The Military-industrial Scientific Research System of the Academic Master Chapter 176

Chapter 176 The inspiration brought by drinking water (

Zhong Shihong, who was smiling just now, froze in place with a strange expression.

 Other people who came with him also showed various expressions of surprise and uncertainty.

Chang Haonan was the only one among everyone present who was not particularly surprised.

 The situation was similar to what he had expected.

Electro-hydraulic beam machining is an electrochemical machining method. In principle, micro-cracks and remelted layers will not be produced in the formed pore structure. The main problem is that the local edge quality is not stable enough, so the detection adapted to this processing method will Focus on the area around the orifice.

However, EDM is still thermal processing in nature, and recasting will inevitably occur during the drilling process.

Although the high-pressure internal flushing liquid inside the hollow electrode can quickly wash away part of the molten material during processing, the remaining part may still produce a remelted layer with very irregular thickness after cooling, affecting product quality.

  If the processing method is changed without corresponding improvements in the inspection process, problems will naturally arise.

 It's just that in actual operation, the relationship between the thickness of the remelted layer and the processing current, pulse width and environmental parameters is very close, so Chang Haonan did not dare to insist on this result before seeing the test results.

  But it works now.

“There is no problem with the cost, and we hope to get the test results as soon as possible.”

Zhou Zexuan nodded and took out two turbine blade samples from the optical inspection table next to him:

“The Electron Microscopy Center currently has ongoing tasks, but your situation is special after all. I can apply to jump in the queue.”

 After finishing speaking, he turned around and left.

 With Zhou Zexuan's operation, everyone did not have to wait too long to get the results of the electron microscope test.

"We randomly selected 16 air film holes on the blade for testing. The results showed that the average thickness of the remelted layer in the holes was 25 microns, but the situation of each small hole varied greatly. The thinnest one was only 14 microns, and the thickest one was 14 microns. It's 45 microns…”

As Zhou Zexuan read out the results of the test report little by little, Zhong Shihong's face became darker and darker.

 He is not a person who cares about face, but this slap in the face came too quickly...

 After all, he had vowed a few days ago that Factory 410 would definitely have no problems with EDM drilling technology.

Chang Haonan's performance was as normal as ever. He took the report from Zhou Zexuan and looked at it. After making sure that there were no other issues worth noting, he handed it to others.

 The air in the room became a little anxious.

"this…"

Even though he is very reluctant to admit it, as Chang Haonan initially guessed, there was a loophole in the post-processing and quality inspection process.

 What makes Zhong Shihong even more ashamed is that Factory 410 had previously received a letter from Yan Zhongcheng and others from Fucheng, requesting a self-examination of the production process of engine hot-end parts.

 But they just re-sampled according to the usual testing procedures, and restarted production after finding that there were no problems with the results.

 Hence, the quality problems existing in the processing of the inner wall of small holes have been missed.

 The evidence is right in front of you. Since you are wrong, you have to admit it.

"After we return, we will hold a factory-wide workers' meeting. We need to review this matter."

However, the 611 Institute is very urgent for the turbojet 14B.

  After all, it involves Feifa matching work, and there is also pressure from foreign users who have expressed their intention to purchase.

 So before reviewing, you still have to solve the problem first.

  The evening after returning to Factory 410, the first thing held was a small-scale technical seminar.

“Based on the current domestic situation, it is definitely hopeless to switch to electro-hydraulic beam machining in the short term. Therefore, we have no other choice but to find a solution based on EDM technology.”

Zhong Shihong set the tone at the beginning: "Hey Gong, can you consider reducing the thickness of the remelted layer during the processing by reducing the current intensity or shortening the pulse width?"

Those sitting here are all old technologies. Now that the problem has been determined to be the remelting layer, some basic principles are still not difficult for everyone.

 The middle-aged man known as He Gong is called He Tao, who is the section chief responsible for the EDM drilling process.

  Unfortunately, there is still a distance between the basic principles and actual operation.

He Tao shook his head decisively:

"The material processing of turbine blades is inherently difficult. Although reducing the current intensity can alleviate the remelting problem, it will affect the accuracy and position of the opening. The current current of 8 amps is already what we have determined after testing in our section. Minimum current to maintain processing quality.”

“As for shortening the pulse width, that is beyond our control. We need to replace it with better and more precise electrodes, and the clamping equipment also needs to be replaced..."

 He did not continue, but the conclusion was already very obvious.

Nowadays, this EDM small hole processing machine tool was developed after several years of hard work in the 410 Factory. Where can I find more advanced equipment?

 The manufacturing industry is sometimes like this. A single move can affect the whole body. Even if the principle is very simple, it often takes a long time to achieve a breakthrough if you want to implement it on the production side.

“Since there is no way to reduce the thickness of the remelted layer during processing, we can only consider the post-processing process.”

Zhong Shihong looked at another engineer.

The other party coughed twice slightly, and then said:

"I just looked at the test results of the electron microscope. The current 0.2mm reamer can only remove the burrs and residue on the inner wall of the small hole. Judging from the metallographic structure of the remelted layer, it is very hard and cannot be reamed through mechanical means. Completely removed.”

"In addition, turbine blades themselves are thin-walled parts that require high deformation. The mechanical reaming process is very difficult and very inefficient. There are hundreds of holes in the phosphor film on each product. If every small hole is processed If you do it again, I'm afraid it won't take 100-200 working hours. Calculating, one engine will take about two months. "

 The progress of the discussion came to a standstill for a while.

Deep hole processing is always a difficult problem in the mechanical manufacturing process. Due to its special working environment, turbine blades have more stringent manufacturing requirements. The number of air film holes is large and the diameter is small, so many commonly used polishing methods cannot be used.

 In fact, with the technical strength of Factory 410, it cannot even detect the thickness of the remelted layer.

 This is also an objective factor why they have not discovered this problem before.

 Chang Haonan, who had been sitting next to Zhong Shihong since the beginning of the meeting, had not spoken.

 He listed several major current problems one by one on the notebook in front of him.

 First of all, there must be something with high enough hardness so that the remelted layer can be removed. According to the results of the discussion just now, steel reamers cannot meet this requirement.

  The second thing is that this process cannot cause damage to the blade itself, and the clamping process should be simple enough.

 Finally, the processing efficiency must be high enough. It is best to be able to process hundreds of air film holes on a blade at the same time rather than one by one.

Chang Haonan, who had no idea for a moment, almost unconsciously picked up the cup in front of him and took a sip of water.

 The fried meat with sprouts for dinner was a bit cumbersome...

 At this moment, a flash of inspiration suddenly flashed through my mind.

 It seems...this process is somewhat similar to mouthwash, or teeth cleaning?

 Can we consider using water...

No, what about using fluid doped with high-hardness abrasives to remove the remelted layer?

I can't contact the editor, let's talk about 174. The general content is that the existence of the remelting layer was discovered through testing, and by the way, the protagonist was asked to brainstorm the layout issues related to the production of large aircraft.

 (End of this chapter)

Chapter end