work that is can. ISO Class 8, SAE Grade 5, generally use Ml35 SAE1035 DIN C35, the small size of the nut does not require heat to achieve the required mechanical properties, large size to go through heat treatment (quenching + tempering), this point GB3098.2 Said very understand. ISO Class 10, SAE Grade 8 General use Carbon steel can be heat treated to meet its strength requirements. Such as SAE1035 and other carbon steel. One thing we must be aware of is that unlike nuts and bolts, the force is mainly compression rather than extension, so the strength of the nut is not only material-related, but also depends on many factors including accuracy, pitch, nut chamfer , Nut thickness. Flat washers materials used mechanical properties of flat washers generally used angle material manufacturing, such as Q235A, hardness requirements but not high can be used to thicker plate rolling to achieve the required hardness. Spring washers and other loose washers are generally made with 65Mn 70 # or S 50CM-S 70CM, subject to heat treatment (quenching + tempering) rivets, pin rivets, pin type general materials and bolts the same, but some rivets Hardness is not too high, and even some require HRB60 or less, generally normalized material hardness HRB70-80, so some to be annealed to meet the performance requirements. Self-tapping screws generally C1018 C1020 C1022 and other materials, but some domestic manufacturers to save costs, cut corners, the use of 18 # 15 # 20 # more with some manufacturers with Q235A, and then carburizing the surface done, so made of self-tapping nail it Heart toughness not up to requirements, easily broken. Stainless steel fasteners I do not know much, it seems that SUS304 is very common. Materials Other special requirements If the company is to be used for welding fasteners, arc welding and gas welding generally have no requirements on the material. If the customer is using spot welding, then obediently use low carbon steel to do, if we must increase the intensity, you can use some low-carbon material containing Mn higher. Here is just a very simple example, many of which are noticed in actual production. When the customer designated to use a certain type of material, and the company did not have this material for a time, or the material is not easy to purchase in the market, you can understand the use of this fastener customers, in line with the mechanical properties of the request Make a written request for replacement material. Some purchasing customers are not very professional fasteners, the choice of materials are not necessarily the best, as we specialized in the production of fasteners manufacturers, customers can give better advice to achieve double benefit. Of course, the fastener material to pay more attention to these, such as the material must be used before the expiration date (I wrote a special article on this area before), the surface rusty material used to make some full-threaded fasteners or For the surface to be worn fasteners, the material center of the organization there are shrinkage of the hole should not be used to make polishing head screws ... ... The ever-changing application of materials, used properly, the water for the chicken soup, improper use, as a result of small Waste, increase costs, large companies may have to lose a lot of money!