southeaster Posted September 28, 2009 Share Posted September 28, 2009 Hello, I have a problem I hope you experts can help me with. I have had 250mm diameter disks cut from 6mm mild steel plate. Some of them are warped, and I have heard that heating the plate can 'destress' it and cause it to pull flat. Is that true? And if so, to what temperature does it need to get to? Could I do it by heating over a gas ring? Quote Link to comment Share on other sites More sharing options...
thecelticforge Posted September 28, 2009 Share Posted September 28, 2009 You may get lucky with dry ice, but I would go with heat, and then lay in a bed of sand and instantly cover it with sand. It should take about 25 minutes to be able to handle it at the most. Make sure that the entire plate is heated evenly to at least a medium red temp. I don't know if it will work, but if I were going to do it, that is what I would try. Quote Link to comment Share on other sites More sharing options...
arftist Posted September 29, 2009 Share Posted September 29, 2009 I don't think heat alone is going to straighten the plates and certainly not the heat of a gas ring. Getting them hot and then pounding them flat would work though. Quote Link to comment Share on other sites More sharing options...
Dragons lair Posted September 29, 2009 Share Posted September 29, 2009 arftist, What do you think caused them to warp in the first place. Heat them on the other side with a rosebud let them cool. Learned from my old forman. I had welded 8 1X1 tubes vertical on a 10 ft 1X1 tube. Ended up with a 6 in warp. Old Matato said I show you how. Flipped it upsidedown, heated 8 places. Warp grew to 9+ inches. Said go eat lunch. Came back to a dead streight tube. The more we fab the more we learn. Ken Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted September 29, 2009 Share Posted September 29, 2009 Depend on where the warp came from. If the plate was warped before they burned them out, it's gonna be tough. Otherwise it's from the shrinkage right at the edge from burning. Usually it's pretty easy to hammer around the edge. Not straight on the edge, just lay the edge flat on the and hammer your way all the way around. Don't get too aggressive, you can go around more than once. It should relax as you pound the edge. Done it many times. Dragons Lair: Yeah same thing. In your case it was the weld the shrunk the part. In this case it's the edge that has shrunk. Quote Link to comment Share on other sites More sharing options...
arftist Posted September 29, 2009 Share Posted September 29, 2009 arftist, What do you think caused them to warp in the first place. Heat them on the other side with a rosebud let them cool. Learned from my old forman. I had welded 8 1X1 tubes vertical on a 10 ft 1X1 tube. Ended up with a 6 in warp. Old Matato said I show you how. Flipped it upsidedown, heated 8 places. Warp grew to 9+ inches. Said go eat lunch. Came back to a dead streight tube. The more we fab the more we learn. Ken Thats fine for you you Ken, with forty plus years of experience. The OP wanted to know if he could use a gas ring for heat. Do you think he would know how to shrink bent plates with heat? Quote Link to comment Share on other sites More sharing options...
Dragons lair Posted September 29, 2009 Share Posted September 29, 2009 I never said he could with a gas ring. I only stated what i would could do with a torch. And what i was taught. Grant, I had assumed the plates were flat befor cut. I don't bother cutting warped plate even with digital hight control. The only way anyone will learn is to try. Ken Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted September 29, 2009 Share Posted September 29, 2009 I straightened out a bent conveyor side plate with heat. It was approx. 12" x 3/16" stainless, and had about a 4" side bend in it. It had fallen off of the trailer as it was being loaded. Ran the rosebud up and down the bend to get it hot, then slapped a wet rag on the side I wanted it to bend towards. That shrank that side of the plate drawing it back straight. It took several applications of heat, and wet rag to get it drawn back into shape, but went very easy. This is a method used in autobody shops to repair dented sections. It doesn't have to be red hot, sometimes just as you see the color changes happening is good enough. Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted September 29, 2009 Share Posted September 29, 2009 (edited) Dragons Lair: I was just trying not to "assume" anything. What did I say that bothers you? Edited September 29, 2009 by nakedanvil Quote Link to comment Share on other sites More sharing options...
southeaster Posted September 29, 2009 Author Share Posted September 29, 2009 Thank you for sharing your expertise! The plates were laser cut, from rolled mild steel plate. So I guess the warping came from edge shrinkage. I don't have a rosebud head, so perhaps I could use my high flow LPG torch? And could the gas ring be used before hand to get the temperature up a bit? I am nervous to hammer the disk - it is a rotor which needs to be flat and spin true, and I would be worried hammering would distort the surface. The sand bath sounds simple - medium red heat, and leave it to be. I think I will try that first. The wet rag also sounds good, but seems like it requires much more skill and judgement. I will try that next if the sand bath doesn't help. Thanks again to all of you. Quote Link to comment Share on other sites More sharing options...
