Hexagon bolt connection is a kind of fastener which is widely used in industrial production and life. It is used in transportation tools, airplanes, automobiles, ships, machines used in factories, electronic products used in life and so on. The main reason why the hexagon bolt is selected is that it is easy to disassemble. However, this feature will lead to the automatic loosening of the hexagon bolt in some cases, resulting in the loss of preloading capacity.

In the rapid work of parts, the loosening of hexagon bolt will lead to very serious consequences. If the hexagon bolt of the machine in operation suddenly loosens, the light will cause the whole factory to come to a standstill, and the economy will suffer losses, and the heavy will cause the workers to have potential safety hazards and safety accidents. For another example, in the running aircraft, cars, etc., the loose hexagon bolts will threaten the safety of people's lives.

In our development history, safety accidents caused by a small screw can be said to be everywhere.

Case 1

On June 10, 1990, during the flight of British Airways flight 5390, a windshield in the cockpit suddenly flew off, and the captain's upper body was sucked out of the plane. Fortunately, with the efforts of the vice captain, he landed safely at Southampton airport. The cause of the accident was that the windshield had just been replaced in the cockpit, and 84 of the 90 fixing screws were less than or shorter than the standard.

Case 2

At 18:35 on November 6, 2017, a female worker in a factory in Shenzhen was knocked down by another punch which suddenly collapsed nearby when she was operating the punch. After rescue, she died. The reason was that there was no anchor hexagon bolt installed on the base of the collapsed punch, but only one hexagon bolt was installed on the side, and it was loose during long-term operation. Finally, the center of gravity imbalance led to the collapse.

When the hexagon bolt is impacted or collided, why the tighter hexagon bolt will also loosen? Let's take a look at the working principle of the hexagon bolt first. It mainly uses the inclined plane circular rotation and friction of the object to enter the fastener parts step by step, and the tightness of the thread between the two objects is particularly important.

When the hexagon bolt is vibrated violently and for a long time, under the frequent vibration, the originally tightly occluded thread will produce tiny gap or even deformation, and the working state of the machine is mostly long-time and repetitive movement, when accumulated to a certain extent, it will lead to the loosening of the hexagon bolt. In addition to the loosening caused by severe vibration, the hexagon bolt will be loosened by embedding, gasket creep and thermal expansion, strong impact and so on.

Since the hexagon bolt will be loose for so many reasons, how can we effectively prevent the hexagon bolt from loosening? Here are some relaxation methods.

1. Add flat washer - increase the contact area, reduce the pressure, prevent loosening, but this method of disassembly is frequent, and is only limited to prevent relatively weak screws from loosening, and can not play a strong effect of preventing screws from loosening.

2. Self locking nut is self-locking by friction, which can prevent the relative rotation of nut and hexagon bolt, and play the role of preventing screw from loosening. But it is a high-end product with high cost.

3. Split pin is used to fix the screw, but in the process of mechanical movement, in this way, the pin may be damaged, the screw nut is easy to wear, the screw teeth are broken, the screw and the screw teeth are easy to slide, and the screw anti loosening performance is unstable.

4. Double nut - use tightening force to make double nut achieve anti loosening effect and increase weight. It is only limited to relatively weak looseness and can not play a strong role in preventing looseness. Improper use in practice can not play the role of anti loosening, and the anti loosening performance of screw is unstable.

5. Lockwire is one of the more traditional methods of anti loosing, which is widely used in aircraft related fields. However, in this method, the pin may be damaged, and the scope of use is limited.

6. U-shaped nut changes the shape of the nut, directly destroys the screw body of the nut, indirectly destroys the screw teeth of the hexagon bolt, resulting in the falling off of the hexagon bolt and the instability of the screw anti loosening performance.

7. Lock nut - at present, Aozhan mainly has two kinds: nylon lock nut and all metal lock nut. Nylon lock nut mainly hoops the hexagon bolt through the tension of nylon ring. The essence of metal lock nut is that the embedded steel plate is perpendicular to the nut axis and parallel to the nut end face, and the profile angle and pitch of the last thread are changed by the embedded steel plate, The elasticity of the steel sheet is used to prevent looseness.

The loosening of the nut is very important. In the case of no absolute guarantee that the nut will not loosen, regular maintenance and inspection is the best way to eliminate the hidden danger of safety in time.

Many users can not tell what is different between high-strength nuts and ordinary nuts. In fact, it is easy to distinguish them as long as they know their specifications and other characteristics. The so-called high strength nut is a special bolt with high strength and high fatigue resistance used in special equipment or engineering. Of course, the general high-strength nuts are used with high-strength bolts to achieve better use effect.

