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Brazing-titaniumsuccessful if well prepared.SOLUTIONS with Effective, Practical Advice
Brazing-titanium is readily performed in a furnace either in vacuum or in a dry argon atmosphere with dew point lower than -55 °C. Titanium is one of the reactive metals, so called because they react with oxygen to form an adherent and stable oxide. The formation of layers of titanium oxide gives to this metal and to its alloys exceptional corrosion resistance. This quality and its property of high strength to weight ratio at intermediate temperatures (called also specific strength) make titanium alloys invaluable for those applications that best exploit the unique capabilities of these materials. Titanium oxide must be removed by mechanical or chemical means just before brazing otherwise, if left in place, it would hinder wetting.
An Article on Filler Metal for Brazing-titanium Alloys was published (4) in Issue 46 of Practical Welding Letter for June 2007. A short introduction to the different types of Titanium alloys as described by their main phase in the microstructure is given in the above article and also in our page on Titanium Welding. The influence of alloying elements on Titanium microstructure is outlined in PWL#022. To receive each month at no cost our publication Practical Welding Letter please subscribe.
Heat treatments of titanium alloys are established by taking into account the temperatures at which phase transformations occur. Brazing-titanium should be performed at temperatures that do not compromise the mechanical properties expected in the base metal. Therefore the Brazing-titanium filler alloys should be selected so that their brazing temperature is within the recommended range for heat treatment of the alloys to be brazed. Titanium commercially pure and alpha alloys should be brazed below the beta transus temperature (that at which the phase changes from alpha to beta), otherwise a coarse grain microstructure could develop with impaired ductility. The suitability of selected filler metal for Brazing-titanium should be verified by testing to make sure that design requirements for strength and ductility are met after brazing and that there is no danger of galvanic corrosion from the brazing alloy in the actual service. The following Table shows a few of the most common filler alloys used for Brazing-titanium. It should be noted that many more proprietary alloys are commercially available, and that a few other that were used for academic study may not be readily found in the market.
Filler metals are available as powders and as foil, sometimes maid by compacting amorphous powders obtained by rapid solidification. The main suppliers advertise their availability for advising on filler metal selection and on corrosion resistance. Resources 1. - Articles: Brazing Titanium for Structural and Vehicle Applications State-of-the-Art of Titanium-Based Brazing Filler Metals Experiments in Vacuum Brazing of Titanium EB Brazing of Ti for Construction in Space An Article on Filler Metal for Spot Brazing Titanium to Nickel was published (4) in Issue 81 of Practical Welding Letter for May 2010. An Article on Low Temperature Brazing Filler Metals for Joining Titanium was published (4) in Issue 103 of Practical Welding Letter for March 2012. An Article on Brazing Titanium to Steel was published (4) in issue 115 of Practical Welding Letter for March 2013. An Article on Filler Metal for brazing copper or steel to titanium was published (4) in issue 133 of Practical Welding Letter for September 2014. An Article on Amorphous Filler Metal for Vacuum Brazing Ceramics to Titanium was published (4) in issue 136 of Practical Welding Letter for December 2014. An Article on Filler Metal for Brazing superconducting radiofrequency cavities (Niobium to Stainless) was published (4) in Issue 145 of Practical Welding Letter for September 2015. An Article on Brazing Titanium was published (3) in Issue 151 of Practical Welding Letter for March 2016. An Article on Minimizing Alpha Case was published (11) in Issue 152 of Practical Welding Letter for April 2016. An Article on Brazing Filler Metal Alloys was published (4) in Issue 166 of Practical Welding Letter for June 2017.
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2. - Information from Commercial Sources: Products and Services Soldering and brazing-titanium and titanium alloys
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