# The Science Of Coating Steel

[Breaking Taps] has a look at “parkerization” — a process to coat steel to prevent rust. While you commonly see this finish in firearms, it is usable anywhere you need some protection for steel parts. The process is relatively easy. It does require heat and a special manganese solution made for the purpose. You scuff up the surface of the steel and degrease and wash it.

Once the part is ready, you insert the part in hot solution which is manganese and phosphoric acid. Rinse and displace the water and you are ready to oil the part.

But what we really liked was the electron micrographs of the steel before and after the process. The phosphates formed in the solution cover the iron and hold oil to prevent oxidization. However, the first attempt wasn’t uniform so it wouldn’t work as well. [Breaking Taps] thinks it was a failure to rough up the piece sufficiently before starting. He also raised the temperature of the bath and got a better, but not perfect, result.

We miss having an electron microscope at work and we really want one at home! The last fun coating project we remember used copper in a strange and wonderful way.

# Categorizing Steel

In the movie Conan the Barbarian, we hear a great deal about “the riddle of steel.” We are never told exactly what that riddle is, but in modern times, it might be: What’s the difference between 4150 and 1020 steel? If you’ve been around a machine shop, you’ve probably heard the AISI/SAE numbers, but if you didn’t know what they mean, [Jason Lonon] can help. The video below covers what the grade numbers mean in detail.

The four digits are actually two separate two-digit numbers. Sometimes, there will be five digits, in which case it is a two-digit number followed by a three-digit number. The first two digits tell you the actual type of steel. For example, 10 is ordinary steel, while 41 is chromium molybdenum steel. The last two or three digits indicate how much carbon is in the steel. If that number is, say, 40, then the steel contains approximately 0.40% carbon.

# Electrical Steel: The Material At The Heart Of The Grid

When thoughts turn to the modernization and decarbonization of our transportation infrastructure, one imagines it to be dominated by exotic materials. EV motors and wind turbine generators need magnets made with rare earth metals (which turn out to be not all that rare), batteries for cars and grid storage need lithium and cobalt, and of course an abundance of extremely pure silicon is needed to provide the computational power that makes everything work. Throw in healthy pinches of graphene, carbon fiber composites and ceramics, and minerals like molybdenum, and the recipe starts looking pretty exotic.

As necessary as they are, all these exotic materials are worthless without a foundation of more familiar materials, ones that humans have been extracting and exploiting for eons. Mine all the neodymium you want, but without materials like copper for motor and generator windings, your EV is going nowhere and wind turbines are just big lawn ornaments. But just as important is iron, specifically as the alloy steel, which not only forms the structural elements of nearly everything mechanical but also appears in the stators and rotors of motors and generators, as well as the cores of the giant transformers that the electrical grid is built from.

Not just any steel will do for electrical use, though; special formulations, collectively known as electrical steel, are needed to build these electromagnetic devices. Electrical steel is simple in concept but complex in detail, and has become absolutely vital to the functioning of modern society. So it pays to take a look at what electrical steel is and how it works, and why we’re going nowhere without it.

# A Guide For Heat-Treating Steel At Home

A lot of colloquial words that we might use when describing something’s durability take on extremely specific meanings when a materials scientist or blacksmith uses them. Things like “strength”, “toughness”, “hardness”, and “resilience” all have different meanings when working in a laboratory or industrial setting than most people might otherwise think.

For the beginner metalworker, this can be a little bit confusing at first but some hands-on practice will help. To that end, this beginner lesson in heat-treating steel from [Blondihacks] demonstrates why it can be beneficial to trade some of the metal’s toughness for improved hardness and just how to accomplish it on your own.

The first part of the lesson is to make sure the steel is high-carbon steel, since most other steels aren’t able to be heat treated. It will also have a specific method for its quenching, either in oil, water, or some other medium. But beyond that the only other thing required for this process is a torch of some sort. [Blondihacks] is using a MAP-Pro torch to get the steel up to temperature, which is recognizable when it turns a specific orange color. From there all that’s needed is to quench the hot metal in whatever fluid is called for. At this point the metal can also be tempered, which restores some of its toughness while maintaining a certain amount of hardness.

