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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

In-situ Radiography of Hydrogen Porosity Growth and Development in Aluminum Welds

In aluminum welding, hydrogen contamination is the main cause of the welding defect, porosity. Porosity in welds can adversely affect the mechanical properties such as tensile strength, fatigue life and ductility. There have been a variety of solutions to help reduce porosity in aluminum welds including finding the source of hydrogen. However, in some cases the amount of hydrogen may be drastically reduced but impossible to completely eliminate. Another approach to this issue is to understand where a pore originates and how it moves and grows within the weld pool. This information may lead to a more innovative method for pore elimination during gas tungsten arc (GTA) welding of aluminum.

42 ENGINEERING↗
DOE OSTI2021

Report on FY 2021 Fabrication and Testing of Qualified Alloy 709 Welds at ORNL

Alloy 709 is a candidate construction material for the Sodium Fast Reactor (SFR). As part of the Alloy 709 ASME Code Case development team under the Advanced Reactor Technologies (ART) Program, this work covers the development of the technical basis for weld fabrication and weld qualification of Alloy 709. This report summarizes the research conducted in FY 2021 and relevant results from previous reporting periods, aimed at welding commercial heat of Alloy 709 plates of relatively high phosphorous (P) level in support of ASME code case data package. Welding, code qualification tests, and associated microstructure characterization were carried out in determining the effect of P levels of weld wire on the weldability of the high P commercial heat of Alloy 709. The Alloy 709 weld creep strength was evaluated though preliminary creep testing.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

High Pressure Electron Gun for Electron Beam Welding and Additive Manufacturing

Electron beam welding is a premier technology for high quality welding. However, e-beam welding is viewed as very expensive method for quality results. Therefore, it is often the last choice for joining metals. U.S. Electron is developing a technology that changes the welding environment. As a result of this pursuit of technology, e-beam welding can be field deployable. U.S. Electron has received a DOE SBIR Phase I grant to demonstrate a proof of principle that the plasma cathode can be installed in an electron gun housing, generate a current and energy enough to weld stainless steel. Under this CRADA, Fermilab proposed to provide a power supply, the necessary safety expertise and the physical location for testing of the initial prototype equipment developed by U.S. Electron.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Testing and Qualification of Molybdenum Subcapsule Welds for MiniFuel Experiments

This report documents the testing and qualification efforts for welding molybdenum components to support MiniFuel irradiation campaigns. Other details such as general weld parameters, weld joint geometries, and performance limits are also provided in this report. The American Welding Society’s specifications were used to select the nondestructive and destructive tests, which include: gross and fine leak testing, internal pressure proof testing, and creating metallographic mounts of welds. Leak testing and metallographic mounts provide qualitative information about the weld integrity, while the proof testing indicated pressure/usage limits of the molybdenum subcapsule. Based on the testing results provided in the is report, the capsule can be exposed to an internal pressure of at least 20.7 MPa (3000 psi). A sealed capsules is also capable of withstanding the 3.2 MPa (468 psi) external hydrostatic operating pressure of the High Flux Isotope Reactor.

42 ENGINEERING↗
DOE OSTI2024

NuMI/LBNF Horn and Stripline Welding

Focusing horns for secondary particles are critical components for creating a stable beam of neutrinos. These components need to survive in a harsh environment and withstand high stresses. Extending the lifetime of the horns is critical as spare fabrication takes approximately two years and has many subcomponents with strict quality control. Two key aspects of the fabrication process include the inner conductor CNC TIG welding and the friction stir welding of the stripline pieces. The process for welding requires steps such as sample welding, x-ray imaging, and tensile pull tests. Having a perfect weld retains as much of the original strength of the base metal and reduces the risk of failure. As FNAL ramps up in power to 2.4MW, the lifetime of the horn and stripline will more heavily rely on continuing to have high quality welding procedures and thorough quality assurance.

Orea, Adrian↗
DOE OSTI2024

Crack Growth Rate and Fracture Toughness of Stainless Steel Welds in Light Water Reactor Environment

Austenitic stainless steel welds play a crucial role in maintaining the structural integrity of light water reactors. Within the reactor core, stainless steel welds endure a harsh service environment including elevated temperature, corrosive coolant, and intense neutron irradiation. Long-term exposure to such a severe service environment could lead to performance degradation. To ensure the safe and economic operation of light water reactors, this study performed crack growth rate and fracture toughness tests on irradiated and thermally aged weld samples harvested from decommissioned reactor components. In a low-corrosion-potential environment, stainless steel welds showed resistance to stress corrosion cracking, and the measured crack propagation rates were comparable to those of wrought stainless steels under similar test conditions. However, a marked decline in fracture toughness was observed in weld samples, particularly in irradiated samples. Fracture instability was observed at ~0.8 dpa, significantly lower than those observed in wrought stainless steels. Further research at higher doses is needed to evaluate the dose dependence of irradiation-induced embrittlement, and to understand the interplay between thermal aging and neutron irradiation in stainless steel welds.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2026

