Strange phenomenon in machined steel tube after machining and black oxidation.

We have had some issues with scratches in a black oxide surface on the inside of a steel tube. Swedish prime quality steel. During investigation we discovered a very strange phenomenon at the bottom of some of the scratches. See attached picture. It's a pattern consisting of perfect rows of dots/holes with a spacing of approximately 8 microns in both axes. One pattern is 15x15 dots and the other 13x9. According to the laboratory these may be imprints from some kind of tooling or measuring equipment. This may be the wrong forum for this question, but maybe someone has seen something similar.

Thanks for the replies in the first, and now closed, thread!

Some more facts:
- Forged Ovako steel blanks. Steel produced in Sweden and forged in the UK.
- We machine the blanks and the inside surface is grinded to Ra 0,4 and then shot blasted (glass GL 4) prior to black oxidation. Then oil is applied.
- No laser machining on the inside of the tube, which is where the phenomenon is found. The outside is laser cleaned for improved adherence to the forthcoming
composite winding.

And by the way:
I’ve started a couple of threads in this forum to try to get some help regarding issues that I’ve encountered. All the time some of the replies imply that my description lacks data or that the pictures uploaded are bad. This time the moderator even closed the thread due to “meaningless topic title”. Why don’t you just be a bit more tolerant. I think that I give you all info I have at the time of starting the thread and expect you to ask questions or tell me to be more specific in the topic title. I realized (a bit too late) that the pictures in the original post was a bit small and intended to fix that. I didn't realize that the topic must be foolproof to be accepted by the administration of this site. You are all a bit like bullies! I’m Swedish and I try my best to get answers from you, but maybe I’m not as great at writing in English or American or whatever you folks understand. Sorry! Humorous comments like "Was that metal from Rockwell?" are, however, most appreciated.

By the way (part 2):
I have received great response in earlier threads from some people, which helped me a lot in the ongoing investigation. Thank you all for that! That time it was regarding Ti6Al4V. Now it is forged steel.

Here's the closed thread: https://www.practicalmachinist.com/vb/general/need-help-very-strange-phenomenon-394373/#post3809209

I agree that it looks purposely added, and a laser makes the most sense. Can you post a picture of a section of a tube that the marks are in?

I wonder if it's some sort of materials marking for tracing if it's used in weapons. I doubt it, but who knows...

[I see you added to your post as I was making my comments. On the "harshness" of the demand for clear titles and full information, it's so that threads can be searched for useful data by future users. Also, it saves forum member's time if enough information is presented at the beginning, rather than have to repeatedly ask for more data.

Don't take it personally, native English speakers have gone through the same thing and worse]

Since you're sure the marks weren't laser etched, I have no idea what could have caused them.

Have you heard with the manufacturer of the material? Might be something they do in their inspection or manufacturing?

I mean if you did not do it than somebody else did obviously.

So, you state that you are not machining inside the tube. Some previous operation, machining or inspection is being performed by someone. Check for the pattern in the tubes as soon as you receive the tubes. Or ask up the supply chain, someone will know.

"Why don’t you just be a bit more tolerant. "

OK, English is not your first language so you are granted some leeway; but be aware that 'just' is the most dangerous and evil word in the entire English language. It is followed closely by 'should', 'we', and 'they'.

Those marks are most likely you new name in Chinese. It will be formally assigned to you in about a year after they take over all of Europe. That will be about 3 months after they finish buying the United States.

Are you able to provide a picture of the actual tube, preferably of both the in and outside? It would make the process of elimination a bit easier. Also, are you doing the ID grind or is a vendor? If it's a vendor, do you know the machine make/model they are using.

-JT

WAG: someone testing material with laser analyser? Guess they're thinking that no one will notice in side a tube?

RicoRider said:

We have had some issues with scratches in a black oxide surface on the inside of a steel tube. Swedish prime quality steel. During investigation we discovered a very strange phenomenon at the bottom of some of the scratches. See attached picture. It's a pattern consisting of perfect rows of dots/holes with a spacing of approximately 8 microns in both axes. One pattern is 15x15 dots and the other 13x9. According to the laboratory these may be imprints from some kind of tooling or measuring equipment. This may be the wrong forum for this question, but maybe someone has seen something similar.

