Solar Atmospheres took on a very difficult brazing job on August 13, 2007. The challenge was to silver braze three 1" diameter copper rounds into a copper bar that measured 3 ½" x 3" x 71" and weighed approximately 225 lbs each. The customer had 130 bars that they needed brazed.
After unsuccessful attempts to torch braze these parts by hand, our customer, Clayton H. Landis Company, from Souderton, PA, called Solar for a consultation. Solar has some very large vacuum furnaces capable of vacuum brazing 34 bars in a single furnace run.
The bars were brazed at 1550o F using a 72% silver/28% copper (BAg-8) brazing alloy, without the use of braze flux, but rather in soft vacuum in the 10 Torr range using partial pressure nitrogen to avoid copper or braze alloy evaporation. 2" thick graphite plates were used to support the 8,000 lb. work load while in the furnace. Since copper melts at 1981o F, the bars would be very soft at brazing temperature and would distort if not completely supported and held level. Following brazing the work load was cooled back to ambient temperature with nitrogen gas at a pressure of 5 psig with a 300 hp radial gas blower and water to gas heat exchanger. On removal from the furnace the copper was completely bright and scale free so no clean up was required.
These copper electrodes, as an end product, are used in a process to manufacture a toxic gas to produce flat panel television screens. This project was finished in one full day.
800.347.3236 x 213