While the process doesn’t require specialized tools, [Blondihacks] does have a hardness tester, a fairly expensive piece of instrumentation that measures how deeply the metal can be indented by a force. By measuring the size of the indentation made by the tool, the hardness can be determined. As it’s many thousands of dollars this is mostly for demonstration and not necessary for most of us, but does go a long way to demonstrate the effectiveness of heat treating and tempering in an otherwise simple environment. If you’re looking for excuses to start heat treating and tempering metal, here’s a great project which creates a knife nearly from scratch.

# When Is Damascus Steel Not From Damascus?

If you grow up around a working blacksmith’s forge, there are a few subjects related to metalwork on which you’ll occasionally have a heated discussion. Probably the best known is the topic of wrought iron, a subject I’ve covered here in the past, and which comes from the name of a particular material being confused with a catch-all term of all blacksmith-made items. I’ve come to realise over recent years that there may be another term in general use which is a little jarring to metalwork pedants, so-called Damascus steel. Why the Syrian capital should pop up in this way is a fascinating story of medieval metalworking, which can easily consume many days of research.

## Damascus? Where’s That?

The Damascus steel you’ll see in YouTube videos, TV shows, and elsewhere is a steel with complex bands and striations on its surface. It’s often used in knife blades, and it will usually have been chemically treated to enhance the appearance of the patterns. It’s a laminate material made by pattern welding layers of different steels together, and it will usually have been worked and folded many times to produce a huge number of very thin layers of those steels. Sometimes it’s not made from sheets or ingots of steel but from manufactured steel products such as chains, in an attempt to produce a result with more unusual patterns. Continue reading “When Is Damascus Steel Not From Damascus?”

# No Need To Buy A Woodchipper – Build One!

Polish YouTuber WorkshopFromScratch finally got fed up with tripping over piles of garden detritus and decided to have a go at building a woodchipper (Video, embedded below). Since they had a ‘small’ 1.5kW gearmotor just lying idle (as you do) it was an obvious fit for a machine that needs torque rather than supersonic speed. The video is a fabulous 20-minute journey through the workshop showing just about every conceivable metalworking tool being used at some point.

One interesting point is the bottom roller, which sits between a pair of removable guides, which should help the thing self-feed without jamming. Whether that was necessary is not for us to judge, but it can’t hurt. The frame looks like it was constructed from at least 1/4″ thick steel, which is expensive if you don’t happen to have a supply to hand. There’s lots to see, everything from thin sheet metalworking, which was plasma cut, constructing the feed and exhaust guides, to box sections being skilfully welded at some interesting angles to make a cart to move the thing. They tell us the blades were constructed from some seriously thick slabs of C45 grade steel, but currently are not hardened. This is planned for the future, but we suspect not something that is easily achieved in the home workshop!

If this channel is familiar, then you might remember the earlier stump grinder they built. If you are drowning in sawdust, but have a log burner, then you’ll appreciate this sawdust briquette machine.

# Steel For Your Fighting Robot

The job of processing video after a large event must be a thankless one for whichever volunteer upon whose shoulders it falls, and thus it’s not unusual for talks at larger events to end up online much later than the event itself. Electromagnetic Field 2022 was last year, but they have continued to drop new videos. Among the latest batch is one from [Jennifer Herchenroeder], in which she discusses the steel used in her team’s BattleBot, Hijinx (Edit: her EMF talk was cut short due to time pressures, so she re-recorded it in full after the event and we’ve replaced the link. The EMF video meanwhile is here). The result is a fascinating introduction to the metallurgy of iron and steel, and is well worth a watch.

To fully understand the selection of armor steel it’s necessary to start from first principles with iron, to look at its various allotropes, and understand something of how those allotropes form and mix in the steel making and metalworking processes. We’re treated to a full description of the various tempering and hardening processes, before a panel-by-panel rundown of the various steels used by Hijinx.

For a Hackaday writer with a past in robot combat it’s fascinating to see how the design of robots has evolved over the decades since the British Robot Wars, and it’s particularly nice to see the current generation as part of our community. However, if you’ve tempted yourself, bear in mind that it’s not all plain sailing.