TIG'ing Mild steel with no filler?

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I am on another website, www.bimmerforums.com and we are discussing welding of Mild steel to mild steel by simply pooling the material together - no filler rod.  I said that this is not ideal based upon EVERY BOOK I HAVE READ as well as this forum and it's professional weldors on here.  So, please, someone go ahead and tell me that its NOT practiced and I'd love to link them to it.
Reply:You can't do it for mild steel, only stainless steel.
Reply:Provide me reasoning because these guys claim to be pro's.  I have done it and as soon as I whacked it with my hammer it cracked.  Yet, apparently I am the one doing it wrong.
Reply:OK then!Other than 40 years of trade experience, I do not claim anything.Lets look at a fused TIG joint -no filler.What have you got ?A bead of weld that has a HAZ - not a big one , but there is one there.Even if the bead is fully penetrated there usually is a bead face depression and consedquently less than plate thickness across the plate- weld bead -plate, profile thickness.Unless the plate and bead is annealed post weld, a slight hardness is likely present- dependent of course on the grade of plate welded.Then you belt it with a big bloody hammer - and it cracks - no surprises there!Filler wire addittion In my humble ,would do the following:Increase the bead thickness.Improve the bead strength and ductility given the suitable grade of filler.Not saying or claiming "what should be ", just something to ponder.Grahame
Reply:OK then!Other than 40 years of trade experience, I do not claim anything.Lets look at a fused TIG joint -no filler.What have you got ?A bead of weld that has a HAZ - not a big one , but there is one there.Even if the bead is fully penetrated there usually is a bead face depression and consequently less than plate thickness across the plate- weld bead -plate, profile thickness.Unless the plate and bead is annealed post weld, a slight hardness is likely present- dependent of course on the grade of plate welded.Then you belt it with a big bloody hammer - and it cracks - no surprises there!Filler wire addittion In my humble ,would do the following:Increase the bead thickness.Improve the bead strength and ductility given the suitable grade of filler.Not saying or claiming "what should be ", just something to ponder.Grahame
Reply:no it cant be done succesfully.. and anyone that tells you you can is full of crapand i said so...however i have "tacked" mild steel together with no filler..gotta be gentile with it though.. if you try to move it before filler is applied then the tacks just break.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I'm not an expert but the reasoning that I have read is that the filler rod contains deoxidizers that are needed to make a strong weld.  You can sometimes weld stainless without filler because it contains some deoxiders in the base metal.
Reply:I will try and find the link but I read quite a bit about this when researching ductile iron.  The melting of the mild steel metalurgically changes the structure of the metal as it transitions from liquid to solid.  The carbon (though it is less than high carbon steel) re-arranges itself in a differnt matrix that is not as strong or becomes less tensile and more brittle.  By adding the filler rod it changes the structure and alloys the steel so when it cools into a solid structure the matrix formed with the carbon and alloys maintains its strength and most of its original properties.That is why different alloy rods are used with different metals and not all rods work on all jobs.  The Stainless Steel has other alloys (I think nickel and some others) that don't change their matrix (structure) during the fusing process.If I remember correctly the link is in one of the forums that was posted here.  I spent quite a bit of time reading it when I was researching Ductile Iron.
Reply:What other posters say above about poor welds with no filler is true. Other than that, why would you not want to use filler? Frankly, I think it's easier to use filler once you get a puddle going. My 2 cents.
