Basic knowledge of hexagonal bolts
Hexagonal bolts actually refer to fasteners consisting of a head and a screw. Bolts are mainly divided into iron bolts and stainless steel bolts according to the material. Iron is divided into grades, and the common grades are 4.8, 8.8 and 12.9. Stainless steel is made of stainless steel SUS201, SUS304 and SUS316 bolts.
A complete set of hexagonal bolts consists of bolt heads, nuts and flat washers
Hexagonal head bolts are hexagonal head bolts (partial thread)-c hexagonal head bolts (full thread)-c grade, also known as hexagonal head bolts (coarse) hexagonal head bolts, black iron screws. Commonly used standards are mainly: SH3404, HG20613, HG20634, etc.
Hexagonal head bolts (hexagonal bolts for short) are composed of a head and a threaded rod (<external thread studs), and the threaded rod is equipped with a nut for fastening two parts with through holes. This type of connection structure is called a bolt connection. If the nut and bolt are rotated, the two parts can be separated, so the bolt connection is a detachable connection.
The comprehensive performance grades of bolts used for steel structure connections are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are subjected to corresponding heat treatment (quenching and tempering). They are generally called high-strength bolts, and the rest are usually called ordinary bolts. The bolt performance grade mark consists of two parts of numbers, representing the nominal tensile strength value and yield rate of the bolt material. The following is an example.
The meaning of bolts with performance grade 4.6 is:
The nominal tensile strength of the bolt material reaches 400 MPa;
2. The yield strength ratio of the bolt material is 0.6;
3. The nominal yield strength of the bolt material can reach 400 × 0.6 = 240MPa level
For high-strength bolts with performance grade 10.9, the material after heat treatment reaches:
1. The nominal tensile strength of the bolt material reaches 1000MPa;
2. The yield strength ratio of the bolt material is 0.9;
The nominal yield strength of the bolt material reaches 1000 × 0.9 = 900MPa level
The meaning of different grades of bolt performance is an internationally recognized standard. Bolts with the same product performance evaluation grade have the same performance regardless of their materials and sources, and can only select the safety performance index level for design.
