Heat will lower the yield value of the fastener. The yield strengths are determined at room temperature. ASTM A193 B7 has a yield strength of 75-105 ksi (75 ksi for sizes over 4 inches in diameter and 105 ksi for material in diameters up to 2-1/2 inches) at 70 degrees, and drops to approximately 53-74 ksi at
approximately 800 degrees. So, if we install a B7 fastener at room temperature expecting each fastener to support a tensile load of 85 ksi, which would not yield the fastener of diameters 2-1/2 inches and smaller.
