Role of Transport Phenomena in the Evolution of Geometry, Composition and Structure
Abstract Fusion welding is used extensively in industries that support the nation's energy supply, defense, infrastructure, and standard of living. Safety and reliability of the welded joints are affected by their geometry, composition and structure. This report provides an account of the significant advances made in quantitative understanding of the geometry, composition and various aspects of the weldment structure with financial support from DOE/BES. In particular, this report provides an account of the research conducted under the grant DE-FG02-84ER45158 in this important area and lists all the publications that document the details of the technical accomplishments that resulted from the work. Investigations of heat transfer, fluid flow and alloying element vaporization during laser welding resulted in a new technique for the determination of the peak temperature in the weld pool and provided a new method to estimate weld metal composition. Studies on the interfacial phenomena in fusion welding resulted in quantitative understanding of the interrelationship between the weld metal composition and geometry and provided new knowledge as to when the surface active elements would affect the weldment geometry and when these elements would have no effect on the geometry. Partitioning of oxygen nitrogen and hydrogen between the welding environment and the weld metal was affected by the extent of the dissociation of diatomic gaseous species which depended on the nature of the plasma formed during welding. The interfacial tension of the liquid metal was also affected by the plasma and the properties of the plasma affected the concentrations of oxygen, nitrogen and hydrogen in the weld metal. Apart from the understanding of the evolution of composition and geometry of the weldments, application of transport phenomena provided useful information about various features of the weldment structure. Quantitative understanding of microstructure of the fusion zone and heat affected zone and grain structure in both steels and titanium alloys could be achieved starting with numerical heat transfer and fluid flow calculations. In addition, the evolution of inclusion composition and structure in steels during welding could also be understood from fundamental principles. The positions of the students supported by the grant are indicated since an important component of the work was the education of many outstanding students who now occupy leadership positions in major organizations in the US. The research sponsored by the Basic Energy Sciences has been recognized by many major scholastic awards. These are listed because they testify to the quality of the curiosity and the commitment of the students that were supported by the grant. Our collaborations with Oak Ridge National Laboratory, Lawrence Livermore National Laboratory and Sandia National Laboratory are indicated because many outstanding scientists from these laboratories shared our goals in advancing quantitative understanding of fusion welding processes and the geometry, composition and structure of welded materials.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States)
- Sponsoring Organization:
- USDOE - Office of Energy Research (ER)
- DOE Contract Number:
- FG02-84ER45158
- OSTI ID:
- 861276
- Report Number(s):
- DOE-ER-45158-1 (FINAL)
- Country of Publication:
- United States
- Language:
- English
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