For the fortress, although the use rate of cement and bricks is quite high, but their price is limited, even if it is reduced, it is only about one and a half percent, which is not a big number for an investment of more than 1,000 fortresses.

In fact, the key to reducing the price of the fortress is in steel, the total amount of steel used is not as large as bricks and cement, but because the overall price is the highest among all the materials in the fortress.

This is still in the interior, with bamboo instead of steel bars, the formation of a reinforced concrete structure, otherwise, all the use of reinforced concrete structure, the whole cost will be unbearable, just the aspect of steel, may be as high as thousands of times.

In order to reduce the cost, Zhao Xin designed to use bamboo to replace the steel bar inside, but in the outer layer, in order to ensure the strength of this fortress, real steel is used.

The outside is the most attacked, after all, the reinforced concrete is not a King Kong indestructible body, continuous attack, there will also be some small damage, these damage for the real reinforced concrete results, the damage is relatively small, but the big bamboo can not bear.

Because, as long as there is a little gap, so that the water can pass through the gaps in the outer wall, into the interior, the bamboo is very strong in strength and flexibility, but can not withstand the water, as long as it is wet, it is easy to rot and deteriorate, and then can not play the role of support, that is the real tofu dregs.

In fact, water and humidity have a huge impact on anything, even real reinforced concrete structures, no exception, in a more humid and cold environment, the action of water and microorganisms will make the steel bar rust, even stainless steel is no exception, in the case of continuous rust, the steel bar will be affected, the strength will be weakened, and even there will be problems.

Iron is an important weapon, in many fields such as military and people's livelihood, have a considerable role, the Iron Age, is also a sign of civilization progress, iron is much higher than bronze.

Under the technical level of the Song Dynasty, the development of cold wrought iron and quenching technology, the iron performance of the Northern Song Dynasty was very high, and the Buren armor was completely destroyed under the premise of the same weight, and the heavy armor of the Liao State and the heavy armor of the Western Xia, and even the Western Xia and the Liao State, spared no effort to get this smelting method.

Iron in the Northern Song Dynasty has begun to be popularized, and farmers have also begun to use tools with a certain amount of iron, for example, at the tip of the wooden shovel, add a layer of iron to increase its performance, and some families with slightly better conditions have even begun to use pure iron, and even steel tools, there are historical records that the iron output of the Northern Song Dynasty is even higher than the end of the Qing Dynasty, and even when the Hanyang Iron Works began to produce iron, 80,000 tons of iron and 40,000 tons of steel, the total amount has also been exceeded.

In this era of the Northern Song Dynasty, the price of steel was very high, and the price of iron reached 80 Wen per catty, which was much higher than the price of later generations, not to mention steel.

For example, Sun Ji is holding the Falling Moon Bow in his hand, when he has not been modified, the price of the bow body and bowstring alone is as high as 800 yuan, and the bow body is only a few catties, and the bowstring is even less, so to speak, the price is more than gold.

It is completely different from later generations, not to mention iron in later generations, even if it is steel, the price is not expensive, each catty is about one or two yuan, that is, less than half a catty of rice, but in this era, it is as high as 10 catties of rice, and the price of steel and fine iron is even more than one stone of rice, and the price of more high-quality products is higher.

The bowstring of the Falling Moon Bow is made of meteoric iron, and more precious materials are added to increase his elasticity and flexibility, the price of such a bowstring is more than 10 times that of gold, especially after strengthening other devices and increasing the length of the bowstring, the price is even higher, and the price of a single bowstring is more than 1500 guan.

The price of the bowstring, of course, is not the norm, and even said that such an expensive bowstring will not be common in the entire Northern Song Dynasty, at most three or five, but it also shows the importance of high-quality steel from one side.

In later generations, steel became more popular, and even iron, like steel, has become the most basic material, to enhance the strength of the Northern Song Dynasty, steel is also a place that must be changed, in fact, with the formula and production method, from iron to steel is not so difficult.

The reason why steel in this era is so expensive, even compared to iron, is 10 times, 20 times, especially some special performance, suitable for the production of magic weapons of steel, even more so, 1000 a bowstring, and how much it can weigh, half a catty to less, that means that the price of this bowstring may be more than 2000 per catty.

This is a terrible price, according to the price of 700 wen one stone of rice, 2000 guan, representing the 3000 stone.

