Why does stainless filler fill porosity?

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So i was welding at work the other day and kept getting porosity in my one weld. After fighting with it for awhile a few people stopped by and said 'just add a dab of stainless'.Its not the first time i've heard it, and i've done it in the past, but what i'm curious about is, why it fixes porosity?Before all the johnny do gooders stop by, i'm not interested in hearing 'the right way to do it is blah blah yackaty smackity' I know the right way, but the right way was designed by an engineer in an air conditioned office not someone hanging from their nuts 300 feet in the air in a blazing hot furnace.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:The way I understand it is porosity is a symptom of oxygen contamination. The chromium present binds readily with the oxygen forming chromium oxides. Your porosity will be eliminated provided the oxygen present is relatively small. The stainless can cause other problems depending on further processes though.Take this for what it is worth. I have no references to back this up.Last edited by shovelon; 10-03-2011 at 12:53 AM.Reason: speellinWeld 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:ha, i'm sure they didn't feel like giving a lengthy explanation to a crybaby.  300 feet in the air in a furnace?   surrrrre you were.   when did they start putting furnaces thirty story's up?  ok,   since i installed high ventilation exhaust systems in a couple of foundy's and for a major tile mfg in corona, ca. i know something about that end of the biz.   since the tile line was running 24/7 we had to run our trunk lines while the ovens were running.   ambient air temp six feet above the oven 135 degrees.   trust me friend, no time for tigging there.the engineer designs, selects materials and methods of connecting them.   he would probably be unhappy that they gave the job to someone that doesn't know what they are doing and can't take instruction from those that do.   you better stay in the shop where you can get the help you need.love these posts,  there's so many of these guys out there today.  all to our detriment.
Reply:the short answer to you question is:1 - Shovelon offered one possible explanation; although oxygen is not normally the major cuprit with gas porosity  in welding.  Nitrogen is more often the problem.2 - Stainless steel can absorb a much greater amount of Nitrogen than low carbon steel.  So adding some stainless steel to the weld pool enables the excess nitrogen to remain dissolved in the steel.  The reasons for this are complicated and I won't go into it here unless someone asks for the details.One reason that adding stainless to mild steel is not a cure-all; doing so can produce welds that may crack.  There are several reasons this cracking can occur; and again it's more complicated than I want to get into here and now.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Originally Posted by fdcmiamiha, i'm sure they didn't feel like giving a lengthy explanation to a crybaby.  300 feet in the air in a furnace?   surrrrre you were.   when did they start putting furnaces thirty story's up?  ok,   since i installed high ventilation exhaust systems in a couple of foundy's and for a major tile mfg in corona, ca. i know something about that end of the biz.   since the tile line was running 24/7 we had to run our trunk lines while the ovens were running.   ambient air temp six feet above the oven 135 degrees.   trust me friend, no time for tigging there.the engineer designs, selects materials and methods of connecting them.   he would probably be unhappy that they gave the job to someone that doesn't know what they are doing and can't take instruction from those that do.   you better stay in the shop where you can get the help you need.love these posts,  there's so many of these guys out there today.  all to our detriment.
Reply:Originally Posted by claymans13Before all the johnny do gooders stop by, i'm not interested in hearing 'the right way to do it is blah blah yackaty smackity' I know the right way, but the right way was designed by an engineer in an air conditioned office not someone hanging from their nuts 300 feet in the air in a blazing hot furnace.
Reply:Originally Posted by fdcmiamiha, i'm sure they didn't feel like giving a lengthy explanation to a crybaby.  300 feet in the air in a furnace?   surrrrre you were.   when did they start putting furnaces thirty story's up?  ok,   since i installed high ventilation exhaust systems in a couple of foundy's and for a major tile mfg in corona, ca. i know something about that end of the biz.   since the tile line was running 24/7 we had to run our trunk lines while the ovens were running.   ambient air temp six feet above the oven 135 degrees.   trust me friend, no time for tigging there.the engineer designs, selects materials and methods of connecting them.   he would probably be unhappy that they gave the job to someone that doesn't know what they are doing and can't take instruction from those that do.   you better stay in the shop where you can get the help you need.love these posts,  there's so many of these guys out there today.  all to our detriment.
