Carbon steel test

[Bwilloughby]

Can anyone explain a easy way to tell if a chunk of steel has is high carbon or has carbon in it?

I read something about the grinder wheel thing where high carbon will have more sparks over mild steel, but to me seems a little hard to determine.

[HWooldridge]

In general, more carbon is defined by more bursting sparks. A piece of low carbon will throw a good spray of sparks (orange to my eyes) with little branching or bursting while higher carbon will have a shorter stream with multiple tails.

Take a piece of known low carbon (A36 or 1020) and touch it to a grinder then take an old file and do the same (don't use a farrier's rasp - they are often surface hardened). These are the usual high and low extremes of what is seen in normal use so gauge the spark appearances with your eye.

Alloys and wrought or cast iron are markedly different from the above so it's best to take a known piece and compare it to what you are testing. At one time, I kept various small pieces of known alloys, including stainless and tool steels, for comparison to pieces that I tested. These have gotten away from me over the years but it's a good practice to observe if you encounter a lot of scrap steel.

[Ralph]

Easiest way is to buy new steel from a reliable vendor and then mark it.
BTW if marking with paint NEVER, I repeat NEVER cut from the painted end. Or allow others to do so, as now you have a new piece of mystery steel ( after it is put back into the metal rack/pile.

The grinding wheel way does work. But you first need to learn a few things about it. My copy of Machineries Handbook ( the 14th Edition) has a section on this very thing. Explains and has some B&W drawings of the different spark patterns.
If you can get some low carbon steel, say like a nail which should be 1008 and some plain jane bar stock ( mild steel) and perhaps an old cold chisel, then you can spark test them all and pay close attention to the spark color, the shape or pattern of the sparks. How bright as well. Then you have a fair seat of the pants gauge. Also it would be best to apply about the same pressure to the metal with the grinder.
There are other publications that show the spark test info, but I can not remember what they are

[Glenn]

BP0020 Spark Testing


This is a reference you may find useful.

[Bwilloughby]

Thanks guys.

For some reason Glenn I didn't think to look in the Blueprints section, Man that becomes more usefull everyday .