We generally see that many bolts with m-heads are ordinary nuts in the market, but not high-strength nuts. On the other hand, the calibration side of hexagon nuts is M30, where M30 indicates the thread specification, that is, the thread diameter is 30mm, grade 10 indicates the performance of bolts, and TZN is the surface treatment method. Other bolts also have their own expression methods, However, the performance grade of bolts with thread shall start with "m":

The performance grades of nuts are divided into 4.8, 5.8, 8.8, 10.9 and 12.9 grades with high strength from small to large. This marking method means that 10 is taken as an example 10 to mark 1/100 of the tensile strength of the bolt, that is, the tensile strength of the bolt must reach 1000MPa, and it may be higher than 1000MPa.

Gb/t3098.1 specifies that the smaller tensile strength of the bolts of this grade must be greater than 1040mpa. The marked yield strength ratio after decimal point, that is, the yield strength of bolt (yield strength / tensile strength) =0.9, namely yield strength = 1000 * 0.9 = 900MPa, the yield strength of the grade bolt must be higher than 900MPa to be considered qualified. Generally, we call the nuts of grade 8.8, 10.9 and 12.9 as high strength nuts.

It should be noted that the specific yield strength values of the three grades of bolts are not given in gb/t3098.1, because 0.8 and 0.9 are the smaller yield strength ratio specified in this grade for high-strength bolts. Since high-strength bolts are used for very important links, there is no spot sale on the market, so it must be reserved to the bolt manufacturer, Therefore, the specific yield strength ratio is generally produced by the buyer by specific values

Hebei Xinli Fastener Manufacturing Co., Ltd. is committed to the production and development of bolt nut fasteners. The products are widely used in the fields of power, steel structure, construction, mining, photovoltaic, machinery, transportation, railway, etc. with fine production technology and strict quality management system, we provide customers with detailed, attentive and reassuring one-stop service.

Anchor bolt, also known as embedded bolt, belongs to a kind of Engineering embedded parts, which is fixed in engineering installation and plays a firm role. That is to say, the concrete components placed during the concrete pouring of the structure are used as the steel bar lap joint of the upper end structure of the wall. In order to facilitate the external construction machinery and equipment basic installation fixed. Now let's talk about the specifications, types and models of anchor embedded bolts?

Anchor bolts are commonly used in 9-shaped, 7-shaped, umbrella shaped, and another is to weld an iron sheet, just like our top support, there is a chassis below, and the bottom is flat, upward reinforcement, welding, and also can be shaped processing, customized processing according to the needs of customers.

Its material is mainly divided into Q235, Q235B, 45 steel and other materials. Mainly used for tower crane base, steel structure, municipal street lamp base embedded.

The coarseness is generally from 14, 16, 18, 20, 22, 25, 28, 32, which can be customized and processed. The project generally requires galvanizing, including hot-dip galvanizing and electro galvanizing.

The function of the anchor bolt is to install (bury) the components in the concealed project in advance. It is the components and accessories placed during the structure pouring, which is used for the lap joint of the masonry superstructure. In order to facilitate the installation and fixation of external engineering equipment foundation.

Hebei Xinli Fastener Co., Ltd. is a professional manufacturer of anchor bolts in Yongnian. Strict material selection, smooth surface, no burr, deep thread, uniform force, no slipping. Customers are welcome to purchase.

Bolt mainly plays the role of connection and fastening, and its quality directly affects the connected parts. In order to prevent the surface wear and corrosion of bolts, most people choose to carry out surface treatment on bolts, and hot galvanizing is a common method. Hot dip galvanized bolts are also called hot dip galvanized bolts. After removing the oil and rust on the bolt surface, they are immerged into the aqueduct containing zinc liquid immediately, and a zinc layer is formed on the bolt surface to prevent direct exposure, oxidation and wear of the bolts.

The surface treatment cost of hot dip galvanized bolt is low, the corrosion resistance is good, and it can keep 15 years without rust during use. The zinc coating thickness of hot dip galvanized bolt is more than 50 microns. The protective film of zinc oxide, zinc hydroxide and alkaline zinc carbonate formed on the surface of zinc layer by atmospheric corrosion can slow down the atmospheric corrosion of zinc layer.

Hot dip galvanized bolts are not only coated with a thick zinc layer, but also formed a zinc iron alloy layer. This plating method not only has the corrosion resistance of electro galvanizing, but also has a strong corrosion resistance which can not be compared with electro galvanizing due to the zinc iron alloy layer. Therefore, this plating method is especially suitable for all kinds of strong acid, alkali fog and other strong corrosion environments.

principle

When zinc is liquid, the hot zinc layer is formed by three steps, and the surface of iron base is dissolved by zinc solution to form zinc iron alloy phase layer. The zinc ions in the alloy layer further diffuse to the substrate to form a zinc iron miscible layer, and the surface of the alloy layer is surrounded by zinc layer.

