Bolt aging period

The bolt limitation period mainly refers to is the high strength bolt magnitude 8.8 or greater, because of the high strength bolt material in the process of rolling, will have the internal stress of some detection not to come out, it is mainly reflected in its carbon content is not uniform distribution in every corner of the material,

material after cold pier shape into a standard bolt placed a period of time, the role of internal stress, fracture appears in a certain period of time, so the bolt in the production is completed, need to natural cooling, in a well ventilated environment, as far as possible,

reduce the internal stress of bolt disappear naturally, disappearing from internal stress to stress in the last time,It’s called bolt aging.

If the aging period of the bolt is up, but the internal stress still exists, then the bolt will fracture in the use process.The raw material itself which is prone to internal stress is also unqualified. Because of its uneven distribution of carbon content, the surface of the material will be uneven or even bent and deformed.

The finish of the bolts produced by such materials also needs to be paid attention to, and many tolerances may not be guaranteed.

The difference between high strength bolt and common bolt

High strength bolts can withstand greater loads than ordinary bolts of the same specification.Ordinary bolts are made of Q235 (A3).The material of high strength bolts 35 # steel or other quality materials is heat treated after manufacture to increase their strength.So what’s the difference between high strength bolts and normal bolts?

From a raw material point of view: high strength bolts are made of high strength materials.The screws, nuts and washers of high strength bolts are made of high strength steel.Commonly used are 45 # steel, 40B steel, 20MnTiB steel, 35CrMoA and so on.Common bolts are usually made of Q235 (equivalent to A3 formerly) steel.

From the point of view of strength level: high strength bolts are increasingly used.Two intensity scales are commonly used, 8.8S and 10.9S, with the most common being 10.9.Ordinary bolts should have lower strength grades, usually 4.4, 4.8, 5.6, and 8.8.