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The Difference Between High Strength Bolt And Normal Bolt
Dec 05, 2017

In the tunnel construction, there is a kind of equipment which is used to start and excavate the machine called shield machine, which has the functions of cutting soil body, transporting dirt and assembling tunnel lining, etc.However, when the shield tunneling is lined with a few pieces of pipe, there is a screw connecting fastening and assembling the pipe that forms the garden pillar, which is a cylindrical wall.Excavation can effectively control the ground settlement, to reduce the influence of the ground buildings and underwater excavation shall not affect the water traffic characteristics of each segment together, form the pipeline, the design into a straight line or a curved tighten fittings, bolt is lining segments.The pipe bolts are divided into ring and longitudinal.Some designs are consistent with the vertical and vertical specifications.

There are two specifications, even two levels of strength, in the design of central and vertical.

In general, the length of the ring bolt is longer than the longitudinal pipe bolts.

Type of pipe bolts:

1.Double head straight pipe bolts

2.Double-head curved pipe bolts

3.Hexagon head arc tube bolt

4.Hexagon head circular screw thread pipe bolts

5.Hexagon flange facing round screw thread pipe bolts

6.Non-standard pipe bolts

High strength bolts are one of the most representative products in special bolts. It has a very high strength and long service life compared with ordinary bolts.

Normally, high strength bolts are enhanced by quenching and tempering treatment, which is called tempering martensite.Once the tensile strength of this tempered martensitic steel is more than 1200MPa, due to the effect of trace hydrogen, the original grain will be embrittled, and the phenomenon of delayed fracture in the process becomes obvious.

Differences between high strength bolt and normal bolts:High strength bolt pipe bolts are made of high strength material.The bolts, nuts and gaskets of high strength bolts are made of high strength steel and are commonly used in 45 steel, 40 boron steel and 20 manganese titanium boron steel.Normal bolts are usually made of Q235 steel.

From the strength level:High strength bolts are widely used.The two intensity levels of 8.8s and 10.9s were commonly used, while 10.9 were in the majority.The general bolt strength grade is low, generally 4.4, 4.8, 5.6 and 8.8.

From the stress characteristics:

High strength bolts apply pretension and resist force through resistance.Generally by bolt rod bolt coupling shear and pressure on the hole wall to transfer shear, tighten the nut when the attack method is small, its influence can be neglected, and high strength bolts in addition to its high strength of materials, put great pretension bolt back, make the connection between components attack extrusion, which has a great resistance force perpendicular to the direction of the screw, and strong, resistance to sliding coefficient and steel varieties are directly affect the bearing capacity of high strength bolt.

According to the stress characteristics of the pressure type and the resistance type. The calculation methods are different.High strength bolt minimum specification M12, commonly M16~ M30, super standard bolt function is unstable, should be used carefully in planning.