Su Chengyu continued: "Although the iron-cast heavy artillery has a great risk, if it is not done well, there is a possibility of exploding. ”

"But," he said, "with a proper method of casting, and the high quality of the iron produced in our ironworks, I can guarantee that a heavy cannon made of iron will never be worse than that made of brass." ”

The biggest difficulty in casting a cannon with pig iron is the cooling of the barrel. Due to the very thick barrel walls of heavy guns, the cooling rate inside and outside the pipe walls was inconsistent. And usually the outer layer cools and shrinks first, while the inner layer is still in a state of thermal expansion, resulting in the outer layer cracking.

In addition, the barrel cools down too quickly, resulting in the formation of white iron. The so-called white iron refers to the combination of carbon in iron and iron to form ferric carbide, which will make the whole metal brittle and easy to crack.

Although Su Chengyu is not a casting professional, he still understands these basic metal processing knowledge. The best solution to the problem of cold shrinkage of the barrel is the Rodman casting method, which cools the inner wall of the barrel with water, so that the inner wall is cooled and contracted first, and the outer wall can also form a "hoop" effect on the inner wall after cooling, and the barrel produced is even more reliable than the bronze cannon.

However, the Rodman method, a nineteenth-century technology, has extremely high requirements for water cooling control, with tens of thousands of parameters, and Su Chengyu cannot remember it at all.

His solution was layered casting. Half the thickness of the barrel is cast first, and due to the small thickness, the problem of shrinkage of the outer layer is avoided.

After the barrel has cooled, the outer layer is cast to bring the barrel to the required thickness. At this time, the outer layer will not be cracked when cooled, and there is even some of the clamping effect of the Rodman method.

In fact, if it weren't for the lack of steel production in the iron field, he really wanted to make steel cannons directly, and the quality would definitely kill all the artillery in this era.

In addition, layered casting can also effectively solve the problem of white iron. In the case of white iron, it can be turned gray by calcination. The carbon in gray iron exists in graphite, which can greatly improve the toughness of iron. However, if the gun body is too thick, it will not be completely burned through, and only the surface will be grayed, and the inside will still be white. Layered casting can cast one layer, calcine one layer, and almost the whole gun can be turned into gray iron.

But the craftsmen present knew that he was so successful, and they all thought that the owner was just sick and rushed to the hospital because he couldn't get copper.

When Su Chengyu roughly explained the layered casting method to them, all the craftsmen listened to it in a fog, and they all wondered what the owner would say.

Only Song Yingxing's eyes lit up, and he took a pen to copy desperately, what white iron, gray mouth, cooling and cracking, he had never heard of it, it simply opened a door to a new world of cannon casting for him.

Su Chengyu drew out the drawings of the artillery iron fan again, and began to arrange specific matters, "The iron fan required for layered casting should also be divided into two layers. ”

It had been several months since the craftsman came to the Su Ji Iron Yard, and he had already recognized this standard industrial drawing, and with Song Yingxing on his side, by the next day, the inner and outer layers of the 24-pound cannon had been made.

Su Chengyu immediately took out the two sets of drawings he had drawn last night and handed them to the craftsman. They are a six-pounder cannon and a nine-pounder cannon.

Although there was an iron model of a six-pounder cannon in the iron yard, it was used to cast bronze cannons, and cast iron cannons required thicker barrels, so they had to be remade.

Since the last time the artillery battalion was formed, the Dragon Guard has four companies of artillery. However, due to the inability to replenish the artillery in the foreign campaign, there were only 8 six-pounder guns.

This matching ratio is very unreasonable, Su Chengyu has always planned to configure 16 six-pounder guns for the artillery battalion, plus 4 nine-pounder guns, to achieve full strength. That's nearly three times as much firepower as before!

After all, the opponent he will face is the more powerful Manchu Eight Banners. In particular, their cavalry shooting and "pig burst" ability is extremely strong, and the lethality should not be underestimated, how many Ming troops were defeated by these two moves.

Although the use of infantry hollow phalanx can effectively defend against the captured cavalry, if the enemy is determined to fight hard, the dragon guard will also pay huge losses.

And Su Chengyu wants to bring the new battalion to the battlefield this time, although their training level is very reassuring, but Su Chengyu does not dare to guarantee that there will be no stage fright, as long as one of the phalanx cannot withstand it, the entire phalanx will be crushed by the cavalry and face slaughter.

So artillery will be the focus of this reinforcement! To deal with the cavalry charging in formation, disrupt the formation with nine-pounder guns at a long distance, and then concentrate a large number of six-pounder guns to form crossfire. When the cavalry arrived, all artillery was dispersed.

Under such ferocious shelling, even the most elite cavalry could not maintain a good formation. The scattered cavalry is much easier to deal with, at least the impact on the infantry phalanx will be reduced exponentially.

Even in the history of European warfare, there are often cavalry that collapse directly under such artillery bombardment.

As for the three three-pounder guns, Su Chengyu planned to throw them directly to the infantry to increase their firepower, which would be called up by battalion-level officers.

When the mud fan of the twenty-four-pounder cannon was sent into the dry shed, Xu Erlu came.

After saluting, he said to Su Chengyu: "The student was eager to listen to His Highness's teachings, so he rode a horse first. More than 100 craftsmen will arrive the day after tomorrow. ”

"You're just in time for the distance." Su Chengyu immediately told him that he would let his four brothers come to Gezhi Academy to teach.

Xu Erlu was also quite excited to learn about this, and said that he would immediately write to his family, and his four brothers would not refuse.

With Xu Erlu, an expert in cannon casting, Su Chengyu relieved himself to hand over the matter of making the fan, and asked him to take the craftsman to make more spare clay fan, so that it could be used for backup when the firing failed.

It would take some time for the mud fan to dry, and Su Chengyu immediately rushed to the firearms workshop.

In addition to increasing artillery firepower, this time he also plans to create an important infantry weapon - rifled guns.

After several actual combat exercises, the Dragon Guard Army has emerged many marksmen with excellent marksmanship. Su Chengyu was ready to select some of the best among them, equip them with rifled guns, and form a chaser team.

As the name suggests, rifled guns are carved into the inside of the barrel with several spiral grooves, and the edge of the bullet is embedded in the spiral grooves, so that the bullet will rotate at high speed after being fired out of the chamber.

Compared with the smoothbore gun with no accurate head, the bullet of the rifled gun can maintain a straight flight trajectory due to the rotation effect, and the shooting accuracy is extremely high. At the same time, the armor-piercing ability of a rotating bullet is much stronger than that of a non-rotating lead bullet.

In addition, the effective range of rifled guns is more than twice that of smoothbore guns, and as long as the marksmanship is accurate, one shot can be fatal at a distance of 150 steps.

In fact, rifled guns appeared in Europe as early as the 16th century, but they were never installed in large areas. The main reason for this is that the edge of the bullet should be embedded in the spiral groove, and the diameter of the lead bullet should be slightly thicker than the barrel.

This makes it extremely difficult to reload, and early rifled guns need to use a hammer to smash lead bullets into the barrel, which is not only slow, but also easy to injure the barrel and cause explosion.