The proof is in the picture!!!

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Okay, now I know everyone has an opinion as to whether not not steel absorbs water. THIS THREAD IS NOT ABOUT THAT!!! In that thread it was stated that preheat was not needed for cutting purposes. I disagree with this and as I said I would do I took a picture of a sample peice I beveled on the burning table to prove this very theory to a fellow worker. This piece was cut in one pass. I cut the bevel first with a preheat and without stopping the cutting process I removed the preheat for the last  several inches of the cut.To do this I used a straight cutting torch set with a neutral flame, placing  the head of the cutting torch against the head of the machine torch, at the same angle, with the same stand off and moved along at the same pace. The preheat flame led the machine torch by about an inch. The initial cut is as smooth as glass, you can barely see any cut lines. You'll notice how ruff the cut finished, even though I was already well into the cut. The cut lines have the appearance of having too fast of a travel speed, but that's not the case. I never changed the travel speed of the machine. I'd also like to add that this piece was taken right off the floor with an ambient temp of about 60 deg maybe a bit more, it was summer time.EDIT: The piece is a 5" x 5" solid bar, notice how the cut mark gets worse as the torch moves away from where the preheating was stopped. Attached ImagesLast edited by lorenzo; 01-23-2007 at 06:18 PM._________________Chris
Reply:You get all the fun jobs..Saturday is a GO!!!!You will be a big help..See you there!......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:Wow, you guys have all the cool tools.  See what you mean.Various GrindersVictor Journeyman torch200cf Acet. 250cf oxygenLincoln 175 plus/alpha2 gunLincoln v205t tigLincoln 350mpEsab 650 plasmaWhen you can get up in the morning, Its a good day.Live each day like its your last.
Reply:Originally Posted by zapster You get all the fun jobs..Saturday is a GO!!!!You will be a big help..See you there!......zap!
Reply:Your an animal lorenzo lol
Reply:I guess you learn something new everyday.  I've never preheated to make a cut.DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:Very cool to see the differences, thanks for sharing.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Originally Posted by littlefuzzI guess you learn something new everyday.  I've never preheated to make a cut.
Reply:What would happen if you maybe did preheat with a torch and came behind it with a plasma?  Same effect I bet.  I have yet to get a perfect cut with either the plasma or torch no matter how steady I think I am.  I have some ideas rolling around in my head for a little cart or something with a variable motor with a jig to hold the torch (ive seen the esab units online) But I dont know what these things do when they come to the end of a plate (have a catcher, roll onto another nonferrous plate to kill the cut?  Saw where someone had made a screw driven torch cutter, but it was a dedicated table.Various GrindersVictor Journeyman torch200cf Acet. 250cf oxygenLincoln 175 plus/alpha2 gunLincoln v205t tigLincoln 350mpEsab 650 plasmaWhen you can get up in the morning, Its a good day.Live each day like its your last.
Reply:Great post, Lorenzo.Thanks for making the effort.Is there any type of preheating technique that can be done with a plasma torch?I feel kind of, er, ignorant, asking such a question.Thanks.MetalBob
Reply:Originally Posted by MetalBobI feel kind of, er, ignorant, asking such a question.Thanks.
Reply:Originally Posted by MetalBobI feel kind of, er, ignorant, asking such a question.Thanks.
Reply:One trick we use to avoid the preheat thing on a bevel is to cut the bevel on the underside of the edge.  That way the torch is aimed at the edge of the plate and receives maximum preheat.  The wedge drops downward falling away from the plate as you do the cut.
Reply:Lorenzo,Although I am not arguing to point over preheating.  I do it on lots of stuff.  But, your test doesn't quite appear to be a true test of the value of preheating alone, but of preheating at a particular cutting speed.  It seems that more than one factor is at work here in determining optimal cuts.  Since you say that you maintain the exact same cutting speed, it would appear that some of the rough cut could also come from the travel speed being too fast once the preheat is removed.  If there is an optimal cut speed at a given temperature, I would think lowering the temperature would probably result in a lower optimal cut speed.  Do you think that if you had lowered the cut speed at the same time you took away the preheat that you could have achieved a smoother cut?  Just curious.Smithboy...if it ain't broke, you ain't tryin'.
Reply:BTW, I have never come close to cutting anything this thick.  What is something like that used for???Smithboy...if it ain't broke, you ain't tryin'.
