In this book, tensile strength of tilted layer functionally graded steels produced by electroslag remelting has been modeled. Vickers microhardness of each layer was related to the density of dislocation of that layer through mechanism-based strain gradient plasticity theory. Yield stress of a specific layer was found by means of its Vickers microhardness through a linear relation. Afterwards, by assuming a power-law relation for stress-strain curve of the corresponding layer, the differences between tensile strength of neighboring elements was related to the tensile strength of the specimen by means of an additional parameter which is equal to the ratio of stress level differences to strain level differences of two adjacent elements in a given layer. Accordingly, tensile strength of the tilted layer functionally graded steels was determined via a numerical method.