Thanks for the replies in the first, and now closed, thread!

Some more facts:
- Forged Ovako steel blanks. Steel produced in Sweden and forged in the UK.
- We machine the blanks and the inside surface is grinded to Ra 0,4 and then shot blasted (glass GL 4) prior to black oxidation. Then oil is applied.
- No laser machining on the inside of the tube, which is where the phenomenon is found. The outside is laser cleaned for improved adherence to the forthcoming
composite winding.

And by the way:
I’ve started a couple of threads in this forum to try to get some help regarding issues that I’ve encountered. All the time some of the replies imply that my description lacks data or that the pictures uploaded are bad. This time the moderator even closed the thread due to “meaningless topic title”. Why don’t you just be a bit more tolerant. I think that I give you all info I have at the time of starting the thread and expect you to ask questions or tell me to be more specific in the topic title. I realized (a bit too late) that the pictures in the original post was a bit small and intended to fix that. I didn't realize that the topic must be foolproof to be accepted by the administration of this site. You are all a bit like bullies! I’m Swedish and I try my best to get answers from you, but maybe I’m not as great at writing in English or American or whatever you folks understand. Sorry! Humorous comments like "Was that metal from Rockwell?" are, however, most appreciated.

By the way (part 2):
I have received great response in earlier threads from some people, which helped me a lot in the ongoing investigation. Thank you all for that! That time it was regarding Ti6Al4V. Now it is forged steel.

Click to expand...

Really weird stuff. It definitely is a pattern caused by some process. Are they deep? From your pictures they look almost like they are projected onto a piece of slag. A shot or two would get a lot more response. You know what they say a picture is worth a thousand words and here people can understand better what is referred to.

The Steel is most likely as you wish and that is top quality however where and who processes it and how they do it can be all the difference. Since you have not encountered it before that means that something has changed. Someone knows about that change. It might be something as simple and likely so that a process has been skipped intentionally as it is believed to be unnecessary.

I have found these kinds of things at times and if they machined out they were nothing to be concerned about. Many times things such as these are a cosmetic thing mostly. The end user may indeed notice the quality is lower due to this feature when paying top dollar for the material and pipe. If the certs are traceable and valid then it should be no problem unless it effects the fit or function of the finished part. It is inside the pipe anyway.

Most all pipe which I have made anything with most often has a finish which is like pipe. Un machined it looks kind of ugly yet it was never anything but acceptable. This is interesting. Just some initial thoughts by me.

Regarding any resistance or perceived indifference to you there really is none. We are a lively bunch and some of us are rather perky. Milland gave a very good appraisal of why the way a thread is titled here is important. Your writing is excellent and your issue is appreciated. In the plate making process before making the pipe up seems the likely place the problem occurs. It may be something as simple as the plate was put aside and somehow was flipped with the wrong side up or down. If later pipe does not have this feature and you never see it nor hear about it again it is likely a fluke. They will sell the pipe off anyway.

I do ask though ….Does this in any way really matter it is on the inside of a pipe? What runs through the pipe? I do feel sometimes with these outfits we get very spoiled with how good and consistent everything goes especially when we get used to it. Changes happen machines and processes constantly change and upgrades in processing equipment and personnel change also. I too notice any variation in anything including raw pipe material and whatever. Once we found material Steel that when saw cut we saw a dang 1/2 inch tap inside which was evidently thrown in to molten steel.

I have seen a lot in my time life goes on. Haven’t thought nor cared about that for ages and Yep it screwed up the saw blade big time. The help replaced a couple of nice saw blades. It softened the tap -the heat but not that much. Lol

It might be a new facility doing the work.

Likely ‘obviously this occurred in the oxidation process and does not imprint very deep at all. Would I do anything to eliminate it? Only if the customer wanted to pay for it.

Perhaps that pattern is on the sizing bar.

How SS tubing is made...
how steel tubing is made - Bing video

Are the scratches/patterns in a consistent location on each piece? If they are, it has to be occurring after you and others start work. If they're random, it is more likely that they are a remnant of the tube mfg processes.

