How to Make High Strength Rail Bolts

High Strength Rail Bolts Materials

Bolts, especially high strength bolts, are more and more used in the rail fastener system along the railway. How to choose the materials of ordinary rail bolts and high strength rail bolts? Let’s talk about it. Bolts and other no mechanical performance requirements of external thread used materials such as low carbon steel fasteners, use Q235A SAE 1015 DIN C15 steel enough, no need heat treatment, can be made from cold working directly. Slightly higher levels of fasteners such as: ISO Class 6.8 SAE Grade 3-4 is to use carbon content of more than 0.2% of steel, such as C1020 C1022 Ml20 ML35, etc. This kind of screw does not need any heat treatment, cold working strength can meet the requirements.

In fact, the higher the carbon content, the more difficult the cold forming, there is no need for the 6.8 screw large and small, the special case is another matter. We are most commonly used is ISO Class 8.8 SAE Grade 5 screws, the general use of carbon steel, ML35 SAE 1035 DIN JIS RCH35K after heat treatment (quenching + tempering), you can also use SAE5140 40Cr, etc. The increase of alloying elements on heat treatment the hardenability of a lot of help, so specification of screw can choose to use alloy steel, not in the center of the medium carbon steel cause we often say "quenching opaque" phenomenon exists.

ISO Class 9.8 10.9 SAE Grade 8, with a low to medium alloy steel material, after heat treatment (quenching + tempering), alloy material in the material has a good combination of mechanical properties of commonly used materials of 40Cr 35CrMo SAE5140 SCM435 SAE4135 SAE4137 JIS SCr440(H) DIN 41Cr4, etc. In fact 45 # can also meet the requirements of mechanical properties, but in the comprehensive mechanical properties than alloy slightly inferior.