LinkedIn - SS Hot Cracking with TIG

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Melted a few puddles today via TIG on some metal of unknown origin, although believe the "links" (5" x 2" x 1" thick) are SS.  The links were freebies from a good friend and am in the process of making a few book ends.  Modulated the pedal with 170A DCEN and 6.5sec post-flow.  RED 3/32" tungsten and 1/16" ER308L filler.  The second photo shows the hot cracking that developed immediately during burn-in.  Why?  Gut's telling me the cracks resulted from no pre heat to the thick 1" section links.  Strange that the first two runs (root pass) on another set of "links" developed no cracks.  Stainless Steel, always said she has the "duende"Mahalo in advance for your insight ~  Attached Images"Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:It is about that time that I go pull out my er312. Works a charm.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Manokai,If that's a free machining grade of stainless then that is the likely culprit.  Free machining stainless alloys have sulfur in them.  The sulfur forms low melting temp compounds in the weld puddle, and this leads to hot cracking.If you know it's not a free machining stainless; then I agree with your guess about the material thickness and lack of preheat.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Have you checked it with a magnet?
Reply:Use 312 stainless filler and it won't crack at all (seriously).Last edited by MikeGyver; 10-15-2014 at 10:08 PM.Welding/Fab Pics: www.UtahWeld.com
Reply:309 stainless rod will work also
Reply:@ shovelon - er312. Have to give it a shot.  Read that 312 has a higher ferritic content and is frequently used for cast iron repairs also.  Thanks!@ A_DAB_will_do - you may be on to something.  There's def machining marks to a few on the link surfaces.  Believe these are 316SS grade from a maritime inventory.  Your logic with sulphur makes total sense.  Mahalo!@ HT-4956 - yes, checked items with a magnet. No attraction.@ MikeGyver - 312, will do!@ That Guy There - no so fast.  Tried three additional passes, over the cracked 308L root, using 309 and the runs hot cracked longitudinally the entire length.  Minimized heat input per pass and she still yielded.  Back to the drawing board with some "312".  Thanks guys."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:303 stainless (the free machining I encounter) will weld ugly due to the sulfur. I only work with food grade stainless, so what other free machining stainless grades are used?Lincoln Precision Tig 185Lincoln Power Mig 256Hypertherm PM 45Everlast 140STSmith O/A
Reply:Looking at the weld profile and the location of the crack (mid bead) I do not believe the cracking is due to the grade of the base metal. It would take considerable dilution for the base metal to reach the middle of the fillet weld.The cracking is probably due to the rapid cooling of the weld combined with the unfavourable weld profile (depth to width ratio of at least 0.5:1 is recommended).That said the easiest solution is 312. It is a wonderful consumable that should be in every fabricator's arsenal and the considerably higher ferrite content makes it very resistant to hot cracking.Schaeffler's diagram and the WRC-1992 can be used to check the cracking susceptibility of the weld metal.Here is a very handy calculator you can use if you do not have a program or do not want to make the calculations yourself.https://www.ewm-group.com/en/practic...r-diagram.htmlDo some test runs for example with 304L base material (1.4306) and various weld metals, you will see that 312 produces a weld with a lot higher ferrite content.Bottom line: Get some 312 and be done with it. Otherwise preheat lightly (80-100C ) and run thick beads.