Reply:Are you sure, you should never weld mild steel without filler?And the science behind your reason is what?The factors that will affect the mechanical strength of any weld metal, whether it was made with or without filler material, will be the cleanliness of the steel surface, the impurity levels in the steel, the steel chemistry and it's carbon equivalent, the purity and effectiveness of the inert shielding during welding, and the cooling rate of the weld.Given a good quality, cold rolled, low carbon (1018 for example) steel, there is little if any reason why a weld made without filler (autogeneous) will have lower strength than a similar cross section weld made with filler.  Silicon and manganese additions in the filler may have a slight beneficial effect of reducing porosity, but this should not be an issue with typical cold rolled steel that has be thoroughly cleaned and properly TIG welded.One of the factors in choosing between ER70S-2, -3, or -6, will be the type of steel and the amount of contaminants such as rust and scale you intent to weld through.  The following link describes the chemistry and recommended application of these various MIG/TIG filler wires.For low quality steels containing high amounts of oxides, or where welding will be done without removing rust and scale, the triple deoxidized ER70S-2 is recommended.  The high manganese content of ER70S-6 may be beneficial in tying up sulfur and preventing centerline hot cracking in steels containing high sulfur.http://www.esabna.com/EUWeb/AWTC/Lesson6_1.htmThe hardenability, and thus the brittleness of the weld heat affected zone (HAZ), is directly related to carbon content, along with other elements such as Mn, Mo, Ni, and Cr, that go into the calculation of the carbon equivalent, and the cooling rate of the weld.  The following link explains how carbon, and the carbon equivalent relate to recommendations for preheat (to slow cooling) and hardness.http://www.esabna.com/EUWeb/SA_handbook/585sa3_2.htmIn the HAZ of low carbon steel, where the region has been heated to just below the melting point, the steel undergoes a transformation from ferrite with cementite (carbides) to austenite with carbon and other elements dissolved.  Upon slow cooling, the HAZ structure with have a coarsened grain structure compared to the unaffected base metal, but will be unhardened and returned to ferrite with cementite.  In a steel with a higher carbon equivalent and where the weld is cooled rapidly or quenched, the carbon that was dissolved in austenite at temperature becomes locked into a new highly stressed, hard and brittle structure called martensite.  The problem here is the HAZ, next to the weld, is brittle, not the weld itself.The alloying elements in filler metal can affect the carbon equivalent of the weld metal, and if the wrong filler was used on a carbon steel, such as 308L stainless steel, the result could be hardenable weld chemistry and a brittle weld.Stainless steel such as 304 or 316, welded with or without filler 308, is almost fully austenitic due in large part to the nickel content, and it remains austenitic upon heating and even under severe quenching.  Austenite is ductile and impact resistant.  Because of its ductile nature and the fact that stainless steels are generally more highly refined (less impurities) than general use mild carbon steels, it is very forgiving to autogeneous welding.
Reply:I don't want to get flamed here, so don't take me the wrong way. I'm not endorsing this by any means, I know it isn't ideal.I work for a sheet metal fab company. We make alot of parts for home appliances like stoves and dishwashers, among other things. The other day I walked over to a guy "TIG welding", and asked to borrow his torch for a second to repair a broken tool. I looked around, and asked him where he keeps his filler. I got a confused look from him. He didn't even know what filler is! He welds brackets for mounting screws onto oven door frames. They are colled rolled mild steel about 16ga. He just lays the frame and brackets in his jig and fuses the pieces together, been doing it for years.Also I have fused mild steel on several occasions building pulsejets. When running these things produce extreme vibration. Extreme enough to rattle my neighbors windows 100 yards away, and have even had broken engine mounts before. None of my fused welds have ever failed.
Reply:There are so many factors involved that affect the process and yes melted steel will coalesce but that doesn't mean it is under the ideal circumstances.  The low carbon steel (mild steel is what the original question was about) will result in excess porosity from the oxygen being released during the process that the filler material has proven to minimize.  Believe me I not in any way saying that you shouldn't autogenous weld mild steel (not high carbon steel, not steel heated to the melting point with a carburizing flame to introduce more carbon), if your comfortable going against what the industry as a whole recommends based on their metallurgical research then go for it. Since this site has a lot of newbies coming and going I hope that anyone who recommends this practice do so with caveats.  I wouldn't want someone welding on something that might impact my safety based on what a few individuals state or experienced that goes against the industry recommendations. There is a reason why filler is used and it's not just to fill in the gaps.
Reply:Originally Posted by 383bigblockThere are so many factors involved that affect the process and yes melted steel will coalesce but that doesn't mean it is under the ideal circumstances.  The low carbon steel (mild steel is what the original question was about) will result in excess porosity from the oxygen being released during the process that the filler material has proven to minimize.  Believe me I not in any way saying that you shouldn't autogenous weld mild steel (not high carbon steel, not steel heated to the melting point with a carburizing flame to introduce more carbon), if your comfortable going against what the industry as a whole recommends based on their metallurgical research then go for it. Since this site has a lot of newbies coming and going I hope that anyone who recommends this practice do so with caveats.  I wouldn't want someone welding on something that might impact my safety based on what a few individuals state or experienced that goes against the industry recommendations. There is a reason why filler is used and it's not just to fill in the gaps.
Reply:Originally Posted by Joe HHe welds brackets for mounting screws onto oven door frames. They are colled rolled mild steel about 16ga. He just lays the frame and brackets in his jig and fuses the pieces together, been doing it for years.
