Chapter 103: The Great Leap Forward in Steel

Ji Wusheng had been watching the blast furnace without saying a word. This time, he decided to let the naturalized citizen workers handle it themselves according to the procedure. He had already discussed and rehearsed the specific smelting process with the workers in charge of the trial run many times, and had also made contingency plans for various possible accidents. In this trial run, he wanted to see if a naturalized citizen foreman like Zhao Youcai could roughly complete the entire workflow without the guidance and assistance of an Elder.

Now, the two blast furnaces and one open-hearth furnace were all staffed with naturalized citizen foremen for each shift, but their work did not completely reassure Ji Wusheng. Every time iron was tapped, slag was removed, or the composition was adjusted, he would come over to take a look and give some guidance. This time, he wanted to see if his best furnace master could work completely independently of an Elder’s guidance.

Seeing Zhao Youcai looking at him, he nodded and said loudly, “Zhao Youcai, you are in command now!”

A look of both nervousness and excitement flashed across Zhao Youcai’s face. He responded loudly, “Understood!” He turned around and began to command the furnace workers to take their positions, waiting for the right moment to officially charge the furnace. He himself stared intently at the flames inside the blast furnace.

“Begin the first charge!” Zhao Youcai suddenly shouted. The waiting charging workers started the equipment and charged a batch of material into the blast furnace.

The material for smelting ferrosilicon was a mixture of quartz sand, coke, pig iron, and quicklime in a ratio of 5:3:1:2.5. Because it was the first charge, the proportion of coke was relatively high. After the 5th batch of material was charged, the proportion of coke could be gradually reduced.

After the charging was completed, Ji Wusheng quietly left the observation platform. The first tap would be in 3 hours. He planned to come back then to see the actual tapping situation.

Three hours later, Ji Wusheng returned to the front of the Special blast furnace. The workers were nervously preparing for the first tap. Ji Wusheng silently inspected the main trough and the slag trough for any foreign objects. This was the first tap of the Special blast furnace, and theoretically, there should be nothing in the two troughs. However, many accidents happened because things that “should have been” did not happen according to common sense.

A slag pot that should have been free of foreign objects was somehow mixed with garbage. The moment the hot slag entered the pot, it exploded like shrapnel, instantly wiping out two-thirds of a blast furnace work shift.

This kind of major accident, caused by tapping without proper preparation, had happened more than once.

Ji Wusheng, following the standard operating procedure, personally inspected every link: whether the clay nozzle of the taphole was intact, whether the diversion gates of the iron and slag troughs were down, whether the spouts of the slag and iron troughs were intact…

“I’ve already sent someone to send a molten sample to the laboratory,” Zhao Youcai was busy directing the workers to prepare for tapping. He had just seen Ji Wusheng arrive and hurried over to report. “The tapping preparation is complete. We are just waiting for the results of the molten sample inspection.”

Ji Wusheng nodded.

“I think there will be no problem this time.”

“Whether there is a problem or not depends on the results from the laboratory,” Ji Wusheng was amused by his confident tone. “You can’t be accurate just by looking!”

“Yes, sir,” Zhao Youcai replied loudly. At this moment, a worker hurried over, waving a piece of paper in his hand. Ji Wusheng knew without looking that it was the result of the molten sample inspection just sent by the Central Heavy Industry Laboratory via wired telegraph.

The worker saw Ji Wusheng was present and was about to hand him the slip. Ji Wusheng shook his head, signaling him to give it directly to Zhao Youcai. Zhao Youcai took it, looked at it, and excitedly crumpled the paper into a ball. He turned around and shouted loudly, telling the workers to prepare to release the first furnace of molten ferrosilicon.

The molds, coated with coke powder, were ready. The workers, holding steel rods, waited nervously by the taphole for the order to open it.

Zhao Youcai pulled the cord of the warning bell, and the bell rang loudly.

“Tap!”

At his command, several workers used an overhead crane to move a hand-cranked drill to the taphole. Zhao Youcai first checked if the clay nozzle of the taphole had any wet mud. After confirming that the taphole was dry, he nodded to signal the start of drilling.

“Steady!” Zhao Youcai shouted, carefully guiding the drill towards the clay nozzle. The temperature at the taphole was the highest in the entire blast furnace workshop, and the strong heat radiation made it difficult for people to stand there for a long time. But Zhao Youcai still meticulously checked the position of the drill bit. When drilling, the drill bit must be aligned with the center of the funnel-shaped deep pit of the clay nozzle. Otherwise, if the clay nozzle was damaged or the taphole was drilled crookedly, it could cause mud to spew out during plugging or slag and iron to spray out of the trough.

“Start drilling!”

The workers began to turn the drill. The drill bit slowly drilled into the clay nozzle. After every few turns, the drill would be withdrawn, and several workers would immediately use a blowpipe connected to the blower to blow out the drilled clay powder. This was to observe the condition of the taphole, whether the red spot had been reached, and to measure the depth of the taphole to determine how much more drilling was needed to avoid burning out the drill bit and drill rod after drilling through.