Performance characteristics:

1. The bolt surface is covered with a thick pure zinc layer, which can avoid the contact between the steel matrix and any corrosive solution, and protect the bolt matrix from corrosion. Generally, a very thin and dense zinc oxide layer is formed on the surface of the zinc layer, which is difficult to dissolve in water and has a protective effect on the hot-dip galvanized bolt matrix. If zinc oxide and other components in the atmosphere form insoluble zinc salt, the anti-corrosion effect is more ideal.

2. It has zinc iron alloy layer and compactness. It shows corrosion resistance in seawater salt spray environment and industrial environment. Due to strong bonding, zinc and iron are mutually soluble and have strong wear resistance.

3. Because zinc has good ductility and its alloy layer adheres firmly to the steel substrate, hot dip galvanizing can be used in various forming processes, such as cold stamping, rolling, drawing and bending, without damaging the coating.

4. After hot-dip galvanizing of steel structure parts, it is equivalent to one annealing treatment, which can effectively improve the mechanical properties of steel matrix, eliminate the stress during steel forming and welding, and is conducive to the turning of steel structure parts.

5. The surface of hot-dip galvanized bolt is bright and beautiful. The pure zinc layer is a plastic zinc layer in the process of hot-dip galvanizing. Its performance is basically close to that of pure zinc and has good ductility.

The difference between stainless steel bolt and carbon steel bolt is that the cost of stainless steel is higher than that of carbon steel, which is more durable, less rusty, more resistant to high and low temperature and corrosion, and has more advantages. The cost of carbon steel is lower. Although it is not as good as stainless steel in some places, it has the advantages of easy smelting and good processing technology.

   carbon steel bolts are generally used in more conventional occasions, such as furniture, building materials, etc., while some industries with special requirements must use stainless steel, especially in the occasions with high safety requirements, as well as some occasions with high exposure, high temperature, low temperature and high corrosion.

Stainless steel bolts are not necessarily corrosion and rust, but stainless steel bolts are better than iron bolts in carrying corrosion and rust. But stainless steel bolts will rust under certain conditions. So stainless steel bolts in what conditions easily lead to rust! What is the cause of rust?

Stainless steel bolts have good characteristics, strong corrosion resistance, high temperature resistance and strong rust resistance. But it will rust in bad environment. For example, stainless steel bolts in very humid conditions, every day the sun, wind and rain. After a long time, there will be some rust. For example, contact with some acid-base chemicals to produce chemical reactions. Cause corrosion and rust. There are also poor stainless steel bolts. For example, SUS201 stainless steel bolts are used in seawater. Due to long-time immersion, SUS201 stainless steel bolts are not suitable for seawater with strong salinity. Cause corrosion and rust. In the use of marine products, it is generally recommended to use stainless steel SUS316 bolts, because 316 stainless steel bolts have more corrosion resistance and better performance.

It can be concluded from the above that stainless steel bolts will corrode and rust under specific conditions. Therefore, this requires the rational use of stainless steel bolts. Stainless steel bolts of different materials are used in different situations. And in different occasions, when using stainless steel bolts, we need to pay special attention to some details, we need to consider more. Try to control the corrosion and rust of stainless steel bolts.

At present, steel structure is widely used in construction, bridge and other projects, wind power tower, transmission tower and other large facilities. The key to the high efficiency construction of steel structure anchorage is the connection performance of anchor bolt, and the assembly of the bolt is mainly by welding and bolt connection. Because of the high technical requirements, high labor intensity, low assembly efficiency and difficult quality assurance for steel structure welding, the bolt connection of steel structure has become the main development direction of field assembly technology of steel structure. The traditional bolt connection between steel structure bolt and anchor bolt is the main form of the link at present.

In order to avoid the location error and large magnitude in the construction of steel structure concrete foundation, our company tested the connection performance of 8.8 steel structure big hexagon bolt and M12, M20 and M24 nested single side high strength bolt of grade 10.9, including the tensile performance of single bolt (Fig. a), shear resistance of single bolt (Fig. b) The tensile shear performance of a single bolt (Fig. C), anti slip performance of bolt group (Fig. d), and the actual pre tension value of bolts and the relaxation after tightening are observed to ensure that the position of steel structure bolts is not affected during the concrete pouring process, the construction accuracy is improved, the number of concrete pouring is reduced and the construction speed is accelerated.