Sharpening Part 7 – The Alchemy of Hard Steel 鋼の錬金術

An Alchemist and his assistants working late at night in his workshop.

Behold, I have created the smith that bloweth the coals in the fire, and that bringeth forth an instrument for his work.

Isaiah 54:16 KJV

The blades we are considering in this post are made from iron and steel, so it makes sense to examine these materials from the viewpoints of sharpness and sharpening. In the previous post we looked at some of the supernatural aspects of making and forging steel. In this post we will examine some alchemical aspects.

This post could be very technical, but I have simplified the description of chemical processes to make it easier for the non-technical Gentle Reader to follow. Please bear with me.

The Alchemy of Mutating Iron to Steel

At the heart of steel alchemy is the hardening process. When carbon is combined with iron in the right proportion, steel is formed. This mutation is easily accomplished nowadays, but for most of human history it was a fiendishly difficult, expensive process. No wonder those who could accomplish the deed were attributed with magical powers.

If steel is heated to within a specific range of temperatures (difficult to measure by eye) and then suddenly cooled, crystalline structures containing small, very hard and relatively brittle crystals called carbides form within a softer matrix of iron. These hard carbides are what do the serious job of cutting, not the softer matrix. At the extreme cutting edge, this structure might be compared to a modern circular saw blade comprised of a relatively soft body to which is attached very hard tungsten carbide cutting tips.

A steel blade dulls when these carbide crystals either shatter, or the pressure and friction of cutting wears away or cracks the softer supporting matrix, allowing the carbides to be torn from the matrix leaving behind gaps of soft, blunt metal. The larger the carbide clumps are and the further the distance between them, the more easily they are shattered and torn away, and the duller a blade becomes with each crystal’s failure.

In a low-quality blade, and given the same number of carbide crystals in a fixed volume of steel, the crystals will form into relatively large and isolated clumps separated by wide rivers and lakes of softer metal, as seen from the viewpoint of a carbide. The steel will crack along these weaker pathways when stressed, and when cutting, the softer material in these lakes and rivers will erode first, leaving the carbide clumps unsupported and vulnerable to failure.

In a high-quality steel blade, by comparison, and given the same number of carbide crystals in a fixed volume of steel, the crystalline clumps are comparatively smaller and distributed more evenly throughout the matrix making it more resistant to erosion, and the carbide crystals more resistant to damage. Such steel is called “fine grained,” and has been highly prized since ancient times for its relative toughness and ability to become very sharp and stay sharp for a long time. This is the steel preferred by woodworking professionals in Japan and is the only kind found in our tools. Without exception.

Impurities and Alloys

All iron ores naturally contain harmful impurities such as phosphorus, sulfur, silicon, and manganese to one degree or another. When these impurities exceed acceptable limits, they can weaken the steel, make it brittle, or make heat treatment results inconsistent. They are often expensive to remove.

There are three approaches commonly used to minimize the negative effects of these difficult-to-remove impurities. The first is simple avoidance of the problem by employing iron ore and scrap metal free of excess amounts of these contaminants. Such ore and scrap are available, but they are not found everywhere and are relatively expensive. For centuries, the purest iron ore has been mined in Sweden.

The second approach is to add purer iron or carefully sorted and tested scrap steel to the pot thereby reducing the percentages of the harmful contaminants. This is called “ solution by dilution.”

Nakaya Takijiro’s saw forge, originally made for forging swords

The third and more common fix is to add chemicals such as chrome, molybdenum, nickel, tungsten, vanadium and even lead to the pot forming steel “alloys.” In their simplest formulations, these chemicals help overcome the detrimental effects of natural impurities, specifically those related to brittleness and unpredictable heat treatment results. Some formulations make the steel less likely to warp and crack despite impurities. Others make the steel more resistant to abrasion and corrosion, or even easier to cast, drop-forge, or machine. 

Steel alloys have serious advantages over plain high-carbon steel in mass-production, reducing material costs by improving the performance of cheaper lower-grade iron ore and scrap metal, improving manufacture characteristics, and achieving higher productivity with fewer rejects even when worked by low-skill workers.

But these alloys are not all fuzzy blue bunnies and fairy farts because edged tools made from high-alloy steels typically have some disadvantages too: Due to their crystalline structure, they simply cannot be made as sharp as plain high-carbon steel, and are more difficult and time-consuming to sharpen by hand.

