new 1/4" A36 plate - is it possible to flatten it at home?

I know, 1/4" hot rolled plate comes out of the mill as coils, and it gets straightened in the steelyard and sheared to length, and it's never or rarely truly straight. I'm wondering if there are any realistic options for straightening a 4x8' sheet of A36 plate in a home shop without a $40k plate roller. I have a track burner and I'm familiar with flame straightening but I don't think I can heat a thin stripe of red that doesn't go too far through the plate. To accomplish a bend, I need to bring the top 1/8" or so of plate to about 1300F without the bottom 1/8" getting above 1200F. I just don't think I can do that on plate this thin.

Driving a vehicle over it won't get it.

Ideas?

metalmagpie

A race time I once knew of (well, owned...) got a fairly heavy plate flat enough to be a work top, by progressively welding it down to a rather heavy frame. I think it involved all of the jacks, clamps, and so forth they had. I presume it would have sprung badly if cut away from the frame. (They showed me the end result, I didn't see it in person.)

Doing that with a 4x8 sheet would be quite a chore.

Is it consistent? Can you support each end and jump around on the middle?

which axis is it bent and how much?

A 4 foot wide shop press, for which you could easily apply 20-50 tons of force, spread out across 4 feet, spacing the force across 2 feet of plate, spreading the load across a foot.. (4 point bending) could correct the bend in the 4 foot wide axis.. would be relatively easy to fabricate. i'm not sure my estimate of 20 tons being enough is accurate, but i know you can relatively easily correct a bend in a 1" wide .25" thick bar, bending it across your knee. but you can't do so within perhaps 6 inches to a foot of the ends of the bar, depending on both your strength and the steel.

but if its unrolled in the 8 foot long axis, that's a lot harder to correct.

metalmagpie said:

Driving a vehicle over it won't get it.

Ideas?

metalmagpie

Click to expand...

But a "BEEG Truck" might.

Put it out front "On the street where you live"....

Seriously, I have the HF plate compactor (with the gas engine)
and that might work.

Especially if you do it on dirt, the plate compactor can overbend
the localized area into the dirt, which is what your striving for.

EDIT: I'll bet that if you do it on wet dirt (or "Mud") it will
produce different results than with dry dirt/gravel.

Well, how flat is flat? What overall do you need, what period of waviness can you afford, how bad is it currently, etc.?

And Strostkovy, we're going to need a real "Yo' mamma so fat" contest winner to get anywhere with jumping...

If it's wavy in the short direction, I think I'd set up a three bar press (two lower bars 1" x 6" x ~54" long, one identical top bar) with the low bars spaced ~6" apart, the upper bar centered, and some way to collapse the upper bar into the lower bars gap. Bars oriented in the stiff direction, of course.

Maybe some 3" square, 1/4" wall tube welded into a rectangle at each end, with the lower bars resting (welded) onto the bottom tube, the upper bar bolted to a bottle jack at the bottom, with the ram resting on a spare piece of 1" plate welded to the upper tube.

Get a buddy, the two of you pump the jacks until you create enough counter bend, move the plate, repeat. Tedious as a get out, but it should work.

Bar and tube sizing pulled from thin air, but I suspect they're in the ballpark for bending a 48" x 1/4" plate over a 6" gap. Narrower the gap, the higher force needed, and the welds have to be done right as you'll have a spring during use, and if a weld gives it won't be fun for anyone nearby. Use at your own risk...

Flame straightening would be unpredictable, indeed, it might pull way too much, or built in tensions in the stock may induce the stock to warp in the wrong direction.

Even press straightening is difficult to maneuver , because the normal sag of the sheet makes it difficult to know if you've accomplished sufficient bend.

I'd suggest peening, but of course this dents the sheet. But you might be able to nest your parts in such a way as to leave uncut strips, and you could peen in the waste areas. Use an air chisel with a blunt point.

Just how 'unstraight' is it. Like a banana, or a few 32's of an inch?

If it's just a few thou out, then you're not living in the real world. I never saw a straight piece of A36 in my life. Between the mill, and where you bought it, it's been handled so many times that if it was indeed straight at one time, it's likely got a minor warp in it now. Forklifts, the way the guy chained the bundle on the truck,, etc etc etc

This stuff is mainly for knuckle dragging, semi literate, mouth breathing guys like me. I clamp it, wedge it, heat it, and beat it into submission......weld it up, and stand back and admire it.

Far as strip heating goes. You always have some differential between the top and bottom of the plate. Just keep it to a dull red, don't go into orange.

If you're actually gonna weld this to something, or even bolt it...….. Start your attachment process in the middle of the plate (like a book), then work your way out. If it's lookin' like it's got too much stress, heat next to the welds to shrink it back a bit before doing the next weld sequence.

If this is going on some kind of frame...weld it up, then shrink the frame to pull the distortion out of it (my preferred way to do it). Heat is your friend.

Attach with the bendy side down, then pull it down as you work your way outward.

Put high spot up and a jack in the middle with chains to the edges. Should make it a lot better. Next time get grade 50 plate, it is usually way flatter than the a36. Or dont mess with it and return for grade 50?

Heat straightening, or heat shrinking more accurately, is not unreliable

Nice set of hinge thingies, welded with art and flair.

Uh oh..... Can you say Ba-Na-Na

Fixture it up so's it will only bend so far when heated. The shims prevent the steel from going farther the other way than you want. Starting in the middle, wedge shaped heating to shrink the stretched part of the member. The clamps do NOT cause the bend, they only restrain the area from expanding when heated. Work your way out from the middle Then stand back, scratch whatever it is you like to scratch, and admire it

It's been a while since I worked with a 4x8 sheet of anything (all 5x10 now) but it surprises me that bending this would be difficult

Rob F. said:

Put high spot up and a jack in the middle with chains to the edges. Should make it a lot better. Next time get grade 50 plate, it is usually way flatter than the a36. Or dont mess with it and return for grade 50?

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This is a good answer, thanks! I have a similar idea. I have used the central jack straightening method before:



That one was a nasty old piece of 1/2" plate but I got it flat enough to use.

How warped is the 4x8 plate? About 5/8" over the long axis. Not 'a few thou' by any means. Nor do I have any such expectation.

I'm going to email my account manager at the steelyard and see if I can wheedle him into letting me bring it back to get run through their plate straightener again, this time sharpening the pencil a little. Regardless, I'll post back here once I find the answer.

metalmagpie

metalmagpie said:

This is a good answer, thanks! I have a similar idea. I have used the central jack straightening method before:

That one was a nasty old piece of 1/2" plate but I got it flat enough to use.

How warped is the 4x8 plate? About 5/8" over the long axis. Not 'a few thou' by any means. Nor do I have any such expectation.

I'm going to email my account manager at the steelyard and see if I can wheedle him into letting me bring it back to get run through their plate straightener again, this time sharpening the pencil a little. Regardless, I'll post back here once I find the answer.

metalmagpie

Click to expand...

Yes, just like that but bigger.
Better to have them do it if possible.