Selection and replacement cycle of riser: an underestimated consumable
The riser is one of the consumables with the highest replacement frequency in low-pressure casting, and its diameter, material, and installation coaxiality determine the filling stability and replacement cost.
The diameter of the pipe determines the filling flow rate
The inner diameter of the riser is usually taken as 40-80mm. For every 10mm increase in diameter, the flow rate under the same pressure increases by about 20%.
Insufficient flow, prolonged filling time, and easy occurrence of cold insulation in the thin-walled distal end. Excessive flow, rapid rise of liquid level, and increased risk of gas entrapment.
The selection of pipe diameter should match the gate area. The ratio of gate area to pipe section is often taken as 1:1.2 to 1:1.5, and an imbalance in the ratio can lead to unstable filling.
Material affects lifespan and aluminum liquid quality
Common materials include cast iron, stainless steel, and ceramic composites. Cast iron has a low price, but is easily corroded by aluminum liquid, and its lifespan is usually 2-4 weeks.
Stainless steel has better corrosion resistance and a lifespan of up to 2-3 months. After surface coating treatment, the phenomenon of aluminum adhesion is significantly reduced.
Ceramic composite pipes have more outstanding corrosion resistance, but they are brittle and prone to cracking during installation. Suitable for scenarios with high costs of continuous production and pipe replacement.
Coaxiality is the core of installation
If the coaxiality deviation between the riser and the mold gate exceeds 1mm, the aluminum liquid will form vortices at the interface and be rolled into the oxide film.
During installation, the alignment should be based on the mold gate, not the furnace mouth. The benchmark is wrong, and it is difficult to ensure coaxiality.
Xinfeng Mold will indicate the recommended diameter and insertion depth of the lifting pipe in the interface design of the wheel hub mold to reduce on-site piping errors.
Determination of replacement cycle
Cannot be changed at a fixed time. Three indicators should be considered: wall thinning, aluminum adhesion thickness on the inner wall, and filling pressure drift.
The thinning of the pipe wall exceeds 30% of the original thickness, and it is recommended to replace it. If the adhesive aluminum layer exceeds 3mm, it will significantly reduce the effective inner diameter.
The filling pressure needs to be increased monthly to maintain the same filling effect, usually indicating that the pipe has been scaled or deformed.
Precautions for replacement
Before replacing the tube, the aluminum liquid in the furnace must be emptied and cooled down. The risk of changing pipes with liquid is extremely high, and it is not recommended to try it.
Before installing the new pipe, it should be preheated to above 300 ℃ to avoid splashing of aluminum liquid caused by cold pipe insertion.
The sealing ring must be replaced simultaneously. The old circle has been compressed and shaped, and repeated use is prone to leakage.
How to calculate the cost account
The price of a liquid lifting tube is often between 800-3000 yuan. Calculated based on monthly replacement, the annual cost is about 10000-36000 yuan.
The loss of waste caused by insufficient pipe diameter may be much higher than the price of the pipe itself. A batch of 200 items with a 3% increase in scrap rate resulted in a loss of over 10000 yuan.
In the supporting suggestions, Xinfeng Mold will list the liquid lifting tube as a vulnerable part and remind customers to stock at 1.5 times.
Practical tips
After replacing the tube, the first mold needs to undergo a filling inspection. The uneven rise of the liquid level indicates burrs or poor sealing at the pipe mouth, and needs to be reprocessed.
Frequently Asked Questions
Q: How often is the liquid lifting tube replaced?
Answer: It usually takes 2-4 weeks to 2-3 months, depending on the material and working conditions.
Question: How to choose the pipe diameter?
Answer: Usually take 40-80mm and match it with the gate area at a ratio of 1:1.2-1:1.5.
Q: What is the requirement for coaxiality?
Answer: The deviation should be controlled within 1mm to avoid vortex entrainment.
Q: Do I need to clean the furnace when changing pipes?
Answer: The aluminum liquid must be emptied and cooled down, and there is a high risk of changing the tube with liquid.
Q: Do new pipes need to be preheated?
Answer: Yes, preheat to above 300 ℃ before inserting.
Q: How much does a liquid riser cost per year?
Answer: On a monthly basis, it costs approximately 10000 to 36000 yuan.
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