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Carbon Steel / Alloy Steel ASTM A325 Hex Head Bolts Black Structural Allen Bolt

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Carbon Steel / Alloy Steel ASTM A325 Hex Head Bolts Black Structural Allen Bolt

Brand Name : HNF
Model Number : 1/2"--32"
Certification : ISO9001:2008
Place of Origin : jiaxing
MOQ : 900kgs
Price : Negotiation
Payment Terms : L/C, T/T, Western Union, MoneyGram
Supply Ability : 500TON / per month
Delivery Time : 15-25 DAYS
Packaging Details : Cartons+Pallets
Name : ASTM A325 High strength Hex head bolts
Size : 1/2 -32
Material : high strength carbon steel
Standard : ASTM A325
sample : free
Production Process : Hot forging
Class : A325
Surface : Black oxide
Head : Hex head cup
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Carbon steel and Alloy steel ASTM A325 Black Surface Hex Head Bolts Allen bolt High Strength


Hexagonal bolts, also known as hexagonal head screws, hexagon head bolts, hexagon head screws, hexagon screws or mechanical bolts, are a common choice in construction and maintenance.Hexagon head bolts, commonly known as hexagon head cap screws, are bolts with hexagonal or six-sided heads.Hexagon bolts have six heads, which is the industry standard for forged head bolts.A common feature of hexagonal head screws is the surface of the gasket directly below the head to produce a better seal.A hexagon head screw bolt is actually produced within a tighter tolerance range and can be used anywhere with a hexagon head bolt.

Several concepts about high strength bolts 1. According to the specification of bolt performance class 8.8 or above, called high strength bolt. The current national standard only listed to M39, for large size specifications. In particular, the length of high-strength bolts more than 10, 15 times, the domestic production is still short.

Distinction between high strength bolts and ordinary bolts:

High-strength bolts are larger than ordinary bolts of the same specification.

The material for ordinary bolts is made of Q 235 (A 3).

High-strength bolt material 3 steel or other high-quality materials, made after heat treatment, improve the strength.

The difference between the two is the difference in the strength of the material.

From the perspective of raw materials:

The high strength bolt is made of high strength material. The screw, nut and gasket of high strength bolt are made of high strength steel. 35CrMoA, etc. Common bolts are made of Q235 steel (equivalent to A 3 in the past).

From the strength grade point of view: high strength bolts, increasingly widely used. Commonly used 8.8s and 10.9s two strength grades, in which 10.9 grade is the majority, ordinary bolt strength grade should be low, generally 4.4 grade. Grade 4.8, grade 5.6 and grade 8.8.

From the point of view of stress characteristics: high strength bolts apply pretension force and transfer external force by friction. Ordinary bolts connect by bolt shear resistance and hole wall pressure to transfer shear force, and the pre-tension force is very small when the nut is tightened. In addition to the high strength of the material, the high strength bolt exerts a large pretension force, which causes the extrusion force between the connecting members and makes the friction force perpendicular to the screw direction very large. The bearing capacity of high-strength bolts is directly affected by pretension, slip resistance and steel type.

According to the stress characteristics, the bearing type and the friction type are divided. The two calculation methods are different. The minimum specification M12 of high strength bolt, commonly used M16 / M30, and the unstable performance of super large size bolt should be used carefully in the design.


ItemBlack Structural Bolt Heavy Hex Head Bolts
TypeFlange Bolt,Carriage bolt, Guardrail bolt,Socket Bolt,T bolt,Square bolt and Wing bolt
GradeGr4.8 Gr8.8 Gr2 Gr5 A325 A490
Standard:DIN933,DIN931DIN6923.DIN603 DIN912 DIN444,DIN315,ASME B18.2.3,ASME B18.5
MaterialStainless Steel: SS201 SS304/SS304L SS316/SS316L SS904L
Steel Grade: Gr.4.8,5.8,8.8,10.9,12.9; SAE: Gr.2,5,8;
Finishing:Zinc(Yellow,White,Blue,Black,Colour),Hop Dip Galvanized(HDG),Black Oxide,Geomet,Dacroment,Nickel plated,Zinc-Nickel plated,Telfon
Production TechniqueCold forging, Hot forming, Machining, Heat treatment, Staming, etc
Stock ProductsStainless steel: DIN6923 DIN912 DIN603 DIN315,DIN933,DIN931,DIN934


Friction type high strength bolt: suitable for steel frame structure beam, column connection, solid web beam connection, heavy crane beam connection of industrial workshop, brake system and important structure under dynamic load.

High strength Bolts: shear connections in structures that allow for a small amount of sliding or are subjected to indirect dynamic loads.

Tensile high strength bolts: when the bolts are pulled, the fatigue strength is low. Under dynamic load, its bearing capacity is not more than 0.6P (P is the allowable axial force of bolts). Therefore, it is only suitable for static loading, such as flange butt joint, T type joint and so on.



High strength bolt connection has the advantages of simple construction, good mechanical performance, removable, fatigue, can use almost permanent. And under dynamic loads without loosening and other advantages, is a promising method of connection, and is currently the most popular building connection method of high strength bolts with special. Wrench nuttightening, bolt pretension to produce huge and controlled, the nut and the plate, according to the interaction of force principle has the same size of the pre pressure connector.

Under the action of pre-pressure, there will be a large friction along the surface of the connecting piece. Obviously, as long as the axial force is smaller than this friction force, the member will not slip, which is the principle of high-strength bolt connection. At the same time, this is the advantage of high-strength bolts.

The high strength bolt connection depends on the friction between the contact surfaces to prevent the joint from sliding, so as to make the contact surface have enough friction. It is necessary to increase the clamping force of the member and the friction coefficient of the contact surface of the component. This point has been fully considered in the design of the cash bolt at the beginning of the design. The clamping force between the components is realized by applying the pretension force to the bolt. So bolts must be made of high-strength steel, which is known as high-strength bolt connections.

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