Steel ingot

Steel ingots are quest items in the Fallout 3 add-on, The Pitt.

Characteristics
These bricks of steel would probably be melted down and used to make parts for armor, weapons, and gadgetry. Being made of pure steel, fresh components to manufacture mint products would be something of a rarity in the Capital Wasteland. Finding all 100 gives you the Mill Worker achievement/trophy. Give them to Everett for special gear.

Locations
If you make one run, and follow the guide below, starting with the Steelyard, the (X/Y) will be used. X shows the number of ingots at that spot and Y shows the number of ingots total one should have in their inventory after picking up the ingots at that spot. If you are not able to pick an Average lock (Lockpick of 50) then you will be unable to get all 100.

Steelyard (79)

 * 1) (2/2) The first two ingots are next to the dead slave as soon as you enter the steelyard.
 * 2) (2/4) You will find two in the first large dumpster to the left by the trailer with the couch on top of it. There are three large dumpsters. You can access this dumpster by jumping over from the roof of the truck. It's also possible to move along the ledge outside the fence to the left of the truck, around the corner and then jump across.
 * 3) (2/6) There are two ingots in the second large dumpster to the left. You can access this dumpster by jumping over from the roof of the nearby building to the far dumpster or by jumping from the roof of the building onto the ledge with the fencing, walking across and dropping onto the dumpster. It's also possible to jump from the first large dumpster (standing on its northern most part).
 * 4) (3/9) There are three in the smaller dumpster next to the third large dumpster on the left (west), there's a dead slave in there as well.
 * 5) (2/11) Head up the stairs by the dumpsters. After you hop the broken fence, go right, then turn left. There are two of them in between the two knocked over barrels.
 * 6) (2/13) Go north along the ledge, outside the fence. Looking down you should see two on top of a freight car (brownish-yellow in color) in the middle. Carefully jump onto the third steel beam from the end (this is the one you need to climb on to get to the ones in #7 below) and walk out till you get to the freight car with the two ingots on it. Drop down and they're yours.
 * 7) (3/16) Continue on top of the train cars to the east and jump from the wooden board down into the dumpster for three more.
 * 8) (2/18) Head back up the stairs from earlier, near the dumpsters. Instead of going right, go left. There is a small building with a small flight of stairs to your right. There are two ingots sitting on a shelf, as well as two first aid boxes. If you pass through the open gate, you went too far.
 * 9) (2/20) After you get the two in the small building head through the gate and go straight until you see a large dumpster. Climb up the stairs on top of the building on your left. Take a run off the end of the roof and drop down into the dumpster. There are two in there. If you get between the generator and the concrete blocks you can get stuck, so the old adage to "save early, save often" definitely applies in this quest. (You can also just fast travel to Downtown if you get stuck, so as to not lose any data, but only if you have killed all of the nearby trogs. Alternatively, you can equip the auto axe and experiment with moving around while slicing against the objects in order to dislodge yourself.)
 * 10) (2/22) Now jump from the dumpster over the barbwire fence to the south. Head right until you reach a dead end. There is a dead slave and two ingots. It may be easier to jump onto the fence to the west first before jumping south.
 * 11) (2/24) Jump on top of the generator just behind you to find a plank and climb back over the fence and head back up the stairs you used to get into the dumpster until you reach the roof. Facing north you'll see another set of stairs that head downward and a pile of gore with a trog eating it at the bottom. Walk down and pick up the two ingots from the ground next to the first aid box and the gore. There may be two or three more trogs down there so be ready.
 * 12) (3/27) Follow the path east and then take a right until you get to a gate. Open the gate and go out to the left. Go down the hill to the end where there is a ditch and a dead slaver. There are three laying next to him. Make sure to bring some Rad-X and grab the gamma shield armor off the dead slaver.
 * 13) (3/30) Turn to your left and continue into the radiated barrels. There are three more ingots in the middle. (Be careful not to miss one!) Note that you can kill the one or two trogs who hang out in this area from the other side of the fence. This is recommended because this is not a good area to get into a firefight in if you're not prepared for the radiation.
 * 14) (2/32) Go to the end of the barrel path and turn left. Go up the stairs and jump across to the building. Turn right (westward). Go to the end of that building's roof and you will see a makeshift bridge (metal structure with some wooden planks on it) crossing over to other buildings. There are two ingots in the middle of the bridge. If you are having trouble making the jump, you can reach this roof by going back up the stairs you came down in #11.
 * 15) (2/34) Continue across to the other side. Stay on the roof of the building and head to its western end. Pass a dead Pitt slave on your left (at the top of some stairs), and around the corner (turn right) there are two more ingots sitting on a lower roof (you would be facing northwest).
 * 16) (2/36) After you get the two ingots on the roof, drop all the way down to the ground. There are two ingots on a shelf (under the roof from where you just jumped down).
 * 17) (2/38) Head south toward the open gates, look left for some stairs with tires. Behind the stairs, you will find two more ingots behind the tires.
 * 18) (2/40) Head south (through the gates) until you can’t go any more and climb the set of stairs to the right (west). There are two ingots on the first landing next to a dead slave named Wild Bill. Be warned, it seems that you can go through the wall and fall through. You can get back if this happens, but it is very difficult to get to the right spot to do so. Although you can wander around then and look up to see all the skeletons inside the giant reactor tower while out there.