Reply:Originally Posted by jrw159Since you are not interested...........As a welding inspector all I will say is that stuff like this provides JOB SECURITY for me. Thank you very much. jrw159
Reply:Originally Posted by fdcmiamiha, i'm sure they didn't feel like giving a lengthy explanation to a crybaby.  300 feet in the air in a furnace?   surrrrre you were.   when did they start putting furnaces thirty story's up?  ok,   since i installed high ventilation exhaust systems in a couple of foundy's and for a major tile mfg in corona, ca. i know something about that end of the biz.   since the tile line was running 24/7 we had to run our trunk lines while the ovens were running.   ambient air temp six feet above the oven 135 degrees.   trust me friend, no time for tigging there.the engineer designs, selects materials and methods of connecting them.   he would probably be unhappy that they gave the job to someone that doesn't know what they are doing and can't take instruction from those that do.   you better stay in the shop where you can get the help you need.love these posts,  there's so many of these guys out there today.  all to our detriment.
Reply:everyone is an expert until their in the ****...plain and simple.Its no different than people without kids saying 'i would never do that to my kids!" Well, come see me when you have kids...Last edited by claymans13; 10-03-2011 at 10:28 AM.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Originally Posted by claymans13and i will say that numerous weld inspectors have suggested it in the past. As long as the weld passes xray thats all they care about. I'm sorry for not wanting to hear from all the people who have abided by every osha standard and went above and beyond osha standards
Reply:just sayin that this has been done for the last 40 years in these boilers, I doubt a dab of stainless filler is going to crumble these power house boilers. I just had a simple question as to why it seems to remedy porosity, but everyone reads WAAAAAY to much into things. I'll be sure to tell the weld tech today who is a boilermaker of 37 years and a weld tech of 22 that he'll lose his job.I'm sure stuff like this has more bearing on more critical jobs, but we're talking about a dab or two of stainless in one out of thousands of welds. Hell, on emergencies the plant tells us to bring 80s AND 309 or MO-10 in the climber with us becuase they want it done. Weld techs don't go in spider climbers and when is costing the plant a million dollars a day there is no WPS, theres only the get it the f done method.Last edited by claymans13; 10-03-2011 at 11:43 AM.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Originally Posted by claymans13everyone is an expert until their in the ****...plain and simple.Its no different than people without kids saying 'i would never do that to my kids!" Well, come see me when you have kids...
Reply:Claymans13 & Pressur_welder we are in the same biz there.  I just had a friend thats a boilermaker black listed from several plants in oklahoma just because some of the guys on his crew were doing this.  I to have used this in a pinch while hanging several hundred feet up in a place hotter than hell & know that my welds have not failed they have been ok for about ten years now. fdcmiami you have no idea what your talking about bro.I stand behind my welding, I just won't stand under it!
Reply:Originally Posted by A_DAB_will_dothe short answer to you question is:1 - Shovelon offered one possible explanation; although oxygen is not normally the major cuprit with gas porosity  in welding.  Nitrogen is more often the problem.2 - Stainless steel can absorb a much greater amount of Nitrogen than low carbon steel.  So adding some stainless steel to the weld pool enables the excess nitrogen to remain dissolved in the steel.  The reasons for this are complicated and I won't go into it here unless someone asks for the details.