Reply:Probably a valid point about different optimal cutting speeds for preheat vs no preheat.Very impressive cut, really beautifully smooth.
Reply:Originally Posted by MetalBobGreat post, Lorenzo.Thanks for making the effort.Is there any type of preheating technique that can be done with a plasma torch?I feel kind of, er, ignorant, asking such a question.Thanks.
Reply:Originally Posted by smithboyLorenzo,Although I am not arguing to point over preheating.  I do it on lots of stuff.  But, your test doesn't quite appear to be a true test of the value of preheating alone, but of preheating at a particular cutting speed.  It seems that more than one factor is at work here in determining optimal cuts.  Since you say that you maintain the exact same cutting speed, it would appear that some of the rough cut could also come from the travel speed being too fast once the preheat is removed.  If there is an optimal cut speed at a given temperature, I would think lowering the temperature would probably result in a lower optimal cut speed.  Do you think that if you had lowered the cut speed at the same time you took away the preheat that you could have achieved a smoother cut?  Just curious.
Reply:Actually, that's a pretty good answer.  Like I mention, my question is based on a complete lack of experience with metal that thick.  I hadn't considered the top side at all.  I am pretty amazed at the quality of that cut up to the point where you remove the preheat.  I know my victor torch is supposed to cut something like 4-6 inches thick with the bigger tips (at least that's what the chart says), but I was always a bit skeptical...Those cuts look like you used a sheer.Smithboy...if it ain't broke, you ain't tryin'.
Reply:It would have cut just as well by slowing the travel, without preheat.Maybe I missed your point.  I'm thinking that you're trying to say that preheat is necessary and that not preheating creates a rougher cut.  What if you didn't preheat, set the travel speed accordingly and cut a plate....then preheat the plate and continue the cut without changing the travel speed.  Which part will look better?It's similar to amperage.  You can typically weld faster with more amperage than with less amperage.  It's like a ratio...more speed requires more heat...just like with your cut.  With your cut, you had travel speed and heat set to work very well together.  You then changed the heat, so you can't expecte it to cut just as well without adjusting the speed accordingly.
Reply:I have no reason to cut 5" steel...yet..But after reading the whole thread...cool!...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 smithboyActually, that's a pretty good answer.  Like I mention, my question is based on a complete lack of experience with metal that thick.  I hadn't considered the top side at all.  I am pretty amazed at the quality of that cut up to the point where you remove the preheat.  I know my victor torch is supposed to cut something like 4-6 inches thick with the bigger tips (at least that's what the chart says), but I was always a bit skeptical...Those cuts look like you used a sheer.
Reply:Originally Posted by Roy Hodges...............................I've cut 7"thick (hts,i think) with a VICTOR journeyman torch, with a #7 cutting tip. BUT- it requires a 3/8"  hose set, large gauges, &will empty a 280cubic foot oxygen tank in about 18 minutes ! & it is very tedious  ! this was in a mud tank of a nuclear submarine .
Reply:Most definatly preheat is required to cut with oxyfuel!Cutting with oxyfuel is a chemical process that uses pure oxygen to oxidize the steel rapidly. Steel however doesn't readily oxidize unless you get it to kindling temperature (which is just above the point of red hot).Thats the purpose of those surrounding orifices in your cutting tip, it actually preheats the little bit of material ahead of your oxygen jet to allow continued cutting -- try lighting a flame and press your oxygen lever without warming the steel-- it wont cut at all.By adding another torch ahead of the cutting torch your basically preheating the plate twice, which makes sense if you want to increase your cutting speed.Which is a good idea that I never thought of until now! Freelance Fabber91 GMC 3500 Portable welding truckLincoln Weldanpower 8000 gas welderMiller CST 250 Smaw/Gtaw inverterMillermatic 210 gmaw line welderHyperterm plasma
Reply:Pre heat makes a big difference in the cut quality beveling 2" plate.I wanna know if any of you can use oxy-acetylene to cut cold steel.  If you can, you really need to patent the process NOW!!!Fact is that you can't.  It's not a matter of whether to preheat or not, it's a matter of how much.
