Literally speaking, heat treatment means heating the gemstone, but it is not that simple and rough.

Liu Tan thought about it carefully for a long time and felt that the heat treatment of gemstones might have something in common with blacksmithing.

So he directly asked someone to deliver the mined tourmaline, well, the worst quality one, to the blacksmith.

The blacksmith was terrified after getting the tourmaline. He had never seen this kind of stone before, but since it was favored by the king, it must be very precious. What if he broke it?

In response, Liu Tan said directly: "Let go and do it. If you do bad things, there will be no punishment, but if you do good things, there will be rewards."

The blacksmith was relieved now. Liu Tan always did what he said, and his credibility was still very secure in the hearts of his subordinates.

Then Liu Tan got a pile of rubble.

He stared blankly at the tourmalines that were about to crumble into slag, then glanced at the blacksmith kneeling below. After a long moment, he asked, "Is this... is the temperature too high?"

This shouldn't be the case. How high a temperature would it take to burn the stone into this state?

The blacksmith was trembling. When he heard Liu Tan's words, he felt his whole body go limp and he almost fell to the ground.

He trembled and said, "No... no, it was I... I accidentally broke the stone."

Liu Tan was puzzled. Smashed? How much strength did that take?

However, it was difficult to find the problem by asking one question at a time, so Liu Tan simply said, "Tell me the whole process again."

The blacksmith felt a little relieved when he saw that the King of the North did not seem to be very angry, but he still stuttered when he spoke.

He started out saying that everything was normal at first. They heated it up using the normal procedure for heating iron. However, the blacksmith didn't know the melting point of tourmaline, and Liu Tan didn't say to melt the stone, so when the initial heating didn't work, he moved on to the next step - forging.

When smelting iron, this step is used to chisel out the carbon in the pig iron. Otherwise, the pig iron will be too hard and brittle and will not be suitable for many places.

As a result, the chisel broke, and the stone that did not melt under high temperature was directly turned into broken stones after a few strokes. The blacksmith was so scared that his legs went weak.

Liu Tan: ...

He knew he had to watch it!

Unfortunately, Huo Guang strictly forbade him to enter any industrial production area, for fear that he would get excited and do it himself again.

Liu Tan had no choice but to say, "No need for forging, just... forget it. I can't explain it clearly. Write down the smelting steps, including smelting bronze, and then I will choose one for you to do."

The blacksmith looked innocent, as he couldn't read.

Liu Tan had no choice but to let the blacksmith dictate, and then Miao Rui wrote it down. At the same time, he was thinking to himself that if he continued like this, would he be able to start large-scale literacy campaign soon?

No, no, no, you can't take too big a step. If you take too big a step, your end may be the same as Yang Guang.

Oh, he is better than Yang Guang. After all, he has Huo Guang by his side and his biological father above him. If he really does something wrong, someone will definitely stop him.

After the blacksmith finished describing all the steps, Miao Rui reworded it in more elegant terms before showing it to Liu Tan.

This time, Liu Tan had a systematic understanding of the smelting steps. He skipped all the parts that required shaping and forging, and focused on heating.

The heat treatment these days is actually not very perfect. However, this imperfect heat treatment gave Liu Tan inspiration, and made him gradually remember that he had come into contact with these things when he was playing with models.

Then he wrote down the order of heat treatment for tourmaline according to this blacksmithing procedure.

The first step is normalizing, which is a preliminary heat treatment process. The heating temperature is not particularly high. According to the mark on the thermometer, it is about 30 to 50 degrees. Then it is kept warm and cooled.

Then quenching and tempering are carried out. These two steps are basically the same as the current iron smelting. Then the tempering process is deleted. Oh, there is no tempering these days, which saves trouble.

Finally, flame heating and surface quenching are carried out. Liu Tan was a little hesitant when writing about this step. This is indeed necessary for steelmaking, but he is not sure whether it is necessary to heat tourmaline.

After Liu Tan finished writing, he looked at the process and fell into deep thought. He always felt that... this process seemed... to be very useful in smelting.

Because he added a few more steps based on the original smelting process, the only thing that was not clearly written was the intermediate forging process.

