Delta ferrite residual content

Delta ferrite forms during cooling from the melt and, depending on the alloy, partially remains in the structure. Too high a proportion makes the weld metal harder and more brittle, increasing the risk of hot cracking. If you want to keep this under control, you mainly need to watch the cooling and choose the welding process accordingly. For high-alloy steels, it is important to keep heat input low and not stay at temperature too long. Then the ferrite content remains in a range that does not destroy toughness.