Effect of Forced Convection Heat Transfer on Weld Pools.
Research and development rept.,
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER ANNAPOLIS MD SHIP MATERIALS ENGINEERING DEPT
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A method has been developed to apply forced convection heat transfer by gas jet impingement to weld metals deposited by the Gas Tungsten Arc Welding GTAW process at heat inputs in excess of 100 kJin. The method involves the use of multiple gas jets directed at the surface of the weld pool to increase convective heat transfer i.e. forced convective cooling. Autogenous bead-on-plate welds were made in a titanium alloy with and without forced convective cooling. All welding variables were maintained constant, only the introduction of the cooling gas during welding was different. The weld pool geometry, temperature distributions, macrostructure and microstructure of the welds were evaluated. The results of visual and macrostructural observations indicate that forced convective cooling forms a refined weld metal macrostructure through control of the weld pool geometry. In addition to grain refinement, forced convective cooling modifies the shape of the weld bead. The depth to width ratio of the weld bead increases and the width of the weld HAZ decreases. The results of temperature measurements indicate that forced convective cooling increases the weld metal cooling rate. By increasing the cooling rate the time at transformation is suppressed and a finer weld metal microstructure is produced. Additionally, the weld pool surface temperature decreases and thermal gradients near the solid-liquid interface also decrease.
- *WELD METAL
- *CONVECTION(HEAT TRANSFER)
- GAS TUNGSTEN ARC WELDING
- TEMPERATURE GRADIENTS
- SURFACE TEMPERATURE
- GRAIN STRUCTURES(METALLURGY)
- TITANIUM ALLOYS
- Properties of Metals and Alloys