properties, types, identification, and heat treating of Rebar

[beat]

What do the codes on rebar represent? What are the percentages of carbon and maganese?


I'm aware that it is a medium to low carbon steel with some amount of maganese and that it isn't the ideal material for blades, but I've found rebar to harden up nearly as well as spring steel. I heard from an old timer that maganese improves its' ability to harden. Is this true?

My heat treating process:

*coal-forge heated and forged with a nearly sharp bevel. (slight case hardening from carborizing coal fire and pounding into edge?)
*normalize/hot filing, 1 or 2 times.
*heat edge to critical temp and quench in light oil (water seems to get it too brittle)
*rainbow temper with spine in the blue/purple range, and edge yellow

Thanks for any shared knowledge or suggestions.

[thingmaker3]

Grade 60 has approximately 60 ksi tensile strength.

Grade 80 has approximately 80 ksi tensile strength.

These are performance standards, not composition standards. Composition can be anything. Rebar can be made from mild steel with stainless jacket. Rebar can be made from fiberglass.

Acceptable working knives have indeed been made from grade 80 rebar.

As for manganese, it can increase hardenability (but not maximum attainable hardness) depending on how much is added. More often, i, it is added in wee ammounts to de-oxidize the molten steel.

[Steve Sells]

The ANSI standards for Rebar, are based not on composition but on strength. So they do not test or blend the melt for C and Mn as they do with tools steels. Like many steels its made from recycled steel, but why pay to test for things that don't really matter much, meaning its a crap shoot. Break and stretch testing is the most common, if this standard is met, then they don't care how much Mn or Chrome may have gotten included.

It is much like if you are making furniture from a hard wood, you want matching wood type, grain pattern and color, but if its for burning in a fireplace, does it matter much?

[ThomasPowers]

As I recall Mn is good for tying up any sulfur in the steel so it doesn't cause trouble, Al was used for "killing" the steel.

[beat]

Al was used for "killing" the steel.

What does "killing" refer to?

Thank you all for sharing your knowledge.

[ThomasPowers]

"Killing" is an old steel making term for deoxidizing the molten steel by adding a strong deoxidizing element to react with any remaining oxygen in the melt.

I picked it up reading old (1900's) manuals.

[thingmaker3]

May well have been the sulper instead of the oxygen. I know it was for tying up some kind of unwanted gunk. :)

[ironstein]

I work with rebar everyday. Mill certifications are delivered with loads of rebar. These certs show the composition of the particular heats that the steel came from. If you are buying new rebar you may be able to find out what the composition is.