Teach you to identify the grade and material of the bolt at a glance

Bolts are common mechanical parts and are often used in many places. They are a type of fastener composed of two parts: a head and a screw. It needs to be used in conjunction with a nut. It is mainly used to fasten and connect two through holes. Components. Maybe you don't know much about the grade and material of bolts. This article will introduce you to the knowledge of bolt material and grade, in the hope that more people will learn to recognize these small properties of bolts.

Bolt

What are the grades and materials of bolts?

The bolt grade refers to the bolt grades of 4.8, 8.8, 10.9 and so on.

Material refers to what material the bolt is made of, such as 45# steel, 35CrMo steel, and 304 stainless steel.

There is a certain relationship between the grade and material of bolts. Low-carbon steel can only produce low-strength bolts, carbon steel can produce medium-strength bolts, and alloy steel can produce high-strength bolts. Some bolt grades stipulate the corresponding chemical composition and mechanical properties, which also stipulate the dead material.

Here is a list of what materials the bolts can be of the common grades. The 4.8 grade can be made of low carbon steel materials such as A3, Q235, and Q195. 5.8 Grade All materials above Q235 are available, no heat treatment is required. 8.8 level thread diameter below 16MM, 35# quenched and tempered heat treatment, 16mm above, 45# and low carbon alloy steel quenched and tempered. 10.9 grade medium carbon alloy steel quenched and tempered heat treatment 35CRMO 40CR etc.

Can high-strength bolts and ordinary bolts be distinguished by material?

Generally divided according to intensity level. (Guide: The selection of fasteners is principled)

The performance grades of bolts for steel structure connection are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, among which the bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel After heat treatment (quenching and tempering), they are generally called high-strength bolts, and the rest are generally called ordinary bolts. The bolt performance grade label consists of two parts of numbers, which respectively indicate the nominal tensile strength value and the yield ratio of the bolt material.

For example, a bolt with a performance level of 8.8, its meaning is:

1. The nominal tensile strength of the bolt material reaches 800MPa;

2, the yield ratio of the bolt material is 0.8;

3. The nominal yield strength of the bolt material is 8000.8u003d640MPa. The most commonly used high-strength bolts are 8.8 and 10.9, and the most commonly used ordinary bolt is 4.8.

So, how to distinguish whether the bolts on hand are high-strength bolts in real life? If the bolt head is marked with 4.8 or 8.8, it can be directly determined from this whether it is a high-strength bolt. Secondly, it can be divided into color, if it is black, it can be estimated that it is a high-strength screw. Furthermore, the sound of torture can also be divided, the sound of high-strength bolts is relatively clear. It can also be polished with a grinder and judged by the sparks. In short, there are many ways to judge whether a bolt is high-strength.

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