Marin first thought of carbon spring steel, after all, the North Sea Kingdom already has the ability to smelt the most basic carbon spring steel, and can also make springs.

But in the end, Marin gave up, why? Because the output of carbon spring steel is low......

It is said to be carbon spring steel, but it is still doped with a lot of manganese. In order to make spring steel, Marin said that he had to import a lot of pyrolite (manganese dioxide) from the Venetians. The production of pyrolite is low, and the reserves in Europe are also low. Therefore, the spring steel made of manganese ore is all used to make springs. Want to make knives...... It's okay to make a few high-quality products, but if you want to install the army, don't even think about it......

You must know that in Marin's plan, the Beihai Kingdom should have tens of thousands of cavalry. The amount of spring steel needed for the saber used by so many cavalrymen...... Anyway, Marin didn't think it was likely......

So, Marlin can only find a way on ordinary steel. Then, it's time for the sword-forging technique......

In the world today, when it comes to knives, Japanese swords are definitely one of the best. The only comparison can be made with Damascus knives made of Indian Uz steel.

However, Uzi steel belongs to natural pattern steel because of the good quality of the ore. After the 17th century, the Damascus knife was lost because the iron ore used to smelt Uzi steel was exhausted. It was not until modern times, when patterned steel was created with new technologies, that the production of Damascus knives was resumed. However, the patterns of ancient pattern steel are naturally generated, not carved, and many modern so-called treasure knives, the patterns on them are actually artificial.

In addition to India's Uzi steel, which is a natural pattern steel, China and Japan have another set of methods to make artificial pattern steel. This is the stacking forging method, which is the way in which hard iron wraps soft iron to make an artificial pattern steel treasure knife. The so-called pattern is actually the traces formed by the external force forging at the superposition of the hard steel on the surface and the soft steel on the sword body.

However, the pattern steel treasure knife created in this way is extremely complex and takes a long time. It is said that in Japan, it takes 15 people half a year to create a top-quality Japanese sword. Even if multiple knives can be processed at the same time, each cutler's energy per year is no more than 12 knives and 20 knives. Moreover, ordinary knifesmiths can't create top-level Japanese knives, and they need senior craftsmen. As a result, the cost of the sword is high. In later generations, a hand-made Japanese knife sold for tens of thousands of dollars.

Of course, that's a top-of-the-line katana. When Japan did business with the Ming Dynasty, it was not so honest and would use such expensive knives to trade. Japan itself lacks iron ore, so they all smuggled Fujian iron from Hu Jian to Japan, and then processed it to make Japanese knives. Many low-level Japanese knives are actually low-profile versions made after the simplified version of the Japanese knives of Min Tie are processed. If it is a high-end version of the sword, it is not worth trading.

How do you get a low-profile version of the sword? It is to use the Fujian iron smuggled by Hu Jian, and let ordinary blacksmiths or blacksmith apprentices work hard to forge it to remove impurities in the iron and make it fine iron. Then, put the red-hot iron on the stove and continue to add fire, and then cover it with charcoal and simmer it to carburize the surface of the blade. In this way, you get a low-end version of the cheap Japanese sword.

Hu Jian's Fujian iron itself was smelted from charcoal, and it certainly contained less sulfur than the iron smelted with coal in the north. After repeated forging by low-end blacksmiths in Japan, the quality of the refined iron obtained is definitely better than that of knives made of northern iron. The surface is then carburized with charcoal. The last knife obtained is definitely better than the knife with high sulfur content made of northern pig iron.

Then, I got a low-profile version of the sword that was stronger than the Daming sword. But this kind of Japanese sword is very economical, and most of the middle and lower class samurai in Japan use this low-grade version of the sword. If they all used top-quality Japanese swords, most of the Japanese middle and lower class samurai would not be able to afford them, let alone equip them with the army. In addition, the patterns on this low-profile version of the sword are mostly hand-carved......

By the time of World War II, the knives used by the Japanese commander He's cavalry were not traditional katanas, but props made with modern steel technology. In fact, the material used in the Japanese Type 32 cavalry knife (the Type 65 cavalry knife is copied from this knife) is high-carbon steel. Therefore, although the reputation of Japanese swords during World War II is famous, the quality is far inferior to that of ancient Japanese swords. It's just that the dirt eight roads still use iron blades, which is so rare. Moreover, the capture of the command knife means the defeat of the Japanese officer, which belongs to honor. As far as the knife itself is concerned, the Japanese command knife during World War II was sprayed as an "iron rod" by professionals......

