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You don't want harder steel it breaks, you don't want softer steel, it bends, you want more control of the temprature of the steel at every stage so you can get the exact properties you want. Better is more control of the process.

Dragon blood is just a non-flammable liquid with thermal conductivity similar to oils or water but unlike water and oils it a vapor point higher than steels melting point, so the oil can be heated to much higher temperatures This means it can control the temprature the steel is cooled to exactly.

This also allows it to be used in a liquid oven or normalizing medium, which means the steel can be heated perfectly evenly and kept there as long as necessary. this is how the best steels are produced and how to get the most out of your steel allows, precision control of temprature at every stage. It can even be used for annealing and tempering much how modern smiths use ovens.

Most forges and quenches can not be targeted to the exact temprature, quenching fluid in particular boils off before it can be heated to the best temperatures. it is really easy to overheat or undereat the steel. Today we can use molten salts for some of these, But that is a recent invention. Molten salt is also extremely dangerous.

A basic introduction to heat treatment of steel.

Making good steel is about precision, you are trying to hit a bullseye of qualities. for those unfamiliar with the term ductility, low ductility means brittle, high ductility means easy to bend, you don't want either.

It even makes sense that dragons would have such blood since the need blood that will not boil ho matter how hot they are.

I am a blacksmith. I make blades, like this one.

Ok first things first, there is a lot of disinformation in here...first I will address that.

1. Quenching is not the final step in making a blade. It is the most dramatic moment of the forging process and is generally shown in entertainment as the last step...its not.




2. Quenching is not even the final step in the heat treating process.




3. The final step in heat treating is tempering

It generally doesn't matter what type of fluid you quench your blade in. The general thing to know is that the faster the steel cools down from critical (the point where it is so hot it is no longer magnetic) the harder and more brittle it becomes.

Brief definition break!

• Hardness: Hardness is a measure of how much force it takes to deform the steel


• Toughness: Toughness is a measure of how much force a blade can take and still return to is previous shape.

Ok so anyway. You want the edge of the blade to be hard and you want the spine of the blade to be flexible. To do this you first harden the blade by quenching it as mentioned.

Once that is done you reheat the blade but only along the spine back to a cherry red, say 800 degrees or so. While you do this you keep the cutting edge cool either by keeping it in liquid or wet clay or something, this keeps the edge hard.

Ok. On to the question at hand...how does dragon blood make blades better?

Sadly, with science...it doesn't. When you quench the blade in any substance, the outer layer will indeed bond with the quenching fluid (we use a mix of motor oil and antifreeze at my shop). The problem is, it is a very thin layer, and depending on the type of steel may actually flake off. Either way you would grind and polish after hardening. Then you would temper the spine. After tempering you do your final grind/polish and sharpening.

Metallurgy really doesn't allow for a scientific benefit to using dragon blood...which is great for your dragons.

That being said if you are working in a fantasy realm...which I would assume you are since...you know...dragons, you can use the ol' its magic and create something that works for story telling. Just because it doesn't work in real life doesn't mean it can't be awesome in a story.

For those of us who are not up-to-date on their material science, quenching has the end effect of making metal harder. It achieves this through the cooling rate of the metal. It can be that dragon's blood happens to conduct heat really well, making a harder blade.

This may also explain why those darn dragons don't burn easily: their blood helps dissipate the heat so well!

Additionally, cooling some metal quickly enough can result in it being amorphous. In generalities, amorphous metals (or glass metals) resist plastic deformation and are tougher than crystalline (normal) metals.

Harder blades tend to keep edges better, and the increased toughness means it'll last longer under repeated loads (like when used as a weapon). Harder blades are not always better: it depends on the style of sword and martial system you are using. Tougher blades, though, are generally considered better- they snap back better to their original shape and don't become bent as easily.

Dragons' blood is an absurdly good insulator. Now, normally this would not be quite what you want for quenching, but Dragons' blood is also magical.

