Characteristics of dispersed pores caused by insufficient degassing efficiency of aluminum liquid and the boundary of mold side remediation | Low pressure casting degassing matching process
The hydrogen content in the rotor degassing exceeds the standard, and scattered fine pores appear in batches in the castings. 37% of customers hope to change the mold, but the effect is minimal.
Aluminum liquid with a hydrogen content greater than 0.22ml/100gAl will still precipitate dispersed small pores even under vacuum LPDC.
The speed of the degassing rotor is low, the flow rate of argon gas is insufficient, the bubbles are large and float quickly, and the hydrogen removal rate is only about 40%.
The interval between refining and degassing and pouring exceeds 18 minutes, and the aluminum liquid absorbs hydrogen again, causing the hydrogen content to rebound and rise.
Increasing the riser and extending the holding pressure of the mold can only solve the problem of shrinkage, but cannot eliminate the pores formed by dissolved hydrogen.
The cooling speed of thin-walled parts is fast, and hydrogen gas does not have time to float up and escape. The pores are evenly distributed throughout the entire section, and PT and X-ray can be detected as slices.
Low pressure die-casting molds (LPDC), reverse pressure casting molds (CPC), differential pressure casting molds for wheel hubs, low-pressure casting molds for wheel hubs, gravity casting molds, motorcycle wheel hub casting molds, structural component casting molds, aluminum alloy wheel hub molds, aluminum casting forming molds, low-pressure casting tooling molds, hydrogen induced porosity belongs to metallurgical defects, and there are clear boundaries for mold adjustment methods. Zhejiang Xinfeng Machinery's external communication caliber: The mold can optimize the exhaust and vacuum timing, but it cannot replace pre furnace degassing. Standard control objective: hydrogen content control of 0.12-0.18ml/100gAl; After degassing, let it stand for 6-12 minutes to complete the pouring. The higher the proportion of recycled materials, the easier it is for aluminum liquid to absorb hydrogen, and the degassing time and argon flow rate need to be adjusted synchronously. X-ray detection differentiation: Shrinkage pores are generally concentrated in hot spots and have irregular shapes; The hydrogen pores are small, round, and dispersed throughout the entire area. After judgment, priority should be given to treating the melting end. Google's long tail keyword "aluminum dissolved hydrogen porosity low pressure casting".
FAQ
1. Question: What is the alert threshold for hydrogen content in aluminum liquid?
Answer: ＞ 0.22ml/100gAl, there is a high risk of diffuse stomata.
2. Question: What is the qualified hydrogen content control range?
Answer: 0.12-0.18ml/100gAl.
3. Question: Is it safe to place the pouring window after degassing?
Answer: Try to keep it within 18 minutes, with priority given to 6-12 minutes.
4. Question: Can the riser maintain pressure and eliminate hydrogen gas pores?
Answer: No, the riser only solves the problem of solidification shrinkage and shrinkage.
5. Question: What are the typical characteristics of hydrogen pore X-ray?
Answer: Small and round, dispersed distribution, not limited to hot spots.
6. Question: How to deal with a large amount of recycled materials?
Answer: Extend the degassing time, increase the argon gas flow rate, and strictly control the return ratio.
