A Comparison of Tensile Properties of Single-Sided and Double-Sided Laser Welded DP600 Steel Sheets

Abstract

Dual Phase (DP) steels are the most commonly used steels in the automotive industry to reduce vehicle weight and improve car safety. DP600 steel is one of the most used steels for the automotive industry because this steel has high strength and good elongation properties. During the manufacture of automotive parts, welding is the most commonly used joining process, and especially the laser welding is getting more and more importance. This study was executed to evaluate how the welding type (single-sided and double-sided) affects the tensile properties of Nd:YAG (Neodymium-Doped Yttrium Aluminum Garnet; Nd:Y₃Al₅O₁₂) laser welded DP600 steel sheets using different pulse frequencies. The laser welded samples were investigated by the methods of tensile test and fractography. Experimental results indicated that the tensile properties varied significantly depending on the welding type and pulse frequency. The tensile properties of the double-sided laser welded joints were significantly higher than those of the single-sided laser welded joints. Tensile strength and elongation of the single-sided and the double-sided laser welded joints increased almost linearly with increasing pulse frequency. The higher pulse frequency resulted in larger fully bonded section size, which led to higher tensile properties. The maximum tensile strength and elongation (611 MPa and 10.06 %) were obtained with the double-sided laser welded joint in the pulse frequency of 8.5 Hz. The tensile strength of this joint was almost equal to that of the base metal, but its elongation value was lower that of the base metal.