Hot-pressure-weldingfor quality bar butt joints.SOLUTIONS with Effective, Practical Advice
(Sponsored Links) Heat is generally applied by flames of oxyfuel torches directed on the surfaces to be joined. Upon reaching the correct temperature, the torches are suddenly removed, not to stand in the way, and the two bodies, solid bars or hollow sections, are brought to contact and upset together under pressure, usually by hydraulic equipment. This variant is properly called the open joint process. Alternatively, when the parts are making contact under pressure before heat application from the outside, also by electrical induction, it is called the closed joint process. In either case flash material is expelled and a bulge is formed at the joint.Hot-pressure-welding is similar in a way to both friction welding (see Friction Welding Processes) and flash welding (see Flash Welding Process), although the source of heating is different. For obtaining the best results the surfaces should be machined square and clean. Some beveling can be used to control the amount of upset. The process as described is performed as a manual operation. The materials to be welded must exhibit hot ductility or forgeability. Therefore cast iron cannot be Hot-pressure-welded. The materials commonly joined by Hot-pressure-welding are carbon, low alloy steels, and certain nonferrous metals. Certain dissimilar materials combinations are weldable by Hot-pressure-welding. Materials that easily form on the surface adherent oxides upon heating cannot be eaasily welded in air by this process, typically among them aluminum alloys and stainless steels. Tests were performed in a vacuum chamber. Advantages
Limitations
The most important parameter is the pressure sequence cycle, possibly being developed by trial and error. Pressure in the range of 40 to 70 MPa (6 to 10 ksi) must be available. Typical application reported, refer to butt Hot-pressure-welding of railroad rails sections and steel reinforcing bars, especially in Japan. For use in the production of weldments for the aerospace industry with delicate materials Hot-pressure-welding can be carried out in closed chambers with vacuum or a shielding medium. Mechanical properties tend to be near those of the base materials, but depend upon materials composition, cooling rate and quality. Hot-pressure-welding can be an economic and successful process for performing butt joints of simple shapes if the materials are easily weldable. Any questions or comments or feedback? Write them down and send them to us by e-mail.Click on the Contact Us button in the NavBar at top left of every page.
To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics. Friction Welding Processes Important Announcementa rich collection of valuable information on Materials, Volume 1, and Metals Welding, Volume 2, from expert Internet Sources, is now available. Buy It Now! at Metals Knowledge.
 POWERED BY:
Click on this Logo NOW! Copyright (©) 2008, 2009, 2010, 2011 by Elia E. Levi and |