Gigacycle Fatigue Strength Evaluation of Welded 316L Stainless Steels for Mercury Target Vessel

At the Materials and Life Science Experimental Facility (MLF) in J-PARC, liquid mercury target for the pulsed spallation neutron source is in operation. An enclosure vessel for the liquid mercury target made of type 316L stainless steel (SS316L) suffers two kinds of cyclic stress during operation. One is the thermal stress due to the internal heating and swings by proton beam trip. The other is the impulsive stress by the pressure waves generated by the proton beam injection. The total number of loading cycles for the former is ∼104, and the latter is ∼4 × 108 for a year operation in the J-PARC mercury target vessel. The target vessel is assembled by an electron beam welding (EBW) and a gas tungsten arc welding (GTAW). However, fatigue data of welded SS316L up to gigacycle is limited. Ultrasonic fatigue testing, applying load cycles by utilizing ultrasonic resonance, for the welded SS316L was performed to investigate the effect of welding on fatigue behavior up to a gigacycle. The result showed that the fatigue strength degradation by EBW and EBW with GTAW were not recognized up to 109 cycles. Crack initiation in welded specimens nucliated at off-center areas of the specimen whereas the cracks in base metal specimen originated at the specimen center.

Naoe, Takashi [Japan Atomic Energy Agency (JAEA)]↗
NASA NTRS1973

Development of the weld-braze joining process

A joining process, designated weld-brazing, was developed which combines resistance spot welding and brazing. Resistance spot welding is used to position and aline the parts, as well as to establish a suitable faying-surface gap for brazing. Fabrication is then completed at elevated temperature by capillary flow of the braze alloy into the joint. The process was used successfully to fabricate Ti-6Al-4V alloy joints by using 3003 aluminum braze alloy and should be applicable to other metal-braze systems. Test results obtained on single-overlap and hat-stiffened panel specimens show that weld-brazed joints were superior in tensile shear, stress rupture, fatigue, and buckling compared with joints fabricated by conventional means. Another attractive feature of the process is that the brazed joint is hermetically sealed by the braze material, which may eliminate many of the sealing problems encountered with riveted or spot welded structures. The relative ease of fabrication associated with the weld-brazing process may make it cost effective over conventional joining techniques.

Bales, T. T.↗
NASA NTRS1972

Electron beam welding of aircraft structures

Requirements for advanced aircraft have led to more extensive use of titanium alloys and the resultant search for joining processes which can produce lightweight, high strength airframe structures efficiently. As a result, electron beam welding has been investigated. The following F-14A components are now being EB welded in production and are mainly annealed Ti-6Al-4V except for the upper wing cover which is annealed Ti-6Al-6V-2Sn: F-14A wing center section box, and F-14A lower and upper wing covers joined to wing pivot fitting assemblies. Criteria for selection of welding processes, the EB welding facility, development work on EB welding titanium alloys, and F-14A production and sliding seal electron beam welding are reported.

Witt, R. H.↗
NASA NTRS1972

Electroslag and electrogas welding

These two new joining methods perform welding in the vertical position, and therein lies the secret of their impressive advantages in material handling, in weld preparation, in welding speed, in freedom from distortion, and in weld soundness. Once the work has been set in the proper vertical position for welding, no further plate handling is required. The molten filler metal is held in place by copper shoes or dams, and the weld is completed in one pass.

Campbell, H. C.↗
NASA NTRS1974

Industrial laser welding evaluation study

High power laser welding was evaluated for fabricating space vehicle boosters. This evaluation was made for 1/4 in. and 1/2 in. aluminum (2219) and 1/4 in. and 1/2 in. D6AC steel. The Avco HPL 10 kW industrial laser was used to perform the evaluation. The objective has been achieved through the completion of the following technical tasks: (1) parameter study to optimize welding and material parameters; (2) preparation of welded panels for MSFC evaluation; and (3) demonstration of the repeatability of laser welding equipment. In addition, the design concept for a laser welding system capable of welding large space vehicle boosters has been developed.