 * 19) (2/42) After you find Wild Bill continue up the stairs where there will be a makeshift shack with three wildmen inside. Kill them and take the two ingots by the fridge on the floor.
 * 20) (2/44) Facing east from the wildman shack, follow the metal catwalk as it crosses over a big pipe and turns left. You should see a few trogs waiting to ambush you on the perpendicular pipe. Continue on the catwalk until it crosses under the same pipe the trogs were on, then jump onto the pipe which runs parallel to the catwalk. As the pipe turns right, you will see a trog brute waiting at the end. Dispatch him and there will be two ingots in the pile of guts he was feeding on.
 * 21) (4/48) Turn around and get back onto the catwalk where the pipe bends. At the wooden planks, drop down to the building below and head for the western edge of the roof. Drop down to the ground and head north around the corner of the building, then turn left down the first narrow alley. You should see an upright mining cart containing four ingots, a med kit and an ammunition box. Watch out as there will be some trogs and maybe wildmen, if they haven't killed each other off yet.
 * 22) (2/50) Now a short way north to a wall. Follow it eastwards. You'll end up following a fence. Follow it around the corner to the right; behind some barrels at the dead end is a dead slave, a combat shotgun and shells, and two ingots.
 * 23)  If you've installed Point Lookout expansion, you may fall through the roof during this next quest, killing you instantly. If it happens, refer to the discussion page here for possible solutions. This can be avoided by saving your game just before the roof section where you fall and go to your dashboard. Reload the game and reload the save and you can walk past (This may not fix the glitch. If it doesn't, an easy way to solve this is to remove Point Lookout from your hard drive and reload your save - also found that by 'firing' or using an auto axe or similar unique weapon, The Mauler or Man Opener, while walking along the rooftop, it will fix the glitch). This glitch can be avoided by walking around in either direction along the narrow rim that just out from the edge of the large silo to your left as you reach the top of the stairs. The ground around the four silos isn't insta-kill territory so if you jump from the rim to the broken fence, or just go around on the roof the back way, you should have no problem.
 * 24) (4/54) Go back around to the south as far as you can go, then all the way back up the stairs past the wildman shack (with the bunk beds and refrigerator), along the catwalk to where you dropped down from. This time don't drop down, keep going up the stairs, then west and up more stairs up onto the factory building. Turn left at the top of the stairs and take the first right. There are four of them in the northwest corner behind a dome next to two first aid boxes. There are also two or three trogs in this area.
 * 25) (12/66) Now go back out to the edge of the roof and climb the stairs to the very top of the structure — you'll hit the mother lode of twleve ingots on the end of the catwalk. Be prepared for a tough fight with four to five wildmen above and trogs coming from below.
 * 26) (7/73) On your way back down (on the level above the turret) you'll see a really long bridge/conveyor-belt extending in the distance to the east. Drop down on there and follow it to the end for seven more ingots.
 * 27) (4/77) Jump down and head back to the roof top with the domes on it (it's the large flat roof at the bottom of all those steps you climbed to get the twelve ingots and the same roof where you get the ingots from #23, just go back up the conveyor belt bridge). Go south until you reach a chain-link fence (behind it are some big pipes). Looking down at the leftmost end of the fence you'll see a roof with three small domes (along the southern edge of the level). You'll have to get down there. Carefully slip around the chain link fence, and then push yourself against the large pipe running down the wall - that breaks your fall into smaller jumps so you'll reach the bottom unharmed. Next, drop down to the platform with the three big silos to the east. Head all the way east and turn right at the fence. (Check to the right after the first silo - there are two ammunition boxes (one locked-average) and a first aid box behind some pipes.) There will be a dead slave with an auto axe and four ingots next to him. Some trogs will attack you after you've picked up the ingots, so be prepared. Again, leaving a trail of mines along the metal walkway next to the silos can kill the trogs before they ever reach you.
 * 28)  When crossing the factory roof - there is a common glitch (on 360 at least) where the roof is not solid, leading the player to fall to their death. A sure fire way to rid of this glitch is to remove the Point Lookout DLC temporarily.
 * 29)  Alternatively, you may try to go from down up, but it requires some tricky jumping. First, go behind the chain-link fence behind which you found a dead slave and two ingots. Jump up the pipes as to go to the main area but instead of going there turn around and jump to the big pipe parallel to the catwalk with the three silos. Now, you normally aren't able to jump into the catwalk so you need some help. Take out some junk and carefully put it on top of the pipe to make a little pile, then jump on it and you should be able to jump over. This requires some skill, as you have no control of where the stuff falls out of your inventory and they tend to fall down. The flamethrower found in the Supply Plant makes it much easier, since it's large but portable, and can do the job by itself.
 * 30)  This can be avoided by saving your game just before walking along said roof section, exiting to the Dashboard and then reloading the save. Save the game again before walking over the roof and the problem should be gone.
 * 31)  Another way of doing it is to start facing east from the wildmen shack and jump onto the stair rail. From there jump to the pipe that meets at a junction. This may require a few tries as it is rather tricky. From there go to the pipe junction and jump onto the section with the three silos.
 * 32) (2/79) Head back down to where all the freight cars are. Walk to the northeast to the collapsed tunnel and you'll find 2 ingots as well as a dead slave. More trogs will come attack you after you pick up the ingots.

