Does anyone have any experience torch cutting really thick steel?

[Alaric]

I have some 10.5” X 6.5” 4340 I need to cut, I would be interested in any advice I can get on the subject or if there is anyone in my area that I could bribe into giving me a hand with that would be even better.
 

I made one attempt at it so far and it didn’t go all that well.
 

I have a Smiths HD-300T torch kit that Smiths says is up to the task and am using a #5 tip with 10psi Acetylene and 70psi Oxygen.
 

I’m 20 miles north of Portland, Maine
 

Thanks,

 

 

Richard Chase

[doc]

As far as I know all pieces of steel have three dimensions, 10.5" X 6.5" leaves one out. Are you trying to cut the 10.5 the 6.5 or is it 1" thick or 1/4" thick and your trying to cut one of those dimensions?

 

We need more information inorder to help you! The difference between 10.5 and 6.5 is 40% and even that makes a big difference when it comes to cutting with a torch!

[ThomasPowers]

really thick so I assume it's one of the thick dimensions.  A tractor torch would help a lot.  Straight lines or curves? 

 

I'd think some folks down near any ship or sub building centers would have the skills.  Do you have the little rollerwheel with your torch?

[Alaric]

The cross section is 10.5" X 6.5", length on the piece I'm trying to cut at the moment is 32". I'd be burning through the 6.5" and cutting for 10.5".

 

Richard

[Alaric]

Straight lines for now, then 2 "U" cuts 3" deep through the 6.5". No track or wheel but I was using a guide.

 

Richard

[ThomasPowers]

Any VoTechs near you with a welding program?  They might be a source of skill and might do it as a class demo---especially if you cover the consumables!  (Or last time I used them I made a contribution to the end of the semester party fund)

[DSW]

I've cut well over 4" with a small torch. One big key was to preheat the cut line to help get things going. We'd soot the line with pure acet, then heat the piece until the soot burned off with a rosebud and then make the cut. Toughest par is maintaining the right travel speed and torch angle to keep the cut going.

 

 

Note you will need a pretty decent acet supply to feed a torch rated for 6". It wouldn't surprise me if you needed to manifold cylinders to stay within the withdrawl rate. Propane wouldn't have that issue though,

[ThomasPowers]

Propane requires a different cutting tip however.

[Jim Coke]

Greetings Al,

 

At the risk of sounding stupid ...  I wonder why you don't just cut it with a band saw...   I have successfully cut that stock with my roll in saw..   You could also just use a 16 in abrasive saw and take it real slow..    I hope this helps some .. 

 

Forge on and make beautiful things

Jim

[Alaric]

If I can't do it with the equipment I have I'll have the local Fab shop cut it for me. I don't see myself doing this very often but I would be nice to have the ability.

[Alaric]

Prior response was in regards to using propane.

I would love to have a band saw of sufficient size to cut this but it would crush me Taiwanese 4"x5" saw

[ThorsHammer82]

what were the issues that you were having with the cut? what experience do you have cutting with a torch? for something that thick its' going to come down to travel speed and torch angle. personally I'd send it out to a water jet, but that's just me.

[Crazy Ivan]

The best advice i ever got with cutting thick steel was to preheat the area to be cut real good. When minimal to zero grinding is desirable (pretty much always) I heat the piece up to a dull red before starting my cut.  I am a structural ironworker and cut 5+ inch steel somewhat regularly. That would be a lot of acetylene though and when i cut stuff that thick its on the companies gas, not mine haha. 

[Iceman_713]

with thick pieces of steel you have to preheat the cut line with something that big you would have to preheat the heck out of it, water jet might be a better option but as others have said, torch angle, speed and preheat.

[forgemaster]

Stick it into a fire, furnace, etc get it as hot as you can, red is good, 4340 is a bit harder to cut anyway, I'd use (for us) a No.24 high speed Propane/LPG cutting tip at about 90 to 100psi of oxy, (a No.24 has a cutting oxy orifice that measures 2.4mm dia).   You will need to have fairly large and preferably fairly short hoses to get the required Oxy flow, the normal "kit cut/weld" size hoses really don't have enough capacity to handle the preheat and cutting oxy required for this sort of cut and if they are long well then you are really pushing the envelope.  When you cut it you will need to go real slow, real smooth, real steady.  If necessary you can weave your cut side to side (slowly) much the same as you weave when you are welding vertical up.  This type of cutting can be done fairly well, just takes experience, and like most things it helps if you have someone to watch do it, before you try it yourself.  If I was to do this sort of thing, I'd use a profile cutting or straight line cutting machine, they just take all the variables that a human with a cutting torch adds to the equation.  If I needed to cut this myself I'd use our 16" capacity semi auto hacksaw, but I figure you don't have one of them.

