Residual Lattice Distortion Energy

Martensite is hard and brittle because carbon strains the lattice. During welding, this can quickly lead to cracks, especially if the material has a lot of carbon. You have to slow down the cooling and relieve the part after welding to let the stresses out. If you don't, the weld or the base material will crack. Check beforehand what you're welding, otherwise you'll regret it later.