Abstract
Maximum cause to make mechanical toughness of the weld metal reduce in the process management is known to be a mixture of nitrogen including in the atmosphere by breaking the shield condition. Mixture of the atmosphere is prevented by blowing the shielding gas such as carbon dioxide, argon, and this mixture to the arc and the molten pool in the gas metal arc welding, but it is easily affected by the wind. Therefore, it has been recommended conventionally that wind velocity should be controlled less than 2.0m/sec. But it is thought that this recommendation value is unsuitable to produce multi-pass weld metal with high mechanical and porosity toughness property. Because this was provided from examination results by only consideration porosity toughness of single-pass weld metal but non-consideration mechanical toughness. In this paper, shielding condition is evaluated not only chemical analysis and mechanical properties of multi-pass weld metal in some velocity wind environment but also visualizing varied shielding gas behavior by the Schlieren method. As a result, it is necessary to be controlled the wind velocity less than 0.5m/sec to produce multi-pass weld metal with good properties. And the calculated velocity of shielding gas should be controlled more than twice the wind velocity.