Reply:I've never tried this, but maybe one of you experimental types could: make a cut using o/a, and have someone shut the acetylene valve halfway through while you complete the cut using staight oxygen. Any takers?If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:Originally Posted by ClanweldI've never tried this, but maybe one of you experimental types could: make a cut using o/a, and have someone shut the acetylene valve halfway through while you complete the cut using staight oxygen. Any takers?
Reply:Originally Posted by ClanweldI've never tried this, but maybe one of you experimental types could: make a cut using o/a, and have someone shut the acetylene valve halfway through while you complete the cut using staight oxygen. Any takers?
Reply:Originally Posted by TEKI've never done it either but I have heard it is possible.
Reply:Believe it or not it can be done.I have used fuel-less cutting often, as a repair/salvage technique to “burn”  hardware out without raising temperature of adjoining parts to melt or kindling.
Reply:Originally Posted by denrepBelieve it or not it can be done.I have used fuel-less cutting often, as a repair/salvage technique to “burn”  hardware out without raising temperature of adjoining parts to melt or kindling.
Reply:[QUOTE=Engloid.  What do you do when you turn off the torch?   ...You turn off the acetylene first...and it stops cutting.[/QUOTE]This is true if you are just shutting it off. However, in a cut, there are more things going on. When you remove the fuel during a cut you still have the molten steel present as a reactant. As stated previously, I have never done this intentionally. I have seen a track torch pop and go out and continue cutting but did not let it go for long.I will try it just to satisfy my own morbid curiousity.
Reply:Originally Posted by TEKThis is true if you are just shutting it off. However, in a cut, there are more things going on. When you remove the fuel during a cut you still have the molten steel present as a reactant. As stated previously, I have never done this intentionally. I have seen a track torch pop and go out and continue cutting but did not let it go for long.
Reply:Originally Posted by EngloidThat's different.  What's happening in your example is that the torch is being blown out by a pop...and then the molten metal is enough heat to re-ignite the oxygen-fuel mix.  If the acetylene cuts off, your cut will stop.  If it was that easy, we'd all just use acetylene to start a cut and then turn it off and go with pure oxygen.
Reply:Originally Posted by EngloidIf you can create heat without electricity, fuel, or friction....enough to cut things apart, I wanna know how.
Reply:A lance has some kind of magnesium alloy and oxygen makes it burn continously.
Reply:there is no magnesium in a lance.  the red rod in the end of a broco rod is rumored to be magnesium but the company reports that it is not.  the lance works the same way an o/a setup does except that instead of using preheat flames as a catalyst it uses an electrical arc.  there is so much o2 running through those things that ones you get it lit you can turn of the electricity and stays lit.  i've done this hundreds of times underwater.  in order to have fire you need to have four things, fuel, o2 heat and chemical reaction  . this is called the fire tetrahedron (used to be called the fire triangle but they updated it).  in this case electricity creates the heat in the presence of o2 and steel, the steel in the rod acts as a fuel.  once the thing is lit you have a chemical reaction taking place that creates its own heat.  i know that if you're real careful you can continue to burn without the preheat flames on an o/a torch.  you can't start a burn, but once the reaction starts you can continue with it, my hand is way to shaky for it to last more than 1/2 or so.  you can also burn with a brazing tip for short distances.  heat it up then shut off the fuel.
Reply:actually you can make a lance out of tubing with a fitting on the end to hook up to o2.  i've seen these used during iron pours to clear out a frozen cuppola.  in this case there was so much heat already present there was no need for any  external catalyst.
Reply:Gasless cut photographs. Proof is in the picture!Okay, I went and made the rounds tonight. I stopped at the outdoor steel rack for a quick gasless cut experiment. Just a common old beat up torch used to hack off a used piece of steel now and then. Cutting cold rusty steel, outdoors, in the dark, at 21 degrees.I would shut the fuel off as soon as a cut started. As the plate temperature went up, gasless cutting definitely got easier.The “straight” cuts seemed like I could have carried on forever, torch leaned forward into the cut. When I tried to get fancy and spell “welding web” I had flameout and would have to chase glowing coals for a restart. This cutting did not seem destructive to the tip at all. The previous “tip wrecking”  gasless work I mentioned was burning into blind holes.NEVER Let oil come in contact with oxygen.   I will not start stupid threads.Don't forget the upcoming air bumper test! Last edited by denrep; 08-26-2009 at 10:02 AM.
