On Sun, 20 Oct 2013 15:08:58 -0400, Ned Simmons
wrote:

On Sun, 20 Oct 2013 13:26:02 -0500, Ignoramus8008
wrote:

On 2013-10-20, Ignoramus8008 wrote:
On 2013-10-20, wrote:
But you can also
just use heat and water. Heating along the bulged side and then
cooling will shrink the metal, eventually pulling it flat. You could
use a big oxy-acetylene torch or a weed burner torch. I would use a
weed burner, actually a few of them, to heat the full length of the
bend all at once.

Eric, thanks. I have a big "Belchfire" fuel/air torch. I may give it a
try.

OK, so, the way to do that would be:

1) Heat along the whole length with a belchfire torch, to perhaps 500
degrees F (measured with pyrometer)

2) Cool rapidly with garden hose spraying water on top

right?

i

You'll need to at least 900F in order to get any significant reduction
in the yield strength of the steel. Keep in mind that if you get this
to work, you'll end up with a plate with waves rather a single hump.
The plate will be flatter overall, but wavy nonetheless. Mechanical
bending will result in small waves as well.

http://www.fhwa.dot.gov/bridge/steel/02.cfm
Greetings Ned,
I have flame straightened some pretty thickstuff, though not 3/4
thick. I did not notice significant waviness. Thinking about it though
makes me think that some waviness would occur.
Eric