Why can't Rebar be heated and bent? What happens?

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After raising my motorcycle, I needed to make my kickstand about 10" longer, so I used a piece of rebar. Then it didn't lean over as much as I wanted, so I figured I'd just bend it out at most 10 degrees. I grabbed an oxy-propane rosebud torch, heated it up to red, and then was easily able to bend it just a little bit by hand (not directly with my hand, mind you--it looked pretty hot). Everything was perfect, I was surprised how easily it all went. Then I went for a ride, put the bike on the kickstand, and watched as it immediately crumpled and the bike fell to the ground. I gave a little tug on the rebar then, and it came off in my hand, broked in half at the area where I bent it. (Given that I'm using rebar to build this bike, you can imagine I wasn't upset about laying it down on the side of the road.)I never would have believed that rebar could be so effected by what I did that I could have easily snapped a 10-inch length in half with my hands, but apparently it happened. Why? How?"To tell which polarity to use go to the bathroom and pour some water down the drain. If it runs clockwise use straight polarity. If it runs counter-clockwise use reverse polarity. Or if it just gurgles use alternating current." -RandomDave
Reply:Re-bar is mystery metal, you don't really know what's in there.  There is also weldable and non-weldable re-bar.  Apparently, you have non-weldable re-bar and something in the makeup of the metal caused it to become brittle enough after heating to easily snap.  I'm sure someone else can come up with the technical reasons why but that is my best explanation.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Rebar can be bent when heated red however you MUST let it cool slowly.  If you heated a small location then the surrounding material will suck the heat away quickly making it brittle.  It is the rate of cooling from red that makes carbon steels hard and brittle.  As mentioned rebar is an unknown.  Some of it has so much carbon in it that I have made a chisel out of one piece hardening and tempering it.  You can test just how hard the bar is by trying to file it.  It is easy to file when it is soft.  If the file skates over it then you have a hard and brittle piece of rebar that is likely as hard and brittle as the file you are using to test it.
Reply:"...Given that I'm using rebar to build this bike..."Surely you aren't fabricating the frame out of rebar?  Am I feeling my leg getting pulled?Paul
Reply:Originally Posted by Wisner955"...Given that I'm using rebar to build this bike..."Surely you aren't fabricating the frame out of rebar?  Am I feeling my leg getting pulled?Paul
Reply:We all want to see a picture of your bike!
Reply:Rebar kickstand???Classy.You might just be a Redneck!!!Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:rebar is kinda just scrap metal.  Doesn't really have a lot of limits on unwanted elements like sulphur, zinc, tin, lead, manganese etc.   probably one of the elements in there got extreme work hardened or had residual thermal stress from being heated and cooled.  What you ended up with is a piece of brittle metal that would crumple or crack from looking at it.i stay away from rebar for any type of welding or forming operation (although I did make a tomato scaffold thing once)  Even the weldable kind is always a guess as to what limit it will crack or break at.  Cheap 1018 or other low carbon steel is a whole lot more predictable.Welding EngineerCertified Scrap Producer
Reply:Maybe the rebar bike is the newest green technology, ride the piss out of it and then just lay it down in fresh concrete somewhere.
Reply:Originally Posted by DesertRider33Re-bar is mystery metal, you don't really know what's in there.
Reply:Originally Posted by joedirt1966Is Re-bar the bologna of the metal world.
Reply:Rebar is a mix of a lot of metals. There is some high carbon steel in the mix. Therefore after heating and bending, if it cooled fairly quickly it hardened and became brittle. It is easy to snap it in half.If you were to bend it to your liking and them put in an oven at 450 degrees you could temper it and slightly soften up the steel increasing toughness and reducing brittleness. some rebar is used by blacksmiths and knifemakers for making knives to beat around.I would bet that heating up the bar after making it to your design will fix your problem, howere it is mystery steel so I would not trust it for a bike that I wanted to keep looking good.
Reply:Some years ago while looking through a section of a book about steel classifications, I found one for rebar made from rerolled railroad rail. Might even have been in the Bible.
Reply:Originally Posted by SundownIIIRebar kickstand???Classy.You might just be a Redneck!!!
Reply:Take a piece of rebar a couple feet long, and do a spark test with a grinder every 4-6 inches. You'd be surprised how much the metal can vary in carbon content in a short distance. Thats not counting any other minor elements.You know, a bike frame made of weldable rebar would be pretty slick.  Maybe some one could do a redneck themed chopper.