“Slow down, don’t rush!” Zhao Youcai stared intently at the drill and the taphole. Starting the drill was a skilled job that required very steady movements to prevent the drill rod from swinging too much or getting stuck. The drill workers had all undergone hundreds of training sessions on a simulated clay nozzle.

“Iron is coming out!” With a loud shout from Zhao Youcai, the warning bell rang again. As the scorching furnace flame shot out, red-hot molten iron surged out from the taphole, flowing down the main iron trough. The taphole was immediately shrouded in a cloud of smoke. The molten iron flowed out from the iron trough and into the molds coated with coke powder. Choking smoke and flames rose from time to time.

As the first tap of molten iron ended, Ji Wusheng quietly left the blast furnace workshop. The rest was normal production procedure. Iron would be tapped approximately every three hours. What he needed to be concerned about was the specific elemental content of each batch of ferrosilicon.

In his office, there was a composition report of the molten sample: silicon content 16.21%, roughly the same as their estimated ratio. Before the smelting began, he estimated that the silicon content of the first five batches would be about 14-20%. Later, as the charging ratio changed, the silicon content would rise to 17-30%.

“A good start,” Ji Wusheng breathed a sigh of relief. He then looked at the overall composition report. This batch of ferrosilicon met the requirements for smelting silicon steel.

The difficulty of smelting silicon steel was greater than that of ferrosilicon. The smelting method prepared by the metallurgy department was to use a converter to smelt silicon steel.

The metallurgy department had four small converters brought from the old world. To be cautious, Ji Wusheng decided to use only the smallest one, a 1-ton converter.

In the old world, the converter method for smelting ferrosilicon required oxygen blowing and argon protection, as well as RH vacuum treatment. Ji Wusheng didn’t have these conditions, so he had to settle for the air blowing method.

Before smelting, the ferrosilicon was first pre-treated in a cupola, mainly for further desulfurization, so that the sulfur content of the molten iron entering the furnace was below 0.005. The residual manganese and phosphorus in the pig iron were not treated. Although manganese had a certain negative effect on the magnetic properties of silicon steel, the manganese sulfide formed by the combination of manganese and sulfur could improve the workability of hot rolling and avoid cracking during hot rolling. As for phosphorus, it had the effect of improving iron loss and strengthening the adhesion of the iron oxide scale on the surface of the hot-rolled sheet, making it less prone to oxidative adhesion and white film after annealing. However, too high a phosphorus content would also make the sheet brittle, so it had to be controlled within a certain content.

As for other various elements, they had to be controlled at extremely low levels, especially nitrogen. Nitrogen had a great influence on the performance of silicon steel. In the old world’s silicon steel converter blowing process, one was to use pure oxygen, and the other was to inject argon gas as a protective gas during steelmaking. However, Lin’gao had neither of these conditions, so they had to make do.

The day after the ferrosilicon was smelted, Ji Wusheng personally took the lead, working with a group of Elders from the industrial sector to trial-smelt silicon steel. Since they had the spectrographic method for semi-quantitative analysis of elements, in preparing the materials, Ji Wusheng for the first time roughly grasped the specific elemental composition and content of the raw materials that were about to be put into the converter, allowing him to prepare the appropriate raw materials accurately. This was of great benefit to the work of smelting special steel.

After a day and a night of hard work, multiple attempts, and adjustments to the ingredients and process, they finally received good news from the molten sample analysis of the Central Heavy Industry Laboratory. They had smelted silicon steel with a silicon content of 3% and a carbon content of less than 0.04%. This steel was the raw material used to roll the silicon steel sheets for electric motors.

The ideal silicon content for motor steel is 2.4-2.8%, but this steel was also considered a qualified material. However, just smelting the appropriate molten steel was not enough. The Lin’gao steel industry did not have a continuous casting and rolling process. The molten steel had to be first cast into steel ingots before it could be used by the hot rolling mill.

The casting of steel ingots used a protective slag process, generally using graphite powder. Graphite powder had a good effect, but it had a significant carbon-increasing property, sometimes increasing by 0.01-0.02%, which was very detrimental to silicon steel, which had strict requirements on carbon content. After consulting various materials, several people finally decided to adopt the process of using carbonized rice husks with a carbon content of 40%, which had been used in domestic steel plants in the 1970s. The ignition point of this material was much lower than that of graphite powder. During casting, the carbon in the protective slag was burned off first, significantly reducing the carbon-increasing phenomenon. Moreover, this protective slag could also absorb a large amount of Al2O3 from the molten steel, which was very beneficial for reducing impurities in the molten steel.

To produce this carbonized rice husk, Ji Wusheng had previously taken people to Xiao Bailang’s activated carbon production workshop to watch the kiln, and after dozens of experiments, he finally made carbonized rice husks with a carbon content of 40%.

After a great deal of effort, the Ma Niao Steel Complex finally cast qualified silicon steel ingots. Then, they continued their efforts and trial-smelted silicon steel with a silicon content of 4.1% for transformers. However, smelting silicon steel with the appropriate content was only half the work. The specific quality of the silicon steel also depended to a large extent on the subsequent cold or hot rolling process.