Reply:For "practical" reasons, I offer this.  When fusing metal together (no filler), joint geometry is a major factor in the decision to add filler or not to add filler. One explanation of metals coalescing or bonding is "plastic deformation". In the technical definition of most welding processes, coalescence is achieved with heating above the melting point with or without pressure and with or without filler. So to get the metals to bond, "filler has to come from somewhere." With an outside corner joint in sheet metal, both edges can flow together. With a lap joint, the upper metal can flow to the lower metal. In a butt joint, with even heat distribution, both metals will flow together; however, there will be some undercutting or more accurately underfilling of the joint due to not having filler. So, once again, there is only one rule about welding chiseled in stone...."THE ARC MUST LEAD THE PUDDLE!"Weldtek
Reply:Originally Posted by 383bigblock  ... The low carbon steel (mild steel is what the original question was about) will result in excess porosity from the oxygen being released during the process that the filler material has proven to minimize.....if your comfortable going against what the industry as a whole recommends based on their metallurgical research then go for it. .
Reply:Pulser,  I wasn't trying to be argumentive and I really didn't think my generalizations were unfounded as seen by some of the responses here from other members.  I am sure you will find someone somewhere doing it differently with success.   What you haven't relayed in your post especially with the airbag example is that most likely, that company performed a significant amount of research on their process and the specific materials they are using.  I would imagine that the raw materials and processes were highly scrutinized, tested and are checked regularly for composition to ensure they meet a "specification".   A regular person  going to a steel yard to pick up some scraps or mild steel for a home project or for a customer needing a structural weldment made doesn't have the  luxury of such a controlled environment.  At the steel yard they point you to the pile of tube, plate etc and you tell them how much.  Therefore, you introduce an uncertainty with the materials that may or may not work the way you need it to during an autogenous weld.  Again, just because it works in the specific application you mention above does not mean that it will work in most applications as a general rule.  I think Engloid makes a good point...weld up some 3/8 plate autogenously and see how well it holds up.
Reply:Good point 383, we did a **** load of up-front development work and weld qualification.  In addition, the daily quality sampling took samples from each machine, at the start and end of the shift, and tested metallographic sections, and did burst to failure.Regarding the 3/8 plate thing.What if you made a series of welds with several different processes.Include, TIG with and without wire, Stick, MIG, Fluxcore, Electron Beam without filler, and whatever else you want to throw in.Now equalize the welds by making them all the same depth of penetration, and grind off any weld reinforcement and undercut to an equal depth, so that the through thickness weld depth was equal across the board.Now machine tensile test samples and measure the tensile strength of the weld metal.What's the difference?  I suspect it would be minimal.
Reply:Got me on that one.  I am not a metallurgical expert.  However I did enjoy the back and forth on the topic.  I think it shows that we can all agree to disagree at times and everyone learns something  in the process.  That's why I love this board.Thanks for the discussion
Reply:Originally Posted by pulserWhat if you made a series of welds with several different processes.Include, TIG with and without wire, Stick, MIG, Fluxcore, Electron Beam without filler, and whatever else you want to throw in.Now equalize the welds by making them all the same depth of penetration, and grind off any weld reinforcement and undercut to an equal depth, so that the through thickness weld depth was equal across the board.Now machine tensile test samples and measure the tensile strength of the weld metal.What's the difference?  I suspect it would be minimal.
Reply:Originally Posted by WeldtekFor "practical" reasons, I offer this.  When fusing metal together (no filler), joint geometry is a major factor in the decision to add filler or not to add filler.
Reply:Wow, lots of discussion here about very little.There's no reason to add filler to a weldment unless:- The chemistry of the finished weld requires it- The joint design and weld bead profile require itI'd suggest that most things fall under those two requirements, though I'd also suggest that one could design just about any sort of joint that could be autogenously welded.  Who really wants to go through all that effort to clean and machine parts, when you can just use a little filler.-Heath
Reply:not to sidetrack, but here ia a question I have: Using 4130, I use both 4130 rod, and er70-s2 filler. I only use 4130 for welds that will be annealed, and re-heat treated. Pretty rare for me. Since 4130 is an alloy, and highly refined, can thin 4130 be fused with no filler? some parts are very thin, and I am tempted to get those micro welds I see, but just can't get when I use filler. Most important for me is the welds don't fail, obviously. These are not structural parts, more like small brackets for dash parts, bodywork studs. Many are .035 wall tube to .053 or the like, dia. is usually 3/8" or 1/2". Small tube... no serious load. Only say 1-10 lb.