Reply:HMMMM very interesting.... How long in the longest continious cut that you made before losing it? Is the first pic you posted of you cutting with the gas off or prior to turning the gas off? What size tip do you use and what where the setting on you guages?_________________Chris
Reply:I didn't say all lances have the same material inside we have lancing rods 11/16 in dia and are 10' long we use a torch to start them and they have rods inside that my distributor said is magnesium, we cut through some really big pins with them and that maybe the reason for the magnesium, as we all know magnesium is  self sustaining when on fire causing a higher burning heat.here is a link to pge group and they state they add a mixture of Ferroaluminum,Alumina,Ammonia chloride and other elements.http://www.pgegroup.com/PGE-Products.pdf
Reply:I didn't say all lances have the same material inside we have lancing rods 11/16 in dia and are 10' long we use a torch to start them and they have rods inside that my distributor said is magnesium, we cut through some really big pins with them and that maybe the reason for the magnesium, as we all know magnesium is  self sustaining when on fire causing a higher burning heat. I did see a supplyer (caldotorch.com) that said the rods inside theyre lance was mild steel.here is a link to pge group and they state they add a mixture of Ferroaluminum,Alumina,Ammonia chloride and other elements.http://www.pgegroup.com/PGE-Products.pdfLast edited by Dipper Welder64; 01-28-2007 at 11:22 AM.
Reply:Originally Posted by lorenzoHMMMM very interesting.... How long in the longest continious cut that you made before losing it? Is the first pic you posted of you cutting with the gas off or prior to turning the gas off? What size tip do you use and what where the setting on you guages?
Reply:i've seen pure magnesium burn and it will go in air, actually i remeber someone in high school stealing some from the chemistry, lighting it and throwing it in the toilet where it continued to burn.  so what i'm wondering is if there is magnesium in a burning bar how does it go out when you shut the o2 off?  wouldn't it keep consuming until it was completely burned up?
Reply:denrep,My point on this thread has to do with the effects of preheating with regard to flame cutting..... the point which I was trying to make and I felt that I did make was that a preheat can imrove cuts preiod, and they do. I know this first hand through experience.As to the quality of your cut and what not I'm not going to argue that because I have nothing to compare. If you say so than I believe you. If you saw my cut in person then maybe you would have yet another opinion... We recieve A LOT of material that is flame cut from outside vendors an I don't feel the cuts are anywhere near as nice.  My post is based on what has worked for me.... my approach is not the law and I don't claim it to be.... I can disagree with other members on comments they make and then go out of way to prove something other wise so that others can make their own evaluation and decide if it is something they want to try on not. I have the ability, the equipment and the materials to do these things that many others don't, so If I can post something that some one may someday use as a way to approach a situation then I have achieved my purpose for posting in the first place.( GENERAL DISCLAIMER: Just to let you or anyone else know because there always seems to be a TONE loss with regard to the attitude of a response. I'm not being defensive in any way except to defend my position.... I'm not lashing out, name calling or just plain old being an A$$!!!! Just explaining my position. )_________________Chris
Reply:Originally Posted by lorenzodenrep, ... I can disagree with other members on comments they make and then go out of way to prove something other wise so that others can make their own evaluation and decide if it is something they want to try on not... ... so If I can post something that some one may someday use as a way to approach a situation then I have achieved my purpose for posting in the first place...
Reply:Originally Posted by rusty ripplei've seen pure magnesium burn and it will go in air, actually i remeber someone in high school stealing some from the chemistry, lighting it and throwing it in the toilet where it continued to burn.  so what i'm wondering is if there is magnesium in a burning bar how does it go out when you shut the o2 off?  wouldn't it keep consuming until it was completely burned up?
Reply:Originally Posted by denrepLorenzo, I'm with you on this. I’m also with you on preheat and cut quality. Your bevel looks perfect. I often see visible flame cuts on finished expensive products that are of far lower quality than your bevel cut. I was mainly responding to those doubting that cutting could carry on without fuel gas.It seems like some may be missing the most basic concept of oxy fuel cutting. The steel is being burned or oxidized, acting as a fuel, not simply being melted and blown away.When this concept is grasped it opens up possibilities, like super clean cutting and burning out assembled parts without damage to adjacent parts.
Reply:Is'nt this cool?    ...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.