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 led Chang Haonan up the steps 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 ones. The equipment produces a batch of products, but other parts are fine. Although there are some flaws, they can be recovered through subsequent finishing. "
"Only the final solidification process is very difficult to control, and the single crystal produced is. The defects at the crystal level are very large, and even a large part of them are not single crystals. There is no way to remedy this later, so we have to temporarily stop production and restart production after the process problems are solved.”
While talking, 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 involved in the project is naturally top secret. However, after finalization, these waste products will not be so sensitive. Although it is still not possible to take them away directly, they can be Take out the crystal photo."
He returned the "perfect" scrap to Ma Liping:
"So, do you think this is a problem with the parameters of the solidification process?"< br>
“Of course yes.”
The latter nodded:
“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, the water-cooling tray at the bottom of the casting, and radiation heat dissipation.”< br>
“But during the process of the casting being 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, and the produced castings are prone to defects, and The larger the size of the single crystal, the more obvious the defects will be.”
“When producing blades using high-speed solidification methods abroad, it is also necessary to fine-tune the pulling speed because the heat dissipation efficiency of the thermal radiation process cannot be controlled. We can only reduce the temperature gradient in the water-cooled part as much as possible to make the entire gradual temperature distribution more even.”
Ma Liping’s expression was a bit complicated, so much so that Chang Haonan stood there and thought for a while after hearing it. A while:
"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?"
"Uh..."
Ma Liping wiped his forehead Sweating:
“Mr. Chang, the reason why this method is called high-speed coagulation method is that it is very fast compared to the traditional power reduction method.”
“It’s just a turbofan 10 The size of this blade 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 why the production efficiency of the third-generation aeroengine is generally low..."
Obviously, he thought Chang Haonan was dissatisfied with their production efficiency.
However, the latter waved his hand:
“No, I mean, since the efficiency of cooling the cold end by thermal radiation is much lower than that of the water cooling plate, why not simply One point, use liquid to cool the entire workpiece?”
“Huh?”
Ma Liping was stunned for a while before speaking with difficulty:
"If all liquids are used, then quenching is not possible?"
"And the cooling effect of water cooling is too good for the growing crystals. Crystals that are suddenly exposed to low temperatures will expand uncontrollably. The crystal form cannot be guaranteed, and..."
Before he finished speaking, he was interrupted by Chang Haonan, who was almost unable to hold himself up:
"Of course it can't be water, water. The difference between the freezing point and the boiling point is only 100°C. The range is too narrow for cold-side temperature control and there is no way to operate it. "
"What I mean is that the thermal conductivity is large, the boiling point is high, and the freezing point is low. , a liquid with a large heat capacity, and the extracted blade roots are directly immersed in it, and heat conduction is used for enhanced cooling, so that the temperature gradient of the entire workpiece can be large and stable, and the crystallization speed and crystal quality can be guaranteed at the same time. "< br>
"The boiling point is high, the freezing point is low, and the heat capacity is large..."
Ma Liping looked at the sky and thought for a moment. He originally thought that 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 there's only... liquid metal?"
Chang Haonan nodded:
"After my initial thought, it's best to use aluminum or tin. As you said, the freezing point is also It can’t be too low, otherwise the sudden strong cold will have an adverse effect on crystal growth.”
This time, Ma Liping did not respond immediately, but paced back and forth in front of the cabinet, obviously thinking about this technology. Route feasibility.
"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 , so a new temperature field will be formed inside the liquid. This temperature field must be controlled at the same time, and we must also consider that our heating method itself is also uneven..."
Don't even start calculating. , even just thinking about it made Ma Liping feel dizzy.
“What if we use a uniform heating method, such as microwave heating?”
Zhong Shihong, who had been unable to interrupt, suddenly suggested:
"This can at least reduce 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.
However, before he doubted whether his level was not 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 burn as much as they burn. The water is heated from the inside.
"It's okay..."
Zhong Shihong shut up immediately when he realized that he had 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...”
< br>
"Can we... really get the 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 tell others, but since I'm in charge, it shouldn't be a big problem..."
(End of Chapter)