Brian Dalder Forum Moderator 180 Posts
Re: What welding rod materials will resist chloride stress cracking?8 February 2011 at 1:29pm
Beyond specifying that recognized welding procedures be followed, you might consider "over alloying" to ensure that the weld metal and heat affected zones have/maintain the same/similar corrosion resistance as the 316L base metal. When 316L stainless steel is welded, there is a tendency for molybdenum (Mo) to be lost during welding. Since molybdenum content is the main difference between 304L (no molybdenum, less corrosion resistant) and 316L (2-3% molybdenum, more corrosion resistant), any loss of molybdenum will lead to a corrosion characteristic in the weld zone that tends toward 304L. So "over alloying" with a weld wire like 317/317L, that contains 3-4% molybdenum, will ensure that the final weldment has molybdenum content equal to or greater than 316/316L and give the corrosion resistance at least as good as the 316L base metal.
I'm having a shell and tube heat exchanger fabricated from 316L stainless steel seamless tubes and 316L stainless steel tube sheets. Steam at 100 to 150 psig will be on the shell side and a soap solution containing 21% to 33% water, 1.2% NaCl, and 1% to 5% free fatty acid at 150 to 175 degrees C will be boiling in the tubes. Can you please tell me if there is any special welding that should be done where the tubes connect to the tubesheets to provide greater resistance to chloride stress cracking. Are there any special welding rod materials that are recommended for making the welds more resistant to chloride stress cracking?
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