And a kind of patterned steel that Marin knows is that No. 45 steel and 60 manganese steel are folded and forged. Of these, No. 45 steel is the sword body, while 60 manganese is wrapped on the outside......

And what kind of steel is number 45 steel? Looking at its label, it is obviously medium carbon steel! It seems that the barrel of the 56 and a half guns of later generations is also made of 45 carbon steel......

Therefore, Marin decided to change the steel used in the blade to medium carbon steel. Although the toughness of medium carbon steel is not as good as that of low carbon steel, and the hardness is not as good as that of high carbon steel, the performance is compromised. Moreover, Marlin has another solution to the problem of surface hardness - surface carburizing......

Medium carbon steel is the blade, and the toughness is better than that of high carbon steel. In the event of a strong impact, it absorbs the impact through bending and deformation, and then returns to its original shape. But if the surface is also medium carbon steel, it is easy to be cut out by the enemy's knife.

If the stack forging method is used, the surface is wrapped with high-hardness steel, and the natural performance is higher. However, in that case, the cost is high. Moreover, not every blacksmith has the technique of stacking forging. Those who can stack forging methods to make treasure knives are all master craftsmen. Moreover, forging is very time-consuming.

But to create a saber for cavalry, obviously not in that way. Not to mention the high cost, the speed of construction is also very slow. Therefore, Marin decided to go with a compromise solution - carburizing the surface of medium carbon steel. In addition, in the quenching, we also use advanced quenching methods that are suitable for knives, rather than simple water quenching.

As for how to carry out surface carburizing? The kind of charcoal stew in Japan is not advisable. Because, with the carburizing method, the carburizing distribution is uneven, and the rejection rate is high. When creating a sword, it is necessary to re-screen the parts that pass them and eliminate the ones that don't.

……

However, as a graduate of the Department of History, Ma Lin had seen a carburizing method in the Ming Dynasty scientific and technological work "Tiangong Kaiwu", which could well solve the problem of uneven carburizing on the surface. Moreover, it is said that this method is still used to this day.

In this method, the formed iron is put into the crucible, then covered with stirred charcoal, tempeh and clay powder, and heated on the outside of the crucible......

Charcoal and tempeh are both carburizing agents that provide carbon for carburizing. The soil powder is a dispersant, which makes the carburizing uniform and avoids the uneven carburizing caused by charcoal stewing.

This carburizing method makes the carburizing of the carburized iron uniform and stable, and the carbon potential is very high (Marin himself does not understand what the carbon potential is, anyway, it is good for carburizing).

Medium carbon steel has good strength, and after this excellent carburizing technology, the strength of the blade must not be bad......

It is said that during the Spring and Autumn Period, the famous craftsmen of the Wu State liked to put hair and nails as carburizing agents when casting swords. As a result, later generations came up with a false version, saying that the cadres Mo Xie and his wife sacrificed the sword with their bodies in order to cast the divine sword...... In fact, the Cadre only used hair and human nails as carburizing agents to carburize the surface of the sword...... Moreover, the legendary blood sacrifice sword is probably also using blood as a carburizer. After all, blood is organic and contains carbon......

……

Finally, it's time for quenching. Ma Lin had read some history in his previous life and knew that there was a clever way to quench swords in ancient times, which was "bathing in the drowning of five animals and quenching the fat of five animals". The resulting sword is very wear-resistant and elastic. And what is the "drowning of five animals"? In fact, it is the urine of livestock. As for the "fat of the five animals", it is naturally the fat of the livestock...... In ancient times, there was a legend that horses were used to quench weapons, and it was said that you could get a sword......

If it is explained from a modern scientific point of view, quenching with "drowning of five animals" is actually salt quenching. And quenching with the "fat of the five animals" is actually oil quenching. Salt quenching and oil quenching are used together, which is a double-liquid quenching, which is a clever sword quenching method. The quality of the sword obtained by this quenching method is that of a bargain......