Hot extrusion was used to make multi-layer clad steel bars with annual ring-like section structure, interlaminated with ductile ferrite and strong martensite steel layers. The mechanical properties of these clad steels were investigated.(1) The improvement in tensile strength (σc) was affected mainly by the layer thickness, as shown by the following equation.(This article is not displayable. Please see full text pdf.) (2) Comparison was made between these clad steels and SCM 4 steels quench-tempered to the same strength level. In tensile behavior, elongation was almost equal for both materials, but a smaller reduction of area was observed with the clad steels. In the strength range of 100∼150 kg/mm2, the clad steels provided higher impact strength. It was found from the impact load-time curves that maximum load was higher with SCM 4 steels, while the time to fracture was longer with the clad steels.(3) Lower brittle-ductile transition temperature was observed for the clad steels with a thinner layer of either the ferrite or martensite phase.