stainless welding

i want to rip the twatty oxidising cat thingy out of the collector box of my
57 reg transalp.

it's simple enough to do apparantly, whip system off, cut the end of the
collector box off with angle grinder, rip out the internals, weld it back
together.

the cat/collector box is stainless, and i've never welded stainless before,
got a mig welder, so is it just a case of getting a little reel of stainless
wire and welding it like mild steel? or do i need a different gas (currently
using a co2 argon mix)

is it easier or harder to weld stainless than mild steel, heard welding alli
for the first time is a bastard with a mig if you havent got the feed roller
set up to slip enough.

i know stainless should really be tig welded, but i dont have a tig welder,
and cant afford one, so unless someone in the nottingham area has, and would
do the job for me for a suitable price, it looks like i have to mig weld it.

 

ISTR you should use pure argon, the carbon in CO2 makes stainless go brittle.
But YMMV, a proper welderman will probably say I am talking crap.

 

Argon/CO2/oxygen is the preferred mix for MIG and s/s. Without the O2 in the
mix, the arc can 'wander'. For an exhaust though I'd use what you've got if
you don't mind the weld rusting a bit and it's not visible. Pure Argon is
required only for ali when MIG welding.

JB

 

I sit corrected.

 

Its likely to be cheaper to go to a local engineer / fabrication shop than buy
all the wire , gas etc unless you intend to do a lot of stainless welding
yourself

--

 

How thick is the material where you are welding? What type of stainless is
it? Ferritic or Austenitic? This will determine what filler wire you need.

Hint: try to stick a child's [1] magnet to it (away from an existing weld
line). If it won't stick it's Austenitic. If it sticks a bit, then it's
Austenitic with a bit of delta ferrite in it [2]. If it sticks very well,
then it's ferritic.

http://homepage.ntlworld.com/chris.hatfield/public/Weldability of stainless steels.pdf
[3]

Your current gas should be fine.

--
Chris H,
FZS1000, two#55
He's predictable, but that's to be expected.
Please remove the numbers to reply

[1] First, find a child. Second, steal magnet. Third, run away from angry
parents...etc.
[2] Good news from the weldability perspective.
[3] Note: You are exceeedingly unlikely to have a duplex or martensitic
stainless steel exhaust.

 

**** me, i just wanted to cut it open, rip the innards out and glue it back
together with the mig welder, maybe i'd be better off taking the exhaust to
a gynacologist so he can extract the cat parts through the end can?

erm... no idea how think the metal is, prolly not as thick as me tho, but
maybe a couple of mil i'd guess, as it's in a pretty exposed position under
the bike, and it gets fucking hot in use (is an oxidising cat, apparantly
that's a few bits of tube with fukin tiny holes in that the exhaust gasses
are forced through, raising the temp and burning the baaaaaaahd stuff off
that is going to kill us all)


as to what type of stainless it is... erm, i'll go stick a magnet to it
later (got no brats so got no brats magnets, will any other type of magnet
do? fanny magnet?)
was it a childs magnet cos they are pretty weak? i have a plastic dish thing
with a GBFO magnet on the bottom, one of those things you plonk on a cages
wing to keep bolts and things in when taking bits off the engine but spends
most of it's life stuck to the side of the tool box,
But i could stick that to the cat, what do i do about the smell of burning
plastic when the cat gets hot on the next ride?


to be honnest i'd rather pay someone to de cat the bugger if i could, i.e. i
take them the collector box, they cut it open, pull guts out, and tig weld
it back together nice and neat, as the bike is still in warrenty, so i dont
want it to be too obvious what i've done, but i want to do it, as with the
restrictive cat bits out of there you get another 10mpg, and a bit more mid
range power.

 

snip>

I've never been worried about changing an exhaust invalidating a
manufacturers warranty but I'd be more inclined to just buy a
different system rather than hack the original about.

If you purchase a replacement system you can always put the original
one back on when you want to sell the bike and Ebay the non-standard
one for about half of it's original purchase price. If you do a cut
and shut on the original system any potential purchaser will want to
knock the price of a new one off the price.

I'll be very surprised if anyone can remove the catalyser and weld the
exhaust back together without it being immediately obvious to even the
most stupid of people so if you cut it about then just accept that
you've cut a chunk of your bikes value with it.

 

The ONLY suitable magnets are those which come with toy fishing sets; they
consist of cardboard fish with paperclips attached and at least two
fishing poles with a piece of string tied on, at the other end is found
the particular magnet solely recommended for this task.

Magnets on a stick (actually resembling a telescopic aerial) with bright
leds attached to the end have been much lauded as the most
indispensable tool here and elsewhere to the point of euphoria, buyers
and users particularly of any similar to the 'rolson' branded one I
recently tried should check that the whole of the magnet and lamp part is
firmly attached to the rod, dropping something: a bolt, a shim into a cam
chain tunnel is then not likely to be aggravated by also having a strong
magnet, led, plastic lens and coin cell batteries added to the collection
of foreign bodies in the nether parts of the engine.

 

Rolson - avoid, mostly.