Reply:312 is actually made for joining dissimilar steels because it's a mix of austenitic and ferritic stainless. 309 is just higher concentrated 'stainless' so when it dilutes into mild steel the weld still has stainless properties.Welding/Fab Pics: www.UtahWeld.com
Reply:303, 416 and 420Fhttp://www.azom.com/article.aspx?ArticleID=964http://www.productionmachining.com/a...-machinable(2)http://www.azom.com/article.aspx?ArticleID=971http://cartech.ides.com/datasheet.aspx?i=103&e=76Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:ManoKaiYour parent metal's thickness is great relative to bead size.If this is your desired weld width - three causes come to mind.1st.   Unhappy filler.2nd.  Inadequate fill produces a concave bead profile.   Structural welds: minimally, wants to be flat across the face - mild convexity is preferred.This allow filler material to shrink, into-itself, in the throat of the bead.3rd.  Were the elements in contact when tacked/welded?  When heavy sections are jointed with a small bead ratio - space must beprovided between the elements for movement [shrinkage].  This type of failure is analogous to 'two-blocking'.2nd. & 3rd. are the same problem - Transverse Stress.  In both cases: longitudinal cracks 'through the throat' commonly occurs.Even a 'convex bead' can crack if the elements are heavy, and the weld bead small, when no allowance is made for the movement/shrinkage - aka pull.Discounting incompatible filler:  the worst scenario is a concave bead, with contact joinery.  A concave bead doesn't have enough metal to save it sole,   and a heavy section 'contact joint' serves as a fulcrum to tear itself apart.The remedy: Research filler alternatives, Increase throat section,Shim the elements apart on soft wire for movement.These considerations can be found in: The Procedure Handbook of Arc Weldingby Lincoln Electric.Throat cracking . . . . . . Sec. - 6.3-18 . . Fig. 6-66Transverse Stress . . . . Sec. - 3.1-2 . . . Fig. 3-3Wire Crush . . . . . . . . . Sec. - 6.1-6 . . . Fig. 6-6OpusAnd back-up . . .http://www.google.com/images?client=...g&ved=0CC4QsAQ
Reply:@ taz00 - appreciate the metallurgical insight and the CE app.  Will be sure to check it out.  Mahalo@ A_DAB_will_do - great sources on the specified SS fillers.  My two LWSs do not have any "312" in stock.  Have to rip some online.@ OPUS FERRO - Paydirt!  You made my day with your diagnosis for the crack failures in SS parts.  The part were indeed tacked (4ea, 2 per side) tight prior to bead runs.  Aside from the using the improper filler as you and others have mentioned, the shallow (concave) bead profile with no micro-gap (space allowance) between the thick section links is probably a contributor to the smoking gun.  As stated, the bead introduced high traverse stresses across the weld throat and the tacked geometry did not allow for any differential movement during the heat/cool cycle.  All three of the Sections and Figures you cited above were spot on!  I have The Procedure Handbook of Arc Welding by Lincoln Electric, but have yet to devour her from cover to cover.  It's a goal of mine over the next 2-3 months.  A must for the serious welder and fabricator interested in knowing the "how" and "why" of all things metal and welding.  Thanks for re invigorating my passion for this classic text. Last edited by ManoKai; 10-18-2014 at 11:59 AM."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:Update:  retrieved 1# of 1/16" 312 filler today from my LWS.  Overlayed the 312 on the cracked 309 welds shown in post #1.  This time, added 2x the amount of 312 filler per dab.  The resultant 312 welds did not crack.  FTR, my baseline post-flow is now 10sec regardless of parent material (ie. SS, mild steel).  Starting to click.....Last edited by ManoKai; 12-31-2014 at 04:51 PM."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:My 312 should be in soon. Stoked to try it out!!
Reply:Originally Posted by ManoKaiUpdate:  retrieved 1# of 1/16" 312 filler today from my LWS.  Overlayed the 312 on the cracked 309 welds shown in post #1.  This time, added 2x the amount of 312 filler per dab.  The resultant 312 welds did not crack.  FTR, my baseline post-flow is now 10sec regardless of parent material (ie. SS, mild steel).  Starting to click.....
Reply:I know a couple guys who use 18 or more sec post flow using under 150 amps. I actually welded with his setup and the tungsten slid in and out real nice
Reply:Originally Posted by motolife313My 312 should be in soon. Stoked to try it out!!
Reply:No mike I wish. I can't tell if the lws lady is playin games or not. It was supposed to come in last Monday. She is selling it to my for only 7 bucks a pound and she gives me a deal on everything I buy so I ain't complaining yet. I found it online all over for 18 or 20 bucks a pound. The brand is uni weld I think. Is that a good brand?ive been using a little 308 308l on mild steel. It seems to flow alot better and give better color then 309. But is 308 ok to use on mild steel or dissimilar metals?
Reply:Originally Posted by motolife313No mike I wish. I can't tell if the lws lady is playin games or not. It was supposed to come in last Monday. She is selling it to my for only 7 bucks a pound and she gives me a deal on everything I buy so I ain't complaining yet. I found it online all over for 18 or 20 bucks a pound. The brand is uni weld I think. Is that a good brand?ive been using a little 308 308l on mild steel. It seems to flow alot better and give better color then 309. But is 308 ok to use on mild steel or dissimilar metals?
Reply:Thanks man!!