It rained for a long time, whether it was a winter rain or an early spring rain, and finally stopped.

After the rain stopped, Li Mengxi, who had been trapped in the house for a long time, immediately rushed out of the city with more than a thousand steel bars.

It rained heavily, the air was cool and the ground was wet.

In the northeast corner of the south city of Julu City, there are a hundred large and small earthen kilns arranged in order from large to small. After the rain, the earthen kilns still stand there well.

Li Mengxi directed everyone to put a group of ten steel bars into each earthen kiln.

A total of one thousand steel bars were placed in one hundred earthen kilns, ten of which were placed in each kiln.

After that, he ordered people to prepare the yellow mud and take the wooden boards to wait. He also ordered people to bring in charcoal. There were charcoal troughs built in the earth kiln. Fill the charcoal trough with charcoal, and then spread a layer of red-burning charcoal.

After setting the charcoal fire, Li Mengxi gave the order, "Seal the kiln!" he shouted.

The soldiers who had been prepared in advance did not dare to delay, so they quickly sealed the entrance of the kiln with yellow mud, sealing it tightly. But before it was over, the soldiers used wooden boards to block it again, and covered it with a layer of mud.

In a short time, it was completed.

A charcoal fire was lit in the earthen kiln, and the kiln entrance was sealed tightly so that no one could see what was going on inside.

The swordsman following Li Mengxi couldn't help but ask, "Military advisor, is this over?"

Li Mengxi turned back and smiled at the knifemaker, "When the kiln is finished burning, it will be finished."

One hundred kilns were built, the shortest one was as short as five feet, the shortest one was as short as a wall, and the long one was more than a hundred feet long. Li Mengxi didn't know how long it would take for the air in these kilns to burn out, and there was another rain outside.

Because of the rain, it was freezing cold, so Li Mengxi simply took the people back and planned to watch again in the afternoon.

After the earth kiln was sealed, the waiting time was long enough from noon in the morning to the afternoon, and Li Mengxi took people to open the kiln.

The soldiers pushed, kicked, or hit with hammers, and the kiln was broken open in three or five blows.

Li Mengxi looked from the first kiln to the back.

As time went on, Li Mengxi noticed that the heat in the kiln became more intense when the kiln was opened. When he looked into the kiln room, it became darker and darker inside.

When Li Mengxi walked to the last kiln, which was the one with a length of 105 feet, he was surprised to find that it had been burning for several hours, and the inside was still smoking and the charcoal was still burning.

This surprised Li Mengxi. Is the kiln too long? There is too much oxygen?

But when I think about it, something is not right. It seems to be because of the charcoal fire. The charcoal fire is not an open flame and burns too slowly. It is not as fierce as the fire of wood. If the fire burns, the oxygen consumption is very fast. How can the kiln still burn for several hours?

There is oxygen.

Li Mengxi originally wanted to bend down and take a look inside, but it turned out that it was too hot inside and the smoke was too choking, so he couldn't go in.

This left Li Mengxi helpless. The kiln was already open, and the air kept coming in. The smoke could not stop until the charcoal burned out.

We had no choice but to have people pour water inside to lower the temperature first, and then send people in to put out the fire.

This second round of experiments is over.

There are a total of 100 kilns, and a total of 1,000 steel bars are placed, with an average of ten steel bars per kiln.

In order to avoid confusion, Li Mengxi prepared a hundred pieces of linen cloth, and wrote the kiln number on each linen cloth, starting from [Five-foot Kiln], [Six-foot Kiln], [Seven-foot Kiln], and then going backwards until [One Hundred and Zero Kiln].

Five feet], write them in order.

Then, take out the corresponding steel bars from the kiln and wrap them individually.

The classification process was of great importance and there was no room for sloppiness. Li Mengxi led the people to do the work in person and did not rely on other people's hands.

During the busy process, Li Mengxi discovered an interesting phenomenon. From the first kiln to the twelfth kiln, the kiln seemed cleaner, but the further back, the darker the kiln became. This showed that the kiln in front was too

Because it is small, there is not enough oxygen in the kiln, and the burning stops after a while, so there is no charcoal ash floating in the kiln room.

Going to the back, the kiln room is getting darker and darker, and looking at the steel bars taken out, the steel bars are also getting darker and darker.

At first, the black color on the steel bars could still be removed by my hands. Later, after fifty kilns, the black color on the steel bars could no longer come off. Even after spitting and holding my clothes hard, the black color could no longer come off.

Li Mengxi walked out of the kiln room holding the slightly heated steel bar. He looked at the steel bar again and again in the bright light. Looking at the black steel bar, he showed a happy smile.

You guessed it right, the earthen kiln can indeed be carburized.

There is a very embarrassing point in the heat treatment process. Originally, the carbon content of the steel made by steel pouring is very suitable, but the necessary heat treatment of the sword, such as the annealing and tempering stage, the sword needs to maintain a certain temperature and keep it warm for a period of time. This can

It will kill you. There is charcoal in carbon steel. If it is stored at high temperature for a long time, it is obvious that a large amount of charcoal will be lost in the outer layer of the sword. This will cause the outer layer of the sword to decarburize and become softer.

Seriously affects the strength of the blade and blade.

In view of this, it is best to carburize and supplement carbon.

However, here is the embarrassing thing. According to the ancient heat treatment conditions, there is no other good heating and heat preservation method except charcoal fire. Once the charcoal fire is burned, the sword still has to be decarburized.

There are two points to consider. One is to keep the sword warm for a long time, and the other is to prevent oxygen from taking effect and avoid decarburization. The only way to achieve both at the same time is to use the charcoal method.

