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In constructing all kinds of equipment and steel structure, parts with discontinuities such as weld defects formed in the welded structure can generate fatigue cracks that results in damage or accidents. In this study, weld zones are investigated with X-rays and the latent images are put on film. Weld zone defects can be verified by developing the film. As weld defects are investigated by radiographic testing and correlated with the welding condition, more appropriate welding conditions can be found. According to the result of X-ray radiographic inspection of butt welding ATOS 80 high-strength steel with a thickness of 12mm, the best conditions for welding without creating weld defects are 4 weld-passes, a protective gas of 20% $CO2 and 80% Ar, a protective gas flow of 20L/min, a welding current of 200A, an arc voltage of 24V, a welding speed of 14.4cm/min, a welding rod angle of 50°, a welding gap of 5 mm with a ceramic base, and sand pre-heating to $160^{\circ}$ Celsius prior to welding.