The Military-industrial Scientific Research System of the Academic Master Chapter 580

Chapter 580 Liquid Metal Cooling Method

After the brief interlude, everyone's conversation returned to the equipment being produced in front of them.

Ma Liping took Chang Haonan up the steps and came to a row of operating cabinets:

“In fact, after the performance parameters of the turbine blades of the Turbofan 10 were determined, we also tried to use new equipment to produce a batch of products. The other parts were fine. Although there were slight flaws, they could be recovered through subsequent finishing.”

"Only the final solidification process is very difficult to control. The single crystals produced have great defects at the crystal level, and even a large part of them are not single crystals directly. There is no way to remedy this later, so we have to temporarily stop work and wait. Production will resume after the process issues are resolved.”

While speaking, he took out a packaged turbine blade from the side and handed it to Chang Haonan:

“This is the most typical one among our previous batch of waste products.”

"Miscellaneous crystals, freckles, component segregation, excessive oxygen and nitrogen content, large primary dendrite spacing, crystal orientation deviating from the direction of stress, in short, single crystal defects written in textbooks are all collected on this product. ”

“Even if you want to deliberately produce such a waste product, it is difficult to do it. If this thing is not related to the Taihang Project and needs to be kept secret, I would like to take it out and show it to my students..."

Chang Haonan took the blade and looked at it over and over.

Of course, it is impossible to see anything with the naked eye. The differences in crystal morphology may not be fully visible even with an ordinary optical microscope. Special equipment is required to detect them.

"The Turbofan 10 is still in the research and development stage, and everything related to the project is naturally top secret. However, after it is finalized, these waste products will not be so sensitive. Although it is still not possible to take them away directly, you can take out the photos of the crystal forms. ”

He said as he returned the "perfect" waste product to Ma Liping:

“So, do you think this is a problem of adjusting the parameters of the solidification process?”

Ma Liping's expression was a bit complicated, so much so that Chang Haonan stood there and thought for a while after hearing it:

“If this is the case, even if we finally find a process that can stably form single crystals, the production efficiency will be very low?”

“It's just that the size of the blades of turbofan 10 is indeed a bit too large and the shape is relatively complex, so we can only work slowly and carefully. This is also the main reason for the overall low production efficiency of the third-generation aeroengine…”

The latter nodded:

Ma Liping was stunned. After a while, he spoke with difficulty:

“If all liquids are used, then it can't be quenched?”

"ah?"

"Well…"

“Mr. Chang, the reason why this method is called high-speed solidification method is that it is very fast compared to the traditional power reduction method.”

“Furthermore, the cooling effect of water cooling is too good for growing crystals. Crystals that are suddenly exposed to low temperatures will expand uncontrollably, and the crystal form cannot be guaranteed at all, and..."

“No, what I mean is that since the efficiency of cooling the cold end by thermal radiation is much lower than that of the water cooling plate, why not simply use liquid to cool the entire workpiece?”

Obviously, he thought Chang Haonan was dissatisfied with their production efficiency.

Ma Liping wiped the sweat from his forehead:

“Of course yes.”

"When high-speed solidification is used to produce blades abroad, the pull-out speed must also be finely adjusted. Because the heat dissipation efficiency of the thermal radiation process cannot be controlled, the temperature gradient of the water-cooled part can only be reduced as much as possible to ensure a gradual temperature distribution throughout the entire process. More average.”

"But when the casting is pulled out of the insulation area, the heat dissipation gradually becomes mainly radiation, and the heat dissipation efficiency drops sharply, causing the temperature gradient at the solidification front to continue to decrease. The produced castings are prone to defects, and the larger the size of the single crystal , the defects become more obvious.”

However, the latter waved his hand:

“Of course it cannot be water. The difference between the freezing point and the boiling point of water is only 100°C. The range is too narrow for cold-end temperature control and there is no way to operate it.”

“The solidification technology used in this equipment is the currently popular high-speed solidification method. The temperature gradient is controlled through the insulation heating zone in the furnace and the water-cooling tray at the bottom of the casting and radiation heat dissipation.”

Before he finished speaking, he was interrupted by Chang Haonan who almost couldn't hold himself any longer:

"What I mean is to use a liquid with a large thermal conductivity, high boiling point, low freezing point, and large heat capacity. Directly immerse the roots of the extracted blades in it and use heat conduction for enhanced cooling. In this way, the temperature gradient of the entire workpiece can be large and high. Stable, the crystallization speed and crystal quality can also be guaranteed at the same time.”

“It has a high boiling point, a low freezing point, and a large heat capacity…”

Ma Liping looked at the sky and thought for a while. He originally wanted to know where there could be such a magical thing.

But I soon realized that I was wrong.

There is a large class of materials that meet this requirement, but they are not usually considered “liquids”.

“Then it's just...liquid metal?”

Chang Haonan nodded:

“From my initial thought, it is best to use aluminum or tin. As you said, the freezing point cannot be too low, otherwise a sudden strong cold will have an adverse effect on crystal growth.”

This time, Ma Liping did not respond immediately. Instead, he paced back and forth in front of the cabinet, obviously thinking about the feasibility of this technical route.

“Mr. Chang, if liquid metal is used, there will be more operable variables that need to be controlled, especially when the cooling rate is increased.”

A few minutes later, he stopped again and looked at Chang Haonan:

"At least we have to consider the temperature change of the liquid metal itself after it comes into contact with the crystal. Moreover, even if the thermal conductivity is relatively large, due to insufficient fluidity, a new temperature field will be formed inside the liquid, and this temperature field must be controlled at the same time. , we should also consider that our heating method itself is also uneven..."

Don't even start calculating, even just thinking about it makes Ma Liping feel dizzy.

“What if we use a uniform heating method, such as microwave heating?”

Zhong Shihong, who had been unable to speak next to him, suddenly suggested:

“This can reduce at least one variable…”

Before he finished speaking, he saw two people opposite him looking at him with complicated eyes.

“You…want to…use microwave…to heat metal?”

Ma Liping's voice was a bit unbelievable.

Just like he did when he faced Chang Haonan.

It's just that before he doubted whether his level was not good enough, now he doubts Zhong Shihong's intelligence...

Microwaves have a skin effect on metals and can only penetrate a very shallow metal surface layer, and cannot heat the entire metal from the inside like boiling water.

"never mind…"

Zhong Shihong shut up immediately when he realized that he had made a bad idea.

“In short, if liquid metal is introduced, the control logic will be extremely complicated, including our next process optimization. Every time one more parameter is introduced, the difficulty of optimization will increase exponentially..."

“Can we...really get results in a few months?”

When the complexity of the model is large enough, it is difficult to calculate the results even with a computer.

Especially at this moment, China's supercomputing is still far behind the international leading level in terms of hard indicators.

“Is this...”

Chang Haonan pushed the helmet on his head:

“I can't say anything about others, but since I'm in charge, it shouldn't be a big problem…”

(End of this chapter)

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