Slag free oxy-fuel cutting...?

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Down at the school, I've been having to cut lots of beveled plate. This time around, it's 3/8" thick, but there's a possibility of working with 1/2" in the future.Anyway, we have a couple of track torches down there... the fuel is propylene, through a manifold system.Well, whenever I cut plate... one edge is smooth (I usually have to play with settings to keep the edge from being gouged or whatever), and one edge is... just not, there is slag on the other plate that doesn't want to come off and takes a long time to grind.Someone showed me one time on 1/2" plate how to cut, and the slag came off with a little bit of elbow grease, but I didn't know what I was looking at (I can't even really identify a neutral flame except for bright, short solid blue preheat cones).Is there any way to get the slag to eject onto the floor instead of rolling and sticking to the other plate? Or at least, get the slag to turn out as "soft" slag? I've been experimenting with coupling distance, preheat temperature, travel speed, etc. and nothing has been working...Keeping it down in the hood...literally!
Reply:your burning too hot, turn your fuel down a little. I used to have the same problem. Give it a shot.Go hot, or go home!
Reply:Travel speed is also a big factor, you are probably going to slow.Have we all gone mad?
Reply:Hello Drake Aldan, there are a few things that you can do to insure the best chance of success. First off, consider the actual thickness that you are cutting, bevelling increases the thickness of the cut. Also consider that the heat being applied is somewhat deflected due to the attack angle of the preheats and cutting stream. Check the suggestions listed on the applicable cutting tip charts for the particular tips that you are using to determine proper size and pressures for the fuel gases and oxygen, more is not always better. Be sure that when the cutting oxygen is turned on it has a nice long cutting stream showing in the center of the flame, if not you probably need to carefully clean it or in some cases replace it, sometimes you will also hear a crackling or sizzling sort of sound, this is a good thing. Bevel cuts often require a bit of preheat in order to cut cleanly, so preheat if you need to, a few practice cuts will likely be required to get this dialed in. As far as cutting speed goes, you can generally consider the amount of sparks that are being emitted from under the cut to help you to set the correct speed, the more sparks that are seen under the cut, generally the better. Here again, it is possible that you will also hear a fairly steady crackling sound coming from the cut when things are cutting cleanly. Even really good conditions can result in some slag on one side of the underside of these cuts, this is generally caused by surface conditions of the plate being cut, it may have excessive rust, millscale, or other surface contaminants that can cause this to happen. Just a few more items for your consideration. Best regards, AllanLast edited by aevald; 11-01-2009 at 04:24 PM.aevald
Reply:We had to cut 1/2" plate today, 24 4x9" beveled pieces for fluxcore work.Slag came clean off. Every single one.AAAND it seems to me that the 1/2" could be cut, without gouging, faster.Could it be that the cutting table setups are optimized for 1/2" plate? Something different about it that makes 3/8" go bad? Tip size? Pressures?!I just kinda got thrown for a roll here. Keeping it down in the hood...literally!
Reply:Drake,Your experience matches mine, as I have found heavier plate(up to 1") easier to cut with oxy-fuel than thinner material(<1/4").If you'll think back to how oxy-fuel cutting works, it's not really the flame on the torch doing the work.  The flame on the torch pre-heats the material.  It's the oxygen stream reacting with the steel that actually causes the cut to occur.  You can shut off the pre-heat flame once a cut is started, just so long as you keep the cutting oxygen flowing and the travel speed correct.  The reaction of the iron with the oxygen produces the heat that causes the steel to rapidly melt.  The heat from this reaction is much greater than the heat from the pre-heat flames of most cutting tips...With heavier plate there's more steel to generate heat in the kerf of the cut....Just my opinion on why it works easier...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:the thicker plate seems to cut easier is because the thinner plate over heats faster.  travel speed and preheat is more critical on the thinner plate to have the same cutting dynamics as you do with thicker plate.
Reply:Proper proceedures, anything from 1/4" on up, straight cut, should be absolutely NO problems making a clean cut.   Clean tips, correct pressures, correct travel speed, etc.   Do the same with an angle cut????   Yes, it's more difficult.   Slag or dross will tend to collect on the bottom edge.   Just the nature of the game.   Done correctly, though, a couple good raps with a hammer will knock it off.
Reply:First off............. DON'T EVER GRIND SLAG  Waste of time, and grinding wheels.Flip the piece over, hit the slag from the underside of the cut.  Use a chipping hammer and strike from the direction of the uncut piece of plate.  Hit at a sharp angle, almost paralel to the plate.  Comes right off.When finish grinding the cut, the remaining slag will fall off as you gently tilt the grinder against the edge, undercutting the area where the slag formedDingleballs aren't the worst thing on the planet.  Most everybody has them sometimes.  If your cut is true, square, and is a drop cut, you be doing good.Slow travel increases slag, and sometimes the metal will fill in the kerf, and reweld itself.  Cut as fast as you can without leaving uncut material."Any day above ground is a good day"http://www.farmersamm.com/