Chapter 244: Pig Iron, Wrought Iron, and Steel (Please vote and subscribe)
After designing the structure of the star-shaped blast furnace, Luo Chong assigned a team to start construction. The huge blast furnace was built in the smelting area in the city. The area of the blast furnace alone occupied nearly 30 square meters, and the height of the main furnace was very high.
The size of the main furnace was wide at the bottom and narrow at the top. It was built on a blue brick platform 1.2 meters high. The bottom diameter was 1.5 meters, and it became thinner as it went up. Not counting the height of the base platform, the furnace alone was 5 meters high. From top to bottom, it was divided into several sections, the furnace throat, the furnace body, the furnace waist, the furnace belly, and the furnace cylinder.
The furnace throat is also the feed port. The feed of the entire furnace is still added from the top of the furnace. The temperature of this place is very low, only about 200 degrees; the furnace body occupies the general height of the entire furnace. This section is about 2.6 meters long, and the temperature also increases from 400 degrees to 800 degrees. The temperature increases as you go down.
Further down is the furnace waist. This section is very short, only more than half a meter, but it is also a node of the entire furnace, because from the furnace waist downwards, the width of the furnace begins to increase, and the temperature of this section also reaches 900 to 1300 degrees.
Below is the core part of the entire furnace, the furnace belly. The volume of the furnace belly is the largest, about 1.6 meters wide, slightly wider than the base below. The height of this section is about 1.2 meters. It is also the hottest part of the entire furnace. The temperature is expected to reach about 1700 degrees, and the furnace belly is also the place where it is connected to the tuyere of the heat storage chamber.
The connection method is also a channel built directly with refractory bricks. Although it looks a bit low compared to the height of the entire furnace, there is no need to worry about the molten iron inside flowing out of the tuyere, because the furnace belly is the hottest in the entire furnace, which is also the place where the iron ore reacts. Before this, the materials thrown into the furnace are still in solid form.
When they react completely and the iron ore melts into molten iron, the molten iron will automatically drop to the furnace where the molten iron is stored because of the heavy weight of the metal, while the slag and charcoal will become liquid slag floating on the surface of the molten iron and enter the furnace together.
Finally, when it is time to tap the iron, the finished product is discharged from the two openings on both sides of the furnace. The lowest opening on the left flows out the molten iron, and the slightly higher opening on the right discharges the liquid slag. In this way, what is finally obtained is molten iron.
The strength of pig iron and steel cannot be compared, but it also has its own characteristics. Pig iron is brittle and, like high-tin bronze, is easy to break, but pig iron is very suitable for casting things, such as iron pots, iron basins and other utensils.
Although the quality of the iron pot made in this way is not very good and it is easy to break, it is suitable for mass production. If the iron pot is made of softer wrought iron, only one can be knocked out, and the difficulty and time of production are not at the same level.
The production of wrought iron is not difficult. The earliest method was to repeatedly beat the pig iron to obtain it. However, since the invention of the steel-making method in the Western Han Dynasty,
wrought iron has entered the stage of large-scale production. The steel-making method is also very tricky. Its process is to add high-quality iron ore powder to the molten iron, and then stir it continuously to allow more carbon to penetrate into the molten iron, so as to obtain steel with a higher carbon content.
However, there is no specific ratio for how much iron ore powder to be added to turn it into molten steel. If you add too much by mistake, the molten iron will become wrought iron instead of steel.
In the Western Han Dynasty, when humans used the steel-making method to produce steel, they often had an experienced furnace head to visually judge whether it had become steel by the color of the molten iron. This was entirely based on experience and there was no basis at all.
Although this method is available, there is still a high scrap rate, but this scrap steel is better than pig iron, that is, wrought iron. After it is produced, there is no need to worry about not being able to sell it. Overall, the steel-making method is a matter of luck. It is completely unreliable to use it to produce steel, but it is very suitable for producing wrought iron.
Compared with pig iron, the performance of wrought iron lies in its ductility, that is, it is soft enough. This may not be easy to understand, so let's put it another way.
For example, use pig iron and wrought iron to make an iron pot, and then use a hammer to hit the bottom of the two pots. The pig iron pot will be directly smashed into a hole, but the wrought iron one, you can only smash it into shape until it is flattened, but it will not break, that is, it is very tough.
Imagine if these two kinds of iron are used to make swords, the pig iron one is likely to be cut off when fighting with the enemy in battle, but the wrought iron weapon may be bent, but it will not break, so it can barely continue to be used, at least it can save a life. If the weapon is gone on the battlefield, it is no different from giving away heads.
Later, when steel was available, the knife makers began to use wrought iron to make the blade, and then wrapped the blade with steel. After forging, such weapons could have good toughness and sharpness, and would not break easily. The saying "good steel should be used on the blade" comes from this.
In addition, in the evolution of steel manufacturing technology, it was not until the emergence of the "steel pouring method" in the early Sui and Tang dynasties that the production of steel stabilized from the lucky mode, and people had a stable way to obtain steel. In this steel pouring method, a large amount of wrought iron was used.
The production process of steel is nothing more than letting the molten iron get the right amount of carbon to transform into steel. When the steel frying method was very unstable, someone thought of changing an additive and directly replaced the iron ore powder with wrought iron.
As mentioned earlier, wrought iron is actually scrap steel with excessive carbon content. Then, wrought iron is directly added to the pig iron molten iron, so that the pig iron can obtain a certain amount of carbon from the wrought iron. After the wrought iron is fused with the pig iron, its own carbon content is evenly distributed to part of the pig iron.
In this way, pig iron with carbonization becomes steel, and wrought iron with decarbonization also becomes steel. The two phases merge, and finally all you get is steel. It must be said that the person who came up with this idea is a genius.
Although the pouring steel method still does not give a specific addition ratio, it is easier to infer. Even if a one-to-one ratio is used, steel can definitely be produced. It's just that the quality of the steel is different, but it's also steel, and this must be acknowledged.
Another point to note is that when using the pouring steel method, because solid wrought iron must be melted into the molten pig iron, you must not directly add large pieces of wrought iron ingots. The best way is to first smash the wrought iron into thin iron sheets, and then evenly put it into the molten pig iron, so that it can melt quickly and merge with the pig iron.
In this regard, the Ming Dynasty was the best. At that time, most craftsmen directly processed wrought iron into iron wire, and then used it as the wrought iron raw material for the pouring steel method. In this way, the wrought iron melted more evenly and faster. The quality of steel in the Ming Dynasty was good, so they could invent better firearms, which had a lot to do with mastering better quality materials.
(End of this chapter)
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