Low Background Steel — So Hot Right Now

The nuclear age changed steel, and for decades we had to pay the price for it. The first tests of the atomic bomb were a milestone in many ways, and have left a mark in history and in the surface of the Earth. The level of background radiation in the air increased, and this had an effect on the production of steel, so that steel produced since 1945 has had elevated levels of radioactivity. This can be a problem for sensitive instruments, so there was a demand for steel called low background steel, which was made before the trinity tests.

The Bessemer process pumps air through the iron to remove impurities. shropshirehistory.com

The production of steel is done with the Bessemer process, which takes the molten pig iron and blasts air through it. By pumping air through the steel, the oxygen reacts with impurities and oxidizes, and the impurities are drawn out either as gas or slag, which is then skimmed off. The problem is that the atmospheric air has radioactive impurities of its own, which are deposited into the steel, yielding a slightly radioactive material. Since the late 1960s steel production uses a slightly modified technique called the BOS, or Basic Oxygen Steelmaking, in which pure oxygen is pumped through the iron. This is better, but radioactive material can still slip through. In particular, we’re interested in cobalt, which dissolves very easily in steel, so it isn’t as affected by the Bessemer or BOS methods. Sometimes cobalt is intentionally added to steel, though not the radioactive isotope, and only for very specialized purposes.

Recycling is another reason that modern steel stays radioactive. We’ve been great about recycling steel, but the downside is that some of those impurities stick around.

Why Do We Need Low Background Steel?

Imagine you have a sensor that needs to be extremely sensitive to low levels of radiation. This could be Geiger counters, medical devices, or vehicles destined for space exploration. If they have a container that is slightly radioactive it creates an unacceptable noise floor. That’s where Low Background Steel comes in.

A person is placed into a low background steel container with sensitive equipment to measure the radioactivity of the body, which may be near the background level. Photo from orau.org

So where do you get steel, which is a man-made material, that was made before 1945? Primarily from the ocean, in sunken ships from WWII. They weren’t exposed to the atomic age air when they were made, and haven’t been recycled and mixed with newer radioactive steel. We literally cut the ships apart underwater, scrape off the barnacles, and reuse the steel.

Fortunately, this is a problem that’s going away on its own, so the headline is really only appropriate as a great reference to a popular movie. After 1975, testing moved underground, reducing, but not eliminating, the amount of radiation pumped into the air. Since various treaties ending the testing of nuclear weapons, and thanks to the short half-life of some of the radioactive isotopes, the background radiation in the air has been decreasing. Cobalt-60 has a half-life of 5.26 years, which means that steel is getting less and less radioactive on its own (Cobalt-60 from 1945 would now be at .008% of original levels). The newer BOS technique exposes the steel to fewer impurities from the air, too. Eventually the need for special low background steel will be just a memory.

Oddly enough, steel isn’t the only thing that we’ve dragged from the bottom of the ocean. Ancient Roman lead has also had a part in modern sensing.

Innovating A Better Printing Platform

Just because you have a fancy new 3D printer doesn’t mean that innovation should stop there. Almost everyone has had a print go foul if the first layer doesn’t properly adhere to the printing platform — to say nothing of difficulty in dislodging the piece once it’s finished. Facing mixed results with some established tricks meant to combat these issues, [D. Scott Williamson] — a regular at Chicago’s Workshop 88 makerspace — has documented his trials to find a better printer platform.3D Printer Steel Print Plate 1

For what he had (a printer without a heated plate), painter’s tape and hairspray wasn’t cutting it, especially when it came time to remove the print as the tape wouldn’t completely come off the part. How then, to kill two birds with one stone? Eureka! A flexible metal covering for the printing plate.

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For Your Binge-Watching Pleasure: The Clickspring Clock Is Finally Complete

It took as long to make as it takes to gestate a human, but the Clickspring open-frame mechanical clock is finally complete. And the results are spectacular.

If you have even a passing interest in machining, you owe it to yourself to watch the entire 23 episode playlist. The level of craftsmanship that [Chris] displays in every episode, both in terms of the clock build and the production values of his videos is truly something to behold. The clock started as CAD prints glued to brass plates as templates for the scroll saw work that roughed out the frames and gears. Bar stock was turned, parts were threaded and knurled, and gear teeth were cut. Every screw in the clock was custom made and heat-treated to a rich blue that contrasts beautifully with the mirror polish on the brass parts. Each episode has some little tidbit of precision machining that would make the episode worth watching even if you have no interest in clocks. For our money, the best moment comes in episode 10 when the bezel and chapter ring come together with a satisfying click.