[Alaric]

I cut 1” and under fairly regularly and have cut up to 2” but never anything like this. I had no trouble getting the cut started but it only cut about 3” deep and the tip overheated very quickly. I assume I wasn’t getting enough gas flow and the flame was burning in the tip.

I’ve pretty much resigned myself to having it cut by the local Fab shop, their water jet can only handle up to 6” but they can flame cutting it.

I suppose I could have at it with the Sawzall but I might die of old age before I finished.

 

 

[petere76]

I have seen ship wrecking yards in Bangladesh cut 5 in steel components. They use big torches but the trick is , they have large acetalyne banks set up in parralel to supply the necessary gas volume. A single bottle set can't supply the volume required. The extraction rate out of the media is too low for the demand. Preheating is another option you may want to look at. Ask if anyone has experience with deep sea submersibles, they have to preheat and post heat for both welding and cutting procedures on the pressure hulls.

Peter

[John Larson]

When steel is high in manganese it won't oxy-fuel cut.

[rockstar.esq]

That's a heck of a challenge and I have no experience with it.  It makes me wonder if there's such a thing as a metal cutting wiresaw.  I googled it and found a youtube video http://www.youtube.com/watch?v=XLtcUh2kixg

 

Wiresaws are used in the construction industry to cut thick masonry wall sections.  Demolition firms bring them to the work- they're much quieter than jackhammers, drilling, or blasting.

[ThorsHammer82]

They use wire saws in the Quarry industry as well. Dimensional stone used for building cladding, pool tables, ect are pulled from the quarry using wire saws and diamond wet chain saws. than taken to a shop to be cut into slabs for this that or the other using a multi-saw rig. that one on steel was sure working slow.

[yahoo2]

It sounds like the weld is scalloping on you, this is where the bottom half of the cut starts to lag back and wander around. I make sure there are no flow restrictions, things like badly crimped hose connections or half blocked flashback arrestors (I take them off). I usually have two tips that put out a perfect shaped flame so I can swap one out on the go, I start a job like this with at least half full cylinders.

 

Umm, what else. I use a little jig that looks like a sled that clamps to the neck of the torch to hold it rock steady and I sometimes tack weld a piece of steel parallel to the cut mark as a guide for the sled to run along. Sometimes you have to lift the back of the torch and have a slight undercut angle, marking the line on the top with a thin angle grinder blade or a centre punch can help with restarting a cut.

 

If the oxidised slag is not coming cleanly out the bottom of the cut and it cools inside the cutting channel you are in trouble, it is very hard to come back and re-cut it to fix the problem when it's 3 inches down and surrounded by slag. If something goes wrong (like a bit of rubbish gets on the tip) you don't just soldier on and hope it comes good, stop and fix it. On the trickier cuts I preheat with a fan forced diesel heater but then the welding gloves burst into flames every time I touch the block of steel and that can be quite distracting :unsure:  Spatterguard helps the sled slide smoothly along the top.

 

That's about all I can think of ATM.

[quick60]

Try Petrogen if you can afford a new setup.  It cuts extrmely well.  Anyone with a production shop would do well to look at this system from a cost saving perspective.

 

http://www.petrogen.com/

[Robert Yates]

By chance are you trying to cut out an Anvil ?

 

Sam

[Alaric]

Several actually, I've given up on doing it myself and the steel is currently at the Fab shop getting cut. I'll post pictures once I get it back.

 

Richard

[DSW]

Try Petrogen if you can afford a new setup.  It cuts extrmely well.  Anyone with a production shop would do well to look at this system from a cost saving perspective.

 

http://www.petrogen.com/

 

 

We had one of those when I worked as a commercial diver. It was great when it worked, but was pretty finicky and took a lot of maintenance. Most of the time it wasn't worth the hassle and we' use something else instead.  I've heard the same things from several of the fire guys whose departments have them. Most like us either use OA or an exothermic torch like a Brocco.  Just whip them out when you need them and stuff them back in the box when done...  A Brocco torch will burn thru anything, steel, brass, concrete, wood... it doesn't matter since it's really an oxy lance. Cuts are generally not clean, but that was never the point of the Petrogen torch anyways for what we'd be using it for.