American Welding Society Forum
would like to know why phosphorus is considered a contaminant and yet it is use in brazing. Please explain. Where can I obtain this type of information. thanks
As P relates to steel,high amounts of P cause embrittlement, small amounts less than 0.05% aid strength and corrosion resistance. It holds various and I think (just educated guessing) similar properties in bronze alloy but proportions are greater by about a power of ten (move decimal to right one place)
Manufacturers of filler metals will make their alloy composition and strength data available.
As I understand it, P is used in some brazing alloys because it gives a very wide melting range and some alloys can be brazed without the use of a flux, but beware. P does cause embrittlement in iron alloys and thws ear therefore only used on copper and copper alloys without nickel. High P also does not like sulphur containing environments.
Sources of information include ASTM Metals Handbook: brazing and soldering.
Hope this is useful.
I've always understod bronze fillers to have the potential to dissolve into base metals, and vice-versa. Heat control is important to avoid this phenomenon. There is a bronze solder being promoted locally for it's efficiency in the HVAC industry due to lower melting temperatures, owing to its P content, which also I understand lends to the toughness of the alloy.
Does a mechinism exist, of which I am unaware, by which P and other potential alloying elements can dissolve into other metals which are kept well below their liquid state?
Regretably, one might describe my mastery of the field of metallugy with the pronunciation "mental-allergy"- it remains rather element-airy.
d - I don't really know the answer to this withiut a huge amount of searching. Brazing's only a very small part of the stuff I'm expected to know about. Certainly diffusion processes exist whereby elements can be transferred in the solid state and I expect that this could be the case with Phos with the formation of eutectics and peritectic phases in the base material. Generally this would be expected to increase with increasing temperature. Solders tend to have much lower melting temperatures than braze materials.
Bronze solder is a bit of mystery to me - bronze being Copper/Tin I am unaware of a solder or braze that is based on this alloy combination but as I said, this isn't really my detailed area.
In prepraring this I realised that there is a separate forum for brazing and soldering here - you have to scroll down a little to find it. Perhaps someone there may be able to assist further?
Sorry- I have grown to use the term "solder" and "braze" carelessly to refer more to the process than the alloy. I do appreciate the interchange.
Stay well & regards
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