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For copper boilers which are silver soldered/brazed the copper grade most specified and acceptable to the boiler inspectors is: -C106 CopperPhosphorus deoxidised copper is the grade of copper where oxygen is removed by the controlled addition of phosphorus during the melting cycle. A slight excess of phosphorus ensures complete removal of oxide. The residual phosphorus remains alloyed with the copper within the specified range 0.013-0.050%. The copper content is 99.85% minimum and the grade conforms to the compositional requirements of British Standard alloy designation C106.C106 is superior to the electrolytic tough pitch copper electrical grade (C101) and should be specified for all non-electrical applications, especially those involving assembly by welding or brazing. Phosphorus deoxidised copper is not susceptible to hydrogen embrittlement which is a serious risk with non-deoxidised grades.Related SpecificationsBS2871.Cu-DHP.DIN 1787.
What about C122? C106 is almost unobtanium around here.ThanksTony
I think the worms are wriggling out of the can here. It seems to me that, in the UK, for a home constructed copper boiler made using silver soldered joints, a boiler inspector will not expect to see material certification. This therefore implies that any nominally pure copper is adequate for the purpose, as has been demonstrated by every amateur boiler maker since records began. The requirements for welded copper boilers are entirely different since the construction method involves melting the copper with a consequent drastic change to the metallurgy. I suspect there is confusion between the 2 requirements. I may be entirely wrong but until some body can show me chapter and verse I shall continue to offer boilers constructed from copper bought, without tracability, from the ME trade, to my club inspector.Cheers,Rod
Even if the boiler was being built to a published design, he would still be within his rights to ask for these in order to verify that the materials used are as specified on the design drawings. Sandy.
I'll re-ask part of Rods post: reworded: Is silver brazing going to result in an oxygen problem the same as welding would??? Brazing doesn't melt the base metal....Pete
Hi Pete,I would suggest you review this excerpt from the same publication."Page 38Brazing CopperOxygen-bearing coppers are susceptible to oxide migration and Hydrogen embrittlement at elevated temperatures. These Coppers should be furnace brazed in an inert atmosphere or torch brazed with a neutral or slightly oxidising flame."
This is where I have always received my definitions:"Brazing - The American Welding Society (AWS ), defines brazing as a group of joining processes that produce coalescence of materials by heating them to the brazing temperature and by using a filler metal (solder) having a liquidus above 840°F (450°C), and below the solidus of the base metals.""The basic difference between soldering and brazing is the temperature necessary to melt the filler metal. That temperature is defined to be 842ºF/450ºC by the American Welding Society (AWS) but is often rounded to 840ºF. If the filler metal melts below 840ºF the process being performed is soldering."I don't know how the rest of the world defines these things but I suspect it is similar.Just trying to clarify....Pete
Another question in all this - does it matter if the boiler is going to be coal-fired or butane fired when complete? I have seen some references in the past to additional issues with alloys on coal-fired boiler
Excellent thread, so to summarise so far (for my future project)Cadmium free,Oxygen free,Phosphorus free,Got it