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Jingle Bell, Jingle Bell......

Not far from the Yamen, in the ruins of the Fuxue that was burned down by the Taiping army, dozens of grass huts were built along the remnant walls, and the sound of metal hammering was always heard day and night in the grass huts, which was the blacksmith of the workshop building weapons, like any rebel, this building weapons has always been a big thing.

The same is true for Zhu Yifeng, the commander of the "Righteous Army", almost on the day he took Huangzhou, he ordered people to post notices to recruit craftsmen, unlike the Taiping Army or the official army often forcibly recruited craftsmen, he explained on the notice the "high salary" of six taels of silver per month, and these six taels are only "basic salary".

Despite this, it took several days of hard work, and the blacksmiths in the city who had previously "absconded" in order to avoid being forcibly conscripted were tempted by "high salaries" and came to work in this workshop, but there were not many blacksmiths, after all, there were more than a dozen blacksmith shops inside and outside the city of Huangzhou, but more than a dozen blacksmiths took more than a hundred apprentices to create weapons such as red tassel guns and broadswords, and the speed was quite fast, especially the former, there was only one iron spear head, as long as the iron material could be supplied, thousands of iron spear heads could be created in a day.

Of course, this does not mean that Zhu Yifeng will put all his treasures on cheap red tassel guns, in fact, almost on the day he established the workshop, he ordered someone to build an iron furnace, the iron furnace is still a traditional Chinese iron furnace, as for the craftsmen, fortunately, in this era, basically every city has an iron foundry - an iron casting workshop specializing in casting all kinds of agricultural tools

Naturally, the casters in the iron foundry will also be recruited into the workshop and become the craftsmen in the workshop. From that day on, the shells of the 32-pound and 12-pound carons were sent to the foundry of the workshop, and the blacksmiths made molds from the shells, but they made not traditional clay molds, but iron molds like casting farm tools.

The reason why the shell was made first was because the structure of the shell was undoubtedly simpler than the others - just a round sphere, of course, this was a solid projectile.

Standing in the foundry of the armory, looking at the hundreds of spherical solid shells stacked on the wooden board on the ground, there is no need to take the bomb, carefully inspected, Zhu Yifeng can distinguish the difference between these self-cast shells and the ship's shells - these shells made of pig iron are cast with two semi-circular blank molds, although the iron mold is used, but the appearance still looks very rough, and there are line marks when the mold is closed, compared to the shells on the ship, although they are also cast of pig iron, but because of the lost wax method casting, So the appearance looks smoother and there are no casting marks.

"Master Li, why are these casting marks so obvious?"

Looking at the casting marks on the cannonball, Zhu Yifeng's brows were locked, and he asked the foundry foreman beside him.

"Big, handsome, this cannonball can only be cast like this, the loss is an iron mold, if, if it is a clay mold, it is estimated that there must be a lot of trachoma on it......"

As a caster in Cheng Kee Foundry, Li Lao, who has cast iron pots and iron plows for decades, naturally knows the disadvantages of this clay mold, and of course knows the disadvantages of this iron mold.

"Dashuai, unless you use beeswax to make balls and molds, the line marks on this bullet will definitely not be able to go, or you have to use wrought iron, if you use wrought iron, you can use a file to remove the line marks......"

Wrought iron......

Is there so much wrought iron in Huangzhou City?

That wrought iron isn't enough to make weapons!

As for these shells cast with iron molds, none of them are white cast iron that can not be forged and machined, the reason why the iron mold was chosen at the beginning is because it is convenient to integrate, unlike the clay mold that must rely on time to wait for drying, in fact, Zhu Yifeng originally preferred to use the sand mold, but in the end he chose the mature technology, and the iron mold used for thousands of years in various foundries - for thousands of years, the Chinese people have been using iron molds to cast agricultural tools and iron pots.

However, the iron mold also has shortcomings, from the point of view of metal casting and metallography, the thermal conductivity of the iron mold is good, resulting in too fast heat dissipation, so that the pig iron liquid has a large degree of supercooling when cooling, and the cementite in the molten iron has not had time to precipitate the graphite has been solidified, so the cementite in the iron mainly exists in the form of iron carbide, that is, white iron. Of course, due to the large degree of supercooling of molten iron in the solidification process, the metal crystalline particles on the surface are relatively dense and the body tube is relatively smooth, that is, it looks very good.