Reply:Lots of recycled metal in this bike. Check out the rebar foot clutch, and the wrench hand shifter. Attached ImagesMiller Thunderbolt AC/DC (Sold)Miller Dialarc 250HFMiller MM251Miller MM200 (Sold)Miller MM130Miller Spot WelderVictor O/A rigMiller Spoolmatic 1 (Sold)
Reply:Originally Posted by Bob WarnerRebar is a mix of a lot of metals. There is some high carbon steel in the mix. Therefore after heating and bending, if it cooled fairly quickly it hardened and became brittle. It is easy to snap it in half.If you were to bend it to your liking and them put in an oven at 450 degrees you could temper it and slightly soften up the steel increasing toughness and reducing brittleness. some rebar is used by blacksmiths and knifemakers for making knives to beat around.I would bet that heating up the bar after making it to your design will fix your problem, howere it is mystery steel so I would not trust it for a bike that I wanted to keep looking good.
Reply:'Rebar' can be many different steels.  Sometimes even within the same length of rebar.  And therein lyeth the wee bite o' thee issue.Rebar is steel.  But steel is just an alloy of iron and a small bit of carbon and sometimes some other elements.  But -how much- carbon is in that piece of steel?And -what- and -how much- of any other possible elements are alloyed in that piece of steel?  Steel is an alloy with many different properties that vary depending on -exactly- what is in the alloy and then on -how- that alloy was heat or work treated.So, rebar is steel but you don't necessarily -know- what alloy is in that piece of rebar.  And sometimes you don't care or even need to know, so as long as the rebar meets its physical specs you might not know or care exactly what the metallurgy is.  And much rebar is actualy made and spec'd that way, based on meeting certain physical performance specs and NOT on metallurgical alloy specs.How about some STAINLESS rebar?  ASTM A955 spec covers stainless rebar, used often for its non-magnetic properties.So yeah, sometimes rebar is like bologna.  Bed rail pieces can also be like bologna too.And Gale, rebar is NOT "tool steel".  Sometimes it may (or may not) have enough carbon in it to be able to be quenched and tempered, but it would rarely have the other desired alloying elements that make "steel" into "tool steel".  Because those other tightly-controlled amounts of alloying elements are rather expensive to get and put into steel just to make rebar out of.  Hey Bob Warner, how about some nice VAR/VIM 154CM rebar?  Maybe some D2 rebar?  Ooooh, how about some S7 rebar?          Not likely, eh?  Rebar alloy composition can (and often WILL) vary throughout the length of the bar based on the alloy varying within the melt as the ladle contents are poured out in the stream.  The begining of the pour will be different than the middle of the pour which will be different than the end of the pour.  All normal and expected for rebar, but not necessarily what a closely-controlled spec for say a nice tool steel would allow.  Same thing with the steel alloy for say some ER70S-6 welding wire.    Closely controlled specs on processing and alloy composition cost more.Rebar is rebar.  Tool steel is tool steel.  They are NOT the same thing.  The best laid schemes ... Gang oft agley ...
Reply:Originally Posted by MoonRiseRebar is rebar.  Tool steel is tool steel.  They are NOT the same thing.
Reply:Rebar is typically bent cold.  I build schools for a living and attached is a test report for the typical 60,000 PSI bar we use.  Rebar is designed to be used primarily in tension. Attached Images
Reply:I expect rebar quality has changed from 40 years ago. Back then steel imports was less than than 90 percent of the market.
Reply:Originally Posted by SundownIIIRebar kickstand???Classy.You might just be a Redneck!!!
Reply:cool lookin bike man!
Reply:This is the first couple pages of the AWS specification for welding rebar.http://files.aws.org/technical/D1-4scope.pdfContrary to many comments made above, there are specifications for different grades of steel used to make rebar, it is not some mystery mix of pot metal and scrap Yugos.I know nothing about rebar, so instead of just pulling some BS out of my A%%, I googled it.
Reply:There's no accounting for what's in rebar. Check this article out. Kinda scary.  http://www.window.state.tx.us/border/ch09/cobalto.htmlOriginally Posted by dakookNot a Redneck, something worse an ADV rider.