Supply plant (18)

 * 1) (3/82) Enter the supply plant and head down the hallway.  In the second room you will come across three ingots, a few paces before you reach the second terminal. When entering this room you will come across several trogs and two Wildmen fleeing from the pursuing trogs.
 * 2) (8/90) Continue on to the lower level of the factory, be careful jumping to ground level that you do not set off a powerful tripwire trap. Follow the tracks all the way to the end, take the hallway to the right (after the shelves containing various meds) and follow the track around the bend. You'll come across either a couple of wildmen and/or a couple of trogs. There are eight ingots in an overturned mine cart. A dead wildman may lay on top of the ingots, hindering your retrieval of them; this can be resolved either by moving the corpse by attacking it with the auto axe, or by just picking it up via the pickup button (clicking the right stick [aka R3] on consoles) and moving it out of the way.
 * 3) (6/96) Now head back to the shelves with the first aid box, and then down the hallway to the left (when facing the shelves). You will come across a door on your right with the skeletons of Tom and two other former factory workers, with bobby pins laying everywhere. Pick the lock (average skill needed) on the door to find six ingots. (Breaking the lock without the Infiltrator perk will make it impossible to get these ingots) If only four ingots are found in Tom McMullin's room of death, the next two can be found by backtracking to the Automated Maintenance terminal and proceeding down the hall through the northernmost doorway. There are several trogs or wildmen, again, if they have not already killed each other. The two ingots can be found in an overturned mine cart.
 * 4) (1/97) Continue up the stairs until you reach a room with a bed and a pitching machine. The Man Opener (a unique version of the auto axe) can be found on the bed, and to the right of that is an ingot on the dresser.

Abandoned area (3)

 * 1) (3/100) Return through the abandoned area which links the Steelyard and The Mill. As you reached the end of the caged catwalk you will see the trog you saw climbing above you earlier. After disposing of it, head through the hole it made in the fence (to the right of the door). To the left there is a pair of mine carts. The upright cart has the last three ingots in it. Note: The first time you enter, these ingots will be inaccessible. Returning to the area from the steelyard after you collect at least ten ingots will reveal a trog which has torn a hole in the fence, allowing you access to the mine cart.