hot rolled steel cutting problem

[arnoldino]

hi,

we have a trumpf laseer cutter in our workshop, and I would like to ask for help.
there is a specific material finish what the machine does barely cut.
I'm looking for someone, who can explain me what is this material finish.
so our clients often get their material to cut it. I've meet a few times this strange, red-ish surface.
I met it in S235 and S355 quality too. but there was materials with the same quality with grey surface too.
have somebody met this red surface?
as far as I remember, I red at least two different manufacturers on those plates.
it has something to do with the JR, J2+N, JR+N codes after in the material specification?

 

[drossfree]

the red finish might be a coat of primer paint which would definately cause a lot of problems cutting

 

[Foostrap]

Not sure what the material name or specs are, but I've seen this reddish mild steel. It actually cuts really well with a laser.

 

[ianwood40]

Yes I have seen the reddish colour particularly on 350 grade mild steel it does not seem to case a problem, maybe the finish is a primer (as mentioned) or something else that is the problem. Can you post a pic of the redish surface?

 

[arnoldino]

hi,

here are some photos about the plates, and some pieces that I've cut from it.
the cutting is very rough, the edges are rough, the cutting has huge slag on the bottom, I have to hit with the hammer to get the pieces out from the table.
it looks like the molted material can not leave the cut, and on the bottom it welds together.
I have seen at least two different manufacturers on those plates. but I've seen normal, grey tables from those manufacturers too, with the same grade.
this week, one of our client got the material for an order. he brought 5 plates, of the same grade. 3 of them were with this red finish, and 2 were normal grey colored. of course I was suffering to work with the red plates. when i cut the greys, I didn't change anything in technology tables, either feed or pressure, every single piece fall out from table, and they had a very nice cutting edge.
so it has nothing to do with any machine setting (alignment, focus position, ...), it is something with the material.

a little video how it was cutting hese 15mm thick, s235 grade mild steel, with reddish finish

http://www.youtube.com/watch?v=4LEWOOlQ824

and more pics

I tried to burnish it, to get rid of red surface, but no luck

I really would like to resolve this material issue, because a lot of clients bring such material, and always we have to work a lot to get the pieces out of the table than deburr with hammer, and burnish the edges.
any advice would be appreciated.

 

[drossfree]

try spraying wd-40 on the surface before cutting i found sometimes on a rusty or painted surface a light coat of oil helps

 

[arnoldino]

I tried it, but does not help.

nobody knows what kind of material could be this?

regards,
arnold

 

[jetrep]

Is there some reason you can't find out from the company supplying the material?

If the material is that problematic to cut I would ask management to look into it and quite possibly establish standards/requirements for customer supplied material.

 

[arnoldino]

One of the supplier sad that is simply rust. But I don't think so. If it is rust, than how is that some plates have on both side this red surface. If they hold the plates outside, than the water raches only one side of the plate, and will rust on only one side.

Of course I would establish those requirements, but I don't know haow to exclude this type of material. The certificates of these materials show exactly the same as the normal grey tables.

 

[arnoldino]

hi,

I got a tip.
Somebody says, maybe during fabrication, the hot rolled steel plate is cooled with water.
Can somebody comment this tip?
regards
arnold

 

[kach]

That coloring on the steel could be a couple of things.
1. Red Oxide primer (as mentioned in an earlier post)
or
2. This steel may in fact be weathering steel (also known as Corten steel)

I wish I could help more, but that's all I've got.

 

[xtremeLASERtag]

At our shop, we call this stuff "Red Scale." It is possible to cut through it but we usually have to slow down the feedrate and adjust the cutting conditions of the laser accordingly at least on the two 1997 3000W Mazak lasers with FANUC controllers (fixed foci). A fellow laser operator told me that this is just the scaling or finish that some companies use to prevent rust. Anyway, usually with red scale plate, we get it blasted before it gets cut usually and it seems to do alright. Though there are some times where it would burst on the pierce, then we reduce the duty a bit and adjust the piercing time in the cut condition program. Also in my experience, the mill test reports for these red scale plates have a higher or lower (I can't remember) Si content when compared MTRs with blue steel. Not sure if it makes that big of a difference. Honestly, If i were in your position, what I would do is slow down the feedrate a bit, manually override laser power, frequency, duty, and gas until you have found your new cutting conditions for red scale because it literally just looks like you're undercutting. Or get it blasted. This is all I got for you. (backstory) I've been doing this for only 5 months, but was classically trained on old machines and I have a high interest in lasing fundamentals and science.

 

[arnoldino]

hello,

thanks for the comments they were very instructive.
although I realised in this week that the red finish is paint.
it can be washed with water but not completely, and the normal cut parameters are right in 90%.
somebody told me to try some welding protection solution to wash it.
i will try it for sure, but if somebody has a comment on this too, I really would appreciate it.

regards,
arnold