This study investigates the effects of the material properties and the fatigue behaviors in the SM490A material weld specimens, which are made by same method of railway vehicle structure, due to the heat-treatment and the grinding. In the fatigue behavior, the heat treatment affects the fatigue life. The S-N curves of both base metal specimens and butt weld specimens are reversed at some cycle by with or without heat treatment. The grindings on the beads make the fatigue limit decrease in the all specimens. But the reinforcement removed, the fatigue limit increases at the high cycle. Also, this study investigates the fatigue life estimation by examining butt weld bead profiles. The butt weld beads, which are welded by semi-robot method, have non-uniform bead profiles described by angle θ, radius ρ and height h. The stress concentration factors Kt, are changed by each different θ, ρ and h. In combination among θ, ρ and h, as θ becomes lower and ρ and h become higher, Kt increases. And the fatigue life for the AAY specimens can be estimated very closely using only butt weld bead profiles.

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