Of course, additives like chrome, nickel, moly and especially tungsten are costly.

Some manufacturers cite the higher costs of high-alloy steels to justify higher prices for their products. However, what they never say out-loud is that labor costs are much much less when using high-alloy steel because skilled workers are not necessary. And because high-alloy steels produce fewer rejects, quality control is easier, overall productivity is higher, warranty problems are fewer, and profitability is increased. Indeed, without high-alloy steels, factories would need to train and hire actual skilled workers and professionals instead of uneducated seasonal workers destroying the world’s current mass-production model. Egads! Walmart’s shelves would be bare!

My blacksmiths make only professional-grade tools for craftsmen that value ease of sharpening and cutting performance above corporate profits. They charge more for plain high-carbon steel blades than for high-alloy steel products because labor and reject costs are higher. So if a manufacturer brags about the excellence of the high-alloy steels they are using rest assured increased profits are their motivation, not improved cutting performance. Caveat emptor baby.

Blacksmith

Japanese Steels

The best plane and chisel blades are made from plain, high-purity, high-carbon steel. In Japan, the very best such steel is made by Hitachi Metals mostly using Swedish pig iron and carefully tested industrial scrap (vs used used rebar and car bumpers), and is designated Shirogami (White-label) No. 1. They also make a steel designated Shirogami No.2 containing less carbon. Another excellent steel for plane and chisel blades is designated Aogami (Blue-label) No.1 and No. 2.

Aogami, like Shirogami, is made from extremely pure iron, but a bit of chrome and molybdenum are added to make Aogami steel easier to heat treat with less warping. Aogami can be made very sharp, but it is not quite as easy or pleasant to sharpen as Shirogami. Some of the plain high-carbon Swedish steels are also excellent.

If worked expertly, either of these steels consistently produce the highest quality “fine-grained” steel blades.

Let’s compare the sharpening characteristics of these two steels. To begin with Shirogami steel is easy, indeed pleasant, to sharpen. It rides stones nicely and abrades quickly in a controlled manner.

Aogami steel, by comparison, is neither difficult nor unpleasant to sharpen, but it is different from Shirogami steel in subtle ways. It takes a few more strokes to sharpen, and feels “stickier” on the stones, but it will still produce fine-grain steel blades and performs perfectly.

Inexperienced people lacking advanced sharpening skills typically can’t tell the difference between blades made from Shirogami, Aogami or Swedish steel and steels of lesser quality. But due to the difficulty of forging and heat treating Shirogami or other plain high-carbon steels, a blacksmith that routinely uses them will simply be more skilled and have better QC procedures than those whose skills limit them to using only less-sensitive high-alloy steels.

Professional Japanese woodworkers insist on chisel blades made from Shirogami steel. Some prefer Aogami for plane blades believing the edge holds up a bit better. My plane blacksmith and carving chisel blacksmith prefer to use Aogami because it is easier to work and more productive (especially in the case of carving chisels), but for a little extra they are happy to forge blades from Shirogami or Swedish Steel.

I own and use Japanese planes made from Shirogami, Aogami, Aogami Super, Swedish steel, and a steel called “Inukubi” meaning “dog neck” which was imported to Japan from England (Andrews Steel) in the late 1800’s. Of these, Shirogami No.1 steel is my favorite. It’s a matter of personal taste.

Beware of a plane blacksmith that refuses to use plain high-carbon steel and tries to charge you more for Aogami or Aogami Super steel.

The Challenges of Working Plain High-Carbon Steel

What makes plain high-carbon steel so difficult to work, you ask? I’ve never even forged a check much less a tool blade, but I will share with you what the blacksmiths I use and swordsmiths I know have told me in response to this question.

First, plain high-carbon steel is much more difficult to successfully heat treat because the range of allowable temperatures for forging and heat-treating is narrow. Heat it too hot and it will “burn” and be ruined. Quench it at too high or too low a temperature and it will not achieve the desired hardness. Miss the appropriate range of temperatures and the blade may even crack, ruining it. Yikes.

