ASTM A320: Best For Low Temperature Service
Different bolts have different uses, and are therefore tailor-made to withstand a wide variety of conditions. Selecting the finest type of head bolt for your use therefore means understanding their different properties, and how the materials it is composed of are compatible with the use you intend them for.
The ASTM A320 Petrochemical Grade Bolt
The ASTM A320 is one of many petrochemical grade bolt types specified by the American Society for Testing Materials or ASTM. This kind of bolt comes in L7, L7M, B8, and B8M varieties, among others.
This particular type of bolt is of alloy steel material intended for valves, flanges, pressure vessels, as well as fittings. It also works best under a low-temperature service.
As specified by the ASTM, the bars of this type of bolt must be hot-wrought and processed further through any of two ways: first, centerless grinding; or second, cold drawing.
When using austenitic stainless steel, this must be solution annealed or else annealed and strain-hardened.
In order to ensure its quality, this type of bolt undergoes a series of strength and temperature strengths, which are also used for other types of bolts but at different specifications.
Beyond the A320: Characteristics Of Bolts
Most bolts need to meet specific standards that are set relative to their material make up. Some of the most common properties include tensile strength, elongation, hardness, and yield strength.
As such, bolt materials are also subjected to a series of mechanical tests, such as hardness testing, tension testing, and impact testing.
Each material is made to meet a specific impact energy absorption requirement called the Charpy Impact Energy Absorption. It also has its respective recommended test temperature, to which it should also conform to ensure its optimum performance.
It is critical for users to source their bolt supplies only from trusted suppliers to make sure that bolts purchased have adhered to the abovementioned specifications of the ASTM, and have undergone proper temperature and strength testing.