Cold drawn steel pipes undergo work hardening during the process. During cold drawing, metals undergo plastic deformation, with multiple slip systems initiating within the crystal structure. Dislocation movements intercept each other, causing many dislocations to become pinned, leading to dislocation pile-up while the dislocation sources cease activity. This sequence of events results in reduced mobility of dislocations and a significant increase in dislocation density within the crystal. As further plastic deformation occurs, stress increases and becomes sufficient to initiate motion in the pinned dislocations, causing screw dislocations to inter-slip, while edge dislocations cannot inter-slip. This leads to dislocation intersection, increasing the number of immobile levels.