The bolt is one of the most common metric fasteners. Its simple design allows you to connect parts with different technical and operational characteristics. There are several classifications of bolted hardware, but in terms of reliability of fastening, the most significant is the separation according to the degree of resistance to physical loads. Functional stability and durability of the target structure depend on this property. The most attractive in this regard are high-strength bolts used in motorcycles, industrial units and critical building structures.
Product Overview
The base is formed by a metal rod with a thread, as well as a head, designed to capture a suitable size with a key. More often use elements with hexagonal heads, which are considered the most reliable. The material used is alloyed carbon steel that can withstand heavy loads on the structure. However, there are other brands of alloys used. These and other requirements for the manufacture of this hardware are regulated by GOST 52644. High-strength bolts must also correspond to a certain reliability class. For entry-level products, for example, the marking is 8.8 in terms of strength. This is a common type of fastener made of hardened steel. In especially loaded structures, it is assumed to use bolts, the strength class of which corresponds to the markings 10.9 and 12.9. A distinctive feature of this hardware is the ability not only to withstand a constant static load, but also multiple cycles of installation and dismantling operations.
Operational features
Compared to conventional fasteners, high-strength products can be used not only under conditions of increased mechanical stress, but also under thermal and other negative influence factors. Primary properties are fluidity and tensile strength. The balanced distribution of high-strength bolts along the line of sheathing or connection allows you to evenly distribute the load, thereby ensuring the reliability of the structure. During operation, the master calculates the nominal temporary resistance, which is indicated in N / mm 2 . The minimum tensile strength will depend on the number indicated on the marking. For example, 10x100 will result in 1000 N / mm 2 . Also, the features of this type of hardware include resistance to the destruction of the structure under the influence of moisture, that is, protection against corrosion damage.
Hardware Dimensions
To indicate the parameters of the product, a special marking is used - M16-48. In accordance with it, elements can have the following dimensions:
- Length: 40-300 mm.
- Diameter: 16-48 mm.
- Thread length: 6-18 mm.
- Head height: 8-24 mm.
- Head diameter: 19-53 mm.
- Coating thickness: 25-40 microns.
It is important to emphasize that all of these dimensions are interconnected. That is, for example, at a certain length, restrictions are imposed on the thickness of the rod and the thread pitch. This is due to the fact that even the controlled tension of high-strength bolts does not always allow moderate force to be applied to the hardware, protecting it from breakdowns and deformations.
Connection Requirements
Installation operations are carried out only after a thorough analysis of the technical operating conditions of the target structure or operating mechanism. In particular, when choosing a hardware based on dimensional characteristics, the twisting coefficient, optimal mechanical properties and parameters of auxiliary fixing accessories are preliminarily calculated. Do not forget that high-strength bolts during installation form a bunch with nuts and washers, which must correspond to the bearing rod in geometric parameters.
During installation, the following operations are performed:
- Preparation of hardware with a check of its condition.
- Preparation of the working surface (cleaning, degreasing).
- Connection on high-strength bolts using a special tool. Allowed to use hand wrenches or wrenches with optimal torque.
- Control of the operation performed. The reliability of the fasteners, its geometric correctness and tension force are evaluated.
- Sealing, sealing and priming joints.
High Strength Bolt Applications
This type of fastener is mainly used in heavy industry and construction. In production, such bolts are used in the assembly of cars, engineering units, specialized equipment, etc. As for the construction industry, in accordance with GOST, high-strength bolts are recommended for use in buildings and structures that take on temporary, permanent and special load. For example, metalware can connect parts of structures that during operation will be subjected to seismic, explosive and vibrational vibrations. There are no strict restrictions on usage environments. High-strength alloy is successfully used in temperatures up to -60 ยฐ C when exposed to aggressive chemicals.
Conclusion
An optimal connection can be created only if the appropriate fasteners are used. The design of high-strength hardware certainly improves the quality of the docking unit, but for this it is necessary to choose the type of thread, the shape of the head, size, etc. For example, as noted by the same GOST, high-strength bolts can have full and incomplete threads. In the first case, part of the rod receives a โcleanโ surface, and in the second, corrugated along its entire length. Therefore, the intended purpose of such bolts will be different. Pay attention to the methods of applying protective coatings. The main enemy of metal fastening is rust and in order to protect the structure from its spread as much as possible, it is necessary to initially choose products that have undergone galvanic treatment or anti-corrosion galvanizing. This mainly applies to use in the exterior surfaces of building structures and vehicles.