When making charcoal, the entire kiln will be sealed in the second half of the process. At that time, in the sealed environment, the oxygen in the kiln will be consumed, creating an oxygen-deficient environment.

Moreover, the structure of the earth kiln itself determines that it can be kept warm for a long time. It is an anoxic environment and can be kept warm for a long time, so it is naturally suitable for heat treatment of swords.

Moreover, the earthen kiln has another benefit. During the process of the kiln, the charcoal will volatilize everywhere and fall on the sword, and a certain amount of charcoal will penetrate into the sword. This not only does not decarbonize the sword, but also infiltrates it.

Carbon, which greatly improves the quality of the sword.

After collecting all the steel bars, Li Mengxi took people to the blacksmith camp. There was a heavy iron clamping platform in the blacksmith camp.

One hundred steel sheets were placed on the spot. Next to the iron clamping platform, Li Mengxi held a thin wooden board in his hand. On the thin wooden board were several layers of white paper. If you look closely, you can see that there are fine grids drawn on the white paper.

There are also words.

This chapter is not over yet, please click on the next page to continue reading! From the first row down, the first row of the table is, [Five-foot kiln], [Six-foot kiln], [Seven-foot kiln]... going down in sequence,

It took several pages.

On the horizontal side are three options: [Broken or not], [Rebound after bending or not], and [Degree of bending].

There were idle craftsmen gathered around to watch, but Li Mengxi let them go and did not chase them away.

The test begins. First, take a ruler and draw a scale on each steel bar. Then, tie a hemp rope to the gap at both ends of each steel bar.

After all these preparations are completed.

The first set of tests consisted of ten steel bars in a five-foot kiln, from which three were randomly selected.

The knife maker picked up a steel bar, aligned the mark drawn on the steel bar with the middle of the iron clamping table and put it in. Then he pressed two heavy iron weights together. After they were fixed, the knife maker began to slowly pull the hemp rope.

(crossbow string).

Li Mengxi observed attentively, and he saw that the steel bar slowly began to bend under the slow pull of the knifemaker.

After not much bending, there was a bang and the steel bar broke.

The swordsman felt guilty and quickly raised his head to look at Li Mengxi and carefully explained, "I didn't even use any force..."

"It doesn't matter." Li Mengxi comforted, "Continue."

As he said that, Li Mengxi took a writing brush and put a check mark in the first row of the table, after [Five-Child Kiln] and [Break] in the vertical column.

For this first set of tests, Li Mengxi had some expectations. The kiln was too short and there was too little oxygen in it. The fire was extinguished within a short period of time after the kiln was sealed. This meant that the quenched steel bars were not tempered at all.

Another point is that all the steel bars are cast to have uniform specifications. Casting is indeed poor in strength.

After that, the test continued, and the three steel bars in the first group all broke without exception.

The test continued. For the six-foot kiln, three out of ten were selected for testing. The same was true for the seven-foot kiln, the same for the eight-foot kiln, and the same for the nine-foot kiln.

When I tested it downwards, the change was not obvious, and the steel all broke when I pulled it without exception.

This is not because there is a problem with the experiment designed by Li Mengxi, but rather that the experiment was designed extremely well. The length of the kiln body increased by a very small step one foot at a time. The range of changes was very delicate and the data was sufficient.

The changes are small and inconspicuous, but they do exist.

When it reaches kiln No. 20, the steel bar can draw a certain obvious arc during the bending process, and it is not so easy to break.

This is enough to show that as the kiln body becomes longer and the charcoal burning time in the kiln becomes longer, the temperature in the kiln gradually increases, which is reflected on the steel, that is, the degree of tempering of the steel gradually increases.

At this point in the experiment, Li Mengxi actually had an answer. He had determined that batch heat treatment could be achieved by controlling the kiln chamber space, thereby controlling the oxygen, then controlling the heating time, and then controlling the heating temperature.

Due to the steel material, the strength of the cast iron steel bars is really poor. As the tests continue, the steel bars gradually become more and more flexible, but when stretched to a certain extent, they will inevitably break.

Li Mengxi made some judgments about the performance of steel bars. The steel bars used as crossbow arms should be neither too hard nor too soft. Hardness and toughness conflict with each other. The higher the hardness, the lower the toughness; the higher the toughness, the lower the hardness.

If the hardness is too high, the steel bar will be too brittle and will break when pulled. If it is too soft, it will bend when pulled and have no strength. Even if it is soft, it will deform when pulled and cannot rebound.

After one hundred sets of tests, Li Mengxi recorded three hundred sets of data. Without exception, as many as three hundred steel bars tested were all broken.

Among them, Li Mengxi did not see any samples that could not rebound under tension and bending deformation. In other words, all the steel bars were too hard, but none had too strong toughness.

If hardness and toughness are compared to the positive and negative poles of the data, the goal is to find the tempering temperature that has both toughness and hardness. Then, in this earth kiln, the tempering temperatures are all at the "hardness" pole, that is to say

, half of the data is missing, the data is far from enough.

Looking at the broken steel bars everywhere and the large number of intact ones left, what should I do with these useless steel bars?

After thinking for a moment, Li Mengxi ordered, "Take these steel bars back and melt them."

After a pause, Li Mengxi added, "Melt it and make a hoe."

A question is, if there are more than 100,000 people working in the fields in spring, and each person has a hoe, will it be enough?

The answer is, not enough.

The yellow turban refugees, who were chased by the army, threw away their helmets and armor. They even threw away their life-saving knives and guns, and even their hoes were hard to find.
To be continued...