In contrast, the only advantage of iron molds is that they speed up the production rate and do not have to wait for the molds to dry in the shade like mud molds. This point is particularly prominent in Gong Zhenlin's iron mold during the Opium War more than ten years ago, but the white mouth of the iron mold cannon is very serious, because the cooling speed is too fast, although it is relatively smooth, but almost all of the white iron is generated, resulting in an increase in brittleness and a decrease in the performance of the artillery.

This is true on artillery, and it is no different on shells.

Although he studied metallurgy in college, after all, after graduating from university, he has not touched anything in this major for many years, and the metallurgical knowledge of university professors in the 21st century is more based on the modern industrial base, and his understanding of the current primitive metallurgical technology is even far inferior to these craftsmen. However, it is difficult to solve a series of technical problems such as blowing air in the blast furnace, and all he can do is to make targeted and gradual improvements.

In addition to the so-called wrought iron, can't ordinary white cast iron be forged and machined? Picking up one of the 12-pound shells and carrying this shell, Zhu Yifeng's mind was malleable annealing - that is, the malleable annealing of white cast iron, making it malleable cast iron, that is, it is kept warm for a long time at a high temperature of about 950C, so that the iron carbide in its structure decomposes and is converted into a malleable cast iron structure.

"So, Master Li, can we build an annealing furnace?"

Putting down the cannonball in his hand, Zhu Yifeng casually drew the structure of an annealing furnace on the ground, the structure of the flame annealing furnace is not complicated, in fact, it can be said to be very simple.

“…… The shells made of pig iron were then spread in several layers of the hearth, covered with river sand and filled with the voids, and then heated and insulated with river sand......"

When explaining this intention, Zhu Yifeng only listened to Li Shisheng next to Li Lao and muttered softly.

"It's just to take the iron and burn it in the furnace, but it's not easy to grasp the heat."

Li Shisheng's words made Zhu Yifeng look at this young man in his twenties, he is the son of Li Lao, malleable annealing in ancient times, China has also used, but it is empirical, they only know that burning can reduce the brittleness of white cast iron, but as he said, the heat is not easy to master, so it is not widely used, even if it is an expert, it may not be able to burn a reason.

"The heat is well controlled, and the temperature of this annealing is ......"

The graphitization of cementite is carried out at 910~960C and 730~780C. In 910~960C thermal insulation, the graphitization of eutectic cementite and secondary cementite is mainly carried out. The higher the heating temperature in this temperature range, the faster the graphitization process proceeds. However, if the heating temperature is too high, such as more than 1000C, it is prone to the appearance of flake graphite, which damages the properties of malleable cast iron.

For Zhu Yifeng, who studied metallurgy, he naturally knew this temperature, but these people in front of him obviously didn't know what more than 1000C and what graphitization was, so he only said half of the words, and then changed his words.

"This heat is actually about the same as the melting point of silver and borax, when the silver and borax begin to melt, the heat is on the line, and it can be kept warm, and we can use this as the heat to control the heat of the simmering fire......"

Of course, this is not what Zhu Yifeng learned in a textbook, but a material that he accidentally saw among celebrities in modern metallurgy, but it did not prevent him from borrowing this experience at this time.

"Dashuai, this heat is so simple??"

Although Da Shuai just said a word casually, it was enough to make Huang Lao Crooked and the others open their eyes wide, of course, what surprised them even more was that Da Shuai actually told them the reason directly, isn't this equivalent to directly giving away the family that eats with both hands?

"It's as simple as that, okay or not, you guys try it first, well, by the way, there's still a cannon mold there? Have you sent it? ”

As soon as the conversation changed, Zhu Yifeng returned to the intention of returning to the armory workshop this time - artillery!

Although the "Righteous Army" now has fourteen Caron guns on the Express, in addition to the two 12-pounder guns, the other 12 are powerful 32-pounder guns, but this does not meet the needs of the "Righteous Army", not to mention that they now have an army of 20,000!

It is impossible to make a gun, in contrast, casting a cannon is undoubtedly the most realistic, before the Taiping Army Jintian Uprising, it was not in Jintian to open a furnace to cast cannons. However, what Zhu Yifeng wants is not the kind of "earth cannon" of the Taiping Army, what he needs is a 12-pounder caron cannon!

"Dashuai, the old man of the wooden model was already made before the morning today......

Without waiting for Li Lao to finish speaking, a herald hurriedly ran over, stood upright, and after saluting, the herald said breathlessly.

"Marshal, Chief Li, please hurry back to the yamen, there is an urgent military situation!"