Hella, R.↗
NASA NTRS1975

Solid state welding processes for an oxide dispersion strengthened nickel-chromium-aluminum alloy

Solid-state welding processes were evaluated for joining TD-NiCrAl (Ni-16Cr-4Al-2ThO2) alloy sheet. Both hot-press and resistance spot welding techniques were successfully applied in terms of achieving grain growth across the bond line. Less success was achieved with a resistance seam welding process. In stress-rupture shear and tensile shear tests of lap joints at 1100 C, most failures occurred in the parent material, which indicates that the weld quality was good and that the welds were not a plane of weakness. The overall weld quality was not as good as previously attained with TD-NiCr, probably because the presence of alumina at the faying surfaces and the developmental TD-NiCrAl sheet, which was not of the quality of the TD-NiCr sheet in terms of surface flatness and dimensional control.

Moore, T. J.↗
NASA NTRS1975

Weld bonding of titanium with polyimide adhesives

A conductive adhesive primer and a capillary flow adhesive were developed for weld bonding titanium alloy joints. Both formulations contained ingredients considered to be non-carcinogenic. Lap-shear joint test specimens and stringer-stiffened panels were weld bonded using a capillary flow process to apply the adhesive. Static property information was generated for weld bonded joints over the temperature range of 219K (-65 F) to 561K (550 F). The capillary flow process was demonstrated to produce weld bonded joints of equal strength to the weld through weld bonding process developed previously.

Vaughan, R. W.↗
NASA NTRS1976

Welding at the Kennedy Space Center

Welding plays a major role in the design, manufacture, and construction of the ground support equipment at the Kennedy Space Center. Three applications of welding are described, i.e., an example of the structural welding of a girder in a mobile launcher (presently designated mobile launcher platform), an example of the repair welding of crawler/transporter shoes, and an example of the welding of the liquid hydrogen and liquid oxygen storage spheres and vacuum jacketed piping in the propellants system. This welding technology was developed during the Apollo and earlier programs. It is now being applied to the Space Shuttle.

Clautice, W. E.↗
NASA NTRS1978

Automatic Welding of Stainless Steel Tubing

To determine if the use of automatic welding would allow reduction of the radiographic inspection requirement, and thereby reduce fabrication costs, a series of welding tests were performed. In these tests an automatic welder was used on stainless steel tubing of 1/2, 3/4, and 1/2 inch diameter size. The optimum parameters were investigated to determine how much variation from optimum in machine settings could be tolerate and still result in a good quality weld. The process variables studied were the welding amperes, the revolutions per minute as a function of the circumferential weld travel speed, and the shielding gas flow. The investigation showed that the close control of process variables in conjunction with a thorough visual inspection of welds can be relied upon as an acceptable quality assurance procedure, thus permitting the radiographic inspection to be reduced by a large percentage when using the automatic process.

Clautice, W. E.↗
NASA NTRS1980

"Foreign material" to verify root fusion in welded joints

Foil or thin wire at weld root is used to verify weld penetration. When weld is adequate, material mixes with weld and traces of it diffuse to weld crown. Spectroscopic analysis of samples identifies foreign material and verifies root has fused. Weld roots are usually inaccessible to visual inspection, and X-ray and ultrasonic inspection techniques are not always reliable. Good results are obtained with use of gold/nickel alloy.

Kleint, R. E.↗
NASA NTRS1982

Evaluation of solar cell welds by scanning acoustic microscopy

Scanning laser acoustic microscopy was used to nondestructively evaluate solar cell interconnect bonds made by resistance welding. Both copper-silver and silver-silver welds were analyzed. The bonds were produced either by a conventional parallel-gap welding technique using rectangular electrodes or new annular gap design with a circular electrode cross section. With the scanning laser acoustic microscope, it was possible to produce a real time television image which reveales the weld configuration as it relates to electrode geometry. The effect of electrode misalinement with the surface of the cell was also determined. A preliminary metallographic analysis was performed on selected welds to establish the relationship between actual size and shape of the weld area and the information available from acoustic micrographs.

Klima, S. J.↗
NASA NTRS1982

U.S. welding technology - Constraints to space implementation

U.S. and European efforts to develop welding techniques for satellite solar arrays are described. Soldering practices in the U.S. have benefitted from Mo solders, which are well fitted to Si solar cell material thermal characteristics. Analyses have indicated that welds are the preferred method for interconnections and bonds. Extensive work has been done with the parallel gap resistance method (RW), which involves process heat generated by passing a current through resistive layers. Confining the primary heat input to the interconnector/cell contact interface results in welds being formed beneath both electrodes. Pulse welding has become the dominant RW technique in Europe, while ultrasonic welding is used in the U.S.; silver is employed as the interconnect material on both continents. The bonding techniques have been developed empirically instead of theoretically. An IR inspection technique has been produced for monitoring the weld temperature.

Stella, P. M.↗