Factors Influencing the Microstructure and Mechanical Properties of Ultra LowCarbon Bainitic 100 Tungsten Inert Gas Multipass Weldments

摘要

The U.S. Navy has maintained a continuous research, development and certificationprogram in HSLA and ULCB steels with the intent of someday totally replacing the HY steels now used in ship construction. A major advantage in using HSLA and ULCB steels is their increase in weldability over the HY steels which now require large amounts of preheating to prevent crack formation in the heat affected zone. Up until the present day, however, low carbon HSLA and ULCB steels have not been used with a dedicated low carbon weld wire. In the present work an attempt was made to correlate the mechanical properties (tensile strength, yield strength and Charpy impact energy), chemical composition and microstructure of a series of autogenous multirun TIG welds on ULCB steels. It was found that good combinations of weld strength and toughness could be achieved with appropriate choice of weld metal chemistry and TIG welding power, but that there was a ceiling of about 2.Owt.% molybdenum which could be tolerated before weld metal embrittlement became evident.