For the foundry, winter does not exist, there is heavy snow outside, but the factory is as warm as spring.

During this period of time, Chen Zhan had already made four sets of iron cannon molds with clay molds, one set of tiger squat guns, two sets of Fran machine guns, and a cannon iron mold made after perfecting and perfecting the shoddy drawings given by the chief steward.

Grand Steward, this cannon is called Grand Steward brand six-pounder cannon.

The barrel of this cannon is four feet five inches long, and the muzzle is two inches and seven minutes, which is the same as the Hongyi cannon, the tail end of the barrel is large, the muzzle, the thinnest pipe wall near the muzzle is only one inch and three minutes, and the thickest chamber is only three inches, which is much thinner than the pipe wall of the Hongyi cannon.

At first, Chen Zhan doubted that such a thin pipe wall would explode as soon as it was released, but Qin Chuan, as long as he could figure out the central water cooling method and control the cooling rate of the artillery, he would have no problem at all.

Chen Zhan was still full of doubts, but not long after the iron mold was completed, it hadn't completely cooled down, so he couldn't build that big steward brand six-pounder cannon for the time being.

What he's going to do today is a tiger squat cannon.

Compared with the Franc cannon and the Napoleonic cannon, the only advantage of the Tiger Squat Cannon is that it is light, very light, and one person can carry it all over the mountain.

So, this thing still has to be there, and in the mountains and other complex terrains, this thing is a sharp weapon.

Of course, this thing needs to be improved.

The tiger squat cannons of the Ming army were all forged in wrought iron, which was very time-consuming and labor-intensive, and Qinchuan had to directly use iron molds to cast pig iron, which saved time and effort and could be manufactured in batches quickly.

Originally, he only planned to use the iron mold preheating method, but Chen Zhan magically made a hollow inner mold, and when he cast an iron rod with a diameter of two inches, he added a finger-thick wooden stick to the sand mold to create a hollow.

With a hollow iron mold, it is possible to test the central water cooling method.

Knowing that Chen Zhan was going to start casting cannons, Qin Chuan came early, pointing shirtless next to a stove.

Li Xuejing also came, taking a booklet to observe and study on the side.

Of course, Yan Sanqi also came, and if he wanted to cast a good cannon, he couldn't do without high-quality pig iron.

Qin Chuan doesn't understand iron smelting, but he understands the principle, and he has been mixed in forums in later generations, so when it comes to iron smelting, Yan Sanqi was amazed.

Under his fingers and Yan Sanqi's continuous exploration, he finally found a set of iron smelting methods that can be regarded as top technology in the current era.

Improving the Dajian furnace, improving the blast technology, and using coke smelting to increase the furnace temperature by about one percent compared with the previous Dajian furnace, Qinchuan estimates that it should be able to reach nearly 1,400 degrees, and can turn pig iron into liquid molten iron.

Yan Sanqi and Chen Zhan built a No. 1 blast furnace in the gun factory, and now they are letting the apprentices blow the wind to boil molten iron.

There was a refining furnace next to it, not a square pond of wrought iron, but a shaft furnace, in which a crucible made of graphite powder was placed, and under the crucible was a pile of burning coke, and two apprentices were blowing wind next to it, and the shaft furnace was burning.

When the pig iron in the blast furnace turns into molten iron, it will flow into the crucible in the shaft furnace from a channel, and because the temperature in the shaft furnace is also as high as 1,200 degrees, the molten iron can still remain liquid after flowing in.

At this time, two craftsmen held long willow sticks, reached into the crucible from above and stirred the molten iron, and while sprinkling toner into it, they used bellows and iron pipes to blow air into the crucible.

This is the use of stirring molten iron to allow the impurities in the molten iron to react with the oxygen in the air to remove the impurities.

However, there is also carbon at the same time, and this process will decarburize the molten iron, so as to obtain wrought iron with very low carbon content, which is the same as fried wrought iron in Fangtang.

After the carbon content of molten iron is reduced, the melting point will increase, and the molten iron will become a paste-like colloidal state, the iron structure is uneven, and the impurities cannot float, so it still contains a large number of impurities, and it needs to be continuously forged to remove the impurities.

