[TheForge] Brazing vs welding

Mon Nov 18 00:31:00 2002

At 08:53 AM 11/17/02, you wrote:
>Pete  and John,  I was told that nickel rod leaves a layer of carbon under 
>the weld and is not as strong as brazing?  In any case this is a close 
>fitting joint  and I am hoping that means brazing will be strong.   If you 
>believe the data from harmony & co a close fitting brazed joint is 
>stronger than the parent metal. Since these are mating halves of a cast 
>iron fracture I wasnt planning to file or grind the joint , just degrease 
>and pickle to clean it.   Does this sound right?  Does it pay to tin the 
>surfaces before joining?

Adam, While the convention is to grind it out like a weld to be sure you 
get good penetration on a massive joint like that...Tinning ,cleaning and 
fluxing carefully, then carefully and evenly heating  both pieces to a 
uniform temperature and forcing them together when you achieve full fluidus 
ought, in theory, to work perfectly...BG...
..once you get them in place, make sure they dont move till the joint is solid.
       Pete


>Adam
>
>
>At 09:42 PM 11/16/2002 -0800, you wrote:
>>At 10:58 AM 11/16/02, you wrote:
>>
>>Adam, there is a special brazing flux for cast iron..There's an 
>>old  blackened red  can that I've had for years that was for that but the 
>>label was burned off years ago..theres some crusty black flux powder in 
>>it.  Might ask the Anti-borax Co.. Most Important for that sort of 
>>repair, is de-greasing.
>>A stronger repair is using nickle rod and a stick welder...an old method 
>>was to buy cast ( literally) iron rods for torch use and use a similar 
>>cast iron flux as for braising.
>>
>>Re Harbor Fright prices..."can't hardly go wrong at those 
>>prices".........Oh yes you can!
>>I figure that the  % of HF tools that are utter crap about equals the $ 
>>you save on the rest..and you have no guarantee on the remainder.
>>
>>Chris; In years gone by, I've used 2 kinds of brazing rod made for stick 
>>welders. One was an aluminum bronze. No idea if it is still available.
>>
>>John CH;  The advantage of using TIG would lie in the shorter time it 
>>takes to reach heat,the more confined heat propagation ( and heat shock) 
>>and the lack of flux because the shielding gas keeps the oxy away. Flux 
>>cleanup can be a real nuisance.
>>
>>This sage advice is probably worth about what you paid for it..BG
>>
>>Pete
>>
>>
>>
>>
>>
>>
>>
>>>a very informative post.  Pete, what do you suggest for brazing cast 
>>>iron?  I have a couple of vises  (actually I have a LOT of vices)  that 
>>>failed where the moveable jaw joins the slide bar.  Would like to try 
>>>and repair them.
>>>
>>>The two drawbacks I have found with brazing forged work are:  cant work 
>>>the piece after brazing if it means heating the join  and that the 
>>>colors dont match.  OTH being able to disassemble the joint w/o damaging 
>>>the components can be very handy
>>>
>>>Adam
>>>
>>>
>>>At 08:58 PM 11/15/2002 -0800, you wrote:
>>>>At 06:20 PM 11/15/02, you wrote:
>>>>
>>>>
>>>>There are a bunch of specialized fluxes available for brazing...or you 
>>>>can use the  same borax you forge weld with.  For gas welding , flux 
>>>>coated rods are handy. You can get rods to match a range of colors and 
>>>>rods that melt at different temperatures so that you can build complex 
>>>>structures is stages. ....
>>>
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