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Jeremy Blohm

Rebar spec sheets

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I requested these from a guy on another forum and I figured I would share them here. Its DEFINITELY not knife steel 

This one is NON weldable rebar 405351611_paper02.jpg.b554e18acb40da6b1b465e49f013f3df.jpg

This one is weldable.

679976222_Paper01.jpg.13bcfa2681fa8dd7b423c6b769f57df9.jpg

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Interesting. Thanks for posting. 

Any idea what makes that top one non weldable? Did the man who gave you the specs say?

Im just curious. Thats enough carbon to where too quickly of cooling could possibly mess with you, but its unlikely, totally doable. Ive welded lots of chrome-moly with far higher Cr and Mo percentages. And that vanadium percentage is too miniscule to matter, i would imagine. 

Seems like it would be quite easy to weld actually. 

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It has to do with construction codes.  Welding can cause hard or soft spots in medium-carbon rebar, either of which throw off the specs due to the risk of failure.  That's why you see a lot of wire-tied rebar on construction sites.  Nobody wants to be blamed for a bridge collapse.

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Ah, i see. I took that the wrong way. I figured it meant "cannot be welded."

Thanks for the info, Alan. 

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How true are these statements? Especially the last bit.

 

Benona: What's your interest in rebar? It's really iffy, especially for a beginning smith, just learning the basics is challenging enough without having to learn to evaluate an inconsistent material. Performance specification means that so long as rebar has the minimum tensile strength, bending moment and rebound it's good. It can exceed any or all specs and often does, it's generally not carefully composed nor well mixed meaning the C and alloy can change unpredictably sometimes in inches.

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18 minutes ago, Jeremy Blohm said:

Performance specification means that so long as rebar has the minimum tensile strength, bending moment and rebound it's good. It can exceed any or all specs and often does

Yes.  True for most steels, though some specs have upper and lower limits to some properties.  

19 minutes ago, Jeremy Blohm said:

it's generally not carefully composed

In the US, production is very tightly controlled, but it is difficult to know what each batch is controlled to.  Often the carbon equivalency (CE) is the main target that is shot for in rebar, and that has several variables, some easier (cheaper) to control than others.  Not all rebar is made to the same specification (as noted above).  Higher grades are more expensive because they are more tightly controlled.  

22 minutes ago, Jeremy Blohm said:

nor well mixed meaning the C and alloy can change unpredictably sometimes in inches

I'd love to know how this would be possible.  There can certainly be heat treat variables in a single piece, but it is pretty dang hard to not have well mixed metal.  

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For a little more on the last statement:

Here is an electric arc furnace (EAF) being tapped.  The metal has already been melted via 3 graphite electrodes pumping in thousands of amps of electricity.  For that size, it is probably about 2000-6000 amps per electrode (3 electrodes, one for each phase of 3-phase power),  generally at about 200 volts.  All that electricity arcing into the metal causes a stirring action, as do the thermal currents (hotter metal near the arcs, cooler metal further from the arcs).  Then the metal is tapped (poured out of the furnace into a ladle).  You can see the melters adding ladle treatments: de-gassers and inoculants.  The larger bars are probably aluminum, great de-oxidizer. 

 

After this, the ladle will be taken to the caster.  It will pour the metal into the caster in much the same way that the furnace poured it into the ladle.  The caster then makes the ingots/blanks that will be rolled into rebar.  

Pour any liquid from one container, to another, to another, then a final pour.  How segregated do you really think it can be?  

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That's what the book says. Now if you talk to the actual people that make rebar they are gonna tell you it is kind of like making Spam. Everything but the squeal goes into spam and what ever re-cycled steel they can find to pour out as rebar. 

I have seen more that one construction project fail and more often than not the rebar is the culprit!!

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I’d be willing to use steel made out of the top heat for tooling. There’s some chrome, silicon and nickel and enough Mn to make it harden easy enough. Should be tough stuff.

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For those curious the CE for the top chemistry is 0.63%.

CE=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15

For the most part, it doesn't really matter what goes into the steel.  Most things can be removed, at least those things that are most likely to get in there that you would want to control.  The biggest exception is Cu.  Easy to get in by mistake (e.g. if copper wiring isn't removed from a car before it is crushed/shredded), and not easy to get out.  Ni is also hard to get out, but it isn't likely to get into the steel in harmful quantities.  I'd be pretty embarrassed to make a heat with that much sulfur though (0.044%!).  I start to worry about quality of steel when S gets above 0.025% (possibly less, depending on alloy/grade).  That is really going to hinder impact toughness and ductility.  

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Thank you Jerrod I appreciate it.

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Just a shot in the dark......

Was this perhaps prompted by a certain video of a rebar axe on Facebook......?

 

:blink:

 

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No it was stated on another forum but now I'm curious about the axe on Facebook. How might I find it.

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Just search for "rebar axe", I assumed everybody that dares make knives had this video shared to their timeline repeatedly :lol:

All fine & well, just not sure you can get an edge like that on rebar......?

 

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