Casting is one of the major methods of producing parts, which are produced annually by millions of pieces. Continuous casting process is one of the common casting methods. Today, continuous casting is an important method of producing steel. Copper Mold or Crystallizer is a major portion of continuous casting process. Design and manufacture of this mold, is a costly and complex stage. The crystallizer has a complex, curved and conical geometry. Crystallizer is simultaneously exposed to mechanical, thermal and abrasive stresses; hence its technical know-how is complicated with many affecting parameters. Crystallizer is distorted and damaged after some time they are used, losses its conical shape and also its coating and its walls are subjected to permanent deformation. These deformations causes a change in the shape of the slab or billet obtained from the continuous casting process. However, considering the cost and geometrical complexity of crystallizer, replacement of these molds by new ones is an expensive method. Therefore, design of a repair method for the faulty crystallizer with a quadrangle cross section was studied and is presented in this thesis. Feasibility of the crystallizer repair was studied and a suitable ironing method was suggested using finite element simulations by ABAQUS software. In this study, ironing and extrusion processes have been investigated to eliminate geometrical distortion and thickness reduction created due to wear in the crystallizer wall. It was concluded that ironing is better and more practical as compared with extrusion process. Ironing is one of the forming processes applied to metal sheets, which is used to produce thin wall canisters and uniform wall thickness pieces after deep drawing process. In the simulations, faulty crystallizers with geometrical and non-uniform wall thickness are considered. To repair crystallizer, a mandrel is inserted into the faulty crystallizer and suitable boundary conditions are defined to model ironing of the faulty crystallizer. Besides ironing process, extrusion of faulty crystallizers was also modeled considering a mandrel inside the faulty crystallizer. Based on simulations in this research, a small thickness reduction of the crystallizer by the ironing process can eliminate geometrical and non- uniform wall thickness, and hence ironing process is approved to repair the defective crystallizer. Thickness reduction that was created by extrusion process is low, however deformation forces and stresses on tools are much larger than the ironing process. Process parameter values such ??as length increase, reduction of thickness and required force were obtained and the simulation results are verified. Because of the complex crystallizer geometry and difficulties in performing the ironing process on conventional presses, a mechanism of converting linear motion to rotating motion is suggested and modeled and proposed. Keywords : Crystallizer, Casting, Continuous Casting, Ironing, Extrusion, Simulation