Chapter 86: Ha Gong Da Still Has a Midterm Exam?

Making a big cannon requires electroslag remelted steel; after remelting to remove impurities, the pressure resistance of this steel is improved. As for heat resistance… the barrel's total lifespan is only a few seconds, but those few seconds can fire one or two thousand shells.

The projectile moves through the barrel for a very short time; the barrel doesn't feel much heat before it's over with a whoosh.

But for thermal power plants, nuclear power plants' inertial guidance—they must endure high temperature and pressure for a long time; in the petrochemical field, corrosion resistance is also needed.

So, the steel used in P92 steel pipes is anything but ordinary!

The internal composition of steel can be detected, but the same composition does not mean the same performance; for high-grade steel, internal structure is also crucial—for example, the common structures in steel are martensite and austenite: the former has a body-centered tetragonal structure with asymmetric atomic arrangement, the latter a face-centered cubic structure with tightly packed, highly symmetric atomic arrangement.

Because the structures differ, the resulting performance differs: martensite has high strength and hardness but is brittle; austenite has low strength but excellent toughness.

In later times, a kitchen knife slicing garlic in half isn't wholly the knife's fault—hardness and toughness are inherently contradictory properties.

And P92 steel certainly requires a special production process; even a slight temperature deviation will change its performance.

At this moment, Qin Miao brought this up, and everyone present got excited: "Which international journal? Let's go look for it……

"I've forgotten it too." Qin Miao said: "I only remember the general steps."

"Go on!"

Later, because industries such as thermal power plants needed P92 steel pipes, purchasing them internationally was expensive; so the East decided to make its own, researching for over eight years until it found the correct process, after which P92 steel pipes became dirt-cheap.

This process, Qin Miao had seen before his rebirth; now, First Heavy Machinery is striving for self-improvement and has resolved to develop it independently, so Qin Miao naturally ought to introduce this process.

First, put the steel ingot into an electric arc furnace to melt it into molten steel.

Next, use an AOD furnace for desulfurization to increase purity.

Then enter an LF furnace to fine-tune the composition, precisely controlling the proportions of the steel.

In later times, the Russians would rather discard scrapped tanks than use recycled metal, always smelting Ural iron ore because its composition is uniform and easy to adjust—using scrap steel? Who knows what elements are in scrap steel; adjusting it would be too complicated!

For P92 steel, the content of its internal components must be extremely precise; the fluctuation of each element's content must be kept below 0.1%!

Next, hot-roll it into shape at 1,200 degrees; this requires a vertical metal extruder for direct forming!

"After hot‑rolling plasticity, comes double quenching; the exact temperature… let me think… I think it's normalizing between 1,040 and 1,080 °C, then tempering between 730 and 800 °C… I might be misremembering—when you experiment, you may need to try several times……

This double quenching is the most crucial step; the temperature must be exact—only within the correct range can the grain size be refined to ASTM8 or above. If you didn't know the answer beforehand, merely testing different normalizing and tempering temperatures back and forth could take a year or two of experimentation.

Researching metallic materials is a lot like opening blind boxes!

"All right, let's give it a try! Not to be outdone, if foreigners can make it, we can too!"

"Mm, everyone, keep it up!"

"Once we produce the P92 thick‑walled pipe, Qin Miao, you'll get the chief credit!"

"Old Factory Director, I'm just saying this casually—the credit belongs to our First Heavy Machinery."

The Old Factory Director looked at Qin Miao with satisfaction, liking him more and more—this kid is firm in his stance, clear‑cut in likes and dislikes, understands technology, and is very humble……

Qin Miao, however, looked at Professor Yuan: "I just got back, and you pulled me in; now the project's been assigned, the remaining work is First Heavy Machinery's—should we head back?"

Ha Gong Da.

Leaves had long since fallen; the cold wind blew whooshing, and occasionally in the early morning one could see that the water outside had frozen.

It was already nearing November, the heating hadn't started yet—this was the hardest time to endure.

Inside the classroom.

"All right, students, we'll end the lesson here. Also, to check your learning progress, we'll have a midterm exam next week—please review the previous material during this time to prepare for the exam."

What?

Some students were stunned.

College only has exams at the end of the term, right? Only finals—where does a midterm come from!

Other students had already heard about it from senior classmates, but…… they still felt some resistance.

Exam, exam, exam—the teacher's magic weapon; points, points, points—the students' lifeline!

While everyone was marveling, Chu Miaomiao kept her head down studying; she had wasted a lot of time and needed to seize every moment to learn……

"Miaomiao, class is over—let's go to the cafeteria together for food," Wang Fang said from the side.

"No, you go ahead; I'll study a bit longer."

"All right, if you hadn't taken leave earlier, you'd surely have placed first……

"Even if Miaomiao took leave, she'd definitely still get first place this time," Liu Cuiping said.

"That's not necessarily true, Qin Miao……

Wang Fang's words rose to her lips, then she stopped—Qin Miao is the sort of person who, even if he never attended class, would surely ace the exam, and everyone firmly believed that.

Chu Miaomiao's hand, which had been solving a problem, suddenly stopped, then she continued writing.

Inside the classroom, the crowd gradually dispersed, leaving only Chu Miaomiao alone, still studying; after who knows how long, she suddenly… smelled a fragrance—could it be… her favorite sweet and sour pork tenderloin?

A lunch box appeared before Chu Miaomiao; she blinked, lifted her head, and her face lit up with excitement.

"San Shui, you're back?"

The next moment she wanted to lunge forward and throw herself into Qin Miao's embrace, but… this was school, and being seen by other classmates wouldn't do, so she forced herself to hold back.

"Mm, I got hungry after getting off the train, ate at a restaurant near the station, and brought you some back—have you caught up on the missed coursework?"

"Not yet… let's… go to your dorm."

"Okay."

When Qin Miao first returned, he had promised to tutor Chu Miaomiao on the missed coursework; unfortunately, before he got back to university, Professor Yuan lured him away, but now that he's back, he certainly must keep his promise.

Tutoring in the classroom is easy to get interrupted; it's better in one's own dorm—quiet.