"The boiler can be made of iron, but the heating pipe is not good, and it is not impossible to use iron, but it is necessary to electroplate some other metals on the iron pipe to prevent rust, the emperor also knows that when this iron is preserved, it must be in a relatively dry place, if the climate is humid, it is easy to rust." Zhang Nan said.

"In the same way, the heating pipe is the same reason, the heating pipe here is flowing with water, and it is easy to say when you use it, but you can't burn the heating all year round, so when you don't use it, if the heating pipe is rusty, it will lead to rupture after a long time, and it will be a lot of money to repair it at that time."

Comrade Li Er also nodded noncommittally after hearing this, although he didn't know what this electroplating was.

"Then there's no solution?" Comrade Li Er asked.

"Of course there is, generally speaking, in addition to iron pipes, the most used heating pipes are steel pipes, as long as the emperor is willing to take out our Datang steel to make heating pipes, the minister is absolutely nothing, but also for the people of Datang thank you to you." However, if you want to lay heating pipes in all major state capitals across the country, I think the amount of steel used should not be less. ”

Zhang Nan said this, but also grasped that it is impossible for Comrade Li Er to use Datang's steel to build this thing, after all, basic industry and output are complementary to each other, Zhang Nan took out the heating is already epoch-making, and now Comrade Li Er wants to apply this epoch-making product to the whole country, which will have to pay a very heavy price.

Although with the shaft furnace ironmaking method, Datang's steel output has made a qualitative leap compared with before, but it still can't catch up with Datang's development speed.

In addition to the necessary weapons and equipment, most of Datang's infrastructure is to use a large amount of steel, the first of which is the track used by the steam train.

Comrade Li Er has realized the importance of steam trains, and with the transportation capacity of steam trains, Datang's productivity has increased by more than one grade. Therefore, most of Datang's steel is used in the laying of railways, and even so, it is still a drop in the bucket and not enough at all.

Originally, Li Er also wanted to build a railway station outside Chang'an City to connect other state capitals, but he didn't know that Datang's annual steel output was not enough for a state capital, Huohuo, so most of the current railways were paved into the mountains to ensure industrial use.

Even Comrade Li Er couldn't even build a tourist railway, let alone the steel to build heating.

"Forget it, this steel is in short supply, let alone repairing the heating, my new army equipment is almost out of production." Comrade Li Er was also very distressed.

In the past, when Datang could not refine steel, Comrade Li Er was distressed, but now that Datang can practice steel, Comrade Li Er is even more distressed.

But now it is painful and happy, after all, the steel that has been practiced has not been wasted, but every catty of steel has been used on the blade.

In fact, there is a fundamental difference between steelmaking and ironmaking, just like making a serving of fried rice, steelmaking belongs to the process of scrambling rice and eggs together, and ironmaking is the process of steaming rice.

Ironmaking only needs to use iron ore and coke to smelt with a shaft furnace, and the raw material for steelmaking is pig iron.

To put it simply, the pig iron is heated to a liquid or semi-liquid state, and then blasted into the iron ore powder to oxidize the silicon, manganese, carbon and other substances in it, and the carbon content is reduced and then reduced until it reaches the steel standard.

The 100-for-steel is the reprocessing of the fried steel, and most of the rails in Datang are made of 100-smelted steel.

The efficiency of this production method is not very high, even if Datang now has enough iron production, the output of steel still cannot go up.

It's not that Zhang Nan doesn't want to use modern steelmaking methods to help Datang increase steel production, but modern steelmaking methods are really not suitable for Datang.

For example, arc steelmaking, first of all, this electricity can not be solved, not to mention the technical problem, although the efficiency of desulfurization and dephosphorization of arc steelmaking is very high, but helplessly, this needs to be started with electricity, Datang still can't do it.

After all, the current Datang has not yet entered the electric age, and the current Datang technology is in a chaotic era, with both traditional farming assistance and the steam era at the beginning, and it can barely reach the shadow of the electric age.

But in general, Datang has not even entered the steam era completely.

And Zhang Nan also has a deep understanding of what it is, the step can't be too big, and it's easy to pull the egg if you step too big.

The current Datang is being pulled to the egg, it seems to be developing wildly, but it has not expanded its width, which is also the most headache for Zhang Nan.

"Alright, let's do this for now, as for this heating, hey, wait until my railroad is almost paved." Comrade Li Er wanted a lot of steel, but he was helpless, and he couldn't rush this thing out.

"Then the minister retired?" When Zhang Nan saw that Comrade Li Er was actually relieved, he immediately wanted to slip away.

"Don't worry, it's not over yet." Li Er saw that Zhang Nan wanted to slip away, and immediately stopped Zhang Nan.

"Your Majesty, what else do you have to do?" Zhang Nan also said with a wry smile.

"The matter of going to Tubo remains the same, as for what you said about slowly laying a foundation in Tubo through this woman, I think it's okay, but Li Su wants to marry her, it's impossible, I locked up Li Su this time, but also to remind him to remember his identity, and what he went to Tubo for, you go to Li Su to explain this matter to him when the time comes."

Comrade Li Er also sighed.

Lao Li couldn't pull this face, after all, he was just glaring at Li Su's crazy beard blowing just now, and now he wants to let him explain this matter clearly to Li Su, it is absolutely impossible.

So this errand work can only be handed over to Zhang Nan to do.

"I understand." Zhang Nan also arched his hand.

After speaking, Comrade Li Er waved his hand and signaled that Zhang Nan could go down, and Zhang Nan also saluted and retired.

"Hey, I hope Su'er can understand my good intentions, this should be the most important thing about national affairs." Li Er also shook his head helplessly. Originally, Comrade Li Er was still very angry about this matter, after all, Li Er's task to Li Su was to go to Tubo to preach, not to let Li Su find a Tubo woman to fall in love, but helplessly, Comrade Li Er really didn't have any good candidates, and Li Su did a good job in the early stage, and it was impossible to temporarily replace people.

Therefore, the current Lao Li can only hope that Li Su can be sensible and focus on national affairs first.