Filler metal

About: Filler metal is a research topic. Over the lifetime, 11152 publications have been published within this topic receiving 86590 citations.

Keyhole gas tungsten arc welding: a new process variant

Abstract: The topic of this thesis is the discovery and development of a robust 'keyhole mode' of the Gas Tungsten Arc Welding ( G T A W ) process. This process variant represents a significant departure from conventional fusion welding processes, and is not explicable by traditional models of keyhole formation and behaviour. To be specific, the well-known keyhole processes of plasma, laser and electron beam welding are dependent on the generation of significance ablation (or 'recoil') pressure. Furthermore, there has been an acceptance that this is an essential characteristic of all keyholes. The power densities associated with G T A W are known to be too low to achieve significant ablation, and consequently this process is regarded as incapable of conventional keyhole operation, unless the circumstances are exceptional. This thesis therefore challenges the established views on two counts: • Keyholes welding is practical with existing GTAW technology; and • Keyholes can be stable even in the absence of significant surface ablation. Defence of these claims necessarily raises discussions ranging from the very practical aspects of work-place applications through to theoretical considerations such as the geometry of surfaces. While this work has endeavoured to address the various issues as they have arisen, emphasis has been placed on the development of a broad appreciation of the topic. It is acknowledged that in doing so it has failed to fully explore many of the areas that have been presented. For example, the relationship between G T A W keyhole surfaces and minimal surfaces may lead to fresh insights in weld pool mechanics. In practical terms such a study might lead to a much better appreciation of various forms of porosity, or potential control strategies based on the detection and interpretation of plasma or surface oscillations. The work begins with an experimentally based exploration of the process before addressing the questions of keyhole stability, formation and the process dependencies. It is hoped this approach will provide an efficient means of presentation, and might provide fresh insights into the physics of gas tungsten arc welding.

Active brazing of carbon fiber reinforced SiC composite and 304 stainless steel with Ti-Zr-Be

Abstract: Carbon fiber reinforced SiC (C f /SiC) was successfully joined to 304 stainless steel with Ti–Zr–Be filler metal by vacuum brazing. The interfacial microstructure was investigated by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), auger electron energy spectroscopy (AES) and X-diffraction (XRD). The mechanical properties of the brazed joints were measured by a mechanical testing machine. The results show that Ti and Zr elements in the interlayer can react with the brazed materials, the brazed joint mainly consists of Ti 5 Si 3 , TiSi, TiBe, TiFe and Zr(s,s) reaction products. The 304 stainless steel constantly dissolved and Ti, Be diffused into 304 stainless steel, which formed the diffusion layers between interlayer and 304 stainless steel. Ti and Be elements have an effect on promoting the formation of α-Fe layer. The maximum shear strength of 109.13±2.55 MPa is obtained at 950 °C with 60 min holding time.

Weldability in dissimilar welds between Type 310 austenitic stainless steel and Alloy 657

Abstract: Microstructural evolution and solidification cracking susceptibility of dissimilar metal welds between Type 310 austenitic stainless steel and Inconel 657, a nickel-based alloy, were studied using a combination of electron microscopy analysis and Varestraint testing techniques. In addition, the effect of filler metal chemistry on the fusion zone composition, microstructure, and resultant weldability was investigated. The good cracking resistance of welds prepared with Inconel A was due to a small amount of secondary phase (NbC) and narrow solidification temperature range. The relatively poor cracking resistance of welds prepared with Inconel 82 and Type 310 stainless steel (310 SS) was a result of a wide solidification temperature range and an increase in the amount of secondary phases. Consequently, it is concluded that for the joint between Inconel 657 and 310 SS, filler material of Inconel A offers the best weldability.