For you guys inferring language issues, I think RicoRider's English is superior to that of the majority here!

Some sort of ID gripper used during tubing manufacture?

Regards.

Mike

LIBS matrix pattern
Patent Report: | US10094782 | Method and apparatus for fast quantitative analysis of a material by laser induced breakdown spectroscopy (LIBS)



US10094782B2 - Method and apparatus for fast quantitative analysis of a material by laser induced breakdown spectroscopy (LIBS)
- Google Patents

Another OES technique that’s turned up, fascinating how things progress, I must have sparked bloody tens of thousands of steel samples over the years, never would have guessed it was going to go laser, given the sheer quantity of ARL units and panylitical ( thermo) in the world someone’s going to make a whole heap of money, traditional spectrometers aren’t that cheap to run, the maintained and spares plus software rent amounts to half a family home a year, there are clever people about!
Mark

It could be the clamp artifact from when it was on the cooling rack? Some high dollar straight forgings are treated like extrusions during cooling and kept in tension to train/tame the grain of the material.

could be from laser cutter chuck also.

Even after grinding the grain impressions can still show.

This is almost certainly not from any sort of gripper. The dimensions of the pattern kind of rule that out from the get-go. 8 micron spacing is .0003" and those appear to be dead nuts regularly spaced - not remotely likely for a gripper. 15 dot grid means that grid is only about .005" square. I'd guess some sort of laser ablation - perhaps for material identification during manufacture? Tough one.

Billtodd said:

LIBS matrix pattern
Patent Report: | US10094782 | Method and apparatus for fast quantitative analysis of a material by laser induced breakdown spectroscopy (LIBS)



US10094782B2 - Method and apparatus for fast quantitative analysis of a material by laser induced breakdown spectroscopy (LIBS)
- Google Patents

Click to expand...

Good job ! @BillTodd


Literally described in abstract and part of claim 1 ~ very rare...

Abstract

The invention discloses an apparatus and method for use with Laser Induced Breakdown Spectroscopy (LIBS) systems that can be applied to the real time analysis of various materials. The invention, in one aspect, provides a layer-by-layer method to remove the undesired coating layer of a material in which a pulsed laser is coupled with high speed scanning optics. To prepare the surface for LIBS, (i) a pulsed laser beam is scanned over an area of the surface to ablate the surface coating layer; (ii) the laser parameters are changed (i.e. pulse duration is made smaller) and the area scanned again to polish the surface; and (iii) the laser parameters are changed again (i.e. pulse duration is made smaller yet again) and the area scanned again with spectrometric analysis of the plasma plume created by the laser (i.e. LIBS is performed).



Claims


1. A method for analyzing bulk material by laser induced breakdown spectroscopy (LIBS), comprising:

(a) scanning a surface layer of the bulk material to ablate said layer with a pulsed laser beam scanned over the area at a first laser beam regime comprising a first pulse duration;

(b) polishing the ablated surface with a pulsed laser beam scanned over the ablated area at a second laser beam regime comprising a second pulse duration shorter than the first pulse duration; and,

(c) scanning the polished surface with a pulsed laser beam within the polished area at a third laser beam regime comprising a third pulse duration of intermediate pulse duration between the first and the second pulse duration, to create a plasma plume of the bulk material having optical emissions that are detected by an optical device.

_________________________________________________________________


Seems to check out with what OP/@RicoRider has experienced / discovered. + ensuing possible corrosion processes.

So maybe they have a borescope + other optics to turn the incoming and outgoing beams for inside Tube work / analysis.

There is a complex layering / set of deposition processes too.

I'm sure if time is taken to read the whole patents and match that up with Canada's NRC (National Research Council's ) publications + various commercial products you can start to figure out how that all goes.

Claim 2 from claim 1.

2. A method according to claim 1, wherein the ablated surface in step (a) is formed by a pattern of laser passes with successive overlapped pulses.

3. A method according to claim 1, wherein in step (a), a crater having a bottom and wall is formed.

4. A method according to claim 1, wherein in step (b), the second beam is directed at the bottom of the crater.

5. A method according to claim 1, wherein in step (c), the pulsed laser beam scans a smaller area than the pulsed laser beam in step (a).

