Fusion Joining Research Articles

Guided Side-Bend: An Alternative Qualification Method for Butt Fusion Joining of Polyethylene Pipe and Fittings

Abstract Historically, the procedure for butt fusion joining of polyethylene pipe has been qualified on the basis of two fundamental tests that are widely recognized within the industry. These are the tensile-impact (T-I) test method found in ASTM F2634-07 and the reverse-bend (RB) or bend-back test as described in ASTM F2620-06. Both of these test methods have been extensively utilized within the industry, and both have some specific limitations as it relates to qualification of butt fusion joining conducted in the field. ASTM F2634-07 is a highly sophisticated testing method involving precision instrumented laboratory equipment. This makes it impractical for an on-site qualification for butt fusion procedures in the field. The bend-back test, on the other hand, lends itself to field implementation, but as the method is applied to a larger diameter, heavy-walled pipe, the practicality of performing the test and safety considerations become a limiting factor. This paper will examine an alternative test method referred to as guided side-bend or full-face testing that appears very promising as an alternative to the RB test as described in ASTM F2620-06. The test method will be fully described, and data will be presented comparing T-I results and traditional bend-back results to those obtained using the side-bend test method. The discussion of the test results and safety considerations of the proposed test method will be addressed, and conclusions will be drawn regarding its future applicability.

Al-to-Mg Friction Stir Welding: Effect of Material Position, Travel Speed, and Rotation Speed

Because joining dissimilar metals is often difficult by fusion joining, interest has been growing rapidly in using friction stir welding (FSW), which is considered a revolutionary solid-state welding process, as a new way to join dissimilar metals such as Al alloys to Mg alloys, Cu, and steels. Butt FSW of Al to Mg alloys has been studied frequently recently, but the basic issue of how the welding conditions affect the resultant joint strength still is not well understood. Using the widely used alloys 6061 Al and AZ31 Mg, the current study investigated the effect of the welding conditions, including the positions of Al and Mg with respect to the welding tool, the tool travel speed, and the tool rotation speed on the weld strength. Unlike previous studies, the current study (1) determined the heat input by both torque and temperature measurements during FSW, (2) used color metallography with Al, Mg, Al3Mg2, and Al12Mg17 all shown in different colors to reveal clearly the formation of intermetallic compounds and material flow in the stir zone, which are known to affect the joint strength significantly, and (3) determined the windows for travel and rotation speeds to optimize the joint strength for various material positions. The current study demonstrated clearly that the welding conditions affect the heat input, which in turn affects (1) the formation of intermetallics and even liquid and (2) material flow. Thus, the effect of welding conditions in Al-to-Mg butt FSW on the joint strength now can be explained.

Bead on plate laser brazing of dual phase steel with two copper based consumables

High strength steels with good formability properties have been developed in recent years, especially for the automotive industry. Joining these metals is however increasingly difficult as the fusion joining processes destroy the carefully constructed microstructure of the steels, resulting in less favourable mechanical properties in and around the joint. A possible solution to this problem is the use of joining processes that require less heat input; laser brazing is one such process. In this work, the brazability of a dual phase steel sheet has been investigated by means of bead on plate brazes produced with two consumables, CuSi3 and CuAl8. Two brazability diagrams are reported and high speed video images are used to explain the differences in operating conditions for these two consumables. Temperature measurements in the steel provide an indication about the temperatures reached during the joining process, which in turn explain the changes observed in the hardness of the steel.

Fatigue properties of laser-brazed joints of Dual Phase and TRansformation Induced Plasticity steel with a copper–aluminium consumable

High strength steels combine good formability with excellent mechanical properties and have developed continuously in recent years. Joining these materials is however increasingly difficult as fusion joining processes destroy the carefully constructed microstructure. To counteract this problem, joining processes which require less heat input have been investigated. Laser brazing is a relatively new technique and a potential candidate which has found application in the automotive industry. In this paper the fatigue lifetime properties of laser-brazed Dual Phase (DP600) and TRansformation Induced Plasticity (TRIP700) steel joints made with a copper–aluminium consumable are reported. Joints created with DP600 steel showed fracture through the steel due to a brass present in the stress concentration region at the edge of the reinforcement. TRIP700 steels show similar results if the applied maximum stress is in excess of 280 MPa. However, at maximum stresses of 230 MPa, failure occurred across the interface between the braze metal and the steel. A basic fatigue crack path model is presented for the two competing failure mechanisms.

Microstructure and Mechanical Properties of an AA6181‐T4 Aluminium Alloy to HC340LA High Strength Steel Friction Stir Overlap Weld

Friction stir welding (FSW) of dissimilar joints offers serveral advantages over conventional fusion joining techniques since no associated melting is involved. In this study, FSW was applied to join AA6181-T4 aluminium alloy to HC340LA high strength steel and a systematic investigation of the microstructure formation, the development of Fe x Al y intermetallic compounds and their influences on the mechanical behaviour is presented. Based on fractography analyses, a possible failure scenario for the joint during shear test is also proposed.

Diffusion bonding of investment cast γ-TiAl

Intensive alloy development studies on intermetallic gamma (γ) based alloys in recent years has led to the development of several aerospace engine components using advanced γ-TiAl based alloys by ingot and powder metallurgical routes. These materials are of great interest to the aerospace industry owing to their very low density and good high temperature properties. Further application of this material will require the development of successful joining and cost effective fabrication methods. Joining of this intermetallic alloy by fusion joining processes, however, requires very careful process controlling, i.e. low cooling rates and very high preheat temperatures. On the other hand, solid state joining processes, particularly diffusion bonding, brazing, and friction welding, can readily be used to join this material. In the present work, successful application of solid state diffusion bonding to weld investment cast γ-TiAl alloys has been demonstrated. A series of diffusion bonds were produced without using an interlayer at temperatures ranging from 950 to 1100°C with different pressure levels and holding times. Bonds have been characterized using optical and scanning electron microscopy. Defect-free bonds were achieved for all the conditions studied. The bond qualities were assessed by shear testing at room temperature. Reasonable shear strength levels were obtained by bonding at 1000 and 1100°C for 3 h at pressures of 20 and 40 MPa, respectively. The bonds were also post bond heat treated at 1430°C for 30 min, which improved the bond quality in all cases.

