Are bolts ordered under the ASTM A193 Grade B8/B8M Class 2 specification available above 1-1/2” in diameter?
The short answer is no. The A193 specification does not cover bolts larger than 1-1/2” in diameter for Class 2 materials. However, the reasoning behind this answer requires further explanation. Class 2 materials get their strength through the process of strain hardening (also known as work hardening or cold working). This process causes the grain structure of the material to elongate which increases the hardness and tensile strengths while the ductility decreases. It is problematic to attempt to strain harden larger diameters of material because the grain structure of the steel will not be consistently elongated, causing differences in strength properties between the interior and exterior of the steel. The outside would be high in strength and hardness, but the inside would be soft and weak in comparison. According to the ASTM A193 specification, “For diameters 1½” and over, center (core) properties may be lower than indicated by test reports which are based on values determined at ½ radius.” For this reason, Class 2 materials larger than 1½” in diameter do not exist in the marketplace and are not manufactured.