Second, even if the temperatures are right, plain high-carbon steel has a nasty habit of warping and cracking during heat treatment resulting in more rejects than steels with additives such as chrome and moly. Strange as it may seem, when the crystalline structures that make steel useful form during quenching, they increase in volume. This change in volume produces differential expansion causing the metal to warp. This warpage can be more or less controlled, or at least compensated for, by a skillful blacksmith, but it takes real skill, extra work, and a bit of luck. Not just any old Barney can do it consistently, so when working plain high-carbon steel, a blacksmith needs to know his stuff and pay close attention.

Other than wastage due to rejects, it doesn’t cost more to forge and heat-treat a blade of plain high-carbon steel. But it takes serious skills and dedication to quality control to make a living working it for 5+ decades.

Let me give you an example of skill and experience as it relates to warpage management of plain high-carbon steel.

The photo below is of a swordsmith the instant before he quenches a yellow-hot sword blade made of tamahagane, a traditional type of plain high-carbon steel made from iron sand, in a water trough. Notice the condition of his smithy: he is working in the middle of the night, the time when the best magicians and alchemists have always done the most difficult jobs because temperatures are easier to judge without unpredictable sunlight confusing things. His posture and facial expression are tense because he is about to roll the bones and either succeed in the most risky part of making a sword, or fail wasting weeks or months of work and thousands of dollars worth of materials. Notice how straight the glowing blade is.

A Japanese swordsmith with a blade poised for quenching Notice how straight the blade is. He has invested months of work into this blade to this point and a misjudgment or even bad luck in the next second can waste it all. Not a job for the inexperienced or timid.

Note that the formation of crystalline carbides in Japanese swords after heat treatment is densest nearest the hard cutting edge. The swordsmith therefore forges the blade straight before quenching it in expectation of it warping to the intended curvature when the crystalline structures at the cutting edge form, as seen in the photo below. This curvature is an intentional design feature that takes years of experience to achieve in a controlled manner.

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After quenching, the warpage is dramatic. Notice the mud applied to the blade before quenching to control the formation of crystalline structures.

If the swordsmith intended to make a straight sword blade, he would have a forged a reverse curvature into the blade to compensate for the warpage that occurs during quenching. Plane and chisel blades exhibit similar but less dramatic behavior.

「折れず、曲がらず、よく切れる」を追求し、極限まで鍛え上げられた凛とした姿に、千年を超える日本刀の歴史と、生きることのすべての力を注いだ刀鍛冶の姿が浮かび上がる。
Both sides of a similar completed sword with the warpage an intentional design feature

The thinner the piece of steel being heat-treated, the more unpredictable the warpage and more likely the blade will develop fatal cracks. Within limits simple warpage can be corrected in thin blades, but not in stiffer chisels or plane blades. In the first few seconds after quenching and/or tempering a blade, the metal is still a bit malleable and warpage can be corrected to some degree by bending and twisting the still-hot blade. An experienced blacksmith will not rely solely on corrective measures but will anticipate warpage and create a curve or twist in the opposite direction when forging to compensate in advance of quenching. This takes skill and experience, and even then, some rejects are unavoidable.

Chemical alloys like chrome, molybdenum, and tungsten greatly reduce warping and the risk of cracking.

None of this is mystical, but tools made from plain high-carbon steels such as Aogami steel and especially Shirogami steel require more skill and experience than those possessed by factory workers, much less Chinese peasants, so mass-production is nearly impossible, labor costs are higher, profit margins are smaller, and advertising budgets are non-existent. No wonder such tools get little attention from the corporate shills in the woodworking press.

While modern chemistry has unveiled the mystery of steel, it has only been during the last 60 or 70 years that metallurgical techniques have been developed making it possible to understand and control steel manufacturing.

The manufacture and working of steel are still magical processes that are the foundation of modern civilization. Make no mistake: without steel and the skill to work it, human life on this planet would be short and brutal.

If you have good sharpening skills but haven’t yet tried chisel or plane blades made from Shirogami, Aogami or Asaab K-120 Swedish steel, you’re missing a treat.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Sharpening Part 21 – The Bulging Bevel

Sharpening Part 22 – The Double-bevel Blues

Sharpening Part 23 – Stance & Grip

Sharpening Part 24 – Sharpening Direction

Sharpening Part 25 – Short Strokes

Sharpening Part 26 – The Taming of the Skew

Sharpening Part 27 – The Entire Face

Sharpening Part 28 – The Minuscule Burr

Sharpening Part 29 – An Example

If you have questions or would like to learn more about our tools, please use the questions form located immediately below. Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google or incompetent facebook and so won’t sell, share, or profitably “misplace” your information.

