Abstract
Spatter formation is a major issue in deep penetration welding with solid-state lasers at high welding speeds above 8 m/min. In order to limit spatter formation, the use of local gas flows represents a technically feasible solution. By using the gas flow, the pressure balance inside the keyhole, and therefore the keyhole stability, is affected. Existing investigations demonstrate a reduction in spatter and pore formation for partial penetration welding up to a welding speed of 5 m/min. However, the effect of the gas flow is not yet clarified for full penetration welding at welding speeds above 8 m/min. By using a precisely adjustable shielding gas supply, the effect of a local gas flow of argon was characterized by welding stainless steel AISI304 (1.4301/X5CrNi18-10). The influence of the gas flow on the melt pool dynamics and spatter formation was recorded by means of high-speed videography and subsequently analyzed by image processing. Schlieren videography was used to visualize the forming flow flied. By the use of the gas, a change in melt pool dynamics and gas flow conditions was observed, correlating to a reduction in loss of mass up to 70%. Based on the investigations, a model of the acting effect mechanism was given.
Highlights
New developments in the field of solid-state lasers has led to the availability of higher power classes at relatively low investment costs
In order to explain the effect of the gas flow on the top-sided melt pool dynamics and spatter formation mechanism in more detail, the process characteristics are illustrated by representing points in time for a welding speed of 12 m/min (Figure 5)
In order to clarify the effect of the changed flow conditions on the melt pool dynamics, the velocity of the detached spatter was determined as function of flow rate and welding speed
Summary
New developments in the field of solid-state lasers has led to the availability of higher power classes at relatively low investment costs. When increasing the welding speed beyond 8 m/min, the key mechanism in spatter formation changes. Based on the interaction of the metal vapor and the rear wall, the melt pool fluctuates and starts to move along welding direction. A study about the influence of a local gas flow at welding speeds above 5 m/min has not been sufficiently investigated so far. AISI304 (1.4301, X5CrNi18-10) at welding speeds from 8 m/min to 16 m/min For this purpose, a novel experimental setup was developed, in order to characterize the effect of the gas flow on the stability of the keyhole and melt pool dynamics. The influence of an affected pressure balance was investigated regarding the gas flow conditions as well as the change in spatter formation. The results are condensed in a description of the acting effect mechanism
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