What criteria do I use to select one brazing alloy versus the other?
I've been using AWS BAg-34 for joining a variety of metals ever since I purchased my torch about a decade ago and have a good supply of this particular alloy on-hand.
This past weekend, I received an impressive quantity of AWS BAg-5 alloy as a gift from a family member. I now need to learn more about brazing alloys...
I've been looking at the spec. sheets for the products I have on-hand:
From the documentation, the main difference seems to be that AWS BAg-34 has 2% tin while AWS BAg-5 does not. I have no clue what the significance of this is other than a hazy recollection of reading somewhere that the addition of tin gives the molten alloy wetting properties to make it flow better into the joint; hence, my choice of BAg-34 as a general purpose brazing alloy at the time, plus the fact that my local welding supply shop had plenty of it in-stock all the time and recommended it. This still doesn't answer the question as to when or why one would select AWS BAg-5 over AWS BAg-34 when BAg-34 seems to have better properties due to the tin in it.
Last night, once again, my local welding supplies shop confirmed that both will do the job but, AWS BAg-34 is "better" than AWS BAg-5 based on their own personal experience of using the product without quantifying what "better" means. The fact that AWS BAg-5 is out there on the market along with AWS BAg-34, suggests that I am missing some information and/or don't quite comprehend something. Can anyone enlighten me? If AWS BAg-34 is "better", why do they make AWS BAg-5? How do I determine when to use it other than reading a specification off a blueprint for some fabrication project?
The manufacturer's product specification sheets for comparing the two alloys aren't of much help for someone who doesn't know enough about metallurgy to grasp the significance of a 2% difference of this metal or that metal in the alloy composition. Can something like this be explained in plain English?
One partial explanation I've gotten so far is that AWS BAg-5 needs to be used for brazing stainless steel food industry equipment without any further explanation as to why. It is not clear to me whether BAg-5 is preferred in this case because the material to be joined is stainless steel or, because BAg-5 is non-toxic when used in food processing equipment or, simply because of some ethnic tradition in the restaurant industry that I might not be aware of. Where do I find basic information like this? Are there any "How to Select a Silver Solder for Dummies" books I could refer to?
Or, is all of this subjective and the choice of brazing alloy is a matter of personal preference based on personal experience the way one would select a 6013 rod while someone else would select a 6011 rod for a given arc welding task -- the end result being the same -- two pieces of metal joined together?
The more I research this, the more confused I seem to get. Is there some sort of rule-of-thumb, expressed in ten words or less, that someone with a hot torch and little knowledge of metallurgy could use to make the selection?