DIN912 HEX SOCKET CUP HEAD SCREW GRADE 12.9 BLACK OXIDE

The hexagon socket head bolts are classified according to the hardness, tensile strength, yield strength, etc. of the screw wire, that is, the level of the hexagon socket head bolts, and what level the hexagon socket head bolts are. Different product materials are required to have different grades of hexagon socket head cap bolts corresponding to them. All hexagon socket head cap bolts have the following grades:

Hexagon socket head bolts are divided into ordinary and high-strength according to the strength of the grade. Ordinary hexagon socket head bolts refer to grade 4.8, and high-strength socket head bolts refer to grades 8.8 and above, including grades 10.9 and 12.9. Grade 12.9 hexagon socket head cap screws generally refer to knurled, natural black hexagon socket head cap screws with oil.

The performance grades of hexagon socket head cap 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, etc. Among them, 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 represent the nominal tensile strength value and yield ratio of the bolt material respectively.