Hardenable Steel Identification

[ChazzC]

Yes, very true, but many other tool steels are also wrapped in paper, it proves nothing.

That was my point: unless the material itself or the original packaging is marked, you can't tell what it is by appearance.

 

[verbotenwhisky]

Fifty three years ago when I took freshman chemistry, the way to identify materials was done through qualitative chemical analysis. This meant dissolving the sample in an appropriate solvent, usually something like aqua regia, and adding various chemical solutions to precipitate out product or create a distinctive color change. Typical metals, besides iron, alloyed in steels are manganese, chromium, nickel, cobalt, molybdenum, and a smattering of others. The definitive work on the subject was "Introduction to Semimicro Qualitative Analysis" by C. H. Sorum.

Beyond that, another analytical method was emission spectroscopy which would yield semi-quantitave results. It required a very expensive and huge spectrograph which created a plasma from the sample with an electric arc and analyzed the emitted spectrum via a photographic plate. Atomic absorption spectroscopy followed and was able to provide accurate compositions of metals. And the x-ray fluorescence spectroscopy mentioned by @graham-xrf is the latest in the arsenal.

The bottom line is that it is difficult, if not impossible, for a lay person to accurately identify a steel alloy. I realize this first hand as I have several tons of unknown steel alloys.

I agree, not that my agreement means much, but in our industry all materials for critical uses require certs which list what it is, where it came from the batch number, etc... and even then we send in coupons to test to ensure it will meet requirements for strength and cycle test. This would not be required if a) there was an easy way to determine this information and B) such methodology were not cost prohibitive.

 

[graham-xrf]

Keeping in mind the practical realities of any test involving getting stuff taken apart enough (i.e. chemistry) or hot enough force it's atoms to expose its contents (plasma), as explained by @RJSakowski, I am not sure there is that much mileage in the colours in the spark shower. Sparks are, after all, little bits of the alloy made temporarily kinda hot. It's the length of the sparks, from the sizes of the chunks that fly off, giving them relative longevity.

That said, a kooky notion might be to get some images, or video, and submit to one of those AI engines that has trawled billions of images, including from anyone who has ever done tool grinding on YT. This would be the longest of long shots, and I'm almost ashamed to suggest it, but it may do better than me invoking radioactive attempts to get a rise out of a chunk of unknownium.

 

[RJSakowski]

Keeping in mind the practical realities of any test involving getting stuff taken apart enough (i.e. chemistry) or hot enough force it's atoms to expose its contents (plasma), as explained by @RJSakowski, I am not sure there is that much mileage in the colours in the spark shower. Sparks are, after all, little bits of the alloy made temporarily kinda hot. It's the length of the sparks, from the sizes of the chunks that fly off, giving them relative longevity.

That said, a kooky notion might be to get some images, or video, and submit to one of those AI engines that has trawled billions of images, including from anyone who has ever done tool grinding on YT. This would be the longest of long shots, and I'm almost ashamed to suggest it, but it may do better than me invoking radioactive attempts to get a rise out of a chunk of unknownium.

I have found that spark properties vary with the grit of the grinding wheel and the amount of pressure exerted so I'm not sure that AI would be able to help much. The best bet would be to build a library of known alloys and compare the unknown.

 

[graham-xrf]

I have not (yet) read the C. H. Sorum book. I know that @RJSakowski has been the whole route of chemical analysis, so I am still in the land of long shot speculations.

My complete fantasy vision of a "handy" test would be to get up an extraction solution concoction that has the stuff in it to chelate, extract, whatever from his list that includes manganese, chromium, nickel, cobalt, molybdenum. Throw in any other substances thought relevant.

So one puts down a blob of it onto the unknown, stirs it about a bit, then sucks it up into an ex-COVID test dropper. Then put some drops into the rest of the re-purposed COVID kit plastic paper chromatography thing where one has swapped out the paper strip for a Hobby Machinist special version, so that over the next minute, one gets a spectrum of giveaway colour lines that reveal the metal ions in there. The intensity of the lines might indicate the relative abundance of each.

[Still going for Hobby Machinist Tightwad -of-the Year award, once the plastic case has been forced open, one can re-use by putting in a new HM trick paper strip]

 

[RJSakowski]

Qualitative chemical analysis requires a whole list of laboratory glassware, a centrifuge, a filtration system and preferably a fume hood. In addition, there is a fairly large list of chemicals, some of which may not be available to the amateur chemist. There are some spot tests for certain metals available but I don't know if other metals would interfere. Iron is the big one since it is the major component in steel alloys. Color tests for cobalt, nickel, etc are essentially the same, just yielding a different color and the overwhelming presence of iron would conceivably swamp the test unless there were a way to remove it. Add to that, you still have to be able to dissolve a specimen which will most likely require a strong acid.

 

[ericc]

I read an interesting paper that studied the difference between 4140 and 1045 sparks. It quoted people saying that an idiot could figure out the difference in 5 minutes. So the researchers grabbed a few people off the street and gave them 5 minutes of training. It turned out that they did pretty well, although not perfectly.

 

[graham-xrf]

I read an interesting paper that studied the difference between 4140 and 1045 sparks. It quoted people saying that an idiot could figure out the difference in 5 minutes. So the researchers grabbed a few people off the street and gave them 5 minutes of training. It turned out that they did pretty well, although not perfectly.

What I want is some trick app where I can just point the "smartphone" camera at the view of the sparks for a couple of seconds, and have it list what steel it thinks they are best looking like.