Greenbeast Posted November 22, 2014 Share Posted November 22, 2014 A couple of times recently i have experienced the corners on a piece of steel cracking. Today was the worst/most demoralising. I spent 5-6 hours tapering 12mm square bar, and noticed some slight cracking but managed to not make it worse. Until i came to scroll them all, the edges opened right up and now they're not worth what i'm meant to be charging for this project. What could be causing this? I'm forging with gas Could it be too hot, too cold (unlikely i think), too rich or too lean burn? Too long in and out of the forge? I spent 90mins doing a pair of them at one point I now face the prospect of replacing a whole days work with not a lot of time to do it in :( Link to comment Share on other sites More sharing options...
Dave Budd Posted November 22, 2014 Share Posted November 22, 2014 do you have any pictures of this cracking? Is it virgin stock or old square bar? I ask incase it is wrought iron that is being worked too cool. Or it could be the sort of cracking/crazing seen when an area becomes fatigued through bending back and forth for ages when not actually hot enough (the sort of thing tat happens to the temporary handle welded on to a lump being turned into an axe) Link to comment Share on other sites More sharing options...
Greenbeast Posted November 22, 2014 Author Share Posted November 22, 2014 virgin mild steel no pics but i can do some tomorrow Link to comment Share on other sites More sharing options...
jmccustomknives Posted November 22, 2014 Share Posted November 22, 2014 Sounds to me like you've got some crappy A36. Just for grins heat a little piece up and quench it in water, try to break it. Since a lot of steels re re-melts the alloys can be all over the place. A high carbon content or other alloys can cause numerous problems. That or you might have some high sulfur coal. Link to comment Share on other sites More sharing options...
arkie Posted November 22, 2014 Share Posted November 22, 2014 (A.) second on what jm said, (B.) forging metal too cold. I often develop cracks in A36 if I get carried away and stretch my hammering past red. Quit doing that and no more cracks. Haven't run into much crappy A36, but will sooner or later. Link to comment Share on other sites More sharing options...
Ric Furrer Posted November 22, 2014 Share Posted November 22, 2014 Does it crack when bent without forging? I too think you have bad steel. Ric Link to comment Share on other sites More sharing options...
Kal Posted November 24, 2014 Share Posted November 24, 2014 All steel is made from remelted scrap. If it came from an electric furnace it is 100% scrap. If it came from a BOP (Basic Oxgen Process) it is 1/3 scrap and 2/3 liquid cast iron from a blast furnace. Whenever a melt shop makes a heat it is done to the spcifics of the order. A36 I believe is low cardon, about 25pts.. Link to comment Share on other sites More sharing options...
ThomasPowers Posted November 24, 2014 Share Posted November 24, 2014 A-36 has a yield strength spec: 36 KPSI; not a strict chemical spec. As such it can vary and I have run into some pretty poor stuff that cracked under forging like was mentioned. Link to comment Share on other sites More sharing options...
Greenbeast Posted November 26, 2014 Author Share Posted November 26, 2014 This is the best photo i could get I'm going to try playing with the temperature of the forge this weekend. I need to put twists in the fire tools i'm making and cannot afford to risk them cracking after the work i've put in to the finials Link to comment Share on other sites More sharing options...
JNewman Posted November 26, 2014 Share Posted November 26, 2014 A-36 has a yield strength spec: 36 KPSI; not a strict chemical spec. As such it can vary and I have run into some pretty poor stuff that cracked under forging like was mentioned. I keep reading this "fact" regurgitated on blacksmith forums, but I would disagree. Here is a link to a legal description of the A36 grade of steel. https://law.resource.org/pub/us/cfr/ibr/003/astm.a36.1997.pdf There is a chemistry listed. There is a range in the chemistry as there is in all steel grades. Can you back up your assertion that there is no chemistry spec? The OP is in the UK where it is unlikely that he has A36. With some smaller suppliers you could get all sorts of mystery metal when buying mild steel especially if you are not buying full lengths. I also agree that you may have ended up with a bad bar maybe a "free machining" alloy either leaded or sulfur added for machining. Was it hot rolled or cold rolled? If you really want to be sure what you are getting you could ask for mill test reports or "certs" I have never had problems forging steel A36 or 44w that I received test reports on. I wonder if many of the problems people have had is steel that does not meet the specs and is then sold without Certs to smaller suppliers. I have to supply certs for the steel I use for most of the things I forge. Link to comment Share on other sites More sharing options...
Judson Yaggy Posted November 27, 2014 Share Posted November 27, 2014 Nice link John, thank you. Link to comment Share on other sites More sharing options...
Chinobi Posted November 27, 2014 Share Posted November 27, 2014 Please do not read this as any form of slight against you, your technique, or experience. I will say that that particular symptom looks "familiar" to me, and from what I have learned at the anvil, and from a few other threads discussing similar afflictions MY situation was/is more than likely caused by taking way too many heats to perform a given task, letting iron sit in the gas forge after it has already come up to temp, working well beyond when I should have stopped, and not keeping the work flat with the anvil face. so every hammer blow both forges AND bends the stock just behind the hammer, then roll 90, and the next swing bends the other axis, now you have to unbend both of those to get back to straight, and all of that is happening in an area that is colder than it should be for such an operation. Most of this experience has been on mild steel from several sources. I can't recall if iv done it to sucker rod, I think I police my temperature more vigilantly on tool steel. So again, I am just saying that's what I have attributed to be causing similar symptoms in MY work, YMMV :) Link to comment Share on other sites More sharing options...
Greenbeast Posted November 28, 2014 Author Share Posted November 28, 2014 time-to-complete was a concern of mine Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted November 28, 2014 Share Posted November 28, 2014 I agree that too much time in the fire can cause the same affects. I was experimenting with a bracelet, and it was in the fire a long time as I was working out the steps needed. Indidn't care about final looks as I was just working out the steps, and tooling needed to make more. It was tapered on the ends, and twisted in the middle. The middle section looks like your finial. Try reducing the time needed to make these. Link to comment Share on other sites More sharing options...
Pat Roy Posted November 29, 2014 Share Posted November 29, 2014 I have seen the comments about A36 being junk steel so many time and yet I don't believe it. Until recently(a vague term for sure), A36 steel was used in building construction (and of course other applications). I find it hardly likely that my structural engineering friends were using material that had no specifications concerning its chemical content. I know that they now generally use steel that is rated at 50 ksi, and I'm sure that has specifications also. Thank you John for trying to set the record straight. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now