Tig Welding 12L14 Bungs

Is Tig Welding 12L14 steel a good idea?

12L14 steel is also know as "free machining steel" and the "L" stands for Leaded.  

Basically lead is added to plain carbon steel and acts as a lubricant and makes carbon steel machine... "like buttah!"

Now plain aisi 1010 or 1018 carbon steel is not difficult to machine at all but when a company is machining hundreds or thousands of a part, 12L14 saves lots of machining time and makes nice smooth parts.

The problem is while the lead is good for machining...its bad for welding.

12L14 should never be welded for critical weldments like lifting lugs, or fittings where high pressure and cyclic loads are encountered.

that said...12L14 CAN be welded.... and there are a few things that help make it go better.

One thing you will notice if you watch the video on this page.  The top of the bead tends to produce weird areas that almost look like undercut.

Because of the lead content, the melting point at grain boundaries is lowered and areas that reach that temperature sort of melt even though they are obviously not part of the weld.

Actually, what is going on is called "incipient melting".  

Lead lowers the melting point of the metal especially at grain boundaries.

So areas near the weld puddle actually begin to melt and then quickly re-solidify.

One thing that helps prevent this is making sure torch and electrode angle is pointing slightly downward.  Another thing that helps is using a medium to low amperage setting.

I used 100 amps for the first pass and 90 amps for the second weave pass...and I almost think 80 would have looked better.

What rod should you use for 12L14?    er70s2?, er309 or er312?  I have used all of these with success.  

...the key is to use just enough heat for the filler to wet out and bond to the surface of the 12L14 ...without melting much of the base metal into the weld.

the terms "Dilution" or "admixture" refer to weld metal that is a mixture of base metal and weld metal. ....usually referring to situations where filler metal is not the same as the base metal being welded...

...because there are times when  a different composition filler metal is used.  (a good example of this is hardfacing).

So... if you can minimize dilution of 12L14 base metal , you often greatly increase your chances of success.

Cleaning the base metal helps a lot to because removing surface oxides allows wetting at a lower amperage.  

another tip is adding a bit more filler metal than usual.

12L14 bungs can definitely be tig welded using either er70s2, er70s6 or er309.

I used 309 for welding the bungs in this video .

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