TheBlueSwell Posted June 29, 2019 Share Posted June 29, 2019 Has anyone ever tried to forge with post-tension cable? I have an opportunity to get about 70 ft of it and I am considering giving it a try as long as it is not galvanized. It seems like it would have a pretty high carbon content, but I would like to know its basic composition if anyone knows. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted June 29, 2019 Share Posted June 29, 2019 Welcome to IFI, have you read this yet? READ THIS FIRST Can't help with the cable Id, in my part of the world, haven't heard of post tension cable. Maybe let us know what it is used for & where in the world it's located. Quote Link to comment Share on other sites More sharing options...
TheBlueSwell Posted June 29, 2019 Author Share Posted June 29, 2019 Post tension cable is the cable they put inside concrete slabs to increase the strength of the slab. Post-tension cable is stretched after the concrete hardens. Its not the same as rebar. See below. "Concrete is very weak in tension but extremely strong in compression. Post-tensioning acts on the concrete structure or elements by compressing the cast-in-place concrete to high pressures. Some advantages of post-tensioned concrete include crack control and lower construction costs. Post-tension materials (PT) can provide thinner slabs and is especially important in high rise buildings in which floor thickness savings can translate into additional floors for the same (or lower) cost. PT can optimize constructability by having fewer joints since the distance that can be spanned by post-tensioned slabs exceeds that of reinforced construction with the same thickness. Architects like having a PT option since increased span lengths also increases the usable floor space in buildings and provides more parking spaces in garages. Post-tensioning has advantages over pre-cast since it has lower maintenance costs over the life-cycle of the structure. Architectural shapes other than rectangles give post-tensioning an advantage over pre-cast, as well, since strands in cast-in-place construction can be curved or swept into place." Source: http://ptestrandcompany.thomasnet-navigator.com/item/all-categories/post-tension-systems-materials/item-1001? Quote Link to comment Share on other sites More sharing options...
Steve Shimanek Posted July 1, 2019 Share Posted July 1, 2019 I did some research once, if i remember it was saying that PT cable is about .70 carbon; I found some in a scrap yard and made a knife out of some. It was a 7 strand cable, and it was harder to forge weld it together than the crane cable with many smaller strands, so i didn't mess with any more of it. It can be done though. Quote Link to comment Share on other sites More sharing options...
Frosty Posted July 2, 2019 Share Posted July 2, 2019 There are tricks for forge welding cable, it's not like regular pattern welded billets. The main problems are getting it clean between strands and keeping the strands together when setting the weld. I've only played with cable a couple times over the years without much luck. My best results were welding in a swage but a swage sucks heat quickly. The most popular trick I know of is twisting it tighter at welding heat. You need to weld the ends so it can't fray and gives you a solid place to hold. Then you bring it to welding temp and twist it tighter, lather rinse repeat. That's what I know about welding cable but 70 point cable sounds attractive for knife stock. Bear in mine I'm not a bladesmith, so . . . Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 2, 2019 Share Posted July 2, 2019 On 6/28/2019 at 10:05 PM, TheBlueSwell said: Post tension cable is the cable they put inside concrete slabs to increase the strength of the slab. Post-tension cable is stretched after the concrete hardens. My experience is they stretch the cable before pouring, then after the concrete sets up, it is then released, putting compression on the pour, even tho part of your detail says compression here : "Concrete is very weak in tension but extremely strong in compression. Post-tensioning acts on the concrete structure or elements by compressing the cast-in-place concrete to high pressures. Some advantages of post-tensioned concrete include crack control and lower construction costs. which is where the term post tension comes from, and agrees with my statement but which is the complete opposite of what you described at first, so now I am confused Quote Link to comment Share on other sites More sharing options...
SLAG Posted July 2, 2019 Share Posted July 2, 2019 Mr. Sells, and Mr. T.B.S., Are describing two different methods of stressing concrete to increase compressive and tensile strength of concrete members. (columns, etc., )The two methods are pre stressing and post stressing. Mr Sells, is describing pre stressing and Mr. T.B.S. is discussing post tensioning. (after the concrete has set) The varieties of these methods is extensive and complicated. For example, post tensioning can have internal wires or external ones, etc. etc. Wikki has an excellent article concerning these two technologies, and their innumerable variations Check out "prestressed concrete", there. Great topic Chaps, SLAG. p.s. post tensioning wires can either be installed outside the cured/set concrete, or threaded through conduit pipes cast into the concrete while it set. Quote Link to comment Share on other sites More sharing options...
TheBlueSwell Posted July 4, 2019 Author Share Posted July 4, 2019 Thanks for the info fellas! I did get the cable but I'm going to let it sit for quite a while before attempting anything. I need to develop my skills first. I'll make a run at it when I'm ready and then post about the results. Quote Link to comment Share on other sites More sharing options...
D.Rotblatt Posted July 8, 2019 Share Posted July 8, 2019 A couple tips about forge welding cable in addition to what Frosty said. Use the step on the anvil rather then the face so there is pressure on three sides and turn it in the direction that it is twisted as you forge weld it so it tightens the twist. I also mig weld the ends so it stays tight. DanR Quote Link to comment Share on other sites More sharing options...
lazyassforge Posted July 8, 2019 Share Posted July 8, 2019 Several years ago before I had heard of post-tensioning cable a gentleman brought several pieces to a blacksmith club meeting and was showing it to me. First of all, it was very clean and stiff for such a small cable. Maybe 1/2” or 5/8” diameter. He asked if it would weld so I took a piece and forged out a little knife. It was not finished well but I had kept it in my drawer in my desk at work. I used it to cut a lot of stuff and the edge held up well. I keep it by the chair now and use it occasionally now. Hope this helps B Davis Quote Link to comment Share on other sites More sharing options...
Steve Shimanek Posted July 8, 2019 Share Posted July 8, 2019 This is the knife i forged from the PT cable the one time I tried it. Quote Link to comment Share on other sites More sharing options...
lazyassforge Posted July 8, 2019 Share Posted July 8, 2019 Steve, pretty cool! I like it. B D Quote Link to comment Share on other sites More sharing options...
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