Quality-Assured Stainless Steel DIN7991 Hexagon Socket Countersunk Head Cap Screws Hex Socket Flat Head Cap Screw Allen Bolts Csk Alloy Steel

The performance grades of internal hexagonal bolts used for steel structure connection are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and heat treated (quenched and tempered), commonly referred to as high-strength bolts, and the rest are referred to as ordinary bolts. The bolt performance grade label consists of two parts of numbers, representing the nominal tensile strength value and yield strength ratio of the bolt material.