Reply:"you are the exact type of person i didn';t care to hear from. But last time i checked when i was on an emergency outtage fixing leaks in a power plant boiler, I was 200 feet in the air in a spider climber, 6 hours after the unit came off line tigging a tube. So yeah, when its that hot, and you have some porosity, and the plant wants the unit back online, you do what you have to do. Guys like you would be laid off before the job even started."so sorry ace,  so, let me get this straight.   you were 300 feet in the air big man and several people dropped by to give you some bad advice on stainless porosity.  so you took your whiney crap here to what?  look for understanding souls.   tell you what ace,  go to google and send us a pic of your location.   show me that furnace (point at which heat is delivered) that is three hundred feet in the air.  oops it's two hundred now isn't it?  were the other advice giver's that dropped by in their spider suits too. lol   i spent a year working with a bunch of boiler dudes and i will say this, the are  hard workers, you bet.  it is tough work.   but that's it.  any one with a strong back and desire to live only to the age of 54 can make it.  personally i think the riggers were the smartest guys on the site.
Reply:That's shovelon and a dab will do. You guys answered the question. I know its not the "right" thing to do but its been done for years and. Was curious why it does what it does.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Here are some pics for some sceptics that say the boilers are not three hundred feet tall.    They are hard to see but the first is the top of the inside of the boiler looking up, second is looking at a wall section, third is looking up at the scafolding from the bottom of the boiler you can hardly see but it is way up there about 280' on this boiler Attached ImagesI stand behind my welding, I just won't stand under it!
Reply:here is another pic to the right is the rear of the reheat section alot of tube leak repairs in this area & as fellow boiler maker bro's know on the other side of that is the superheat section about 300' above nothing Attached ImagesI stand behind my welding, I just won't stand under it!
Reply:Why does stainless filler fix porosity? Please explain more in depth, and don't be afraid to use all the obscure scientific terms. Also, please explain all the downsides to this practice.Sorry if this has been explained before, but with all the bickering I couldn't quite sort it out.Ian TannerKawasaki KX450 and many other fine tools
Reply:Ugh I hate Safeway scaffold.Anyway I talked to the weld tech tonight and.he.cleared it up a bit. Stainless doesn't fix it.persay it hides it. Basically when they xray  the tubes its a quickly shot and since the SS is denser than carbon the xray usually doesn't see through it unless they shoot it longer. He said for me to stop down his office tonight and he'd give me some pics of carbon welds ethics SS filler in them and show me the differences. Weather all this info is accurate is beynd me. But I'm always up for learning something new in this field.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Originally Posted by unknownhere is another pic to the right is the rear of the reheat section alot of tube leak repairs in this area & as fellow boiler maker bro's know on the other side of that is the superheat section about 300' above nothing
Reply:I suppose I should clailrify for fdc. This job has a scaffold in the boiler. As for the climber I'm in those on emergency outtages. I forgot that everyone takes things so litteral on the internet. I'm not sure where I'm coming off as whiny. I never even complained about the porosity problem. Guys walking last offered me.help by saying SS filler will fix it.right up. Other than that I'm done with you since you have offered nothing constructive.to this thread.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Originally Posted by fdcmiamiha, i'm sure they didn't feel like giving a lengthy explanation to a crybaby.  300 feet in the air in a furnace?   surrrrre you were.   when did they start putting furnaces thirty story's up?  ok,   since i installed high ventilation exhaust systems in a couple of foundy's and for a major tile mfg in corona, ca. i know something about that end of the biz.   since the tile line was running 24/7 we had to run our trunk lines while the ovens were running.   ambient air temp six feet above the oven 135 degrees.   trust me friend, no time for tigging there.the engineer designs, selects materials and methods of connecting them.   he would probably be unhappy that they gave the job to someone that doesn't know what they are doing and can't take instruction from those that do.   you better stay in the shop where you can get the help you need.love these posts,  there's so many of these guys out there today.  all to our detriment.
