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What are high strength bolts
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【Summary】What is a high strength bolt and what is the difference between it and an ordinary bolt? When we purchase high strength bolts, we will ship bolts with the number "8.8" or "12.9" printed on the head, these are the more commonly used high strength bolt markings, we usually refer to the bolts above 8.8 strength as high strength bolts The difference between high strength bolts and ordinary bolts is mainly in the following areas.
What is a high strength bolt and what is the difference between it and an ordinary bolt? When we purchase high strength bolts, we will ship bolts with the number "8.8" or "12.9" printed on the head, these are the more commonly used high strength bolt markings, we usually refer to the bolts above 8.8 strength as high strength bolts The difference between high strength bolts and ordinary bolts is mainly in the following areas.
First, the difference is the material. The low material level of high strength bolts is 8.8, material 35# steel heat treatment, and then up to 10.9, material is alloy steel series. The ordinary bolt material level is only 4.8, the material is usually produced using Q235, and does not require heat treatment to temper, so the strength is low, but the corresponding cost will also be low.
Second, the difference in production process. Although the bolt production mode is the same, but the high strength bolt material is harder, so the requirements of the equipment to be high, the accuracy of the mold and damage resistance and are much higher than ordinary bolts.
Third, the surface treatment. After the production of ordinary bolts, because there is no heat treatment, so a simple cleaning is a finished product, while the production of high-strength bolts need heat treatment after completion, the surface will form some spots, so the later also need to surface oxidation blackening.
In order to differentiate the product, the bolt will be marked with a corresponding number on the head to indicate its level, such as "8.8" printed on the head of the bolt, the first is to indicate that its level is 8.8 grade, the material is medium carbon steel, in fact, this 8.8 grade high strength bolts are commonly used, the following table is a standard 8.8 grade high strength bolts The table below shows the test data of a standard grade 8.8 high-strength bolt, the sample size of which is M12*40 hexagonal bolts.
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Introduction to bolt strength classes
Strength grades are classified according to mechanical properties. According to the relevant standards, the bolt performance grade is divided into 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and more than 10 grades, of which 8.8 and above bolts made of low-carbon alloy steel or medium carbon steel and heat treatment (quenching, tempering), commonly known as high-strength bolts, the rest are commonly known as ordinary bolts. The bolt performance grade number has two parts consisting of numbers, which indicate the nominal tensile strength value of the bolt material and the flexural strength ratio. For example.
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The bolt performance grade is composed of two numerical parts, which indicate the nominal tensile strength value and the flexural strength ratio of the bolt material.
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Generally we use most of the fasteners belong to the type of general-purpose parts, its standard type is still quite high, the common fastener parts are the following 12 kinds:
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