This was mentioned in another thread in GQ but I can’t for the life of me find it!
This is a type of steel that is very strong thus can be made much thinner that typical plate steel for the same strenght. It is used among other things for the casings of bombs and artillery shells, armor plating, etc.
The strength doesn’t come just from the alloy but the forging method too.
It has its own specific name and wikipedia entry, but for some reason I cannot find it.
You are going to have to be more specific. There are literally thousands of formulations and processing methods for high strength steel. For instance, the steel that was used in the STS “Shuttle” Solid Rocket Motors (as well as other motor and large pressure vessel applications) was a D6AC steel that was spin forged (i.e. spun up at very high speed and forced against a form). There are other steels with high toughness and impact resistance used for armor, others for thin-wall marine applications, et cetera.
Virtually any steel is going to be stronger than ATSM A-36 standard structural plate. That stuff is like Bubble Yum.
Stranger
In terms of ye olde armor plate, “Krupp Cemented” was a forging process to give armor plate more resistance to penetration. (I think that was the goal…)
There were other types of processes/alloys as well. Each major shipbuilding country developed it’s own unique ways of doing things.
The evolution of naval gunnery and armor metallurgy is a fascinating borometer of the industrial revolution as a whole.
All I remember was that it had a specific name (not a code number) that refered to the hardening process.
Maraging steels were the first thing I thought of when reading the OP.
The comment on bomb casings led me to wonder just what type of steel made up your garden variety GP bomb. This pre-solicitation notice from the USAF Materiel Command seems to suggest that the AF would like to make some improved Mk-84s out of ES-1b, a type of “Eglin steel.”
I believe I found it:
EDIT: Just got Ninja’d 
I think Rearden steel primarily contains bombastic diatribes.
Maraging steel
I’ll bet even ATSM A-36 would poke holes in Remington Steele.
there was a company in Indy that CNC machined bomb & mortar & missile shells & bodies. It was called ERI (Engineering Research INc?) then later in Florida as Southern Research. It was also a division of Babcock & Wilcox in Indy at one time.
They CNC machined a 3D interlacing helix (helical interpolation) on the insides of the exploding housing, which left a series of squares, that would break off and scatter upon detonation.
I asked why, and they told me the primary objective is not to kill the enemy, but very seriously wound them. The idea being, it costs your enemy more to care for a bunch of wounded folks, then it does to carry off their dead carcasses.
I beleive that a heat seeking missile also works like this - it doesn’t always collide with the jet, but rather it detonates near it, and sends chuncks of metal into the jet.
Yes, Remington Steele is easily Pierced.
But Danielle Steele hurts a lot more.
Jeremy Irons is not afraid.
RHA (Rolled Homogenous Armor) I believe is the term you’re looking for.
It’s ASTM A-36, we have to specify ASME SA-36. It’s only in the last few years that ASME allowed it to be used as a head/shell of a pressure vessel, we generally use it as attachments or as very low pressure shells. We try to NOT make bombs.