Grade B7 Bolt

A Grade B7 bolt is a high strength bolt made from alloy steel that has been quenched and tempered. It is often used in high temperature or high pressure applications.

These bolts are common in petrochemical, power and process industries for flanged joints and pressure vessels. Installation usually follows a controlled tightening sequence to reach the required preload.

Hot dip galvanising gives a thick zinc coating that protects against corrosion in outdoor and humid environments. It is different from zinc plating, which is thinner and offers less protection. The coating can affect the fit of the nut, so thread tolerances are often adjusted.

Grade B7 bolts are often made in alloy steel such as AISI 4140 or 4142 that has been quenched and tempered. This gives high strength and good performance at elevated temperatures.

This is a general guide to checking this kind of part. It says nothing about any supplier's parts.

Ask for a mill test certificate that shows the grade, heat number and mechanical properties. On receipt, check the head marking, the thread condition and the coating thickness if galvanised. Also check that the bolts are straight and free from damage.