In half a month, a qiē was ready.

A small blast furnace had been built, and a large pile of coke and iron ore had been prepared, and after it was ready, under the auspices of Zhu Youxiao, more than a dozen iron-making workers from private iron and steel factories immediately opened the furnace to smelt iron.

As iron ore, limestone and other materials are poured in from the material port, the coking coal burns in the furnace.

"Iron, iron."

As the first molten iron flowed out of the discharge port, the expressions on everyone's faces at the scene became excited, but it didn't take long for Zhu Youxiao to be unhappy.

The molten iron came out, but from the consistency, an experienced worker immediately concluded that the quality of the molten iron was not high, and to put it bluntly, the sulfur content was not up to standard.

When the smelted pig iron was tested, it was really too brittle.

"Increase the amount of slag and use the regenerator." Zhu Youxiao commanded on the spot, if you want to desulfurize in the process of blast furnace ironmaking, then theoretically, as long as there is more slag, the more complete the desulfurization, and the higher the temperature, the more sulfur will be discharged with the gas.

Under the command of Zhu Youxiao, the second furnace began to be smelted again.

A worker wields a whip and drives a horse to pull the blast. The regenerator has been burned red due to the injection of gas, and hot air is constantly blown into the furnace, which increases the temperature in the furnace. At the same time, the amount of limestone and other slag has also increased.

Soon another furnace of molten iron flowed out, but the situation was still very bad, and the sulphur content of the molten iron was still too high.

This result made Zhu Youxiao a little crazy, it shouldn't be! How so?

For Zhu Youxiao, steel smelting is limited to theoretical advantages, and the practical aspect is in a blank stage, and he did not understand what the problem is on the spot.

"Your Majesty, is it that the slag is used too much, so that the coke is also used too much." Xu Guangqi guessed, Zhu Youxiao suddenly realized, and instantly understood the problem.

The more slag is used, the coke ratio naturally rises, and the more coke is used. The main source of sulfur in molten iron is coke, and although the sulfur content in iron ore is high, it is still relatively low compared to coke.

Theoretically, the more slag there is, the more sulfur content in the molten iron is reduced, but the more this stuff leads to an increase in the amount of coke, which leads to the opposite result.

"It seems that low-sulfur coal is the only way to do it." Zhu Youxiao sighed, where to find low-sulfur coal for a while? By the way, aren't Handan and Xingtai areas very famous in steel smelting in later generations? There is an expectation that there will be.

"Xu Aiqing, it seems that you still have to handle this matter." Zhu Youxiao put away his disappointment and said to Xu Guangqi.

"Please ask the emperor to command." Xu Guangqi didn't understand, but his admiration for Zhu Youxiao was still very high. Zhu Youxiao said: "You take a few prospectors and go to Cizhou to explore carefully, there should be high-quality iron ore and low-sulfur coal." I'll show you how to detect it in a moment. ”

"Obey." Xu Guangqi is still very happy to take on this task, if there is good mine and good coal, then there will be good iron and steel.

"If you can find it, it's a great achievement." In order to increase Xu Guangqi's enthusiasm, Zhu Youxiao made a verbal promise.

"To do things for the imperial court, Weichen doesn't dare to take credit." Xu Guangqi hurriedly said, this may not be found! You can't talk too much.

Zhu Youxiao smiled, and then showed Xu Guangqi the sulfur detection method of coal on the spot, Xu Guangqi has made rapid progress in chemistry recently, and the basic test methods have been mastered.

After some testing, Zhu Youxiao found that the sulfur content of the coking coal he used this time was as high as 2%, and he couldn't look at it directly, no wonder the molten iron he practiced was unqualified.

Although the molten iron produced was not up to standard, the blast furnace produced 20 tons of pig iron after one day of continuous production, which amazed the ironmakers.

The quality of the molten iron produced has surpassed that of pig iron in the private iron and steel mills in the north. It is not up to standard to use it to produce military equipment, but it is still okay to use it to produce agricultural tools and the like. Previously, when the Ming army was on the battlefield, the war knife held by the military general was cut off, apparently the craftsman used the inferior pig iron in the north to make steel, and the material was very brittle.

"Your Majesty, we can try it with charcoal, it should be able to produce good iron." One of the iron-making masters said to Zhu Youxiao, and Zhu Youxiao was stunned after hearing this, yes! It doesn't have to be coking coal to make iron.

Since the sulfur content of coking coal is too high, it is better to try it with charcoal. The blast furnace used charcoal to make iron from the beginning, and although the temperature is not as high as that of coking coal, the sulfur content is reduced! And there is a regenerative chamber to blow hot air, but you can try it.

"Okay, let's try it with charcoal." Zhu Youxiao took this construction and immediately asked the workers to change the charcoal and go into battle. After changing the charcoal, a furnace of molten iron is still very smoothly refined, but the speed is a little slower, after all, the temperature is not as high as coke, and the efficiency is naturally reduced.

However, the quality of the baked molten iron is excellent, and the sulfur content drops immediately.

This is a very surprising result, these pig iron quality is qualified, and after being turned into steel by frying steel, it can be used to make zuò military equipment.

It's just that the blast furnace of the Royal Military Factory has been tested for a few days, and the process is not very smooth, either there is a small problem here, or there is a small problem, and the problem of Zhu Youxiao's lack of professionalism has been exposed. But fortunately, it was only a small problem, and after working together with the ironmaking masters to tackle technical problems, they were all solved one after another.

In terms of efficiency, it can only produce 15 tons a day, which is 5 tons less than using coke. But it's also very terrifying, and the iron produced is completely enough for military use.

A small blast furnace of only fifty cubic meters is extremely unnatural in this era.

With a daily output of 20 tons, there is an annual output of 7,300 tons of pig iron, and a daily output of 15 tons, and an annual output of 5,400 tons. Just one blast furnace is enough steel for the army.

On average, each soldier consumes 20 catties of steel, and 5,400 tons of pig iron is enough to supply the steel consumption of 500,000 soldiers.

The blast furnace of the Royal Military Factory has a great advantage in the production efficiency of pig iron, but the transportation cost is a drag. Iron ore and charcoal are transported at a cost. However, despite this, compared with the pig iron in the south, there is still a great advantage in cost, at least one-third lower than the pig iron production cost in the south.

Zhu Youxiao did not plan to use the experimental furnace of the Royal Military Factory for production, but planned to build another blast furnace near the iron ore.

The location of the iron and steel production base is also planned, in the later Handan and Xingtai areas, Handan is one of the four major iron-rich mines in China, which Zhu Youxiao remembers more clearly. In the Xingtai area, there seems to be low-sulfur coal, but the memory is very vague. Even if you can't find low-sulfur coal, Handan's iron-rich ore is enough to make people tempted. The high iron-rich content and low impurities not only reduce costs, but also smelt higher quality steel.