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Posted by Bob Engelhardt on February 10, 2008, 7:13 pm
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Why can't you braze with MIG? I.e., why don't they sell MIG brazing
wire? Bob
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Posted by Todd Rich on February 10, 2008, 8:43 pm
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> Why can't you braze with MIG? I.e., why don't they sell MIG brazing
> wire? Bob
Well, I'd say that you can't braze with MIG because it is a different
process. Brazing you heat the parent metal and let the lower melting
point brazing rod be melted from the heat and sucked into the join. MIG
doesn't heat up enough of the parent metal without melting it too.
However if you are asking why they don't sell bronze MIG wire? They do:
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1970868&PMT4NO=37546907
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Posted by Leo Lichtman on February 10, 2008, 9:50 pm
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"Todd Rich" wrote: if you are asking why they don't sell bronze MIG wire?
They do:
> http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1970868&PMT4NO=37546907
^^^^^^^^^^^^^^^^^^^^^^
I believe "brazing" means joining metals with a lower melting filler.
Silvere soldering is also called "silver brazing." So, I believe it would
be appropriate to include MIGing in the brazing category. However, for the
reasons you listed in the main paragraph, I don't see why it works.
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Posted by Richard Smith on February 11, 2008, 3:05 am
Please log in for more thread options Tried MIG-braze round at Kemppi - using SIF consumables
Feels like welding but deposit bronze.
Advantages - is needed these days - is currently indispensable and
used in making new cars
- low / no distortion, as don't melt the sheet metal
- join very high strength HSLA (High-Strength Low-Alloy) sheet metals.
Can't melt them as weld without turning them back to low-carbon
low-strength sheet - whereas MIG-braze preserves HSLA strength
(1000MPa - 4 x traditional sheet strength easily provided)
- preserves galvanising on back surface - thermal cycle is low enough
temperature and short enough that zinc galv does not boil off back
surface (with high strength, sheet is thin - would perforate with
corrosion in no time if galv lost).
The MIG wire quickly became known as CuSi3 (SIF said they soon had
people ringing up asking for "Kew-si-3" regardless of their
brand-named for it). Is Copper-3%Silicon-1%Mn. The silicon would be
a pretty strongly biting "internal flux" as well as a desirable
alloying element for strength. Manganese is probably for strength
alone.
Idea is to keep power well-controlled so no part of the weld much
exceeds 1000deg Celsius. Check this recollection if it's important to
you - if recall rightly, the abs. max temp where the arc is on the
surface is about 1050degC - but even for sheet metal, back surface was
at less then 900degC (metallurgical evidence backed-up claims).
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Posted by Bob Engelhardt on February 10, 2008, 9:59 pm
Please log in for more thread options Todd Rich wrote:
> Well, I'd say that you can't braze with MIG because it is a different
> process. Brazing you heat the parent metal and let the lower melting
> point brazing rod be melted from the heat and sucked into the join. MIG
> doesn't heat up enough of the parent metal without melting it too.
...
But couldn't you just turn down the amps so that you didn't melt the
base metal? You can TIG braze.
Not yet satisfied,
Bob
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> wire? Bob