Weld two plates together and you’ve already bent them. The arc dumps intense, localized heat into the joint, the metal there tries to expand against the cold steel around it, and because it can’t grow outward it upsets instead, squashing plastically in place. Then it cools, contracts, and pulls everything with it. The result is shrinkage and distortion baked into the part: transverse pull across the weld, longitudinal pull along it, and angular distortion as the joint folds toward the side that shrank most. So how do you straighten steel the heat already warped? You use the exact same mechanism, deliberately and in reverse. This is flame straightening. The torch lays a controlled heat pattern into a chosen zone: • Spot heats knock down local buckles and bulges • Line heats pull out gentle bows • Vee or wedge heats, run apex to base, bend a member back about an axis Heat that zone fast and the surrounding cold steel pins it. It can’t expand, so it upsets, exactly like the weld di...