Reply:Originally Posted by fdcmiamiha, i'm sure they didn't feel like giving a lengthy explanation to a crybaby.  300 feet in the air in a furnace?   surrrrre you were.   when did they start putting furnaces thirty story's up?  ok,   since i installed high ventilation exhaust systems in a couple of foundy's and for a major tile mfg in corona, ca. i know something about that end of the biz.   since the tile line was running 24/7 we had to run our trunk lines while the ovens were running.   ambient air temp six feet above the oven 135 degrees.   trust me friend, no time for tigging there.the engineer designs, selects materials and methods of connecting them.   he would probably be unhappy that they gave the job to someone that doesn't know what they are doing and can't take instruction from those that do.   you better stay in the shop where you can get the help you need.love these posts,  there's so many of these guys out there today.  all to our detriment.I hate heat! I would rather work in subzero weather any day!
Reply:Originally Posted by unknownhere is another pic to the right is the rear of the reheat section alot of tube leak repairs in this area & as fellow boiler maker bro's know on the other side of that is the superheat section about 300' above nothing
Reply:Fortyonethirty asked and so I'll offer some more details.Your weld tech is right that the density of stainless steel is higher than that of plain carbon steel (8 g/cm3 vs 7.8 g/cm3 approximately).  However, your weld is a blend of these two materials when you add stainless filler to the weld pool.  So the density of the weld is somewhere between these two values, depending on how much stainless filler was added and how much base metal is melted and incorporated into the weld pool.  TIG welding generates a lot of dilution because the heat input is high relative to some other processes.  (I'm assuming that you're Tig welding at least the roots on the these tubes)I am not an NDT tech, but I've looked at a fair number of X-ray films and I question whether or not you could see a change in density this small on a x-ray.  I'm not absolutely contradicting what your weld tech said claymans13, but I'd sure want to see it for myself.What I think is really going on in this circumstance is this...hang with me here because this gets real complicated real fast...Molten metal acts like a sponge does with water.  Molten metal soaks up the nitrogen and oxygen in the vicinity of the liquid metal.  Usually this is the air we all breath, but nitrogen can also come from surface contamination present on the base metal(rust, paint, grease, oil, etc. all contain things that iron likes to absorb when molten)  Freezing the molten iron is like squeezing a sponge, if there's water in the sponge it all comes pouring out.  Here's why this happens in metals...At low temps the iron atoms in steel are aranged in a pattern called Body Centered Cubic.  The link will show you pictures and provide and explanation of the basics of crystal structure.Steel heated above what's called the A1 critical temperature (when a magnet loses it's magnetism), changes structure. (That critical temp is about 1330F or 730C give or take a few degrees, depending on the chemistry of the steel).  This high temperature structure is Face Centered Cubic.A Face Centered Cubic structures has larger spaces or gaps between the iron atoms.  This equates to more room for other atoms like carbon, nitrogen, oxygen, and other elements that like to sit in the structure interstitially(between the iron atoms).When mild steel cools down below the critical temperature the iron atoms rearrange themselves back into a BCC structure.  Those large spaces between the atoms dissappear.  (Incidentally, this structure change part of the reason that welds distort when they cool)When there is an excess of nitrogen in the molten weld pool, that nitrogen is squeezed out of the freezing metal and forms gas bubbles.  In the case of TIG or MIG welding, the nitrogen gets into the material by way of a loss of shielding gas coverage, or contamination of the base metal(welding over crap instead of cleaning the surface first)This nitrogen trapped in the weld is why you have to grind out porous TIG and MIG welds.  There's no way to remove that excess nitrogen, except to remove the contaminated steel and start from clean metal.  If the contamination is being constantly renewed from, say water and rust and crap on the inner wall of a pipe, the welder is screwed.... In some rare instances the flux in a FCAW wire or on a stick electrode can work to clean up nitrogen induced porosity.  Those fluxes are meant to deal with the nitrogen in the air around the weld as it cools, but they can also work on excess Nitrogen trapped in the weld metal; if there's not too much Nitrogen trapped in the steel....OK, for those of you still following along, here's the meat of the explanation.Many stainless steels (all the austentic 300 series) have a FCC crystal structure at low temperature.  