Pinholes and Purging

UPDATE:

In this original posting I talked about common solutions to Pin Holes.  My apologies for not picking up on this, but in his question Marv B. stated that prior to welding he “tried cleaning them [the components] with Brake Cleaner”.  Welding and Brake Cleaners can be a deadly combination.

There are many warnings on the “everyday” chemicals we use.  Often, I will simply assume that if it’s sold over the counter surely it must be safe.  But the SDS (Safety Data Sheet) for a can of brake cleaner may read, “Do not use this product near open flames, welding operations or excessive heat.  Vapors may decompose to harmful or fatal corrosive gasses such as hydrogen chloride and possibly phosgene.”  This can be debilitating or even deadly to the Welder or those around him/her.

There are many manufacturers of cleaners, removers and degreasers used throughout our industry.  Most are safe when used as directed, so pay attention to the product labeling and review the products Safety Data Sheet (SDS).  Please use caution when determining how your weldment will be cleaned.  Only use approved cleaners to the manufacturer’s instruction.  Read the warnings and review the products SDS.  As my old boss used to say, “Somebody wants you home tonight.”

Thanks to Steve 'Brewdude' Garn who shares his experience on welding and brake cleaners at (http://www.brewracingframes.com/safety-alert-brake-cleaner--phosgene-gas.html).  I also want to give a special Thanks to the loyal readers that pointed my over-site. You come to us for good advice and I should pay attention to details when giving it.

PWC

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Hi Paul,
I was doing a search over the internet and came across your contact information.  If you don’t mind, can you help me with a problem?
I am machining a Bearing Housing made out of 1045.  I have to plug and weld some cross holes.  I am using 1018 for the plugs.  I am also using a tig welder to eliminate too large of a weld.  My problem is that I am getting pin holes in my weld.  Is it because I am not preheating the part.  or is it because I am welding 1018 to 1045?
We didn’t machine the parts dry so maybe there is a light film of coolant on the parts but I tried cleaning them and that didn’t seem to help.
If you could reply back that would be great or go ahead and give me a call.
Thanks!!!
Marv B.

Hey Marv,
The welding of the materials shouldn’t be a problem.
Let me ask, the machined port looks to be made up of 3 different drilling operations.  Are all 3 completed before the plug is welded in?
The reason I ask…
If the port to be plugged is drilled first (others drilled after welding) trying to weld a plug in the hole creates a condition I’ve dealt with most of my career.  When trying to seal weld the only opening in any cavity the air (or gases) in that cavity heat and expand. During that expansion a pin-hole will form at some location in the weld (just on solidification) to allow that expanding gas to escape.  Molten metal makes a poor seal 
Pipe-Welders see this same condition when finishing the root pass in a purged pipe.  If they don’t build an alternative location for the gas to escape the gas will blow through the final weld crater.
I also dealt with this condition on Flare Bevel Groove welds on a robotic application of a manufacturer where I served as Weld Engineer.  We were able to remedy that with a punched whole on the faying surface of the joint.
Not sure if this is your condition, but if you’re trying to seal the only opening, it sure could be.
Let me know.
PWC