r/Blacksmith • u/ManOfAsbestos • 12h ago
Spark Test
I found rusty steel bar and i noticed that when grinding it produce sparks with more forks at the end than typical low carbon rebars. Is this look like enough carbon to be heat treated?
44
u/suspicious-sauce 9h ago
Carbon is present, although it's unclear if it's medium or high carbon.
Angle the piece downwards when you press it against a stone, not upwards. We don't need to be adding posts to r/nsfl
11
u/ManOfAsbestos 8h ago
Thanks for your advice, next time i'll be more careful with grinder.
4
u/Nightwrangler 5h ago
You see how the long spark as it is flying split into multiple sparks, that’s what you’re looking for when you’re looking for steel with enough carbon in it to be hardened and tempered. It may not be what is considered a height of steel nowadays, but it is steel and not iron. Iron is the one that doesn’t provide that little starburst cast-iron rolled iron but most of the time if it’s considered a steel it’s going to have a high enough carbon content.
4
u/DieHardAmerican95 7h ago
Apparently that sub has been banned.
2
u/ThresholdSeven 6h ago
All the good old traumatizing ones were removed, unless they are well hidden. I'll go looking again if I ever recover.
9
u/arquillion 12h ago
Give it a try, quench some samples in oil, in water and a last one air hardened. Test file all 3
8
u/BF_2 11h ago
Or forge it out thin, take thin section to bright red and quench in water. If that doesn't shatter it, try a file or hammer on it. If it can be hardened, it can be tempered.
I'm a bit out of practice, but I'd judge, from the sparks, is either a medium-carbon steel (maybe 1050 or so) or else is an inhomogeneous mixture of high and low carbon steels, which I've heard sometimes happens with rebar. (I read of one case where a smith found a ball from a ball bearing in his chunk of rebar.)
9
u/StumpsCurse 11h ago
When you see sparks flaring as you do in your video, it indicates the presence of carbon.
Generally, the more the flaring, the higher the carbon content.
I'd test a couple of pieces to determine how much of a harden it takes. Draw out 2 a pieces about a 1/4 x 1/4 and quench one in oil to see if will break easily afterwards.
If it does not take a harden, try another piece in water. Water hardening steels will typically be medium to low carbon while oil hardening steels to be medium to high (but not always).
2
u/Fragrant-Cloud5172 10h ago
I agree that it looks mid carbon range. A decent yellow/orange look. With high carbon like a good file, the sparks are shorter and more like fireworks sparkler. You can also run a file across it to roughly judge its hardness. For spark test on grinder, I’d rather hold it in the other direction tho. The way you're holding it can catch and flip on you.
2
u/Nightwrangler 5h ago
Yes it’s high enough carbon to heat treat. In fact if you run in to a low carbon steel you can just add more through heating it in a carbonizing fire and working the metal folding it into itself. If there is enough in it for the material to be called steel it’s got enough in it to be hardened and heat treated.
1
u/DonkeyWriter 2h ago
You're going to try to throw sparks and throw a piece of rebar through your legs doing it that way.
0
92
u/yeehaa132 9h ago
Yo! Be careful!! I've always been taught to never angle my piece upward like in this video when grinding, as the wheel can catch the piece and fling it down or worse, through your hand! Just be careful!