Model for Estimation of Thermal History Produced by a Single Pass Underwater Wet Weld.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Thermal history calculations for single pass underwater wet weldments were made by solving the appropriate beat transfer equations using the three-dimensional Crank-Nicholson finite difference method. The Adams approach, which defines the fusion line temperature as a boundary condition, was adopted. Tsai and Masubuchis semi-empirical correlation, defining the surface heat transfer coefficient of underwater weldments, was used to determine the heat loss through the surface of the welded plate. As expected, the calculated cooling rates in heat affected zones HAZs of underwater wet welded ferritic steels were found to be somewhat faster than equivalent cooling rates calculated for the same weldments generated in air. However, the effect of water temperature on cooling times in the HAZ between 8000 and 5000C the parameter conventionally used to measure the cooling rate in the HAZ was found to be minimal. These calculations suggest that HAZ microstructure of underwater wet welded ferritic steels should be independent of water temperature. This prediction was confirmed by microstructural studies of samples of ASTM A516 grade 70 steel which were underwater wet welded at water temperatures of 31 degrees, 10 degrees and 30 degrees C respectively and for which suggest that HAZ microsructures were obtained in each case.
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