Progress in joining of advanced materials Part 2: Joining of metal matrix composites and joining of other advanced materials

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure–mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Part 1 (STWJ, 1998, 3, (3), 105–126) dealt with solid state joining, fusion joining, and joining of intermetallics, while Part 2 covers joining of metal matrix composites and joining of other advanced materials.

Progress in joining of advanced materials: Part 1: Solid state joining, fusion joining, and joining of intermetallics

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure–mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Part 1 deals with solid state joining, fusion joining, and joining of intermetallics, while Part 2 will cover joining of metal matrix composites and joining of other advanced materials.

Progress in joining of advanced materials: Part 1: Solid state joining, fusion joining, and joining of intermetallics

Progress in joining of advanced materials: Part 1: Solid state joining, fusion joining, and joining of intermetallics

Progress in joining of advanced materials

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure-mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Coverage includes solid state joining, fusion joining, joining of intermetallics, joining of metal matrix composites, and joining of other advanced materials.

Progress in joining of advanced materials

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure-mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Coverage includes solid state joining, fusion joining, joining of intermetallics, joining of metal matrix composites, and joining of other advanced materials.

Welding of rapidly solidified Alloy 8009 (Al–8·5Fe–1·7Si–1·3V): preliminary study

Abstract Alloy 8009 is a rapidly solidified, dispersion strengthened Al–8·5Fe (wt-%) alloy designed for high temperature (up to 400°C) aerospace applications. Both fusion and solid state joining techniques were shown to produce bonds. Fusion techniques destroyed the base metal microstructure with primary Fe3Al, loss of solute, formation of larger aluminium grains, and the formation of grain boundary FeAl3 and intermetallics enriched with silicon and vanadium. Solid state friction stir welding did not cause a significant modification to the dispersoid population but there was a loss of solute to dispersoid/matrix interfaces.MST/3500

Advanced metals for aerospace and automotive use

Aerospace systems and automobiles with improved performance require materials with enhanced characteristics compared to conventional state-of-the-art materials. For automobiles, this is particularly true for power-train use as opposed to body use. These improvements will come from advances in synthesis/processing rather than from the traditional frenzy to define microstructure-property relationships. For both types of applications, characteristics such as strength, temperature capability, ductility and “forgiveness” (fracture toughness, fatigue crack growth rate, etc.) must be as high as possible, while parameters such as density and cost must be minimized; the latter is of general concern for automobile use and relatively inexpensive light aircraft. Because of their low density, the light metals based on aluminum, magnesium, titanium, and the intermetallic titanium aluminides are particularly attractive for both types of applications. In this paper, advanced materials in general are discussed, followed by a consideration of advanced materials specifically in aerospace and automobile applications. Various methods of synthesizing and processing the lightweight metals with enhanced physical and mechanical properties are then presented. The processes discussed include ingots and castings; rapid solidification; mechanical alloying; production and use of nanostructured materials; spray deposition; vapor deposition processes; thermochemical processing; metal matrix composites; and fusion joining.

4640732 Apparatus for fusion joining of thermoplastic pipes : Trevor Stafford, Whitley Bay, United Kingdom assigned to British Gas Corporation

4640732 Apparatus for fusion joining of thermoplastic pipes : Trevor Stafford, Whitley Bay, United Kingdom assigned to British Gas Corporation

‘Lipidic particle’ systems as visualized by thin-section electron microscopy

Lipidic phases, containing ‘lipidic particles’ (cardiolipin/egg lecithin in the presence of Ca 2+ and egg lecithin/dioleoylphosphatidylcholine/cholesterol) have been investigated with an alternative thin-section method, using rapid cryofixation and freeze substitution according to Müller et al. (Müller, M., Marti, T. and Kriz, S. (1980) in Proc. 7th Eur. Congr. on Electron Microscopy (Brederoo, P. and De Priester, W., eds.), pp. 720–721) in combination with low temperature embedding in Lowicryl HM20 according to Humbel et al. (Humbel, B. and Müller M. (1984) in Proc. 8th Eur. Congr. on Electron Microscopy (Csanady, P., Röhlich, P.; Szabo D., eds.), pp. 1789–1798). With this method one can visualize a honeycomb structure with local fusion (joining) points between bilayers which is compatible with the structures hypothesized for lipidic particle-containing systems.

WT4 Millimeter Waveguide System: Mechanical Design of Sheathed Waveguide Medium

The mechanical design of the sheathed waveguide medium for the WT4 System provides means for the fusion joining of waveguide modules into a continuous transmission line and for limiting the distortions added by the joining and installation processes. In addition the fusion-joined steel sheath guarantees a much higher degree of protection for the medium than is present in any of the existing long-haul transmission lines. A summary of the development program of the sheathed waveguide medium used in the recent field evaluation test is presented herein. Results are given of the study conducted to establish the welding procedures used and steps in the evolution of the welded coupling design are reviewed. A discussion is given of the behavior of the two-stage mechanical filter that attenuates the effects of the irregular soil forces acting on the sheath. Estimates of the field test losses attributable to the joining and installation processes are also given.