The practical application is indeed such, a small screw, its role is not to be ignored.

Especially for the installation and use of some high-strength bolts, there are strict requirements for the tensile strength of bolts.

When we calculate the tensile performance level of bolts, we should multiply the cross-sectional area of bolts by its original design value, and then judge whether it is within the allowable range.

If large equipment is to be secured, high-strength bolts and a cement foundation must be poured into an integral part to prevent the heavy machinery from working to produce strong vibration.

• 

• 

Installation requirements

When installing, it is necessary to check whether the specified thread size of the high strength bolt meets the requirements, and whether the tail chamfer of the thread and the return groove of the connecting part of the thread head are qualified.

Especially for the traditional high strength water stop bolt, after the installation is completed, there is no way to be removed like ordinary bolts. The high strength water stop screw is all a one-time connection. Once the installation is completed, it can not be removed.

In the field of fasteners, the vast majority of threads are tightened from left to right, which is also the standard thread we commonly use, also known as the right thread.

If it is left-handed screw thread, the square can be reversed, because most people belong to the right hand work, left-handed will actually only a few, so the thread design of high strength bolts are adopted right-handed screw thread scheme.

Some high strength stud two ends have thread, in some special use environment, need one head is right thread, and the other head is left thread, as long as the axis in the middle of the rotation to rotate in one direction, can lock the thread of the two heads at the same time, is not very magical?

The pedal of the bicycle we ride is left thread, this is because the direction of our foot pedal is to the right, and the thread is left, it will only be more and more tight, human wisdom is not very magical.

Important process

Another important process for high strength bolts is heat treatment. Because the material of high strength bolt is relatively hard, the material should be annealed before cold pier forming.

So after the reproduction, heat treatment should be carried out to adjust the performance of high strength bolt to the design requirements.

Whether the heat treatment meets the requirements is critical to the final quality of high-strength bolts. The heat treatment is a seemingly simple job.

But must be able to each post staff clear operation responsibility, improve the operator’s awareness of heat treatment knowledge.

High strength bolts will expand in heat and contract in cold during heat treatment, so heat treatment workers must have a testing tool in hand to monitor the changes of bolts at any time to prevent quality problems.

After heat treatment, the surface color of high-strength bolts is a kind of soil color, black or gray. After the bolts are transported and checked, it is likely that bolts of different specifications will be mixed together, so the design of the furnace used for heat treatment of high-strength bolts should also be scientific.

Carbon steel bolts after heat treatment, will be divided into 4.8, 8.8, 10.9 and 12.9 classes, of which 4.8 is the common bolt, 8.8 is the medium carbon steel bolt.

Only class 10.9 and 12.9 bolts are considered high strength bolts, and of course there are class 14.9 high strength bolts, but we rarely use these. The hardness parameters of each bolt level are also different.

Let’s take the 10.9 grade bolt as an example. The nominal tensile strength of the bolt material after heat treatment is 1000MPa, and the tensile strength ratio of the bolt material is 0.9.

The nominal yield strength of the bolt material is 1000×0.9= 900Mpa level