Mild steel hydrogen assisted cracking??

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So, today I was told over on tractorbynet that I was wrong when I said mild steel is not susceptible to hydrogen assisted cracking.  Since he said I was wrong, I looked for some data to support his point.I expected to find nothing, but I did find one listing: http://products.asminternational.org...ch9001113.htmlThis was for 7024 on A36 steel.Hydrogen-Induced Cracking of Welded Truss Gusset PlatesWilliam F. Jones III, Consulting Metallurgical Services, Inc.From: Handbook of Case Histories in Failure Analysis, Vol 1, K.A. Esakul, Ed., ASM International, 1992Abstract: Six cracked A36 steel gusset platesDave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Interesting..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Strange no body ever cared when we were building false work for bridges or over passes in the pouring down rain. Head back to the gang box for more 7018, and some carpenter type left the lid to the gang box open, and we would have to pour the water out of the can of rod. Attached ImagesDon’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Originally Posted by CEPStrange no body ever cared when we were building false work for bridges or over passes in the pouring down rain. Head back to the gang box for more 7018, and some carpenter type left the lid to the gang box open, and we would have to pour the water out of the can of rod.
Reply:Originally Posted by InsanerideThey probly had confidence in your welds CEP.
Reply:Originally Posted by CEPNo it's not that, they just didn't want to get out of the office when it's raining.
Reply:There has to be several factors to create a situation of hydrogen being trapped in the weld.  You can eliminate hydrogen entrapment if you extend the time it takes for the metal to cool after welding.  There isn't any atom that is smaller so hydrogen atoms are like little marbles and an iron atom is like a truck.  If the material remains at an elevated temp the hydrogen will migrate out of the weld bead.  The faster it cools the more risk you have of hydrogen being trapped in the matrix.   I notice that the description did not say what thickness the plates were.  Structural steel is made to a specification of strength unlike SAE alloy numbering system.  A heavy section like one inch A 36 plate will have a bit more carbon in it than a quarter inch plate.  The reason for this is when the plate comes out of the rolling mill it cools.  The heavy plate will cool more slowly so it will not be as strong as the 1/4 inch plate which will cool faster.  This hardening effect is not as pronounced as a high carbon steel but it does happen.  To compensate the steel mill uses an A36 alloy that has more carbon in the thick material than in the thin material so that when they cool at different rates both pieces have similar strength.   So yes a really low carbon content thin piece of mild steel like A36 will not need concerns for hydrogen entrapment.  Weld it to a piece of A36 an inch thick without low hydrogen rods you likely will have a problem.  In fact at one inch you still might have problems because the weld will be quenched by the cold surrounding thick metal..   And that is why some people might have noticed that I urge people to preheat.  By preheating you slow the cooling rate and allow more time for the entrapped hydrogen to migrate out of the weld.  The Brits use an awful lot of rutile electrodes E 6012 & E 6013) unlike us who go to the church of the Low hydrogen.  They compensate by going to the church of preheat:')
Reply:I weld A36 structural steel on a daily basis at work. We are only allowed to use 7018. All metal must be preheated with the torch to sweat out any hydrogen and all rods come out of a shop oven and we bring them to the work site in a portable oven that has to plugged in at all times. All welders hold all position CSA W47.1 certification with the CWB and smaw process. This is low hy structural code work. If it starts to rain, QC will show up to ensure we build/construct a canopy or rain cover with fire blanket. If you want to eliminate underbead cracking with mild steel, you need to weld with low hy.Last edited by snoeproe; 08-20-2014 at 09:05 PM.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:before we could weld anything structural we had to preheat to get rid of surface moisture and slow cooling. 7018 and in a oven. Attached Imagesi.u.o.e. # 15queens, ny and sunny fla
Reply:Originally Posted by lotechmanThere isn't any atom that is smaller so hydrogen atoms are like little marbles and an iron atom is like a truck
Reply:Your right.  I recollect a guy who did laboratory welding and they tested his assemblies with helium.  Their instruments were so sensitive they could read one atom getting through the seam.... At least that is what he told me.
Reply:Originally Posted by 76GMC1500There is one that is smaller, helium.  As you move to the right on the periodic table, atomic diameters decrease.  This is caused by having more protons in the nucleus which pulls the electron valences in closer.
Reply:You just can't beat a good ole 7018 when you need stuff to stay stuck together, although this is the first I've seen of a 7024 with hydrogen issues causing the weld to fail... Maybe it was a bad batch of rods? I've seen that before with a box of 7014Real welders know how to penetrate!(Equipment)Whatever can be used to beat my opponent into submission!
Reply:Originally Posted by docwelderbefore we could weld anything structural we had to preheat to get rid of surface moisture and slow cooling. 7018 and in a oven.
Reply:Originally Posted by Gerry1964Thats how it should be Doc, I think people tend to do too many short cuts nowadays, Cant remember the last time i saw a site welder with an oven, which you really should have for 70xx rods
Reply:api 1104 appendix b.Local 597
Reply:"Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:I've never heard such so much bullsh!t in all my life.....I weld with a plasma welder and that method uses water and alcohol continuously during the welding process......with that much H2O in the direct weld vicinity you think the weld seam would disintegrate if you so much as looked at it.....never happened.Ian.
Reply:Hydrogen cracking is a very real issue. especially with submerged pipelines. It is a real concern on structural and bridge work as well. Humidity, wire, rods, preheat, post heat, operator common sense. all factors in hydrogen cracking! API1104 appendix B tells you about it. It is for IN-Service welding. ALSO in appendix A in GIRTH WELDS Standard H2s (Hydrogen Sulfide) plays a role in cracking.  API1104  Annex B B.1 General : For hydrogen cracking to occur, three conditions must be satisfied simultaneously. These conditions are: hydrogen in the weld, the development of a crack susceptible weld microstructure, and tensile stress acting on the weld. To prevent hydrogen cracking at least one of the three conditions necessary for its occurrence must be minimized or eliminated. For welds made onto in-service pipelines, success has been achieved by using low-hydrogen electrodes or a low hydrogen process and, since low hydrogen levels cannot always be guaranteed, using procedures that minimize the formation of crack-susceptible microstructures. The most common procedures use a sufficiently high heat input level to overcome the effect of the flowing contents. Preheating, where applicable, and or the use of a temper bead deposition sequence can also reduce the risk of hydrogen cracking BAM
Reply:This little film might make things more understandable.      For the person playing around with 1/4 inch thick steel there is no problem.  If you are involved in heavy sections like 3/4 thick precautions are necessary.  Over my career I have seen people cheat on their preheats.  It is not a smart thing to do.  If you are welding anything over 3/4 bring out the tiger torch.  Even getting it to 100 C is better than room temp.