Sharpening Part 6 – The Mystery of Steel

“The most beautiful experience we can have is the mysterious. It is the fundamental emotion that stands at the cradle of true art and true science.” 

Albert Einstein, The World as I See It
https://hdwallsbox.com/wallpapers/l/1920x1080/52/fantasy-art-magic-blacksmith-1920x1080-51111.jpg

The blades we are considering in this series of posts about sharpening are made from iron and steel, so it makes sense to examine these materials from the viewpoints of sharpness and sharpening. Let’s look at some of the supernatural and legendary aspects of working steel first.

Steel Magic

Steel is a magical substance. Since ancient times, the blacksmiths that worked it were sometimes seen as gods, sometimes as wizards. Regardless of local traditions, the power blacksmiths possessed to combine and shape the elements of earth, wind, water, fire and even spirit into the tools and weapons of everyman’s trade was seen as magical.

Even the blacksmith’s forge and anvil were seen as magical in and of themselves, and rituals incorporating them were widely believed to keep evil at bay, provide good luck and blessings, and even to cure ailments.

There were several extremely famous magical blacksmiths back in the mists of time. Allow me to present two of them to you.

Vulcan the God

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Vulcan (aka Hephaestus), Roman god of fire and blacksmithing. Archaic relief from Herculaneum (National Archaeological Museum, Naples).

The bas-relief stone carving in the photo above is of Vulcan, the Roman god of fire and blacksmithing, also known as Hephaestus to the Greeks. This carving was excavated at Herculaneum, located in the shadow of Mount Vesuvius near Pompei. Herculaneum was an ancient Roman town destroyed by volcanic pyroclastic flows in 79 AD. The word “volcano” comes from the word Vulcan, so a stone carving of Vulcan retrieved from a town totally destroyed by Vulcan’s namesake is tragically ironic in the extreme.

Die Schmiede des Vulkan (The Forge of Vulcan) by Velázquez, Diego 1599–1660) Museo del Prado, Madrid, Spain.

The painting by Diego Velázquez above is from a scene in the Roman poet Ovid’s Metamorphoses where the god Apollo visits the god Vulcan in his forge to tell him that Venus, Vulcan’s wife, is being naughty with Mars, the god of war. Apollo is on the far left and can be recognized by his crown of laurel and shining aura. Vulcan stands next to Apollo with a shocked and incredulous expression on his less-than-beautiful face (nice abs, but his beard needs a lot of work). Vulcan’s assistants have stopped their work on armour (decidedly 15th century in style) astounded by both the sudden appearance of Apollo and the news he delivers.

Obviously, Venus and Vulcan were not a happy couple. Legend says that whenever Venus was unfaithful, Vulcan grew angry and beat hammer on anvil so fiercely that sparks and smoke rose up from the top of Mount Etna on the island of Sicily, under which he had built a forge, creating a volcanic eruption.

Perhaps Apollo is sharing this tidbit of news just to help out his old buddy Vulcan, or perhaps his reason for snitching is malicious. Whatever the reason, I think it’s safe to assume people loved drama in the 1600’s too. Nothing new under the sun.

My point is that Vulcan (Hephaestus) was not only worshipped in ancient Greece but had a presence in popular culture that ranged from before an Etruscan tribe drained the swamps that became Rome in the 10th century BC, to as late as the 1600’s. And I won’t even get into Trekkie lore. Now that’s an influential craftsman.

Wayland the Smith

Wayland the Smith (Vølund Smed) 1873 sculpture. Stockholm Sweden.

Wayland the Smith was another famous blacksmith, metalworker, and magician. He was said to be a Lord of the Elvish folk who learned his trade from either giants or dwarves.

While not as old as Vulcan in human history, Wayland’s legend survives throughout Europe, and the products of his forge were central to heroic traditions of many peoples and kingdoms since the days of the first Viking longboats.

He is credited in Norse, Germanic, and Anglo-saxon legends and literature with forging magical objects of great renown, including rings of power, the impenetrable coat of ring mail worn by Beowulf during his epic battle with Grendel, the magical sword named Gram that Sigurd used to slay the dragon Fafnir, and even King Arthur’s sword Excalibur. Not just scribblers, but even Alfred the Great, king of the Anglo-Saxons c.886~899 on the island that would later become England, wrote of him.