We feature a lot of timekeeping projects here, but none can compare to the Clickspring clock. If you’re still not convinced, take a look at some of our earlier coverage, like when we first noticed [Chris]’ channel, or when he fabricated and blued the clock’s hands. We can’t wait for the next Clickspring project, and we know what we’re watching tonight.

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Home-Made Metal Brake

Sometimes, the appropriate application of force is the necessary action to solve a problem. Inelegant, perhaps, but bending a piece of metal with precision is difficult without a tool for it. That said, where a maker faces a problem, building a solution swiftly follows; and — if you lack a metal brake like YouTuber [makjosher] — building one of your own can be accomplished in short order.

Drawing from numerous online sources, [makjosher]’s brake is built from 1/8″ steel bar, as well as 1/8″ steel angle. The angle is secured to a 3/4″ wood mounting plate. Displaying tenacity in cutting all this metal with only a hacksaw, [makjosher] carved slots out of the steel to mount the hinges, which were originally flush with the wood. He belatedly realized that they needed to be flush with the bending surface. This resulted in some backtracking and re-cutting. [Makjosher] then screwed the pivoting parts to the wood mount. A Box tube serves as a handle. A coat of paint  finished the project, and adding another tool to this maker’s kit.

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A Tech That Didn’t Make It: Sound On Stainless Steel Wire

For a brief period in the 1940’s it might have been possible for a young enamored soul to hand his hopeful a romantic mix-spool of wire. This was right before the magnetic tape recorder and its derivatives came into full swing and dominated the industry thoroughly until the advent of the compact disk and under a hundred kilogram hard disk drives. [Techmoan] tells us all about it in this video.

The device works as one would expect, but it still sounds a little crazy. Take a ridiculously long spool of steel wire the size of a human hair(a 1 hour spool was 2.2km of wire), wind that through a recording head at high speed, magnetize the wire, and spool it onto a receiving spool.

If you’re really lucky the wire won’t dramatically break causing an irreversible tangle of wire. At that point you can reverse the process and hear the recorded sound. As [Techmoan] shows, the sound can best be described as… almost okay. Considering that its chief competition at the time was sound carved into expensive aluminum acetate plates, this wasn’t the worst.

The wire recorder lived on for a few more years in niche applications such as airplane black boxes. It finally died, but it does sound like a really fun couple-of-weekends project to try and build one. Make sure and take good pictures and send it in if any of you do.

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Impressive Custom Built Blacksmith’s Forge

[EssentialCraftsman] is relatively new to YouTube, but he’s already put out some impressive videos. We really enjoyed an episode dedicated to a fixture in his shop, his large custom blacksmith’s forge.

The forge is a custom cast vault of refractory that sits on a platter of fire bricks suspended on a heavy-duty rotating frame. Two forced air natural gas burner provide the heat.  The frame is plasma CNC cut steel welded together.

A lot of technical challenges had to be solved. How does one hold a couple hundred pound piece of refractory in such a way that it can be lifted, especially when any steel parts exposed to the heat of the forge would become plastic and fail? When the forge turns off, how do you keep the hot air in the forge from rising into the blowers and melting them? There were many more.

We were really impressed by the polished final appearance of the forge, and the cleverness of its design. Everything is well thought out, and you can even increase the height of the forge by propping it up on more fire bricks. We hope [EssentialCraftsman] will continue to produce such high quality videos. We also enjoyed his episode on Anvils as well as a weirdly informative tirade on which shape of stake (round or square) to use when laying out concrete jobs. Videos after the break.

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From Shop Floor Dust To Carbon Steel

[Chandler Dickinson] did his monthly sweep of the floor in his blacksmith’s shop when it occurred to him that all that metal dust had to go somewhere, didn’t it? So he did the only reasonable thing and made a crude foundry out of cinder blocks, melted his dirt in it, and examined what came out the other end.

His first step was to “pan” for steel. He rinsed all the dirt in a bucket of water and then ran a magnet at the bottom of the bucket. The material that stuck to the magnet, was ripe for reclaimation.

Next he spent a few hours charging a cinderblock foundry with coal and his iron dust. The cinderblocks cracked from the heat, but at the end he had a few very ugly brittle rocks that stuck to a magnet.

Of course there’s a solution to this non-homogenous steel. As every culture with crappy steel eventually discovered, you can get really good steel if you just fold it over and over again.  So he spend some time hammering one of his ugly rocks and folding it a bit. He didn’t get to two hundred folds, but it was enough to show that the resulting slag was indeed usable iron.

He did a deeper examination of the steel last week, going as far as to etch it, after discovering that the metal sparked completely differently when sanded on one side versus the other. It definitely needed work, but all seemed to have worked in the end.

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