There are three main materials for grade 12.9 bolts (12.9 wedge anchor, 12.9 through bolt): carbon steel wedge anchor, stainless steel wedge anchor, and copper.
(1) Carbon steel (such as carbon steel Wedge Anchor Bolts). We distinguish low carbon steel, medium carbon steel, high carbon steel and alloy steel based on the carbon content in the carbon steel material.
1. Low carbon steel with C% <0.25% is usually called A3 steel in China. Abroad, they are basically called 1008, 1015, 1018, 1022, etc.
2. Medium carbon steel 0.25%
Alloy steel: Add alloy elements to ordinary carbon steel to increase some special properties of the steel: such as 35, 40 chromium silver, SCM435
3. 10B38. Fangsheng screws mainly use SCM435 chromium-platinum alloy steel, whose main components are C, Si, Mn, P, S, Cr, and Mo.
(2) Stainless steel (such as stainless steel threaded rods). Performance grade: 45, 50, 60, 70, 80, mainly austenite (18%Cr, 8%Ni), good heat resistance
Good corrosion resistance and good weldability. A1, A2, A4 martensite and 13% Cr have poor corrosion resistance, high strength and good wear resistance. C1,C
2. C4 ferritic stainless steel. 18%Cr has better forgeability and stronger corrosion resistance than martensite. At present, imported materials on the market are mainly made in Japan.
Taste. According to the level, it is mainly divided into SUS302, SUS304 and SUS316.
3) Copper. Commonly used materials are brass…zinc-copper alloy. H62, H65, and H68 copper are mainly used as standard parts in the market.
12.9 The influence of various elements in bolt materials on the properties of steel:
1. Carbon (C): Improves the strength of steel parts, especially its heat treatment properties, but as the carbon content increases, the plasticity and toughness decrease
And it will affect the cold welding performance and welding performance of steel parts.
2. Manganese (Mn): Improves the strength of steel parts and improves hardenability to a certain extent. That is to say, the intensity of hard penetration is increased during fire production.
It can also improve surface quality, but too much manganese is detrimental to ductility and weldability. And it will affect the control of coating during electroplating.
3. Nickel (Ni): Improves the strength of steel parts, improves toughness at low temperatures, improves resistance to atmospheric corrosion, and ensures stable heat treatment
The treatment effect is to reduce the effect of hydrogen embrittlement.
4. Chromium (Cr): It can improve hardenability, improve wear resistance, improve corrosion resistance, and help maintain strength at high temperatures.
5. (Mo): It can help control productivity, reduce the sensitivity of steel to temper brittleness, and play a significant role in improving the tensile strength at high temperatures.
Big impact.
6. Boron (B): It can improve the hardenability and help make low carbon steel produce the expected response to heat treatment.
7. Alum (V): refines austenite grains and improves toughness
8. Silicon (Si): Ensures the strength of steel parts. Appropriate content can improve the plasticity and toughness of steel parts.
35CrMo steel is an excellent material for engine grade 129 connecting rod bolts and can meet the mechanical property requirements of grade 12.9 bolt materials.
It is a feasible process to adopt nitrogen protection heat treatment for 12.9 grade connecting rod bolts, thinning and cooling of the rod part, and thread rolling after heat treatment, and can be produced
Produce high-quality, high-precision bolts
The performance grades of bolts used for steel structure connections 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, and 12.9.
Among them, bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and have been heat treated (quenched and tempered), commonly known as high strength bolts.
The rest are commonly called ordinary bolts. The bolt performance grade label consists of two parts of numbers, which represent the nominal tensile strength value of the bolt material and the
Yield-strength ratio. For example, a bolt with performance level 4.6 means:
1. The nominal tensile strength of the bolt material reaches 400MPa;
The yield strength ratio of the bolt material is 0.6:
2. The nominal yield strength of the bolt material reaches 400×0.6=240MPa performance level 10.9 high-strength bolts. The material has been heated
3. After processing, it can achieve:
1. The bolt material has a nominal tensile strength of 1000MPa.
2. The yield-to-strength ratio of the bolt material is 0.9:
3. The nominal yield strength of the bolt material reaches 1000×0.9=900MPa level
10.9 grade screws require medium carbon alloy steel quenching and tempering heat treatment, such as 35CRMO 40CR and other materials
The bolt grade inspection index is the tensile strength of the bolt. It doesn’t matter what the material is, what’s important is mechanical indicators such as tensile strength
Post time: Apr-16-2024