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Publication Number: FHWA-HRT-13-102
Date: November 2013

 

Optimization of Grade 100 High-Performance Steel Butt Welds

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Publication No. FHWA-HRT-13-102
FHWA Contact: Justin Ocel, HRDI-40, (202) 493-3080, justin.ocel@dot.gov

Introduction

The development of high-performance steels (HPS) began in the early 1990s as a result of cooperation between the Federal Highway Administration (FHWA), the U.S. Navy, and the American Iron and Steel Institute (AISI). Out of the extensive research performed, three new weathering grades of HPS were created that had minimum yield strengths of 50, 70, and 100 ksi. These are referred to as HPS50W, HPS70W, and HPS100W. All three are represented in the American Society for Testing and Materials (ASTM) A709 “Standard Specification for Structural Steel for Bridges” material specification.(1)

In the development of the HPS grades, three advisory groups were formed to oversee and guide the development of the steels in terms of their design, welding, and corrosion aspects. One of the aspects considered by the Welding Advisory Group (WAG) was how to butt splice HPS100W plates together without matching strength consumables. At the time the research began, matching 100-ksi-yield weld consumables were available but were also much more expensive than typical welding consumables for steel bridge fabrication. Therefore, the WAG wanted to demonstrate the use of “optimized” welding as a potentially useful option for the HPS steels under certain circumstances. Optimized welding harnesses triaxial internal constraint, which wider and thicker plates can use to develop through-thickness stresses and demonstrate an apparent increase in yield strength. Therefore, for particular combinations of joint width and thickness, an undermatched weld consumable could develop strengths equivalent to matching consumables. In this case, the “joint” is the butt splice between two different plates. Optimized welding is an attractive option in welds joining HPS plates of differing strength or when weld consumables match the HPS steel in terms of toughness but not in strength. Matching or overmatching welds are not necessary when optimization can be achieved.

This TechBrief reports the results from two final tests in this overall research project. However, the results from the prior tests published in references 3, 4, and 5 will also be included in order to present the full circle of findings. The work published in references 3, 4, and 5 was the result of funding provided by the WAG (from FHWA, AISI, and the Navy) along with some supplementary funding by the Pennsylvania Technology Alliance.

 

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