However, the forging process is neither easy nor difficult. If the conditions are not met, if you want to get steel, you can only forge it repeatedly to constantly remove impurities in the steel, make the composition uniform, make the structure denser, and refine the grains.

After Liu Tan added the step of forging on another piece of paper, he sat there in a daze for a moment.

Is he... coming up with the forging method for hundred-fold steel again?

This feeling is... quite familiar.

Whenever he wants to do something, he always produces some by-products. This kind of thing hasn't happened for a long time, and he misses it.

Liu Tan had an idea. If he had the hundred-refined steel, he could add something to the gifts he would give to Liu Che and Liu Ju when he returned.

He handed the paper to the blacksmith and said, "Get these two things out quickly, they will be of great use to me!"

The blacksmith was stunned when he heard this. Wasn't he just talking about stones? How come there was another thing?

However, since Liu Tan gave the order, he had to do it accordingly.

In fact, no matter what it is, the most difficult thing is to sort out the production process. If you have the production process and follow that process, it will be easier.

Especially tourmaline. The original tourmaline, which was not of particularly good quality, became transparent and beautiful after processing. In addition, it is colorful in itself. Even someone like Huo Guang, who was used to seeing good things around Liu Che, couldn't help but be attracted to it.

Among the many colors of tourmaline, watermelon tourmaline is the most popular. Watermelon tourmaline is a tourmaline with multiple colors, usually alternating between green and red, hence the name watermelon tourmaline. However, watermelons didn't exist back then, so Liu Tan didn't know what to call this tourmaline. He simply said, "Let's ask my father or mother to give it a name later."

He thought these two would be happy to give him a name.

With such processing methods, tourmaline becomes very presentable, but it cannot be given as a raw stone all at once, it still needs to be processed.

Liu Tan's idea was to inlay a whole set of jewelry with tourmaline. Even though the empress had set jewelry that she could not wear on New Year's Day, there were frequent banquets during that period, so she would always have the opportunity to wear it.

Liu Tan spent a lot of time choosing necklaces, bracelets, hairpins and earrings. He was not good at color matching, so he simply chose pure red. After all, it was New Year's Day, so he wanted a festive atmosphere, and cold colors were not suitable for winter.

As for the style, he didn't care. He was not particularly knowledgeable about jewelry. Moreover, the styles that were popular in later generations might not be liked by people in this era. It was better to be cautious on a solemn occasion like Zhengdan.

Then Liu Tan selected the largest tourmaline. This tourmaline can be said to be the largest one produced in the entire mining area. It is about three feet high and one foot wide. Even in later generations, it is a very rare size.

A tourmaline of this size is a rare treasure in itself. Liu Tan did not process it further, but just asked someone to make a base to place it on, and gave it to Liu Che.

Then he selected some other tourmalines of good quality for inlay, which were used to inlay the scabbard of the sword.

Bailian Steel now has its initial product, but Liu Tan is not particularly excited about it.

Because this method of steelmaking consumes too much manpower and material resources, although it is very sharp, it is destined to be a luxury in the hands of the nobles. If you want to promote it and equip all soldiers with such weapons, it is basically impossible unless Liu Tan can find a more time-saving and labor-saving method, or the population is large enough to supply production.

Not to mention the hundred-fold refined steel, even the horse harness has not been widely promoted until now, and has only become popular among the nobles. What Liu Tan worried about before, that it would be stolen by the Huns, is basically impossible to happen. Even if the Huns got the production method, with the Huns' financial resources and their poor smelting skills, it is even more impossible for them to equip all their cavalry with new horse harnesses.

However, after a while, Liu Tan might be able to equip the army of the Northern Border Kingdom, or the cavalry of those small towns on the border, with new horse harnesses.

After all, he has a home in the mine. Although these are all his, and the treasury of the Northern Kingdom is needed to equip the horse harness, he still pays taxes!

This is also the point that makes Liu Tan most satisfied with the Han Dynasty at present. No matter who you are, you have to pay taxes. Of course, nobles and wealthy families have many ways to avoid taxes, but this is unavoidable.

Anyway, as long as he doesn't evade taxes, when the treasury is full, he will have money to do many things.