This is one of many differences between stainless steels and mild steel.  (Not all stainless steels have this trait)  They never undergo this shift from BCC to FCC and back to BCC when they are heated and cooled during welding.  If the weld keeps an FCC structure at room temp, then there is a much higher chance that the nitrogen contaminating the weld will stay hidden in the spaces between the iron atoms, and won't bubble out as gas porosity.By adding some Stainless Filler to a mild steel weld, you are encouraging the weld to retain an FCC structure (and room for a bunch of excess Nitrogen) when it freezes.  Whether or not the trick works depends on the chemistry of the filler metal used (high Ni stainlesses work better than high Cr stainless alloys) and how fast the weld freezes (slow cooling promotes the transition from high temp FCC back to BCC at room temp)Now, all of this sounds just great.  But every silver lining is surrounded by a black storm cloud.Because the filler metal and the base metal mix during welding, the chemistry of the weld is some combination of the two materials.  Adding stainless (too much or too little) and or cooling too fast or too slow, can produce welds that are brittle and highly likely to crack.  Causing excess nitrogen(or oxygen) to be retained in the weld metal can have a variety of side-effects.  Most are bad, and result in a weaker weld.Even if the weld doesn't crack, it still may not have the strength, ductility, and toughness of either the base metal or the stainless filler metal.  It could be better, or worse than what's needed.  What you get is a total unknown, and theres no practical way to figure out whether the weld is good or bad in the field.  At best you could try to duplicate what was done in the shop and then test the resulting weld.  But this is still a crap shoot.  This is what gets some of the engineers and some inspectors pulling their hair out.  Fear of the unknown.I won't wade into the debate over whether or not the practice of 'fixing' porosity prone-mild steel welds with stainless steel is good or bad.  But this is my understanding of what's going on, and why adding stainless filler to a porous mild steel weld seems to magicly cure porosity. Originally Posted by claymans13Ugh I hate Safeway scaffold.Anyway I talked to the weld tech tonight and.he.cleared it up a bit. Stainless doesn't fix it.persay it hides it. Basically when they xray  the tubes its a quickly shot and since the SS is denser than carbon the xray usually doesn't see through it unless they shoot it longer. He said for me to stop down his office tonight and he'd give me some pics of carbon welds ethics SS filler in them and show me the differences. Weather all this info is accurate is beynd me. But I'm always up for learning something new in this field.
Reply:Thanks DAB, that was enlightening. Your explanation tends to make me think that there is a threshold for contamination, and when it's passed, the excess contaminant is squeezed out when the weld freezes. I've noticed that there are different kinds of contamination too, when a contaminant is present on the weld surface and when wind blows through sheilding gas have very different results. I suppose this has to do with type and quanitity of contaminant. There is another fix I've found, not quite as effective as stainless, but similar results can be achieved with switching to -6 filler instead of my usual -2. What do you think of this practice? I've never done pipe or boiler type work, mostly ornamental and architectural, and the engineers just spec the size of the weld bead. Do the engineers on this type of job spec the filler down to the last number?Ian TannerKawasaki KX450 and many other fine tools
Reply:Wow, now that was an explanation Dab. Being relatively new in the field I like to see things like this so I can further understand why things do what they do. According to some people I was a crybaby for asking these questions and being detrimental to the craft of welding.  I suppose those who follow blindly and don't ask questions when told to do something that clearly doesn't make sense to them are pioneers of this craft instead.Again, I thank you for that very in depth explanation. People like you are what this craft needs. Now that I understand it better I can make a more educated decision when presented with the problem.Last edited by claymans13; 10-04-2011 at 02:39 PM.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Fortyone, Yes, there is a threshold for 'contamination'.  That threshold is called the solubility limit.  That is, how much of "A"(Nitrogen for example) will dissolve in "B"(Steel).   