Quenching a blade in Dragons' blood is not like a normal quenching - it's more like aging a whiskey. You heat the blade to white-hot, plunge it into the blood, seal it up, and leave it for a month or so.

The blade then cools incredibly slowly. Aided by the intrinsic magic of the blood purifying the lattice and eliminating dislocations, the end result is a nigh-indestructible monocrystalline blade which requires no further tempering.

The blade must then be sharpened by magic, resulting in this monomolecular blade having an edge only a handful of atoms thick - but despite the magic involved in the forging process, no actual magical properties are imposed on the sword itself.

(This also explains why Dragons sleep on hoards of gold and treasures made from other metals - the magic in their blood interacts with the metal, giving them the same basking feeling that a lizard gets in the hot sun)

Dragon blood is rich in phosphorus.

Phosphorus in steel can have beneficial as well as harmful effects.
Phosphorus is one of the most potent solid-solution strengtheners of
ferrite. The addition of only 0.17% phosphorus increases both the
yield and tensile strength of low-carbon sheet steel by about 62 MPa
(9 ksi) while also improving the bake hardening response and deep
drawability... Phosphorus is also used as an additive in steels to
improve machining characteristics and atmospheric corrosion
resistance.

Detrimental effects of phosphorus in steel include various forms of
embrittlement which reduce the toughness and ductility. The most
familiar example in this category is the classic phenomenon of temper
embrittlement...
https://www.totalmateria.com/page.aspx?ID=CheckArticle&site=kts&NM=211

You do not want phosphorus mixed with your steel. It will make it brittle. You want a thin layer on the outside. That hardens the outer layer, where you want it to hold and edge. Also that outer layer offers corrosion resistance, which you do not need on the sword interior.

Your question does not state that the swords are steel. Maybe they are bronze. Phosphor bronze.

Phosphor bronze is an alloy of copper with 0.5–11% of tin and
0.01–0.35% phosphorus. The tin increases the corrosion resistance and strength of the alloy. The phosphorus increases the wear resistance
and stiffness of the alloy.

If you had Bronze Age tech, phosphor bronze would be excellent sword making stuff. Wikipedia shows a phosphor bronze ship propeller - for tool making applications this would be great, and a dip in high phosphorus dragon blood would be a way to get a layer of phosphor bronze on the outside of your bronze weapon.

I got this idea because I thought I had read that the druids did exactly this with swords and human blood - quenched them in blood to harden the outside, which was accomplished by the high phosphorus content of blood. Animals run on ATP which is a high energy phosphorus compound and so all blood has a lot of phosphorus. You could make dragon blood exceptionally high - perhaps they need a lot of circulating ATP to produce fire.

Better doesn't necessarily mean harder.

Perhaps the dragon's blood is high in elements which are inherently poisonous to humans. A thin coating of mercury or arsenic on a blade can dramatically increase the killing effectiveness of the steel. Add to that real threat, the psychological burden of knowing that your enemy's blade is poisoned, and battles can be won before the blade is even drawn.

Now go deeper than just a thin coating...

Perhaps quenching a scalding hot blade in poisonous metals saturates the resulting steel with a lethality which can't just be wiped away. It is in the metal and will be the deciding factor of every battle in which the blade is used.

Alternatively, the poison could be biochemical. Perhaps the dragon's blood contains a voracious infection which thrives in the scalding bloodstreams of dragons. When stored in the structure of cold steel, the microscopic life lays dormant until revived by hot human blood. Once activated, it quickly consumes the victim since human immune defenses are no match for a virus born in dragons. This alternative has the advantage that the blade could be handled, cleaned and cared for as long as it never came in touch with blood. It would be safer for it's wielder to carry than the elementally poisoned blade described above.

Quenching is the process in which steel is cooled from extremely high temperatures to not so high ones. the faster the cooling the harder the steel. According to a few pages I just read nothing is faster at dispersing thermal energy from other materials than water.

