1. Name
Cylindrical head hexagon socket head screws, also referred to as hexagon socket head bolts, cup head screws, and hexagon socket head screws, have different names, but they mean the same thing. Commonly used hexagon socket head screws include grade 4.8, grade 8.8, grade 10.9, and grade 12.9. Also called hexagon socket screws, also called hexagon socket bolts. The head is either a hexagonal head or a cylindrical head.

2.Material
Carbon steel and stainless steel.
Carbon steel hex socket head screws have the characteristics of high strength and low cost, and are an economical and practical fastener. It is used in some places, such as low-load test pieces, daily necessities, furniture, building wood structures, bicycles, motorcycles, etc.
Stainless steel has the characteristics of corrosion resistance, high temperature resistance and good toughness, and is often used to make high-demand screws and nuts. Stainless steel hex socket screws are widely used in equipment connection in pharmaceutical, food and other industries, as well as in chemical equipment, electronic equipment and other fields. Because of its strong anti-oxidation and anti-corrosion capabilities, it is not easily oxidized and rusted by the environment, so it can adapt to harsh environments.

3. Specifications and types

The national standard number of hexagonal socket head screws is GB70-1985. There are many specifications and sizes. The commonly used specifications and standards are 3*8, 3*10, 3*12, 3*16, 3*20, 3*25, 3 *30, 3*45, 4*8, 4*10, 4*12, 4*16, 4*20, 4*25, 4*30, 4*35, 4*45, 5*10, 5*12 , 5*16, 5*20, 5*25, 6*12, 6*14, 6*16, 6*25, 8*14, 8*16, 8*20, 8*25, 8*30, 8 *35, 8*40, etc.

4.Hardness
Hexagon socket bolts are classified according to the hardness of the screw wire, tensile strength, yield strength, etc. Different product materials require different grades of hexagon socket bolts to correspond to them. All hexagon socket bolts have the following grades:
Hexagon socket head bolts are divided into ordinary and high-strength ones according to their strength levels. Ordinary hexagon socket bolts refer to grade 4.8, and high-strength hexagon socket bolts refer to grade 8.8 or above, including grade 10.9 and 12.9. Class 12.9 hexagon socket head bolts generally refer to knurled, oil-stained black hex socket head cup head screws.
The performance grades of hexagon socket 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. 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 the yield strength ratio of the bolt material.
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