It's not so much an issue with flange warpage as it is the potential for weld cracking near or in the K area. Welding highly restrained joints such as those associated with doubler plates induces residual stresses. All steel is not entirely homogenous, and variations in mechanical properties exist. In addition to the normal variations, the process of mill rotary straightening alters the mechanical properties by strain hardening the K area. Material variations in the K area may include a reduction in ductility and toughness resulting in reduction of CVN values, an increase in hardness, yield strength and ultimate strength, and an increase in the ratio of yield to ultimate strength.