Lag Bolt Anchor, Toggle Bolt Wall Anchor, Lag Bolt Concrete Anchor

In our daily use, if the bolts are made of carbon steel, there are two situations:

One is high-strength bolt and the other is ordinary bolt. In case of stainless steel bolts, there are two cases: 304 stainless steel bolts and 316 stainless steel bolts. Among these two differences, stainless steel bolts are easy to understand, because 304 and 316 have made a clear boundary. These two different stainless steel materials produce bolt products.

However, when we purchase carbon steel bolts, many users are used to calling the bolts made of carbon steel as iron screws. In fact, this statement is completely unscientific. From the point of view of materials, there are two versions of high-strength bolts and ordinary bolts. What are the differences between high-strength bolts and ordinary bolts?

What is a high-strength bolt?

Carbon steel materials are divided into high-strength materials and ordinary materials. Carbon steel bolts produced with high-strength materials are called high-strength bolts. For example, we use 45 steel to produce stud bolts, and we use 35 steel to produce inner hexagon bolts and outer hexagon bolts. After forming these bolts, there will be a heat treatment process. After completion, the grade of the bolts will reach grade 8.8. Although they are also carbon steel materials, they are called high-strength bolts due to the improvement of grade performance. Bolts made of high carbon steel are also called high-strength bolts, such as grade 10.9 hex bolts made of 40como alloy steel, and grade 12.9 bolts made of 35CrMo alloy steel. These grades are one level higher than grade 8.8, so they should be called high-strength bolts.

So what is a common bolt?

Bolts made of ordinary carbon steel are called ordinary bolts. For example, we use grade 4.8 external hexagon bolts made of q235s materials, such as grade 4 hexagon nuts made of A3 steel materials. After the production of these materials, they only need to be cleaned or electro galvanized. They do not need heat treatment, so they are called ordinary bolts.

From the above, we can find a rule that the so-called high-strength bolts are the bolts with mechanical properties of grade 8.8 or above and need heat treatment, which are called high-strength bolts.

Bolts or nuts below grade 8.8 are called ordinary bolts or ordinary bolts. Basically, they are all grade 4.8 and are not subject to heat treatment.

Bolts made of high-strength steel or requiring large pre tightening force can be called high-strength bolts. High strength bolts are mostly used to connect bridges, rails, high-voltage and ultra-high voltage equipment. The fracture of this kind of bolt is brittle fracture. In order to ensure the sealing of the vessel, the high-strength bolts used in ultra-high pressure equipment need to be prestressed.

Quality and application of high-strength bolts

The advanced manufacturing represented by large aircraft, large power generation equipment, automobiles, high-speed trains, large ships and large complete sets of equipment will enter an important development direction. Thus, fasteners will enter an important stage of development. High strength bolts are used for the connection of important machinery. Repeated disassembly and assembly or various installation torque methods require high strength bolts. Therefore, the quality of its surface condition and thread accuracy will directly affect the service life and safety of the host. In order to improve the friction coefficient and avoid rusting, seizing or seizing during use, the technical requirements stipulate that the surface should be treated with nickel phosphorus plating. The coating thickness shall be within the range of 0.02 ~ 0.03mm, and the coating shall be uniform, dense and free of pinholes. Bolt material: 18Cr2Ni4W, 25Cr2MoV steel; Bolt specification: M27 ～ M48. Because this kind of steel is easy to form a passive film on the surface, which will make the bolt unable to obtain a chemical nickel phosphorus layer with good adhesion, special pretreatment measures must be taken to remove the film first, and measures should be taken to prevent its regeneration, so as to ensure a good adhesion between the plated coating and the substrate. At the same time, due to the large geometric size of the bolt, it is difficult for the nickel phosphorus plating treatment and the quality inspection of the process.

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