Introduction to Flange Bolts and Nuts

Introduction to Flange Bolts and Nuts

What are flange bolts and nuts? 

The flange bolts and nuts are the type of fastener mainly composed of a hexagonal head, a flange plate (the gasket below the hexagon is fixed together with the hexagon), and a screw (a cylindrical body with external threads). It needs to be matched with a nut and used to tighten and connect two parts with through holes.

This type of connection is called bolt connection. If the nut is unscrewed from the bolt, it can separate these two parts. Therefore, the bolt connection is a detachable connection.

Flange bolts are a common type of fastener. They are widely used in highway and railway bridges, including industrial and civil construction, cranes, excavators and other heavy machinery, with a wide range of applications.

Classifications of flange bolts and nuts

1. Hexagonal flange types: 
There are two types of hexagonal heads. One is flat headed and the other is concave headed.

2. Surface color category: According to different needs, the surface is coated with dacromet that is white, military green, colored yellow, and anti-rust dacromet.

3. Category of flanges: Depending on the location of use of flange bolts and nuts, the size requirements for the disc vary. There are also flat bottomed and toothed types, with toothed ones serving as anti slip agents.

According to the force distribution of the connection, there are ordinary and hinged holes. The flange bolts and nuts used for hinged holes should match the size of the holes and be used when subjected to lateral forces. In addition, to meet the need for locking after installation, there are holes in the rod, which can prevent the bolt from loosening when subjected to vibration. Some flange bolts without threads need to be made thin, called thin rod flange bolts. This type of flange bolts is conducive to connection under variable forces. There are specialized high-strength bolts on the steel structure. The head will be made larger, and the size will also change.

Common materials for flange bolts and nuts

1. High carbon steel C%>0.45%. The material of hexagonal flange bolts and nuts is currently not widely used in the market.
2.  Medium carbon steel 0.25% hex head bolts and nuts are commonly referred to as 35 # and 45 # steel in China, and commonly referred to as 1035, CH38F, 1039, 40ACR, etc. in foreign countries. It is mainly used for grade 8 nuts, grade 8.8 bolts, and grade 8.8 hexagonal products.
3.  Low carbon steel with C% ≤ 0.25% is commonly referred to as A3 steel in China. It is commonly referred to as 10081015181022 in foreign countries. It is mainly used for grade 4.8 bolts, grade 4 nuts, small bolts and nuts and other products without hardness requirements. (Note: The drilling tail nail is mainly made of 1022 material.).
4. Alloy steel: Adding alloying elements to ordinary carbon steel increases some special properties of the steel, such as 35, 40 chromium molybdenum, SCM435, 10B38. Hexagonal flange bolts are mainly made of SCM435 chromium molybdenum alloy steel, with main components including C, Si, Mn, P, S, Cr, and Mo.

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