The reason why this situation occurs is because of the development of one or two thousand years, in the Warring States period, it gradually entered the Iron Age, and the year before last, the development of iron reached a certain level, and the average blacksmith can skillfully make pig iron and wrought iron.

But from iron to steel, it is not so easy, the reason is very simple, even in later generations, alloy steel is endless, all kinds of stronger, more unique performance of alloy steel, the generation of second, and even some are the cornerstone of industrial development.

In the absence of a chemical system, there is no intuitive understanding of steel production, and even steel is an alloy of iron and carbon, and the amount of carbon in the steel alloy is determined by some indicators of steel, not to mention other trace elements added.

In the absence of a systematic method, steelmaking still uses the most primitive method, under the premise of constantly building and beating, and gradually cleans out the excess carbon in the steel, so that the carbon reaches a certain level.

There is no perfect method, even for an experienced blacksmith, it will take at least ten times to produce steel once, and worse, maybe hundreds or thousands of times.

For example, the hemp steel that appeared in the Han and Tang dynasties once made the Tang knife crown the whole world, and it was also the fundamental force of the Tang Dynasty, but because of the loss of the secret recipe, it disappeared in the historical corridor, on the one hand, because of the confidentiality relationship, on the other hand, the probability is too low.

If it is said that the production of hemp steel has mastered all the means of making hemp steel, and every time it can perfectly present the smelting of hemp steel, there will be no such problem at all, even in the peak era of hemp steel, the most outstanding craftsmen may be able to succeed once five or six times.

Not to mention, when hemp steel is lost, smelting steel is an unavoidable thing, occasionally successful, and even produced more than imagined fine iron, some magic weapons were born in this way, but these processes are not replicable at all, and even the entire feudal dynasty does not have that kind of steel, with repeatability.

As a result, it is possible to give birth to rare treasures, just like ancient ceramics, some special circumstances, kiln changes to produce fine ceramics, and even later generations can not reproduce, later generations are more developed, more perfect quality system, but ceramics are a lot more mediocre.

It is not that the technical level of later generations is not as high as that of feudal society, but because a kiln change and a rare treasure are caused after countless failures and losses.

From this point of view, steelmaking does not know this, with the most primitive smelting method, the cost of labor, the cost of various fuels is huge, because of the relationship between a few and uncertainty, the real steel, the quantity is not only very scarce, the price is also very expensive.

In the ordinary fortress, more iron, a little steel, and even when building the structure, it is on the outside, but these are the root of the cost of the fortress, even if a large number of bamboo is used as a substitute, the outermost side, at least four or five tons of iron and about 500 kilograms of steel will be used.

The specific gravity of steel is very large, generally about 7.8, that is to say, a cubic meter of steel, up to 7.8 tons, that is to say, the entire outer layer, not even a cubic meter of steel, you know, the outer side has a circumference of dozens of meters, a height of dozens of meters, calculated, the area is not a lot, so the steel bars and iron bars used are very fine.

Even so, the price is extremely high, latte 80 per catty, the price of a ton is about 160 guan, steel is even more expensive, 1000 jin of refined iron, his price alone is more than 800 guan, that is to say, the combination of the two, almost occupies more than half of the price of the fortress, more than 1600 guan.

Cement and bricks, because of the simplicity of the production process, there are not so many imaginary heads, even if it is to improve the process, where is the price of itself, the reduction is limited, but if the price of iron can be reduced to less than 10 Wen, the price of steel can be reduced to about 30 Wen, and the reduction can be much more.

A ton of steel is only 20 guan, and 500 kilograms of refined iron is only 30 guan, what does it mean, the largest expenditure close to 1500 guan, maybe only 200 guan can solve the problem, saving about eighty or ninety percent.

In fact, the price of steel in later generations was not much more expensive than iron, and in some cases it was even cheaper.

General iron, or iron ore, there will be impurities in it, and these impurities are removed, which is pure iron, that is, wrought iron, and then add various carbon and trace elements to finally form a relatively strong alloy.

However, under a certain premise, for more general steel, the amount of impurities can be controlled, one-time molding, different from iron after firing mature iron, and then add carbon, steelmaking furnace with excellent performance, directly add iron ore, and some additional materials to add it, directly out is steel, accurate product control and formula, so that he can be molded at one time, and forged into a variety of products, compared to the blacksmiths with the method of beating, I don't know how much easier, reducing the price of ninety percent, it is also a normal thing.