Thinking about it this way, it seems that making a fortune by relying on metaphysics is not a bad idea. Liu Tan's original plan was to make the living standards of the people in the Northern Border Kingdom reach the average level of the Han Dynasty in ten years.

To be honest, Liu Tan didn't even dare to tell anyone about this goal. If he did, even Huo Guang would probably think he was daydreaming.

Unexpectedly, with the help of metaphysics, he was able to shorten the ten-year time a lot. If he continued like this, maybe five years would be enough. Even if there were mines in other places, five years would not be necessary.

Liu Tan was thinking about all this while selecting tourmalines. When he picked out a dark green tourmaline, he subconsciously asked someone to make a pair of wolf head earrings with it, and the eyes were inlaid with red tourmaline.

To be honest, when he gave this order, he was still thinking about the great cause of revitalizing the economy of the Northern Territory, and he said it almost subconsciously.

When everything was ready and placed in front of him, Liu Tan was stunned when he looked at the pair of wolf head earrings.

He hesitated for a long time, but finally ordered someone to change one of the wolf head earrings into a wolf head stud earring. After all, based on his observation, Lu Xuan seemed to have a hole in his left ear only.

As for whether it would be appropriate to give the other person earrings, he thought about it and felt that it was better than giving a ring or a bracelet - well, these days, bracelets are actually a very common accessory for men.

After these tourmaline jewelry were made, the honeycomb coal to be taken to Chang'an was also almost ready. Since it was just for display, there was no need to bring too much in the first batch, and people could just send it over later.

It's time for Liu Tan to take his men on the road.

This time, except for Jiang Chong and Sang Qian who stayed behind, everyone else went back with Liu Tan. Everyone looked very excited. Although they had only been in the Northern Border for a short time, they had done a lot of things. Moreover, Liu Tan was generous and rewarded everyone with a lot of things, including tourmaline and coal, the specialties of the Northern Border, which they could take back and show off.

Only Jiang Chong and Sang Qian were left behind. Compared to Jiang Chong's excitement about being the master of the house, Sang Qian looked a little resentful.

He also wanted to go back to Beijing, and he even thought that after returning to Beijing this time, he would never come back even if he had to throw a tantrum in front of his father!

Unexpectedly, he was not included in the quota to return to Beijing, and he still had to do hard labor here!

Even if he didn't have to work under Liu Tan and could take charge on his own, what would happen? He was just an agent. When the talent sent by Chang'an arrived, wouldn't he still have to step down and let the talented people come?

Sang Qian nearly cried when he thought of this, but to prevent Liu Tan from noticing, he wiped his tears and said, "Your Highness, I cannot bear to leave you."

Liu Tan shuddered at his embarrassing words and stopped making hypocritical farewells. He turned around and got into the car. He had better leave quickly.

Even if one is in Liu Tan's position and has everything he needs, traveling in winter is still very uncomfortable.

When he finally saw the city wall of Chang'an, he finally breathed a sigh of relief, turned around, rode his little white horse, and walked towards Prince Liu Ju who came out of the city to greet him.

Everyone was very surprised that Liu Ju went out of the city in person to welcome the King of the Northern Territory. He had gone out of the city to welcome Liu Tan before because Liu Tan was an envoy. Of course, the most important thing was that the person traveling with Liu Tan at that time was Kunmi of Xiao Wusun.

This is the one who is truly worthy of Liu Ju’s personal deployment.

Now... when the princes return to the capital, is it necessary for the crown prince to welcome them in person?

But Liu Ju didn't care what others thought, he just applied to Emperor Wu of Han, and Emperor Wu of Han agreed!

Liu Tan rode over and said, "It's cold, why did His Highness come here in person?"

Liu Ju looked at Liu Tan and found that although they had only not seen each other for a few months, his younger brother seemed to be more mature than before, with clearer facial features and his eyes wide open with surprise. Well, he was still so handsome and cute.

Liu Ju resisted the urge to rub his brother's head and said with a smile, "It's not that cold. It's just that I haven't left the palace for a long time, so I'd like to stretch my legs. Um, are you alone, brother?"

Liu Tan said, "Huh? No, there will also be Huo Guang and others."

Liu Ju shook his head: "No, I mean... didn't you meet little Kunmi on the road?"

Liu Tan: "Ah?"