[mjr6550]

I know that this subject has been covered before, but I could still use some advice. I have a rusty I-beam that I want to make into a large cross. Along with that I want to "write" some words and dates in the web. I would like to leave the rust on the I-beam unless that is not practical.

I tried cutting and "writing" and had trouble getting clean cuts. I tried 00 and a 000 tips using about 5 psi/15-20 psi. The cuts want to melt back together. I tried not to wait too long before hitting the O2. Since I could not see the metal turn red I hit the O2 and when it did not cut heated just a little more. Also, I had the O2 control on the handle full open and controlled the O2 at the torch end.

I attached photos of front and back.

Thanks.

[Arclight Ironworks]

Torch manufacturer? Base metal thickness? Experience level in operating an O/F torch?

We run Smith/Miller OxyAcet and OxyPro torches. Medium Duty rigs. In our OxyAcet rig with an MC12 tip in "00" for cutting 3/8" steel, we run 10psi for the fuel and 20psi for the O2. Yields a kerf width of 50thou.

You need to achieve a neutral flame while dialing in your torch, and be sure to preheat your base metal before injecting the oxygen. The base metal will approach a near-puddle and begin to sparkle. Then it's time for the oxygen boost.

As with anything, you need to test and learn what works for your tactics amd your torch. There are always minor variables and details that are required for success. Cuttting clean letters in i-beams is not a "light off the torch and produce perfect results" the first time.

[noddybrian]

I would say that trying to cut steel that rusty with O/A is something you would only do when cutting scrap to a size so it fits in a skip or trailer - the torch cuts by oxidizing the steel - rust is iron oxide & has already got to a point it won't react much more with O2 if it's thick so it won't cut - my suggestion would be roughly mark out the cuts & letters - carefully clean about 1/2" width where the cuts will go with a grinder on BOTH sides then re-mark accurately & cut as carefully as your experience allows with as previously mentioned a neutral flame - that way you get a fair cut & the overall effect is still the original weathered surface - the small area ground will quickly blend in as the HAZ from the cut oxidizes quickly.

[Lightning]

I don't know how thick your steel is, but I would go up a size or two on your cutting tip, and I would up the oxygen pressure some, even higher than the recommendation from the cutting tip manufacturer. When I was having similar problems, that's what solved it for me.

[Poland308]

I run a real small cutting head like that on my work truck setup. I run 30-40 on the oxygen and about 7-10 on the acetylene.

[mjr6550]

Thanks for the replies.

My experience is pretty much what you see in the photos-very little.

The torch body is a Victor 100FC. I don't recall the number of the cutting attachment. It is a Victor clone. The cutting tips I was using were 00-3-101 and 000-3-101. I looked at the 00 tip that came with the torch (I bought the torch used). The center hole and perimeter holes connect, at least at the face of the tip. The other tips I bought (Victor clones) do not look the same.
Because of that I decided to try a 0 tip using about 7.5/35. I cleaned the steel a bit also. The cuts are a bit better. I made a pretty clean cut through a flange that varies from about 1/4" to 3/8" thick and pretty clean cuts through the web, that is slightly less than 1/4". I also went away from the cleaned steel and it cut just about the same. When I was cutting a curved line I probably went a little fast or moved the torch away from the line. You can see where I messed up the line getting back on track. I also cut a round hole to see how that worked. That seemed to go fine.

Here are a few more photos. Feel free to be critical. I appreciate the feedback.

[Poland308]

Angle of the torch head is also important when cutting.

[Otto Nobedder]

You can also rapidly rust bare metal from cleaning by hitting it with a 50-50 mix of white vinegar and household bleach. Just keep the surface wet until you get the patina you're after, the lightly rinse it with water.

Steve S