identifying unknown steel

[BrokenBiker]

so, i mentioned a while back i was given a volvo coach half shaft for making bits with. it is so far untouched, but no matter what i do with it, its going to want annealing first. im also getting an MAN truck half shaft at some point, and possibly 1 every few months as and when they are available.

my first thought was to cut a section to a very specific size, so i can match the density by volume to a known alloy, but these things are hard, tough and dont like being cut by anything except a chop saw in current state, so getting accurate sizes isnt really viable...then i tried google, but for the volvo i am getting wildy varying result from something as basic as 1045 which i think is en8, all the way up to manufacturer specific alloys that cant be fully disclosed, some say there is a high chrome content, some say there is a blend of chrome, carbon, vanadium and other things.



to add, nothing i make will be structural, or have any real risk involved if it fails...i dont really plan on welding it either until i can get a few test bits cut and punish them to see if it will take a weld properly. so far i have only cut the spline and cap ends off to leave me with a very heavy round bar.


so ideally indentifying them would be great, but just being able to anneal them well enough to be turned without chewing through my carbide inserts would be good for now

 

[hotponyshoes]

You'll probably get a better idea over a bigger piece rather than a smaller bit (as you'll have a lower % of error)

Displacement, blank off one end of a pice of tube (drainpipe?) Put the metal in it. Fill it with water. Remove the metal. See how much water you need to top it back up.
Weigh the metal. Do some maths.
Bit of string tied on to pull it out with. Drop the wet string back in.

Or the easier way, polish a 1" section and pop into the local scrap yard with a box of biscuits and ask them to put the gun on it..

 

[Pete.]

Get it bloody hot like glowing bright yellow and let it cool. If you can now machine it get one with it. If you can't, either throw it in the scrap or buy a grinder.

 

[hotponyshoes]

Ps, a density calculation is going to be vague at best.
Even if you can get your measurements to within 0.1% (and that's unlikely at home) you'll be left with the fact that most grades have an 'allowance' on composition.
So, if a grade has a permitted carbon level of 1.45% to 2.25% you'll be none the wiser if yours is at the higher end of that grade or the lower end of the next grade.

You could make a 'best guess' of the various grades of equivalent density that yours might be but if it's a manafacture specific you'll have no idea.
Ie, a mass-producer might add 0.5% of lead to make machining easier and that might just give your piece the same density as 1045 but you'll never know.

Use density in conjunction with some reasearch, magnet, spark, file, acid tests and so on and you might get there..

 

[Screwdriver]

For the hobby metallurgist you can treat any mystery metal like any other. It will be some form of carbon steel, with the possible inclusion of some rarities like molybdenum etc. In any event, it would be difficult to establish the precise alloy, especially if after a few test runs with coupons, you get similar results with oil/water quench from varying temps.

Even if you could establish the exact composition, would you be able to use that information to perform the required heat treatment; keep it at a specific temperature for a required time etc. Then even if you did that, would it really affect your intended use?

Chances are you can anneal it simply by taking it up to a good solid orange until it is heat soaked all the way through, let it cool down slowly in vermiculite/sand.

Hardening and tempering are similarly forgiving, unless you're going for a spring temper or knife blade. Get it up to orange, quench in oil (safest bet), temper back using a colour chart.

I like the idea of reusing mystery metals but chasing the perfect heat treat is a fools errand. You'll get 90% of the way there with seat of the pants, rule of thumb. If those last few percent for the perfect temper are critical for your application, probably better off buying a known alloy of steel.

 

[Kram]

Density does not change much for steel alloys, I wouldnt think thats a viable way of identifying with out a lot of other tests. When we did reverse engineering it was a minor part of out tests with SEM being the main one.

Have you tried turning it? Its a good way to identify the steel. Carbon steel turns nice and progressivly gets worse with more chrome, like 708m40 and 817m40 becoming much harder to turn with the latter best avoided completely on small lathes, 708m40 is doable but hard work.

