Evaluation of Fillet Weld Qualification Requirements

This report presents the results of a study to determine the suitability of various test specimens for the qualification of fillet welds for steel bridges. The present AWS/AASHTO/ANSI specification uses a groove weld to qualify a fillet weld. A large root opening is used to provide tensile and Charpy V-notch test specimens. The chemistry of a single pass or the first pass of a multiple pass fillet weld is diluted by the base metal. The groove test weld geometry is designed to minimize the dilution of the weld metal at the test location. In addition, the test location in the groove weld undergoes grain refinement from the overlaying welds. This refinement does not occur in single pass fillet welds. The test program evaluated three candidate test specimens in a factorial experiment design that included the following variables: heat input (high and low), type of consumables (weathering, neutral flux, and active flux), and single-sided and two-sided (Dart) welds. At least three replicate tests were performed for each condition.

The results were revealed that the present groove test specimen does not always provide toughness results comparable to the actual fillet welds. The weld root Charpy V-notch specimen provided a more meaningful measure of the toughness of the weld. The shear strength of the welds exceeded the estimated nominal strength by over a factor of 2. The macroetch "T" speciemen presently required in the specification provides a simple means of evaluation both the welding procedure's ability to provide adequate penetration, and the influence of the heat input from a two-sided weld. Recommended changes to the bridge welding code for the qualificaiton requirements for the fillet welds are presented.