"How can steel be used in shipbuilding?" Gao Junshan repeated the engineer's question, and then clearly pointed them in the direction: "Welding technology." As long as we have the welding technology, we can weld steel together, and we can weld it into whatever shape we want. With welding technology, our keels can be replaced with steel, and our ships can be built even bigger. ”

Pan Zide asked: "If steel is used instead of wood to make the keel of a ship, will such a ship not sink?" ”

"It will never be sunk, this kind of steel battleship, even without cannons, can smash the enemy's wooden ship."

Pan Zide said in disappointment: "Unfortunately, how can steel be welded? ”

Gao Junshan replied affirmatively: "It can definitely be welded." With electricity, we can use the arc to melt the steel, and the steel is welded together by welding rods. ”

"What is an arc?" An engineer raised his hand and asked.

"Arcing is a gas discharge phenomenon in which an electric current passes through some insulating medium resulting in an instantaneous spark. You may not understand it at once, but when I have the opportunity, I can do an experiment for you. ”

One of the engineers asked, "Is it like lightning?" ”

"Yes. Lightning is caused by the instantaneous heating of the air when the electric current penetrates the air, and the object will have red light when heated to 3,000 degrees, yellow light will appear when heated to 6,000 degrees, and white light will appear when heated to 10,000 degrees. The lightning we usually see is white, and that's because the air instantly turns 10,000 degrees. ”

Pan Zide asked: "So do we weld steel at a temperature of 10,000 degrees?" ”

"Almost." Gao Junshan replied, "The arc temperature can be as high as 6000~8000 degrees, and with such a high temperature, any kind of steel will be melted." ”

Another engineer asked: "How can such welding technology be done?" ”

Gao Junshan said: "At present, we will definitely not be able to do it, it depends on your engineers to continue to explore and achieve it step by step." ”

Pan Zide asked, "Can you show us a specific direction?" ”

Gao Junshan said: "To master welding technology, first of all, we must be able to produce electric welding machines, at the same time, we must also produce welding rods, and we must also have power supply, which are indispensable. We now have electricity, and the welding machine also needs the technology of voltage transformation, without the technology of voltage transformation, we will not be able to produce the welding machine. ”

"What is the technology of transformer?" An engineer asked.

Gao Junshan took a sip of tea and continued to explain: "If you want to mention transformer, you have to mention the transformer, the transformer is composed of an iron core, a primary coil and a secondary coil, and we can change the number of turns of the primary coil and the secondary coil to change the voltage." ”

An engineer said, "Isn't that easy?" As long as we build a transformer, we can't build a welding machine! ”

Gao Junshan said: "The problem is that we can't even build a transformer now. Although the transformer may seem simple, it is not simple. To build a transformer, we first have to make a silicon steel sheet. ”

"Silicon steel sheets?"

"Silicon steel sheet is a soft magnetic alloy of ferrosilicon with very low carbon content, which is made by hot and cold rolling. Generally, the thickness is less than 1 mm. The addition of silicon can increase the resistivity and maximum permeability of iron, and reduce coercivity, core loss (iron loss) and magnetic aging. It is the only material for the manufacture of transformer cores. ”

Pan Zide asked: "May I ask the mountain chief, so how did the silicon steel sheet come from?" ”

Gao Junshan said: "Silicon steel sheet is a kind of steel sheet rolled from ferrosilicon alloy, as long as this steel sheet is stacked into a shape, and then wrapped on it with enameled wire, it is a transformer." ”

"So, as long as we have ferrosilicon, we can have silicon steel sheets?" One of the engineers asked.

Gao Junshan said: "I just provide you with a research direction, how you make the transformer, it depends on your wisdom." However, this road is very difficult, without ten or twenty years, it is difficult to make a transformer, and the welding machine is even more unthinkable. ”

Pan Zide asked: "Does it take 20 years for a steel battleship to be built?" ”

Gao Junshan poured cold water and said: "I think that without fifty or even a hundred years, we will not be able to build a steel battleship, and now we can only use wooden ones." ”

An engineer was not convinced, and said: "Our current warships are all ironclad ships, can't they be regarded as steel warships?" ”

Gao Junshan said: "The keel of the ship must be made of steel." ”

Pan Zide asked again: "So, with silicon steel sheets, can we make transformers?" ”

Gao Junshan replied: "Theoretically, it is possible. There are also process flows and technical requirements. First of all, the transformer must calculate to determine the output voltage we want, for example, our current voltage is 380, we want a safe voltage of 36, we can transform the voltage through the transformer, and reduce the voltage of 380 to 36. Let's take this unit as volts for the time being, that is, from 380 volts to 36 volts, which can be achieved through transformers. ”

"What is Volt?" Someone asked.

Gao Junshan replied: "It's just a unit of measurement, you don't care what it is." What we need to know is that a voltage of 36 volts is a safe voltage. And for a transformer, its coil windings need to be calculated. How to calculate, I will now give a complex formula. ”

After Gao Junshan finished speaking, he wrote down a set of formulas on a piece of paper: the number of turns of the transformer winding N=U/(4.44*50*Bm*A*Kd*10 to the minus 8th power).

This formula is in the spaceship manual, so he remembers very well, as for what U is, what Bm is, what A is, what Kd is, he doesn't understand, he is not an electrician after all.

After reading this formula, the engineers were all confused.

Gao Junshan said: "Therefore, the road is tortuous, but the future is bright, I believe that with your efforts, we will be able to overcome one difficulty after another and build steel warships for our Chinese Navy." ”

It is difficult for engineers to absorb so much knowledge at once, but they are not willing to miss the opportunity to learn from Gao Junshan, so they continue to ask Gao Junshan all kinds of questions, and Gao Junshan is very patient to answer for them, as long as he knows, or knows some skin, he will give serious answers.

Time flew by, and just as the engineers were having a heated discussion, Captain Deng Shijie walked in.

"Chief, it's not too early, it's time for us to set sail."

Gao Junshan raised his hand and glanced at his watch, only to realize that three hours had passed. He said loudly to his students: "That's all for today's lesson, and we will have the opportunity to further discuss the issues related to transformers and welding machines." ”

Pan Zide said to everyone: "Let's all go back and work hard to build the Shanghai Port well, which is our most important task." ”

Gao Junshan said: "Mr. Pan is right, you must build Shanghai as soon as possible, and the next step is to build Hong Kong, these two cities are the most important cities we open to the outside world." ”

The engineers expressed to Gao Junshan their determination to build Shanghai well, but it was not that Pan Zide urged him to do so, and they had no intention of leaving.

Gao Junshan said goodbye to them: "You all go back!" The construction of Shanghai is waiting for you! ”