Author Topic: Need field tests for cast arn, wrought arn, or steel (Read 766 times)

cannonmn · « **on:** March 22, 2012, 04:38:18 PM »

Bronze is pretty easy, if you cannot ID, carry a small magnet.
The various ferrous metals used for cannon, namely cast iron. wrought iron, and steel are sometimes hard to tell apart. How can I do it when the cannon I'm looking at isn't "regulation" and there's no documentation on it.
Does anyone have a Ronco pocket-sized metals test kit I could borrow? If not, what can I do in the field to determine what the ferrous metal is?

GGaskill · « **Reply #1 on:** March 22, 2012, 06:35:38 PM »

What you need is one of these Xray Flourescence Analyzers. I'd love to have one but a refurb is $15-20K and I am unwilling to pay that much for a toy, even a useful toy.

cannonmn · « **Reply #2 on:** March 23, 2012, 02:35:57 AM »

Thanks, yes one of those would be nice to have for many reasons, but I have to think it is overkill for my present needs. There must be a gerry-rig, affordable way to do that. For example, the old shop standby method of classifying ferrous metals with a grinder is one way if you're in a position to bend the definition of "nondestructive testing" a bit. But unless you do that at night or indoors, you'd need a hood like the wet-plate cameramen, in order to see the sparks well enough. Packing a power supply for a dremel would be a bit awkward, but there are lots of battery-driven rotary power tools available now.

If you can't grind away a part of the metal to be sampled, maybe there's a portable hardness tester? Seems that wrought iron is quite soft, cast iron a little harder, and steel the hardest by comparison, but someone with experience-based knowledge of that please comment-I know cast iron may be quite variable but don't know if it can have hardness in the same range as steel or not. Then you get into the heat treatment of steels and how much the hardness can vary. Any hope here? I have a few cannons lying around that are in the "unknown ferrous metal" category and I can take them into the workshop and do any reasonable testing there.

Come to think of it, since the cannons are portable, maybe I'll make a trip to the local junkyard where they might have one of the fancy testers and see if I can trade a small portrait of Andrew Jackson for a test.

jamesfrom180 · « **Reply #3 on:** March 23, 2012, 03:21:17 AM »

Take a look at this
http://www.esabna.com/EUWeb/OXY_handbook/589oxy16_1.htm

Though taking a chisel and a chip from a barrel might not be practical, it might be easier than grinding. I will look but I think you can then add acid and see if there is a grain structure.

cannonmn · « **Reply #4 on:** March 23, 2012, 03:25:21 AM »

Good idea, wrought will have a grain and steel will not, as I recall. At least when wrought iron corrodes it shows a very distinctive grain almost like sandblasted wood grain.
I called the local recycler and he's personally interested, said he'd come over one of these days when he can get away, with his portable x-ray and "shoot" the items we want tested. Will report back when I get that done.

jamesfrom180 · « **Reply #5 on:** March 23, 2012, 03:47:39 AM »

This does not help my bill-ability but hey its Friday.

Dug out my "The Science and Engineering of Materials" text by Askeland and Phule. No real help but I should be able to track down some grain pictures if I look hard enough, but it helped trigger a long disused synapse. I hated thermal conductivity calculations.

This helps in the fact that Iron and differing types conduct energy differently.
See http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

This would result in a truly non destructive test. A unit mass of material could be heated to a set temperature and placed on the barrel. The barrel would have to be isolated sufficiently enough to minimize its gain or loss of energy, but if a small unit mass was used and since barrels are generally large you can make an assumption that its virtually infinite. Shielding of the test site with a styrofoam cup will also minimize loss to radiation and convection meaning heat transfer would be through conduction. Then you would time the temperature change and then solve for the Thermal Conductivity. Since no touch thermometers are pretty cheep these days I would think with a minimal amount of testing the procedure could be perfected to gain the needed accuracy.

seacoastartillery · « **Reply #6 on:** March 23, 2012, 06:40:41 AM »

John, We don't know if this method has ever occurred to you or not, but with your extensive body of experience with thousands of different pieces of ordnance, you may have already tried a "hands-on" approach. Mike and I have found, in our travels around the United States, that, with a little practice you can ID the metal in most seacoast tubes and especially carriage and chassis parts by feel. Of course the item must be unpainted, but many that we look at, we find in that condition.

Using your innate sense of touch, you can get a surprisingly accurate and unique, tactile response from each of the metals you mentioned. As you rub your index finger lightly across cast iron, you sense that it feels rough even though the surface may be perfectly smooth. Thousands of pores, large and small make cast iron feel this way. Diametrically opposite is wrought iron. Not only is it extremely reluctant to rust, it always feels smooth. If you have ever felt a burnished surface, that is what wrought iron feels like. Steel lies half way between these first two as far as tactile response is concerned and can best be characterized by consistency of feel VS the ever changing feel of wrought iron or cast iron as far as friction goes.