708m40 and 817m40 are common in high strength items and much harder to heat treat - best to reuse them as is, and only screw cut threads - dont try using a tap or die!

 

[voipio]

An X-ray fluorescence detector will give a readout of all of the elements with atomic number higher than about 22, so will narrow down the list of steel types.

 

[DanZac]

An X-ray fluorescence detector will give a readout of all of the elements with atomic number higher than about 22, so will narrow down the list of steel types.

Has anyone got one of those things what he said hidden in their treasure trove behind the old lawnmower engine and rusty nails that are bound to come in handy for something?

 

[BrokenBiker]

An X-ray fluorescence detector will give a readout of all of the elements with atomic number higher than about 22, so will narrow down the list of steel types.

im a home gamer...x rays are stricly for injuries...

thanks for all the replies...im just going to cut a section a sniff bigger than i need, stick it in the forge with the thermocouple, set it at 1000 degrees or so and then let it soak a while, see what happens.

i dont have any need for hardening after ive machined it, or not at the moment anyway, but its cheaper to use this stuff than buying stock (providing its machinable on my lathe after ive annealed it

 

[Screwdriver]

The key to annealing steel is to let it cool slowly. In ur case, easiest to let it cool down in the forge (after you switch it off!).

Ideally you'd cover it in vermiculite/sand/fire blanket but if you just want rid of any hardness (and axles I think** are often induction/case hardened) then just ruining whatever treatment it has by getting it hot will probably be fine.

 

[BrokenBiker]

The key to annealing steel is to let it cool slowly. In ur case, easiest to let it cool down in the forge (after you switch it off!).

Ideally you'd cover it in vermiculite/sand/fire blanket but if you just want rid of any hardness (and axles I think** are often induction/case hardened) then just ruining whatever treatment it has by getting it hot will probably be fine.

i will probably just turn the forge off and walk away once its had enough of a soak.

i have some en8 that needs hardened so i may set it to about 830, chuck it all in, then when the en8 is ready to come out ill bump the temp up a bit for another hour.

as long as its soft enough to machine im happy. my lathe will turn en16t all day long with decent depths of cut for its size, so if it can be machined as easily or easier then its a success

 

[voipio]

im a home gamer...x rays are stricly for injuries...

Scrap metal merchants are likely to have an XRF analyser. Packets of biscuits, or some beer tokens may help ;-)

 

[Rrobson]

Short of getting it analysed (as suggested a local scrappy or precious metal dealer may have a gizmo to do it) a basic spark test will get you close. Search spark test metal, that will get you surprisingly close if you know what to look for. Some decent videos and texts about

 

[Munkul]

The application it was in, tells me as much information as I'd need to know.
Half shafts not only need to be hard/strong, they need to be tough and impact resistant. So it's unlikely to be a plain carbon steel, unless just induction hardened. Have you checked to see if the centre is softer?
I'd guess at a low to medium alloy steel like EN19 or EN24.
ChatGPT backs up my guess with its own guess of 4140 or 4340.
The splines may be separately induction hardened to a higher rockwell than the rest.

 

[Morris]

The last half shafts I machined were induction hardened to a depth of 3mm or so. Very visible as you cut through them. A spark test may not be very accurate.

 

[Onoff]

Has anyone got one of those things what he said hidden in their treasure trove behind the old lawnmower engine and rusty nails that are bound to come in handy for something?

Hang on, I'll go look...

 

[E T]

I have several LandRover half shafts and they are good to machine with carbide without annealing.
We all know those LandRover half shafts aren't the toughest on the planet, but still.

 

[hotponyshoes]

Screwdrivers suggestion makes sense.

What do you want to use it for?
Cut a test piece and see if it is suitable for the intended use rather than working about exactly what it is!

If you have a very specific requirement then just source some very specific stock to suit.

 

[Onoff]

Compare how it machines to something you know? As in "that looks like..."