Cold-working steel strengthens the metal and increases its ultimate tensile strength (UTS) by manipulating the crystalline structure of the metal at low temperatures. Stress-induced microscopic deformations to the metal from the bending, which are referred to as dislocations, cause a rearrangement in the lattice of the metal. As the material is worked and the dislocations increase, the material eventually builds up a resistance to forming additional dislocations. The dislocations change the average crystallite size, which leads to the Hall-Petch effect. That is, the grain boundaries eventually impede dislocation, and this translate into the material having added strength.