Brazing strength vs low penetration MIG welds

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Question:  Is brazing together material stronger than MIG welds with low penetration?Example:  1/2" EMT conduit brazed together wit 3/32 bronze rod vs .030" MIG wire with the voltage set low enough to not get complete penetration.  The joint is a properly notched T-joint.I was recently told that the MIG weld would be stronger.  True?  False?  It depends?I don't have an O/A setup to test them, therefore I am asking the experts! -Brian
Reply:It depends on the application.  Poorly welded product is poorly welded period.  Brazing finds the pores and hangs on.  I would rather have good braze than a poor weld.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:Originally Posted by lugweldIt depends on the application.  Poorly welded product is poorly welded period.  Brazing finds the pores and hangs on.  I would rather have good braze than a poor weld.
Reply:My understanding of brazing was the joint design was the key to it's strength. A butt joint would be a poor brazing choice, but a lap joint would be super strong.The EMT with the thin edge of a standard Tee, would likely not be the best designed joint for brazing, However if you made a saddle and brazed the saddle to the other pipe that would be very strong.
Reply:Old steel framed racing bicycles were often brazed.  Others were lugged.  Welding them didnt become common untill later.   Brazing can be very strong in the right application.Why not make a proper weld with adequate penetration to hold the joint together?MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Once upon a time, I worked in a machine shop. At the time I was 'ripping keyways' in the bores of something (cast iron or cast steel); using a 'broach' IIRC. Well, I broke one ( the tool, not the part), pulling it in half. It was a tool steel piece about 3/16" wide and maybe 5/8" tall. After the supervisor dicided that I had set up the alignment correcty, he sent me to the weldor. He brazed it back together in a butt braze. This thing was 3/16" x 5/8" tool steel. There was a 'bunch' of tension to pull the broach through that cast material to make keyways. After the fix, I 'pulled' another thousand keyways.  To this day, I'm amazed that braze could handle the tension (40 years later). So anytime Denrep shows brazing, I'm paying attention. 9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:MIG welding is stronger than brazing.Welding is joining the same metals together with the same metal which is about 85,000psi.Brazing is two pieces of metal melted together with a second type of metal which is about 34,000 psi,  Silver brazing about 43,000 psi.With MIG you have to make sure you are getting the penetration necessary.AWS certified welding inspectorAWS certified welder
Reply:Originally Posted by Craig in DenverOnce upon a time, I worked in a machine shop. At the time I was 'ripping keyways' in the bores of something (cast iron or cast steel); using a 'broach' IIRC. Well, I broke one ( the tool, not the part), pulling it in half. It was a tool steel piece about 3/16" wide and maybe 5/8" tall. After the supervisor dicided that I had set up the alignment correcty, he sent me to the weldor. He brazed it back together in a butt braze. This thing was 3/16" x 5/8" tool steel. There was a 'bunch' of tension to pull the broach through that cast material to make keyways. After the fix, I 'pulled' another thousand keyways.  To this day, I'm amazed that braze could handle the tension (40 years later). So anytime Denrep shows brazing, I'm paying attention.
Reply:Originally Posted by Donald BranscomIt was probably TIG'd together with silicon bronze?Thats what i would do.
Reply:Question/answer all in one, Oxymoron.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:ARC, MIG & TIG are "Fusion" methods of welding.  Base metal is heated to molten state while welding, filler metal is added (may or may not be same material as base metal).Brazing is a "Capillary Action" where as the base metal is heated to BELOW it's melting point and a "non ferrous" filler metal is added.  As the heated base metal cools, the applied brazing material is "trapped and bonded" within the pores of the metal.Some brazing alloys (such as Eutectic,Cronatron brands) can give you up to 70,000 psi tensile strength.Each method has it's own applications.
Reply:donald, you are right that a mig weld is stronger, but the original post indicated that the weld was an inferior weld to start with.  in this case the brazed joint would be much stronger.  also i believe that some can argue that a tig'd silicon bronze joint is the same as a o/a silicon bronze joint as the only difference in the two processes is the heat source.  they are still both brazed joints.
Reply:Donald,Brazing isn't  melting  two pieces of metal together with a second type of metal.  If you try to melt the parent material metals, and then insert the "brass",  you are in for a rude awakening, most likely there will be a loud pop and brass sprayed everywhere.  Instead,  the base metal is heated to around 800 degrees so the the pores of the metal begin to open up and the brass can be added at the same temperature so that it can be absorbed into the pores though capillary action, as it cools, the metal is locked in.  The strength of a brazed joint can be affected by a number of factors including overheating of parent material, filler material, joint design, and filler composition.  But,  what I have seen is that it generally will have 45kpsi tensile strength if done at optimal conditions.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:If the conversation is specific to an improper mig weld, then glue, sticky foam tape, screws or even bubble gum may be stronger than the improper mig weld, depending on how bad the weld really is.   Why are we even bothering to have a conversation about the strength of bad mig welds versus anything??   This is a PROFESSIONAL welding forum, not Bubble Gum Welders Anonymous... weld it right or pay someone else who can to do it for you!MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Thanks for the answers.  They are pretty much what I was thinking.The question came to me actually as a statement by a friend of mine.  I am working on a small project that involves 1/2" EMT conduit.  The guy that gave me the pattern for it used an O/A setup and brazing rods to assemble it.  I am using a Millermatic 211 for the same project.  The comment was something like "It doesn't matter if you get full penetration on the conduit, as anything you put down with the MIG will be stronger than the brazed joint."  I knew that it just didn't sound right, but wanted to verify it.Thanks again for the help.Brian
Reply:A bad weld could be no better than some used bubble gum, as already said and pointed out.  Same as a bad brazed joint.A good welded or brazed joint but a bad design could still be no good, as the design could be why the 'thing' fails.Weld it right and at least from the welding standpoint you'll be good.  Then it's just up to the design, including the overall material selection, as to whether the 'thing' is good or not.Brazed butt joint on sheetmetal would not be all that strong, but a brazed lap joint on sheetmetal could be plenty strong.  Etc, etc.  The best laid schemes ... Gang oft agley ...