AISC


2.3. Use of Heat in Fabrication

2.3.1. Is it permissible to use controlled heat to straighten, curve or camber structural steel shapes?

Yes. AWS D1.1Section 5.26.2 permits heat-straightening of members that are distorted by welding and stipulates rules for this procedure. These rules are equally applicable for all heat straightening or curving. Furthermore, the AISC Specification Section M2.1 and a discussion in the AISC Manual (Part 2), provide a sound basis for the use of controlled heat to straighten, curve, camber and form structural steel. The proper control of heat application generally involves the use of rosebud tips on torches to disperse the applied flame and temperature indicating crayons or similar devices to monitor the induced temperature.

2.3.2. Is it permissible to accelerate cooling of structural steel after the application of controlled heat?

Yes, however for cyclically loaded structures, the steel must first be allowed to cool ambiently to 600 °F. Because the maximum temperature permitted by the AISC Specification Section M2.1 for heating operations is below any critical metallurgical temperature for the material being heated, the use of compressed air, water mist or a combination thereof should be permitted to accelerate the final cooling. The limitation for cyclically loaded structures is more historical than technical in nature. As a fair balance between the needs of the fabricator and the concerns of the owner, it provides an added safeguard to prevent the abuse of excessive cooling and undesirable residual stresses should accepted procedures not be strictly monitored.

2.3.2. Is it permissible to accelerate cooling of structural steel after the application of controlled heat?

Yes, however for cyclically loaded structures, the steel must first be allowed to cool ambiently to 600 °F. Because the maximum temperature permitted by the AISC Specification Section M2.1 for heating operations is below any critical metallurgical temperature for the material being heated, the use of compressed air, water mist or a combination thereof should be permitted to accelerate the final cooling. The limitation for cyclically loaded structures is more historical than technical in nature. As a fair balance between the needs of the fabricator and the concerns of the owner, it provides an added safeguard to prevent the abuse of excessive cooling and undesirable residual stresses should accepted procedures not be strictly monitored.