What
are the best techniques for Stainless Steel Welding?
That's like asking what’s the best way to go fishing? It depends upon a great
deal of things, does not it? A great deal of things like what type of
stainless, what thickness, what’s the application, and for what industry?
Let’s
focus on three industries:
Food
service, Aerospace, and Nuclear.
1.
Food Service
Most
stainless steel in the food service industry is 300 series stainless. Type 304
.063" thick stainless steel to be exact. If you go to any Fast food
counter and check out each of the counters, shelving, cookers and such, you
will notice it is made from welded stainless steel sheet metal. Food service
codes demand 304 Stainless Steel Welding to
be used in food preparation areas because it does not rust easily. All welds
are supposed to be performed in such a way to not trap bacteria and other crud.
Back sides of stainless steel welds must be guarded with argon so that they are
not sugared and full of pits that could trap bacteria such as salmonella. All
wire brushing should be done with a stainless steel brush and welds which are
not perfectly smooth should be blended smooth with some type of abrasive wheel
and then cleaned with alcohol.
Stainless
steel alloys used in the aerospace and aviation industries are varied. There
are tons of them. Austenitic stainless steels such as 321, 347, 316, and 304
are common, but so are martensitic stainless grades like 410 steel Ascoloy, and
Jethete M190. Another family of stainless used on commercial aircraft is the
Precipitation Hardening variety. A PH in the end such as 17-4ph 17-7ph
indicates that the steel is precipitation hardening. That means holding it in
high temperatures for extended time allows the steel to liquefy. PH grades are
sometimes much more difficult to weld than the right 300 series because of
alloy elements and complex metallurgical reactions to Stainless Steel Electrodes.
3.
Nuclear
Nuclear
piping systems use a whole lot of stainless steel and the majority of it is TIG
welded. Or at least the root pass is tag welded. Most of the stainless piping
is basic 304L stainless steel but other grades like 316 are used also. Tag root
passes with stick fill is pretty common with heavy wall socket but anything
beneath schedule 80 is usually just Tag welded all the way out because x beam
results are much better that way. Stick welding is kind of difficult with
stainless.
There
are all kinds of other applications for welding corrosion resistant alloys like
boat propellers, headers and exhaust, and marine components such as parts. One
thing to remember is that they distort easily so precautions such as heat
sinks, chill blocks, and minimizing heat input are all techniques to use.