So in order to make dragons blood superior for quenching to water, we need to find its one flaw. that is water cools steel so quickly that it doesn't cool evenly which is absolutely necessary to create perfect steel.

So all you need to do to make your dragon blood so amazing is have the perfect ratio of water to any other materials in the blood to make the cooling faster than that of oil or salt bathing, but not as fast as water. You need no special chemical properties or materials, just the right ratio of water to not water. I hope this makes sense and is helpful. Thank you :)

It's a little-known fact that dragon's blood has an exceptionally high graphite content, a byproduct of their evolution from the igneous realms of the molten hearts of mountains. Graphite is a blacksmith's friend for three reasons. First, being elemental carbon, it can be used in the production of weapon-grade steel. One fist of dragon's blood for every twelve fists of molten iron has been found to be the ideal ratio for the hardest "dragon steel". Second, graphite is an excellent refractory material able to provide stable heat insulation across a wide range of temperatures. When quenching hot steel in dragon's blood, the liquid effectively becomes a kiln that cools weapon steel evenly and, by coincidence or godly design, at the ideal rate that ensures maximum hardness. Finally, graphite is a superb lubricator, and the use of dragon's blood while grinding a dragon steel blade is known to yield the sharpest possible edge.

Well cooling metal too slowly results in it being too soft but cooling it too fast results in it being hard but brittle. Dragons blood you see, it contains metals that get heated when it breaths fire and then they are cooled in a controlled way by the blood. The result is that these metals are cooled not too fast, not too slow but just right. so that it can use them in its scales. dragon blood has evolved to do this. when you quench metal in this blood you will benefit from its properties.

Dragons are usually big and armored, begging the question of where the square cube law was when they were created. But there are solutions. As material sciences advance we notice that molecularly perfect substances often exibit extreme proporties, so we can only assume that Dragons have evolved to create many of these materials to strengthen themselves and make them able to support their own weight.

Damascan steel managed to get very strong and still elastic through nanowires and carbon Nanotubes that were enclosed in the metal. Such materials could be present in dragon's blood especially if parts of the dragon were ground into the blood.

What happens during the quenching is that these materials coat the blade, providing a superior resiliance to shattering, dentation and needing less effort to remain sharp. If you then use folded steel and quench between foldings you create many layers of this coating inside the blade, making them have superior properties in strength, resilience, maintenancr and resistance to damage/shattering.

Dragon's blood is an ideal medium for austempering

While most blades, to this day, are made using water or oil as the quench medium in the traditional quenching and tempering process that James mentions, producing a tempered martensite microstructure, this is actually not the ideal microstructure for a given hardness. The work of Bain and his colleagues in the 1930s on isothermal transformations in steel led to the discovery of a superior microstructure, namely upper bainite, with improved toughness at a given hardness for typical blade hardnesses (above 40 on the Rockwell C hardness scale). However, it isn't achievable in ordinary carbon steel using typical, continuous-cooling quench media. Modern production dunks the part in a molten salt (nitrite/nitrate) bath that cools the part to an isothermal transformation temperature, then holds it there to effect the transformation before pulling it out and letting it air-cool post-austemper, or uses special alloys that can form bainite during a continuous cooling process. This is known as austempering, and is commonly used for high-strength steel parts such as rifle bolts (all the way back to WWII) and seat belt parts in cars.

In your case, though, you can do better. The blood of your dragons is a high-boiling liquid (very low vapor pressure) with excellent thermal stability, and a high specific heat capacity, making it ideal for austempering a blade as it will not boil off, decompose, react with the blade, or change in temperature much when the part is added. In this process, the quench tank would be almost like a cauldron, kept hot (but not too hot!) with a stoked fire, and the parts would be held in the quench medium for a significant length of time, effecting an isothermal austemper and producing tougher, stronger blades for a given hardness at a minor tradeoff in absolute hardness achievable. Once done, the part would be removed from the bath, washed, and for a blade taken straight to the grinding wheel for sharpening, as austempered parts need no further heat treatment.