The phenomenon of cold work embrittlement (CWE) in the P-added high strength interstitial-free steels has been associated with the segregation of P to the ferrite grain boundaries. This segregation by P is believed to decrease the cohesive strength of the grain boundaries by weakening their bonding. Hence, the resistance of the steel to brittle fracture, i.e., intergranular fracture, is greatly decreased. The goal of the present study was to investigate the segregation behavior of P during the different stages of processing (prior to and after coiling, and after cold rolling and annealing) in Ti and Ti+Nb stabilized interstitial-free steels. It was found that a considerable amount of segregation of P to the ferrite grain boundaries occurred during the coiling process in Ti-stabilized interstitial-free steels. However, with the addition of Nb in the Ti+Nb-stabilized interstitial-free steels, the segregation of P was decreased in the as-coiled condition. The P content on the ferrite grain boundaries in the final cold rolled and annealed condition was found to depend on two factors; (1) the segregation of P in the as-coiled condition, and (2) availability of Ti to form phosphides during the annealing process. It was confirmed in this study that the addition of P decreases the CWE resistance of the steel. Furthermore, it appears that the CWE resistance of the TiϩNb-stabilized interstitial-free steels is improved by the presence of solute Nb on the ferrite grain boundaries.KEY WORDS: segregation; ULC Steels; cold work embrittlement; thermomechanical processing.is essential to cause TE, the exact mechanism of TE is still not clearly understood.The phenomenon of temper embrittlement in ULC steels has been also documented and is called secondary work (SWE) or cold work (CWE) embrittlement. [23][24][25][26][27][28][29][30] The CWE phenomenon is defined as the susceptibility of the sheet material to intergranular fracture during the secondary working of a deeply drawn part or while in service. The CWE phenomenon is attributed to the segregation of P to the ferrite grain boundaries which is believed to reduce their cohesive strength and, hence, cause intergranular fracture along the ferrite grain boundaries. 23,29,30) It has been shown that the Nb-containing steels have a better CWE resistance than the Ti-containing steels. 24,31) This has been attributed to the partial stabilization of C in the Nb-containing steels. It is believed that carbon increases the grain boundary cohesion and increases the CWE resistance. [32][33][34] Furthermore, Erhart and Grabke have shown that as the C concentration on the grain boundaries is increased, the concentration of P on the grain boundaries is decreased which would also improve the CWE resistance. 35) Although it is known that the segregation of P to the ferrite grain boundaries causes CWE, its segregation behavior during the different stages of thermomechanical processing of interstitial-free steels is not known. In this study, the segregation behavior of P during the different stage...