6. A method according to claim 1, wherein in step (b), the pulsed laser beam scans a smaller area than the pulsed laser beam in step (a).

7. A method according to claim 1, wherein the material is heterogeneous.

8. A method according to claim 1, further comprising the step of measuring the intensity of radiation from the plasma.

9. A method according to claim 1, further comprising the step of measuring the concentration of a component of the material from the intensity of radiation from the plasma.

10. A method according to claim 1, further comprising the step of measuring the depth at which the plasma is created.

11. A method according to claim 1, wherein the optical device is disposed substantially collinearly with the optical path of the laser beams.

12. A method according to claim 1, wherein said bulk material is a soil sample.

13. A method according to claim 1, wherein said bulk material is a metal sample.

14. An apparatus for depth spectroscopic analysis of a material, comprising: an energy source for generating pulses of energy in the form of a first laser beam of predetermined pulse duration for ablation of the surface layer of the material; an energy source for generating pulses of energy in the form of a second laser beam of predetermined pulse duration, said second laser beam having a pulse duration less than said first laser beam; and, an energy source for generating pulses of energy in the form of a third beam of predetermined pulses duration, said third beam having intermediate pulse duration, to form a plasma emitting radiation representative of a selected component present in said material.

15. An apparatus according to claim 14, further comprising a detector for measuring the intensity of radiation of the selected component at different depths of crater.

16. An apparatus according to claim 14, further comprising a depth profile evaluator for determining the depth of the crater for each radiation intensity measurement.

17. An apparatus according to claim 14, wherein the energy sources can be one, two or three lasers disposed such that their optical paths are substantially collinear.

18. An apparatus according to claim 14, wherein the pulse duration of the first, second and third laser beams are about 200, 9, and 30 ns respectively.

19. An apparatus according to claim 14, further comprising a delay generator.

20. A method for analyzing bulk material by laser induced breakdown spectroscopy (LIBS), comprising the steps of : (a) scanning a surface layer of the bulk material to ablate said layer with a pulsed laser beam scanned over an area;(b) polishing the ablated surface with a pulsed laser beam scanned over the ablated area; and,(c) scanning the polished surface with a pulsed laser beam within the polished area with overlapped spots in order to avoid corner sites or edge sites of the scanned area.


__________________________


Emphasis added in BOLD.

Worth checking out independent claims + other patent citations by the examiner (in some cases).

RicoRider said:

<snip> all good...

By the way (part 2):
I have received great response in earlier threads from some people, which helped me a lot in the ongoing investigation. Thank you all for that! That time it was regarding Ti6Al4V. Now it is forged steel.

Click to expand...

I remember that I/ we dug deep on your Ti6Al4V tubes / mysterious patterns, implex here had some good things to share about Titanium and it's different phases,

What did you conclude in the end ? Re: Ti6Al4V application / tube thing ?

__________________


And FWIW I ignored your first title as I didn't remember your handle,

and the title was non descriptive,

So I was immediately drawn in by your second - more technical title.

So for me I was grabbed by,


Strange phenomenon, - check

in machined steel tube, -check

after machining, -check

and black oxidation, -check,

^^^


"Strange phenomenon ", On this forum could literally have been mysterious ten legged spider being chewed upon by a three legged rat -(with that title). Or how insects spontaneously manifest in cheese ((the) Royal Society* (proceedings) circa 1660-ish ) Before Hook and Newton dog-piled in.

"Strange Phenomenon in machined Steel tube " - that would have prompted me to take a 1 second peek.

But for me the rest is relevant.


______________________________________________________________________________________


* History of the Royal Society | Royal Society

The "Tags" field for this thread would be largely inoperable.

25 charters + "LIBS" - ,

Laser Induced Breakdown Spectroscopy .

Counter thread bumpity -

No thread linking feature ... (on this forum).

Strange "hammered" surface while turning Titanium grade 5 Ti6Al-4V (annealed)

From the CNC (sub forum).


@RicoRider so what happened ?