Of course visual classification is notably accurate as well. A uniform rusting indicates steel, a distinct pitting pattern denotes cast iron and the rust in low spots only (wood grain effect) denotes wrought iron.

Mike and I rate visual discernment at 70% and tactile at 85% accuracy. So, unless you are doing a real scientific study, you can "Know" with some certainty, easily and without expensive equipment.

Mike and Tracy

shred · « **Reply #7 on:** March 23, 2012, 07:50:21 AM »

Etching a small area with appropriate acid (nb: I do not know which one), and inspecting under a magnifier/microscope would probably work. The grain structure is very different between those.

GGaskill · « **Reply #8 on:** March 23, 2012, 09:50:30 AM »

There is a device for hardness testing called a Shore (Schorr) Scleroscope that might be what you are looking for. See this site near the bottom for some info. See this site for some pictures. Found another auction where one sold for $70. There are lots of references on google.

Seems that wrought iron is quite soft, cast iron a little harder, and steel the hardest by comparison ...

In my experience, cast iron is harder than soft steel although heat treated steel can be harder than cast iron. But I would guess that there isn't much heat treated steel involved in the antique cannon business.

cannonmn · « **Reply #9 on:** March 23, 2012, 12:28:46 PM »

The boss at the recycling place was kind enough to come over with his xray analyzer, looked to be the exact same type as pictured above, and "shot" some stuff I had layed out as a trial. The results were pretty surprising. I was always sure no aluminum would show up in anything made prior to about 1900, but several items much older (say ca. Civil War) had 3% aluminum or so, no idea how that happened, I'm certain the items are original. Anyway, if anyone is intersted in seeing the xray analysis of the elements in these objects, I will post them one or two at a time, along with a brief description of the object tested..

GGaskill · « **Reply #10 on:** March 23, 2012, 01:25:04 PM »

I was always sure no aluminum would show up in anything made prior to about 1900, but several items much older (say ca. Civil War) had 3% aluminum or so, no idea how that happened, I'm certain the items are original.

Metal refining in the days prior to ca. 1900 was a much simpler and less effective process and lots of things were mixed together due to ignorance and inability to separate things. Even the iron and steel making business produced products of uncertain quality and uniformity until they finally realized they needed to get everything but the iron out first and then add the alloying elements intentionally and in the proportions they desired.

Aluminum is the most common metal on the earth's crust and it is not hard to believe a little could easily creep into any melted metal unintentionally.

cannonmn · « **Reply #11 on:** March 23, 2012, 03:13:08 PM »

OK here are the first few. It is beginning to look like wrought iron makes itself obvious by having the fewest elements, at least according to the Xray thingy. Numbers of the items below correspond to those in photo above. The man operating the machine told me that the process does NOT detect the element carbon.

#3 Italian serpent gun, we are certain it is wrought iron

Si – 1.95
S – 1.42
Fe – 96.34
Cu - .30

#4 Tolley Pentagonal Rifle Tube only, ferrous metal unknown

Si – 1.00
S – 1.91
V - .04
Mn - .37
Fe – 96.22
Cu - .18

#5 Tolley Pentagonal Rifle Trunnion Band only, ferrous metal unknown

Si – 1.73
P - .24
Ti - .75
V - .36
Mn - .07
Fe – 95.10
Co - .47
Cu - .15
Zn - .15
Pb - .97

#6 Whitworth 2.75 in. bolt, ferrous metal unknown

Al – 3.04
Si – 5.10
S – 4.39
Ti - .16
V - .07
Cr - .06
Mn - .30
Fe – 86.39
Cu - .10
Zn - .23
Pb - .17

cannonmn · « **Reply #12 on:** March 23, 2012, 03:18:48 PM »

A few more:

#7 B/L cannon model attributed to H.L. Mann, barrel,
ferrous metal unknown

Si – 1.65
P - .55
S - .53
Ti - .14
V - .17
Cr - .06
Mn - .36
Fe – 96.54

#8 Bar Shot shank-certain it is wrought iron

Si – 1.54
P - .12
S - .79
Fe – 97.54

#9 Bar Shot end piece-certain it is cast iron

Al – 2.38
Si – 4.70
P - .06
S – 1.13
V - .12
Fe – 91.16

GGaskill · « **Reply #13 on:** March 23, 2012, 06:49:40 PM »

The man operating the machine told me that the process does NOT detect the element carbon.

