Floyd,
Most important is that you want to make sure that they don't freeze and to the opposite extreme make sure that you don't overheat them in the summer in that steel box. I know some people including myself store them in ammo cans,to transport them I use my flight box which is cloth or a small cooler which protects them mostly from the summer heat but also the cold winter days that I decide to fly on.
William

Floyd; 
When I first started with electric , I was always nervous about the fear of fire , and stored them in a metal box or a fire safe ,These small safes , such as you store documents in ,are really cheap at places like office supply stores or Lowes. Then as I got rather casual about the dangers and justified my lax attitude by thinking about all the hobby shops that have rows of storage charge batteries just sitting open on the shelves. 
The real danger comes if the batteries are impacted , or during charging operations. You could at least transport them in a fire safe , I suppose. A real crash often ( or usually )  causes a fire , but then you don't crash do you?
Keith

My experience with lipo fires is that while they may burn at a high temperature, the duration is low, maybe 10 seconds of fury before it goes weak.

I dare say it'd be like hitting the steel box with a blow torch for about 10 seconds, it may blister the paint, and get too hot to touch but it's unlikely to go any further than that.


Don't quote me on this though!

I saw a video of a test where they took a Lipo, stabbed with a screwdriver and put it into a flimsy metal cash box and closed the lid. Mind you they did this very quickly!

The metal case contained the fireball and thy flimsy latch and metal box contained the fire. The toxic smoke came out however.

Probably the best box is the fire proof safe that can lock.

I use a foam lined metal case that has two latches.

Fred Cronenwett

And what would happen if you stored 4, 5 or 6, lipo packs  ie  your flying batteries in one metal case?? I doubt it would be just a 10 sec deal, films I saw was much much more intense , as when one cell goes it makes enough heat to light off the other cells in the pack, and then the pack is easily hot enough to light off the other lipo packs.
I still maintain that a ceramic safe would be much safer

Randy

This is the storage advice that I found on a RC helicopter web site, they also have the videos I was talking about

http://www.rchelisite.com/lipo_battery_charging_and_safety_guide.php

LiPo Battery Handling & Storage Keep LiPo battery packs WELL out of reach of children.

Do not put battery packs in pockets or bags where they can short circuit.

Do not store or transport or store batteries where they can come into contact with sharp or metallic objects.

Do not store your LiPo pack in extreme temperatures below 0C or above 50C.

Always store your LiPo pack in a safe and non flammable container away from flammable objects. A LiPo Sack or metal / ceramic storage container is best.

Always store your LiPo’s partially charged. They will maintain their performance levels over time and there’s no need to cycle them unless stored for periods longer than 3-6 months.

--- Notice they say a metal or ceramic container can be used

Fred Cronenwett

 "Do not store or transport or store batteries where they can come into contact with sharp or metallic objects. "


Hi Fred

NOT that they would be the experts , but they did say keep away from metal objects, I think a steel ammo box would qualify ?? 
If I used a steel box to store my batteries , I think I would surround that box with brick, easy to do, and cheap and most important SAFER.

Regards

Randy

Some may think that storage in Fort Knox in a lead lined vault, surrounded by Kryptonite is barely adequate. Others may differ.