The limit is a function of temperature, and of "A" and "B".  More Nitrogen will dissolve in hot or liquid steel than, say Argon, at a given temperature.   It's never just one gas, but a mixture of several where all are competing for space inside the gaps between iron atoms.  The rules change if you change "B" as well.  I can't quote you exact numbers, but soluability for gases in molten steel also depend on the chemistry of the steel.Under some circumstances a small trace of Nitrogen is beneficial for a weld.  The same is true for Oxygen.  In contrast, Hydrogen is almost never good to have in a finished weld.  Different gases have different effects on the finished weld properties.Yes, surface contamination will be different from atmospheric contamination.  It's not always possible to ID the source of the contamination based on appearance though.  I speculate that the differences are often things you can't see with the naked eye.Yes, your -6 filler metal is higher in Silicon than the -2.  Silicon affects the fluidity of the molten puddle and silicon is also a deoxidizer.  Gas porosity is a function of not just Nitrogen dissolved, but also oxygen, hydrogen, etc. Silicon is used in the steel mills to strip oxygen from molten steel in the furnaces.  If you ever see steel labeled as 'killed' then you know that silicon or aluminum were used to clean contaminants out of the molten steel, improving the consistency and quality of the finished product.  These aren't the only way to produce clean steel, but they are common.By switching to a higher Silicon content filler metal you scavenge or clean more oxygen out of the weld metal.  Doing this can lower the oxygen content + nitrogen content down below the threshold were porosity will form.  Silicon will also leave more slag or glass on teh surface of the weld.  This may mean more cleanup post welding.  The change in puddle fluidity from -2 to -6 filler metals may make welding more difficult, particularly when doing out-of-position work.Usually, on critical work (like boiler tubes, structural steel, etc) yes, the designer or engineer of record will specify exactly what AWS class of filler metal to use on each weld.  On some applications, this extends all the way to a specific brand of filler metal.  Manufacturers will even test every lot of filler metal to ensure that it provides the expected weld chemistry and mechanical properties.   Originally Posted by fortyonethirtyThanks DAB, that was enlightening. Your explanation tends to make me think that there is a threshold for contamination, and when it's passed, the excess contaminant is squeezed out when the weld freezes. I've noticed that there are different kinds of contamination too, when a contaminant is present on the weld surface and when wind blows through sheilding gas have very different results. I suppose this has to do with type and quanitity of contaminant. There is another fix I've found, not quite as effective as stainless, but similar results can be achieved with switching to -6 filler instead of my usual -2. What do you think of this practice? I've never done pipe or boiler type work, mostly ornamental and architectural, and the engineers just spec the size of the weld bead. Do the engineers on this type of job spec the filler down to the last number?
Reply:You're welcome.  What I wrote is just my interpretation of what I've been taught.  There's even more going on during welding than I touched on in that explanation.  I skipped over things that weren't directly related to the question and simplified some of what's going on because I don't understand how all the pieces fit together yet.All that said, none of that explanation will help when the foreman barks 'Why isn't it done yet?!" when you're working on those boiler tubes.  And I doubt it would sway anybody from doing what's expedient in the middle of an unplanned shut down.  But, maybe it will help you to decide what to use to make the best of an imperfect situation.  Or help you to know when you've crossed that line between, "This isn't approved, but works" and "I have no clue what will happen if I do this".  The latter is a very bad place to be working... Originally Posted by claymans13Wow, now that was an explanation Dab. Being relatively new in the field I like to see things like this so I can further understand why things do what they do. According to some people I was a crybaby for asking these questions and being detrimental to the craft of welding.  I suppose those who follow blindly and don't ask questions when told to do something that clearly doesn't make sense to them are pioneers of this craft instead.Again, I thank you for that very in depth explanation. People like you are what this craft needs. Now that I understand it better I can make a more educated decision when presented with the problem.
