Someone's car hit our metal bar gate, so one of the rods is bent as shown in the photo. What kind of a tool can I use to bend this back, so it's straight? Thank you!
Some woodworking clamps are reversable and can act as spreaders, like this model. I have another style of the "quick grip" clamps that have a mechanical advantage on the grip mechanism and they are reversible. They can't apply a ton of force, but for that square tubing, you might not need as much as you think as long as the spreader can get a good grip.
The other thing that comes to mind is a common scissor style jack included with cars for emergency tire changes. You would need a padding material to not scratch the bars, but they can literally apply a ton of force to spread apart the bars.
Pounding on iron of that sort tends to do nothing but make you sweaty. It'll bounce a lot without bending, and chances are there's play in the panel as a whole. Heating it is not necessary and will cause surface damage.
I'd pull some ratcheting straps in a full loop around the bulge and all the way to the larger tubing at the other side of the panel (out of frame to the right). Place the ratchet mechanism on the side of the panel away from the bend so that it pulls the bend back into alignment.
Start cranking until you see things moving, and watch what happens to avoid unexpected bending. If needed, have someone push sideways to keep the bent bar in alignment or otherwise direct force.
You'll have to overbend slightly, so some trial and error is in order. Take it slow and keep an eye on all parts of the panel. If the bar on the opposite end starts to bend, back it up with lumber inside the strap.
I would probably start by trying to bend it back by pounding on it with a hammer, although you might want to clamp a piece of wood to it then hammer on the wood so that you don't mar the finish on the bar too much.
Another option would be to attach a come-a-long to the bar, the other end to something solid (a tree if you have one close by? tow hooks on a car perhaps if not?) and try to pull it back into shape that way. I would be a bit worried about bending the gate or breaking the hinges with that method though (depending on how strong those metal bars are)
Have you tried simply pulling/pushing on it by hand? The bars look like 1/2" (10mm) square. With a span of 36" or so, you may be able to simply take hold at the peak of the bend and push or pull it back into place. If that doesn't work, the jack, comealong, ratchet straps, etc. should do the job.