Reply:It's generally recommended that you weld 4130 with RG60 or ER70 to give the joint some ductility.  It may be stronger to weld with 4130 filler or just fuse the two together, but it will be very subject to cracking, especially if cyclic stresses are involved.
Reply:The recommendation to use RG60 on 4130 is deprecated.  Modern practice recommends using ER70-S2 or ER80-D2 on parts that won't receive post-weld heat-treatment for maximum ductility and strength.I would suggest that this is one of those cases that require filler.  The admixture of ER70S-2 and 4130 is going to create a joint with acceptable tensile strength (slightly less than 4130 in annealed state) and enough ductility to obviate the need for post-weld heat treatment.To restate, you could autogenously weld 4130, but it need to be heat-treated after the fact or the weld would likely be too brittle and crack.-HeathHere's a little food for thought.All the welds on the little engine are fused mild steel. As you can see, pulsejets operate under extreme conditions. They get really hot, and the internal pressure fluctuates from ~150psi to below atmoshperic pressure approximately 150 times per second for this particular engine. Attached ImagesLast edited by Joe H; 09-27-2006 at 07:29 PM.
Reply:engine you state...what exactly will it run at these temps and for how long?i'd hate to have a chainsaw with this engine choice.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:PulseJets are just that.... a Jet engine that pulses based on pressure changes in the main chamber. They produce thrust and are louder than you can imagine.  I watched a guy use a fairly large one on a go kart looking contraption.  By the time it made it to the end of the street the pipe looked like it was about to go to the "white" hot stage.  Very cool but not as simple as it looks. The size and shape of the chamber are real important.  Joe what does the wife say you fire it up.
Reply:The wife doesn't sat much as long as I stay up to date on the child support checks Zap, that engine is sized for a model airplane, but built a bit heavy. I was thinking of making a mosquito fogger from that one.That engine is just a baby, with a 1" exhaust pipe. I've built engines with 7" exhaust exits, large enough to fly an ultralight airplane, or make a drag-kart, or even make my canoe go sa fast that I chickened out a half throttle.
Reply:Originally Posted by Joe HHere's a little food for thought.All the welds on the little engine are fused mild steel. As you can see, pulsejets operate under extreme conditions. They get really hot, and the internal pressure fluctuates from ~150psi to below atmoshperic pressure approximately 150 times per second for this particular engine.
Reply:Lincoln's TIG training video provides two examples of welding without filler metal.  The first was an edge weld and the second was a lap joint.  Both using mild steel.Just my .02IronheartIronheart...Beat it to fit, paint it to match
Reply:So does Miller's
Reply:ok i got to and my $0.02 to this can you tig carbon steel with out filler well yes.should you NO just because you can get some sheet metal to stick dose not mean it will work for thicker stuff like it dose for stainless steel so it is one of thoese just dont do it things. add filler doit right the first timeChuckASME Pressure Vessel welder
Reply:I welded aluminum to stainless before too...Does that mean that I should build an aluminum trailer and weld a steel hitch on it?      Lincoln makes 80% of its income from wire sales. ....and people think they will have the R&D budget of Miller, who does 80% of all welding machine sales in the country.
Reply:I welded aluminum to stainless before too...that must have come out real good....   ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterI welded aluminum to stainless before too...that must have come out real good....   ...zap!
Reply:well i guess i won't try that tomorrow......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapster  well i guess i won't try that tomorrow......zap!
Reply:Explosion welding is how steel is welded to aluminum. It is the right process for the job and alot of Navy ships were built that way. The right process for the job and the right procedure for the process and the right application for the part.These little do and don'ts will go on forever.Weldtek
Reply:Originally Posted by WeldtekExplosion welding is how steel is welded to aluminum. It is the right process for the job and alot of Navy ships were built that way. The right process for the job and the right procedure for the process and the right application for the part.These little do and don'ts will go on forever.
Reply:Nah, rocket science is easier.All this drama over what amounts to nothing.  One can autogenously weld many things, sometimes there's a good reason, other times there's not, just like any other process or procedure.  There is no argument here, please move along.-Heath
Reply:The guy at www.tinmantech.com claims he can weld aluminum to mild steel using a torch.  He doesn't elaborate much and says the process is too difficult to even bother explaining.
Reply:Fused lots of BI 16 ga with tig and carbon arc never had aproblem. Iwork for one of the largest sheetmetal contractors in the world and fusining is used on regular bases. I agree with ZAP and others that filler should be used,but have seen literally tons welded without it.