jimmy seale Posted September 29, 2009 Share Posted September 29, 2009 maybe heat then use a 2x4 to hammer on?,good luck,jimmy Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted September 29, 2009 Share Posted September 29, 2009 One way around this is to have them cut out 2 - 3 mm big and machine or grind off (without over heating) the heat affected zone. Quote Link to comment Share on other sites More sharing options...
southeaster Posted October 4, 2009 Author Share Posted October 4, 2009 Report back: I left them on a three ring gas ring for about 20mins. It got very hot - but not glowing at all. Then into a sand bath, and about an hour later removed it - no change. Next I tried a high flow blowtorch (LPG), but after 15min or so I could see I was not going to get it to glow. Into the sand anyway, and no change after it had cooled. So a friend who has access to a press has taken the plates and will try and bend them straight(er). I will report back once that is done... Quote Link to comment Share on other sites More sharing options...
David Einhorn Posted October 4, 2009 Share Posted October 4, 2009 If you are going to do a lot of them, and precision is required, then you might wish to consider having them laser cut. Nick, one of the professional smiths near here does mass production items for mail-order catalogs and told us that he has shifted over to having just about everything laser cut for him. Quote Link to comment Share on other sites More sharing options...
Dragons lair Posted October 5, 2009 Share Posted October 5, 2009 Even though I have O/A setups and a CNC plasma table if it needs to be right or tight it goes to the laser shop. Ken Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted October 5, 2009 Share Posted October 5, 2009 How true do these rotors have to run when they are spinning, and what is the application? Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted October 5, 2009 Share Posted October 5, 2009 Doubt pressing will do, the edge is still shrunk. Quote Link to comment Share on other sites More sharing options...
arftist Posted October 5, 2009 Share Posted October 5, 2009 I think I would be looking at waterjet cutting for this project. Quote Link to comment Share on other sites More sharing options...
primtechsmith Posted October 7, 2009 Share Posted October 7, 2009 Waterjets will also create some warping. I ran two jets for a while cutting a lot of materials from aluminum to brass, bronze, copper, mild steel, and stainless. The mild steel and stainless both would want to buck up off the table while cutting. 60,000psi of water and abrasive causes some heat to occur while cutting. I used to run the 2nd shift and would cut out the lights on the floor to save some energy on big jobs and you can see a glow following the cut....pretty cool to see happen... Also waterjets do couse somewhat of a bevel when cutting a radius unless the operator puts in some compensations for it....it is not much but could affect the outcome depending on your tolerences. I think about all cuts do that no matter what...not sure though. Can only speak for what I have seen first hand. Just my .02......loved the waterjet. One of the cooler jobs I have ever had. Peyton Quote Link to comment Share on other sites More sharing options...
southeaster Posted October 7, 2009 Author Share Posted October 7, 2009 Thanks for all the comments. These disks are laser cut. I used to use waterjet cutting but the prices seem to go up and up so I switched to a laser cutting place that worked out MUCH cheaper. Very interesting to hear about the heat from waterjet cutting! Did that mean it made clouds of steam? The application is for wind turbines - see my site Wind power generator and alternative energy - small scale homemade turbines. I would be happy with 0.5mm tolerance. Better than that would be good! Less than 0.1mm is irrelevant. Quote Link to comment Share on other sites More sharing options...
superflux Posted November 23, 2009 Share Posted November 23, 2009 Unless a steel item is cold cut with a water cooled band saw (and even then to an often imperceptible degree) there WILL be edge shrinkage. Here's what happens...The heat will expand the steel, but when cooled back to ambient, it becomes smaller than it's original size. Since the edges (cut line) get hotter than the center, there will be more shrinkage at the perimeter and the buckling will be seen as "belled" or dome shaped. When am fabricating Oxy-ace cut plate, my trick is to cut it slightly (1/8" or 3mm) oversized. Then using a hammer (flat faced for large, thin parts and ball peen for small or thick items) pound the edges. By doing this, you are "stretching the edges" and relieving the strsses and therefore letting the hot/cut area to get back to it's original size. Since you cut (per my suggestion) the part oversized, and after smithing the edges will also expand its dimensions, it will need to be ground back to proper size. As with all metal working, there is no hard fast rule as to how much to beat on the edges since the variables are not controlled, ie. torch tip size, speed of travel (inconsistent speed too), thickness variations etc, etc, etc you get my point? Experience will have to be everyones' teacher. Of course, you can over work the edges and the result will be the same. On thicker material ... 10mm (3/8") or thicker, place part on edge and use a ball peen and pound the edges. You will note that on the thin stuff, you are thinning out the edges and on the thicker material it will be "upset" and therefore thicker at the edges. This is why no matter which way you go, if final dimension is critical, you gotta cut it oversized. Just beat the edges...trust me, it is magic! A final note, if you try (getting clever and smartter than the iron!) and heat the entire part, the warp will be completely unmanageable! As you found out with the gas ring exercise. Quote Link to comment Share on other sites More sharing options...
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