B7 vs. Grade 8

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DID YOU KNOW?

B7 vs. Grade 8

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We are often asked what the difference is between ASTM A193 B7 and SAE J429 Grade 8 Threaded Rod. Below, we break down the specifics of each so our customers can get a better understanding of them.

B7 Threaded Rod and Studs

ASTM A193 B7 is a chromium molybdenum alloy steel. B7 achieves its strength through a heat-treating process where it is quenched and tempered at 1150 degrees F. For high-temperature applications, B7 steel is in high demand because of its tensile strength and excellent heat resistance. It is used in high temperature and high-pressure applications, including in industries and jobs where high temperatures and high pressures are reached. Pressure vessels and valves in the oil and gas industry, in chemical and petroleum facilities, and pipe flange connections are typical applications for B7. It can have a variety of finishes, which can affect the temperature rating. Finishes such as yellow zinc, black oxide, and hot-dip galvanizing will help with resistance to corrosion. B7 is one of the strongest materials that AATP carries for threaded rod and comes in any length up to 12 feet.

Grade 8

Grade 8 (SAE J429) is a medium carbon alloy steel with one of the highest tensile strengths available. With a minimum tensile strength of 150 ksi and a minimum yield of 130 ksi, Grade 8 has a higher tensile and yield strength than other steel grades such as Grade 5 and B7. It is also quenched and tempered at 800 F leading to its strength. Grade 8 has 0.28-0.55% carbon, 0.030% max phosphorus, and 0.050% max sulfur.

All America Threaded Products will dual certify to ASTM A354 BD and SAE J429 Grade 8. ASTM A354 BD is used for structural bolts, while SAE J429 Grade 8 is an automotive specification. Both specifications are heat treated and tempered at 800° F, which creates a very strong part but increases brittleness more than comparative specifications. These high-strength bolts are typically used in standard temperature and pressure level applications such as general-use construction projects. The preload or thread tension in a fastener is higher with Grade 8 quality steel. Therefore, Grade 8 is typically used for threaded bolts in demanding applications such as automotive suspensions for large trucks and tractors.

This table shows the mechanical properties of B7 and Grade 8: