Brazing Filler Material

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Old 10-11-18, 08:01 PM
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Brazing Filler Material

I don't have a welder. So, when I need to "weld" metal (usually alum. or steel) I use MAPP gas and brass/bronze or aluminum rods. This works OK most of the time, but occasionally I have a situation where the MAPP is just not quite hot enough. I find in those situations, I can use either 45% or 56% silver solder and do a satisfactory job. However, I have two concerns: strength and cost. If I make a lap joint the strength seems to be more than adequate. However, if I make a "T" of thin wall tubing, I question the strength because the silver solder does not make much of a fillet and the surface area in contact is not great. Having said that, I have tried to bend or break said joint and it seems pretty strong. In any case, I would like to know if there is a less costly filler material with similar flow/strength characteristics as silver alloys. In my searches, it seems it goes from soft solder to silver solder (many alloys) to the brass/bronze high heat type material.
 
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Old 10-12-18, 05:28 AM
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Silver solder is technically a brazing rod because of the temperature it flows at.
Bronze brazing rod is not as strong as silver solder but if you are proficient you can build up a bronze rod braze for more structural strength but you would need an oxy-acetylene torch for better flame control.


There is a true silver solder often called silver bearing solder that is stronger than normal soft solder but not by much and it is difficult to build up for structural strength.
 
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Old 10-12-18, 06:39 AM
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Just our of curiosity, what is it you are "welding" ?

If doing enough a small 120V pocket MIG is pretty inexpensive.

My first welder was a kit and had everything and was around $200, had that for close to 30 years and did many car projects.
 
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Old 10-12-18, 08:33 AM
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Knowing what you are soldering/brazing would help. If you have a "T" type joint and want it to be stronger I would tend to stay with silver and install gussets for additional strength.
 
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Old 10-12-18, 08:55 AM
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Most of my brazing is general purpose that could range from small repairs of mild steel objects to hand fabrication of something from sheet stock or thin steel tube. I have had good success with thin material (+- 1/16") using Bernzomatic bronze flux coated rods. With only a MAPP torch (high heat air/gas bernzomatic), as the base material gets thicker, it either takes a lot of gas to get it hot enough for the bronze or it doesn't quite get there. My main concern with the silver alloys is that they require (from what I've read) very close tolerances in the base metal fit so that capillary action carries the alloy into the joint. Repairing or hand fabricating stuff doesn't always give an accurate fit. I'm trying to find out if there is an alloy that is more forgiving for this type of use and will still work at the lower temps that I can provide with the MAPP torch. My brazing work is too occasional and intermittent to warrant the purchase of more expensive equipment.
 
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