The chains on the legs of the statue above probably represent his maiming and imprisonment on an island at the pleasure of an evil Norse king upon whom he took a bizarre revenge involving unconventional drinking bowls and jewelry. Is Wayland’s slavery one of the reasons blacksmiths have wrapped chains around their anvils since ancient times, or is the purpose just to secure the anvil and mute the bright ringing sound they make? Another mystery…

Wayland’s influence in modern times is not insignificant. For example, Leonardo Da Vinci’s fascination with flying machines was probably stimulated by the legends of Wayland building and using a winged contraption to escape slavery. And unlike Daedalu’s deadly device in Greek legend, Wayland’s didn’t melt.

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Daedalus (the bald guy) and his son Icarus (the falling guy) using wings to escape the island of Crete, home of labyrinths and monsters. Against his father’s advice, Icarus flew too near the son melting the wax securing the feathers that made the wings function. Oops.

The legends of Wayland the Smith were once deadly serious matters.

In a lighter vein, the writings of J.R.R. Tolkein, the author of the most popular works of written fiction in human history (no kidding), were influenced by these legends.

The Blacksmith’s Shop

While some blacksmithing traditions such as those involving Vulcan and Wayland are decidedly pagan in origin, others fit well with Christianity. For example, the ring of the blacksmith’s hammer on his anvil was once believed to strengthen the chains that bind the devil in hell barring him and his demons from God-fearing folk’s hearths. In darker times in human history the blacksmith’s workshop was believed by many to be a safe haven from evil forces, one that Satan and his imps actively avoided.

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The village smithy. Notice the horseshoe on the wall in the background, and its downward orientation. Due to the lack of char marks on the wall, we can tell this is not where the smith normally hangs horseshoes to cool. There is method to the madness.

Here is a link to a charming story about why blacksmiths ring their anvils and how to make sure a horseshoe brings you luck at work and at home. I encourage you to read it. Legend of the Ringing Anvil

The Japanese Smithy

If you have ever spent time in small one-man traditional smithies of the sort where our blacksmiths labor to produce the tools we carry then you know the other-worldly atmosphere typical of such workplaces. Imagine walls and exposed wooden roof beams blackened with 70+ decades of soot, the compacted but lumpy dirt floor, the darkness of carefully-managed sunlight (the better to judge metal temperatures by eye), the bitter smells of charcoal fumes, straw ash, flux, hot steel and burning oil; the roar of forced gas forges; the sounds of grinders and the antique leather belt systems that drive them; and finally the terrible racket and vibration of spring hammers and ringing anvils. A man that could work alone in a place like that 12 hours a day for 70 years is not afraid of your run-of-the-mill demon.

It’s quite a sight to see a craftsman working in such an environment. They often start late in the morning to avoid noise complaints from the neighbors, and work until late at night doing heat treating when sunlight won’t interfere with the colors of the hot metal.

By noon their arms are black to the elbows and charcoal smudges are on their faces. The sight of a small, wizened 82 year-old man with strong sinewy arms staring into yellow-hot steel as he hammers the hell out of it is a truly medieval scene. Something of the ancient magic of Vulcan and Wayland can be felt in such places.

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Mr. Junichi Takagi, Japan’s last adze blacksmith, passed away April 2, 2019. A kind man, talented blacksmith and excellent sharpener. He will be missed especially since he had no apprentices and no one will carry on his work.
Mr. Takagi working on his wet grinder in August 2018.

In the next post we will examine some alchemical aspects of the Mystery of Steel.

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YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Sharpening Part 21 – The Bulging Bevel

Sharpening Part 22 – The Double-bevel Blues

Sharpening Part 23 – Stance & Grip

Sharpening Part 24 – Sharpening Direction

Sharpening Part 25 – Short Strokes

Sharpening Part 26 – The Taming of the Skew

Sharpening Part 27 – The Entire Face

Sharpening Part 28 – The Minuscule Burr

Sharpening Part 29 – An Example

If you have questions or would like to learn more about our tools, please use the questions form located immediately below. Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google or incompetent facebook and so won’t sell, share, or profitably “misplace” your information.