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This paper investigates the characteristics of GMAW of various sheet steels grades ranging from HSLA, dual phase, to martensitic. From the arc welding point of view, the dual phase and martensitic steels behave similarly to conventional high strength steels. Regarding the properties of GMAW joints, the static and dynamic mechanical testing were conducted and compared along with the weld metal microhardness and microstructure. Results show that while the strength of the sheet steel weld, in general increases with the base material strength, Joint Efficiency, defined as the ratio of the strength of joint to the strength of the base metal, decreases with the increase of martensite fraction in the sheet steel. Martensitic steels, especially, exhibits reduced weld strength due to softening of the HAZ. However, fatigue strength of these steels is not adversely affected by the softened HAZ, and is insensitive to the strength of the steel.