Cylinder head hexagon socket screws, also known as hexagon socket bolts, cup head screws and hexagon socket screws, have different names, but they have the same meaning. Commonly used hexagon socket screws also have 4.8, 8.8, 10.9 and 12.9. Also called hexagon socket bolt, the head is hexagonal and cylindrical. According to the material, there are stainless steel and iron.
Iron is classified according to the strength grade of hexagon socket bolts. There are 4.8 grade hexagon socket screws, 8.8 grade hexagon socket screws, 10.9 grade hexagon socket screws and 12.9 grade hexagon socket screws. Hexagon socket bolts of grade 8.8-12.9 are called high-strength hexagon socket bolts.
In the process of steel structure construction, high-strength hexagon socket bolts are often used. What is a high-strength hexagon socket bolt? It should have high-strength friction and pretension. However, for convenience, people often omit “friction” and “pretension”. There are two misunderstandings:
Misunderstanding 1: Bolts with a material grade exceeding 8.8 are equivalent to “high strength”
Compared with ordinary bolts, the core of high-strength hexagon socket bolts is not the strength of the material itself, but the form of stress. The so-called stress form is the shear resistance when preload and static friction are applied.
The high strength mentioned in the bolt standards of the United States and the United Kingdom is only 8.8 and 10.9, while ordinary bolts have not only 4.6, 5.6, but also 8.8, 10.9, etc., so you cannot rely on materials to determine whether it is a high-strength hexagon socket bolt.
Misunderstanding 2: The bearing capacity of high-strength hexagon socket bolts is higher than that of ordinary bolts
The strength of high-strength hexagon socket bolts is not determined by its carrying capacity, but by high rigidity, high safety performance and strong destructive resistance.
High-strength hexagon socket bolts mainly have the characteristics of small elasto-plastic deformation in terms of high strength and high joint stiffness. Therefore, under a certain combined load, the use of high-strength bolts cannot reduce the number of bolts, but the deformation is small and the stiffness is large, so it is very suitable for occasions that require high stiffness.
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