Effect of Weld Metal Strength Mismatch on the Deformation and Fracture Behaviorof Steel Butt Weldments

摘要

Considerable Naval and industrial experience has indicated the engineeringutility of using weld metal having strength greater than the plates being joined (over-matching). Overmatching shields the weld region, which typically has lower toughness than the plate and is often the site of defects, from the high strains that develop during an overload. This practical advantage, coupled with the ease of achieving overmatch in lower strength steel alloys (80 ksi yield strength or less) has led to codification of overmatching as a requirement in most structural design codes and fabrication specifications. However, overmatching has certain economic and technical disadvantages which undermatched (weld metal strength less than plate strength) systems might alleviate. This report reviews investigations concerning the deformation and fracture characteristics of simple mechanical test specimens containing butt welds, focusing on how the relative strength of the weld deposit and the plate influences these characteristics. All analytical and experimental evidence available indicates that plastic strain concentrates into the zone of the lowest material strength in a transversely loaded weldment. Thus, plastic strains in undermatched weldments concentrate in the weld deposit while in overmatched weldments they concentrate in the plate.