As for the greenhouse on the other side, it is used to wash coal.

Mainly through the impact of water flow, the raw coal with different specific gravity is separated into different grades, and dust and waste rock are removed to reduce the ash and sulfur content.

However, the refined coal obtained in this way is not directly applied, but sent to the earthen kiln behind the greenhouse for smoldering.

I saw that on the ground were rows of grave-like earthen kilns, and in the chimneys made of bricks, yellow-brown smoke was rising unhurriedly.

The smoke was so choking that it made people cry and cough from afar.

Secretary Ma immediately put on a mask and goggles for his son. Then she and the guards also protected themselves, but Wang Yu was stunned.

Zhao Hao asked the guards to give him a set, Wang Yu followed his example and put it on, and suddenly felt that his breathing was much smoother, and his eyes were no longer tearful. I couldn't help but admire it again...... He didn't like to come to the steel mill very much, largely because the smoke was too smoky.

I didn't expect Zhao Gongzi to have a way to deal with it.

Uncle Wang, who was wearing a mask, could finally continue to introduce to Zhao Gongzi that this was making coke - relying on the heat of bituminous coal burning in the kiln itself, heating the coal layer by layer, and after eight to ten days of smoldering, the coke matured. Then inject water to extinguish the coke, remove the ash in the cold furnace, and the unburned part is coke.

Although in Zhao Hao's view, this method is not only time-consuming and has a low coking rate, but also the most fatal flaw is that the ash content is too high, which greatly reduces the effectiveness of coke. However, before 01 explored a practical coke oven, this was already the world's leading level.

It would take more than 150 years for Europe to learn how to make steel from coke.

~~

Today, I couldn't wait for the coke to come out of the kiln, but Zhao Hao was still next to the iron-making furnace and saw a pile of tarnished and grayish fuel...... That's the coke that was made before.

The inner wall of the cylindrical iron-making furnace, which was more than a foot thick and mixed with salt, was fixed on the outside by a circle of solid logs, and then the whole furnace was tightly clamped with wrought iron rings like hoop barrels.

Wang Yu told Zhao Hao that to build such a furnace, it would take a few months to say less, and he could not be rash and greedy. Otherwise, once cracks appear in the salt mud, it will be wasted, and it may also cause danger.

Such an iron-making furnace can hold more than 2,000 catties of iron ore. Before ignition, a layer of coke, then a mixture of mineral sand and pulverized coal is spread in the furnace, and after it is spread layer by layer, it is ignited from the bottom and the refining begins.

Next to the iron-making furnace, there is also a huge blower, and at each end there are two men wearing calf-nosed robes, pushing and pulling rhythmically to supply air to the iron-making furnace.

The iron-making master introduced to Zhao Hao that after the ore in it is melted into molten iron, it will flow out of the waist hole of the iron-making furnace. This hole is plugged with mud beforehand. Every hour during the day, the mud plug is pierced and the molten iron flows out.

After the molten iron is cleaned, immediately use a fork to pull the mud, plug the hole again, and then continue to blast and smelt, wait for an hour and then open the hole to release the molten iron.

This method does not seem to be as elaborate as the crucible method. However, in the crucible method, the ore is not in contact with the coke, which makes the coke only play the role of fuel, but does not play its role as a carburizer, reducing agent and material column.

On the contrary, this method of direct mixing and calcination can give full play to the four major functions of coke, and the quality of the steel is naturally higher.

~~

Zhao Hao stood far away, waiting for the next opening in a place where the blazing fire could not be burned.

Fortunately, although only half of the iron-making furnaces in Wangji Steel Mill are working, there are as many as ten. In a short time, a hole was opened in a furnace.

Although Zhao Hao was far away, he could also feel the scorching heat contained in the fiery red molten iron. He watched the molten iron for a moment, and it flowed into a square pond next to it along the stone diversion trough.

Wang Yu told Zhao Gongzi that the molten iron that flowed out was pig iron. If you want to use pig iron for casting, you can inject it into the mold and cool it down. But this kind of pig iron ware is too poor in quality and worthless, and Wang Ji has never disdained to make it.

And they will smelt the pig iron into mature iron in that pond.

The pond is made in the same way as the iron-making furnace, but the height is only one and a half feet. A slightly higher brick platform was built with bricks next to it, and the ironsmith and apprentice all stood on the platform to operate it, so as not to overflow the molten iron in this wave.

When the molten iron flows into the pond, the ironmaker quickly sprinkles the prepared fine mud powder evenly on the surface of the molten iron.

"Stir-fry!"

After the master's order, several apprentices violently stirred up with willow sticks and fried the pig iron to mature iron. The willow stick will burn off two or three inches every time it is fried, and it will have to be replaced with a new one when it is fried again.

This is the well-known 'steel frying method', which can oxidize the silicon, manganese and carbon in pig iron, and reduce the carbon content to the category of steel or wrought iron. If the temperature can be two or three hundred degrees higher, the time to witness the miracle will come...... Unfortunately, it can't be done yet.

'Latte fried as a dish, it's really worthy of its name. Zhao Gongzi couldn't help but secretly admire.

He knew that according to this method, most of the fried products were actually steel, and it was low-carbon steel. But in the eyes of the craftsmen at this time, this step can only be called wrought iron.

It is the difference in definitions that leads to this divergence.

In Zhao Hao's concept, pig iron, steel, and wrought iron are all a kind of iron-carbon alloy. Among them, the carbon content of more than 2.11% is pig iron, and less than 0.02% is wrought iron. In between is steel. Therefore, steel can also be divided into high-carbon steel, medium-carbon steel and low-carbon steel according to different carbon content...... Anyway, as long as the carbon content is between pig iron and wrought iron, it is all steel.

But the craftsmen of the Ming Dynasty will definitely not agree with Zhao Gongzi's hasty classification.

Yes, 'steel' is absolutely sacred in the eyes of craftsmen in this era, and only a small part of steel with few impurities and high hardness will be given the title of 'steel' and used on the blade. But anything that has not been tempered, whether you have low-carbon steel, medium-carbon steel, or even high-carbon steel, is all classified as wrought iron......

Therefore, in Zhao Hao's First Five-Year Plan, it is not an easy goal to require an annual output of one ton of tool steel.

~~

Even if it is a large iron smelter like Wang Ji, more than ninety percent of the products are 'wrought iron' products...... Some were cast into various tools, weapons, and armor. Some of them are directly divided into squares in the pond, and after cooling, they are taken out and hammered into round pieces, and they are directly sold.

The 01 Institute purchased a large number of wrought iron billets produced by Wang Ji, and the quality was naturally very good, but it was still far from enough to make guns and cannons. However, it must be repeatedly forged to remove impurities before it can be used...... It can be used to make guns. If it is used to make cannons, the cost is too high.

Eventually, less than 10% of the high-quality wrought iron will be used to make 'steel'.