Interesting. I see the analysis of #7 totals 100%; #8 totals 99.99%; and #9 totals 99.55%.

#3--100.01%
#4--99.72%
#5--99.99%
#6--100.01%

The manufacturer of the XRF tester is at Westec next week and I will talk to them. Odd that carbon is not detected; seems like that would be an important constituent of steels. Did the tester have any reference materials with it?

cannonmn · « **Reply #14 on:** March 24, 2012, 02:03:11 AM »

Quote

Odd that carbon is not detected; seems like that would be an important
constituent of steels.

Have been reading up on the XRF process itself, whether in a big lab machine or handheld, the basic technical process does not lend itself to any element with atomic number less than 12 (magnesium.) Carbon has atomic no. 6, so that's obviously out. Most of the stuff I've found on the web applies to the older, big lab machines where the sample had to be ground up and prepared a very specific way. The latest handheld machines like the one the gent brought over yesterday seem like they don't require any surface preparation of the material.

cannonmn · « **Reply #15 on:** March 24, 2012, 02:33:14 AM »

#11 Experimental 3.4 in. Navy B/L Rifle Tube, presumed to be English forged steel
Al – 1.91
Si – 14.87
P - .04
S - .68
Mn - .06
Fe – 82.08
Cu - .15
Zn - .198
Pb - .11

#12 Experimental 3.4 in. rifle trunnion band, presumed to be forged steel
Al -2.19
Si – 16.49
S - .62
Mn - .09
Fe – 79.68
Co -.51
Cu - .07
Zn - .11
Pb - .24

cannonmn · « **Reply #16 on:** March 24, 2012, 02:42:14 AM »

I think the tests have done what I wanted, to identify cast vs. wrought iron vs. steel. This may be taking a leap, but I think everything with over 95% iron (Fe) is wrought iron, everything below 90% Fe is steel, and the one cast iron sample is in the middle with 91% Fe. So I went back to the previous posts and put the Fe percentages in bold to make them easy to spot.
Do you think my method is accurate?

Cannoneer · « **Reply #17 on:** March 24, 2012, 05:00:39 AM »

I suppose this could be considered as fitting in with this topic (at least in a roundabout way). Some years ago this bronze presentation model of a French 75 was up for auction, and the seller described the gun as being made of cast iron. I sent him a message requesting that he do a magnet test, and he responded that a magnet would not stick to any part of the metal cannon, but he was still certain (because of its appearance) that it was made of cast iron.

cannonmn · « **Reply #18 on:** March 24, 2012, 05:18:48 AM »

Nice looking model, looks like it would shoot, almost.

Here's the photo of the test objects, with the addition of what I determined their compositions to be based on the XRF analysis. Legend: S=Steel, CI=Cast Iron, WI=Wrought Iron. Is my rule correct, namely that those showing particularly low in iron content are in fact the steel items?

GGaskill · « **Reply #19 on:** March 25, 2012, 05:29:23 PM »

... but I think everything with over 95% iron (Fe) is wrought iron, everything below 90% Fe is steel, and the one cast iron sample is in the middle with 91% Fe. ... Do you think my method is accurate?

I think you have too few samples of antique cast iron to make any blanket statements about its general composition. If you can impose on your scrap dealer for some additional testing, I would suggest getting more samples (especially samples of known material), and taking multiple readings on each piece to see how much the chemistry varies within each piece.

The thing that chemically differentiates wrought iron, cast iron and steel is the carbon content, wrought iron typically having very little, steel having not much and cast iron having several per cent.. And the XRF tester gives no input on carbon content. Furthermore, the chemistry of iron and its alloys was poorly controlled before the early 20th Century with alloying elements more dependent on the iron ores than on knowledgable chemical additives.

I think physical hardness tests will give greater satisfaction but still not 100% accuracy.

jamesfrom180 · « **Reply #20 on:** March 26, 2012, 05:01:02 AM »

Reliance on one method for determination would be inconclusive for me. But for a quick shop guess you may see some benefit. I would be leery of saying just by iron content something is wrought iron verse steel. By utilizing tightly controlled heating methods you may get WI with high carbon content. This will in effect yield steel. My question would be how deep into the piece is the XRF reading. I am certain bone hardening and other treatments will yield surficial changes in overall chemistry. Driving of elemental carbon into the iron latices has been known for along time to yield stronger iron. I forget the actual differences but grain size is considered an organizational step above composition. Something about structures and so forth. So saying a piece is steel or iron may be a tough call on something like a blade. Benefit is barrels usually have more mass.

Cool you got to play with someone else toys.