Stainless steel is a fascinating metal to weld. I
have spent many years welding different grades of stainless steel.
Needless to say I have picked up a few tricks along the way to make the
process a little bit easier and of course to produce better welds.
Welding
stainless can be difficult if you don't know what you are doing. It
reacts to excessive heat by warping and distorting once it cools.
Everything shows up in stainless. What I mean by that is if you weld
with too much heat you can see it by the heat marks left in the metal
along with any distortion. It also scratches very easily so you must
take care when welding on a metal table.
One of the best things
to do when welding stainless is to use a heat sink such as brass or
aluminum. I usually clamp a piece of 3/8 brass behind the seam of the
weld. This absorbs the heat and also prevents any burn through. The
trick with stainless is to put as little heat into it as possible,
especially with thin material. It's worth the extra time to make sure
you have the heat sinks in place before beginning your weld. This
allows you to actually weld the entire seam without interruption.
Have
you ever noticed that when you get to the end of the weld and you pull
the heat off it always tends to turn a dark gray. That's because you
are carrying all the heat with you and by the time you get to the end
it's at its hottest point. A little trick that I discovered on accident
is when you get to the end of the weld and you take your foot off the
pedal. Wait until the weld pool solidifies and then touch the tungsten
to the metal and hold it there till your gas stops flowing. You'll
notice that the color will come back to the weld. Depending on how long
you touch the tungsten to the end of the weld. You can actually get
that nice salmon color back. You can only do this with a setup that
uses a foot pedal. If you are using a dry rig system where you have to
use a lift arc this is not possible.
I have built many stainless
steel tables for commercial kitchens. We would add hat channels to give
the table more stiffness. Any welding would be done on the channels and
not the actual table. This keeps it looking clean.
Lets say you
had a 5 sided box as a base. The bottom was open and you wanted to weld
a pipe in the center of it. No matter how small you kept the welds, the
base would still warp and twist from the heat. This depends on the
material thickness. I am talking about 14 gauge material. You have to
have a frame to keep the base from warping. I have tried several
different methods using heat sinks and clamps but they have all
produced some amount of distortion. The best way was to add either a
few channels underneath or an actual frame with angle iron.