Low carbon steels have been joined using an infrared processing technique with copper as the filler material. Single lap specimens were prepared. The joining temperatures were 1100 °C, 1125 °C, and 1150 °C with joining time ranging from 0 to 2 minutes in flowing argon. Excellent wetting between the base materials and the filler was observed for all samples. The joint shear strength was determined with a specially designed fixture to minimize the bending moment of specimens during testing. The measured joint shear strength varies from 240 to 300 MPa depending on the processing conditions. The maximum strength obtained is about 300 MPa, which can be achieved by processing at 1125 °C for 60 seconds or 1150 °C for only 30 seconds. Higher processing temperatures or longer processing time than these conditions did not improve the joint strength. Joint cross-section examinations revealed that there are no voids in the joint. Microhardness tests performed on the cross sections of joined samples across the joint zone indicate that the joint zone hardness is higher than that of pure copper. Examinations with energy dispersive analysis of X-ray revealed presence of iron in the joint as well as a small amount of copper inside the base materials.