Reply:Originally Posted by A_DAB_will_doSteel heated above what's called the A1 critical temperature (when a magnet loses it's magnetism), changes structure. (That critical temp is about 1330F or 730C give or take a few degrees, depending on the chemistry of the steel).  This high temperature structure is Face Centered Cubic.
Reply:Agreed.  The curie temperature is the temperature at which ferromagnetic materials lose their magnetism.  The transition temperature depends on the chemistry of the steel.  I looked at a few more Fe-C phase diagrams and references on-line after reading your post.  The temperature indicated as the curie temperture is not consistent between the 3 different diagrams I looked up.  Certainly the process is a gradual transition.  As temperature rises, the strength of an iron magnet decays.  It doesn't turn off like someone flicking a light switch at an exact temperature.All 3 of the Fe-C diagrams I checked indicate a change in magnetic properties in and around the same temperature at which the ferrite BCC crystal lattice transforms to austenitic FCC structure.   This is the A1c temperature.   It is coincidental in steel that the BCC to FCC transformation occurs at temperatures similar to the curie temperature.  This is not the case for all other materials.  Magnetism is not a function of crystal structure, I agree.  This is not the conclusion I was trying to reach.  Rather, in steel, the loss of magnetic properties is a reasonable indication that the BCC to FCC phase transformation has taken place. For somebody in a welding shop, this is useful information to have.  Once you've gotten a piece of steel hot enough that it is no longer magnetic, changes are taking place that will affect how a finished weld turns out, and or whether or not you'll see distortion from heating followed by rapid cooling.  It's a point beyond which rapid cooling can cause problems.Research to your heart's content sn0border88.  I'm more than happy to debate the finer points of what I've said.  As I mentioned before, there's always more to learn, and I'm happy to let someone else 'iron in the wrinkles' in what I think I know.  But, if your intent is to come back and provoke some kind of argument, or split hairs seeking some kind of petty moral victory over a complete stranger, then this will be a short conversation.  Life is too short for that kind of nonsense.If I've mis-interpreted the tone of your posting, please proceed with my apologies. Originally Posted by sn0border88The point at which steel loses its magnetism, or the curie temp, is about 1418F and has no relation to the A1 temp or any kind of phase transformation. A few other things stuck out to me as well, but Ill have to check the Fe-C phase diagram before I correct you.
Reply:Haven't thought of this stuff since college.For those that are still following along.  Fe-C phase diagram is basically a chart that maps iron plus various amounts of carbon vs. temperature.  Wikipedia has a  pretty good explanation here:http://en.wikipedia.org/wiki/AusteniteThe picture on the right is a Fe-C phase diagram and it looks like they tried to color code it (color of steel at various temperatures).Keep in mind that this chart reflects essentially slow heating and cooling to the various temperatures (long soak times).Wikipedia has a link to this chart:http://www.sv.vt.edu/classes/MSE2094...es/kimcon.htmlIts a Fe-Fe3C phase diagram.  Some say this is more indicative of what happens when you transition from region to region.   I don't know.  I'm not 100% clear on the reasons for slight differences in the charts.The difference between the two is minimal - at least for 99% of the welding out there.  The heat treater may think different.BTW, when you heat treat, you are essentially drawing  path through different phases.  How fast the metal moves through a phase (especially cooling) is the magic there.If you are heading for college (or I suppose in college), this stuff is covered under Materials 101.   If I remember correctly, the course didn't have a whole lot of math involved.  Mostly reading charts (like the ones above) and answering with things like "rapidly quench from 1400F".With all the work last 10 years or so on cryogenically 'heat treading' metals, I wonder if they ever extended the chart below 0deg F?  Anyone?Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:con_fuse,Try looking at TTT diagrams (Time, Temperature, Transformation) for Fe-C or Fe-FeC3.  The phase diagrams we've mentioned so far are for very slow cooling.  TTT diagrams do a better job of illustrating what's happening when steel cools quickly.http://info.lu.farmingdale.edu/depts...ttdiagram.htmlThe cryogenic cooling you mentioned is more closely described by the TTT diagrams.  That said, I can't say I've seen one that had low temperature data on it.  Will have to do a search and see what's out there.There are also CCT diagrams that describe what happens to steel as it's cooled from high temperatures.  This link has some good info, but still no cryogenic temp data.http://www.msm.cam.ac.uk/phase-trans...s/AP3/AP3.htmlThis link is a good description of cryogenic heat treatment.  But no hard data that I saw.  I'm thinking that the process is still something of a trade secret amongst the people doing it, and so there's not a lot of info being shared.  More searching might prove me wrong though.http://info.lu.farmingdale.edu/depts...treatment.html Originally Posted by con_fuse9With all the work last 10 years or so on cryogenically 'heat treading' metals, I wonder if they ever extended the chart below 0deg F?  Anyone?