Therefore, the iron-making method researched by Qin Chuan and Yan Sanqi requires continuous toner powder to be added to the crucible, and the molten iron can be continuously carburized from the graphite crucible to maintain a certain carbon content and maintain a liquid state.

Moreover, the shaft furnace can always maintain high temperature, coupled with continuous carburizing, so that the molten iron maintains a low melting point and keeps it in a liquid state, and after the impurities in it react with oxygen, part of it becomes gas and floats away, and the other part reacts into other forms of impurities and floats on the molten iron.

In this way, the lower molten iron will contain fewer impurities, resulting in pig iron with better quality and more uniform structure.

This method is similar to the crucible frying method that appeared in Shanxi during the Qing Dynasty.

The result is still pig iron, which is still far from the quality of medium carbon steel or high carbon steel, but it contains very few impurities, and the quality of the cast iron cannon is definitely much better than the quality of the previous iron cannon.

After the molten iron in the crucible was almost fried, Chen Zhan and several craftsmen erected the inner and outer iron molds, which had been coated with fine mud and burned red, in a heated soil pit, and fixed the inner and outer molds.

After making preparations, Yan Sanqi used a long stick to hook off an iron ring embedded in the outside of the crucible, and a fist-sized hole appeared at the bottom of the crucible, and the molten iron flowed out of the hole, passed through an iron pipe made of wrought iron, and flowed into the mold Zheng

After the casting is completed, he fills the soil pit with burning charcoal to wrap the iron mold, so that the outer iron mold can maintain high temperature, slow down the cooling rate, and let the pig iron have enough time to precipitate carbonite.

After the casting, Qin Chuan did not rush to inject water into the inner mold to cool, but waited for natural cooling, and carefully observed the color of the inner and outer iron molds, and analyzed the difference between the internal and external cooling speeds.

After about half an hour, the inner mold cools down first, and the outer mold cools slightly slower because of charcoal heating.

After the color of the iron mold returned to normal, Qin Chuan used two wooden sticks of the same size to touch the inner mold and the outer mold respectively, and analyzed the temperature difference by the different degrees of charring of the two wooden sticks.

After about half an hour, Qin Chuan found that the degree of charring of the woodpipe touching the inner mold was a little higher than that of touching the outer mold.

So, he immediately decided to pour hot water.

Chen Zhan put a thin copper pipe deep into the bottom of the hole in the iron mold, buckled another thin copper pipe to the hole, and then asked the craftsman to open the valve of an iron pot at a high place, and the boiling water went down the copper pipe, flowed into the bottom of the hole, and then pumped out from the copper pipe at the hole, thus forming a water circulation.

The copper tube is very thin, the chopsticks are big, and the holes inside are also very large, only a little larger than the cotton swab stick.

So, the flow of water through the copper pipes is very, very slow.

The cooling rate of the inner mold is only slightly faster than before, and only slightly faster than that of the outer mold.

It's a pretty good temperature.

Qin Chuan was reluctant to get out as soon as he entered the artillery factory, and he had been the chief engineer of the project beside him, and the water injection cooling lasted for nearly an hour, and he was still reluctant to leave.

Until the afternoon, a spy came to report: A large number of spies suddenly appeared in the north of Jingyou, braving the wind and snow to approach the Jingyou sentinel, I don't know who it is, I don't know what the purpose is.

When Qin Chuan heard this, his brows couldn't help frowning.

It's cold, and it's snowing so heavily, who the is idle and wants to attack Jingyou?

Isn't this pure search for death?

I'm afraid that the army will be buried in the wind and snow halfway through.

Qin Chuan didn't care about this, and only asked Jingyou's garrison to strengthen their vigilance.

Anyway, it's snowing heavily, and it's hard to send troops over to help.

……

After spending most of his time in the gun factory, Qin Chuan went to the gun factory with Li Xuejing.

Now the gun factory has assembled three sets of boring machines, and put on a linkage device, and under the pull of a mule, the three sets of boring machines are creaking and drilling the barrels.

In addition to the craftsmen who followed Chen Zhan to make cannons, all the blacksmiths in Mengjiazhuang were working overtime to make boring machine workpieces, striving to complete fifty boring machines before the Chinese New Year, so that the flintlock pistol could enter the era of mass production.

……

The next morning, Qin Chuan came to the artillery factory early.

Today is the day when the tiger squatting cannon dismantles the mold.