Reply:Just a little food for thought. I know this is using CS where SS should be used rather than using SS to cover CS, but the outcome is the same. http://www.ksl.com/?nid=148&sid=11872480jrw159
Reply:Originally Posted by jrw159Just a little food for thought. I know this is using CS where SS should be used rather than using SS to cover CS, but the outcome is the same. http://www.ksl.com/?nid=148&sid=11872480jrw159
Reply:Originally Posted by shovelonDon't know what the material being welded was, but the bad welds were cut out and redone by the contractor.Amusing how the Local Union official accused the contractor of a coverup. Then the power plant went with the non-union contractor again.
Reply:shovelon, it was stated in the video that they should've used " stainless filler " so definatly a stainless pressure weld. It would be my assumption that they figured they could just throw a mild steel root in to save time that it takes to setup purge, cost of argon etc. Then likely filled/cap with stick or stainless tig. I wonder how they got caught? In the act? would definatly be hard to decifer an xray to make that accusation. Nice video JRW, sad thing is when your dealing with boiler pressures/superheated steam your juggling with peoples lives if you cut corners. Weld failure of a steam line in the proximity of a plant would have a catastrophic outcome. At our plant, we've been told if the main steamline ruptures it will engulf the entire turbine floor in 3 seconds, basically boiling anyone in that area instantly, very scary i have the utmost respect for steam!Last edited by Pressure_Welder; 10-17-2011 at 02:02 PM.
Reply:Originally Posted by Pressure_Weldershovelon, it was stated in the video that they should've used " stainless filler " so definatly a stainless pressure weld. It would be my assumption that they figured they could just throw a mild steel root in to save time that it takes to setup purge, cost of argon etc. Then likely filled/cap with stick or stainless tig. I wonder how they got caught? In the act? would definatly be hard to decifer an xray to make that accusation. Nice video JRW, sad thing is when your dealing with boiler pressures/superheated steam your juggling with peoples lives if you cut corners. Weld failure of a steam line in the proximity of a plant would have a catastrophic outcome. At our plant, we've been told if the main steamline ruptures it will engulf the entire turbine floor in 3 seconds, basically boiling anyone in that area instantly, very scary i have the utmost respect for steam!
Reply:Originally Posted by Pressure_Weldershovelon, it was stated in the video that they should've used " stainless filler " so definatly a stainless pressure weld. It would be my assumption that they figured they could just throw a mild steel root in to save time that it takes to setup purge, cost of argon etc. Then likely filled/cap with stick or stainless tig. I wonder how they got caught? In the act? would definatly be hard to decifer an xray to make that accusation. Nice video JRW, sad thing is when your dealing with boiler pressures/superheated steam your juggling with peoples lives if you cut corners. Weld failure of a steam line in the proximity of a plant would have a catastrophic outcome. At our plant, we've been told if the main steamline ruptures it will engulf the entire turbine floor in 3 seconds, basically boiling anyone in that area instantly, very scary i have the utmost respect for steam!