How to determine the temperature control of LPDC aluminum liquid, including the temperature window for furnace discharge, transfer, and crucible insulation?

How to determine the temperature control of LPDC aluminum liquid, including the temperature window for furnace discharge, transfer, and crucible insulation?
The temperature of the aluminum liquid is a variable at the source of the process. If the temperature is too high, the grains will become coarse, shrinkage cavities will occur, and suction will be severe; Low temperature results in poor fluidity, cold insulation, and undercharging; The narrow temperature window is the underlying cause of yield fluctuations in many production lines.
1、 Quantitative temperature standards for various stages of aluminum liquid
A356 mainstream alloy, with a furnace temperature of 720-740 ℃; When the temperature is above 750 ℃, the hydrogen content increases rapidly, and the tendency of casting porosity increases significantly; Below 710 ℃, the refining and degassing effect deteriorates.
After the transfer into the insulated crucible, the insulation working temperature is controlled at 700-720 ℃; This is the stable production window of LPDC, balancing fluidity and suction volume.
The temperature at the front of the aluminum liquid filling at the gate position shall not be lower than 660 ℃. Below this temperature, the flowability will deteriorate and the risk of thin-walled cold insulation will increase.
Aluminum liquid is left to stand in the crucible for 15-25 minutes after refining and degassing, allowing the oxide slag and hydrogen bubbles to float up; Insufficient settling, frequent occurrence of slag inclusion and porosity defects.
The supporting process documents of Xinfeng Machinery distinguish the temperature windows of different alloys such as A356, A357, ZL101, etc.
2、 Specification for supporting degassing, refining, and slagging
The flow rate of argon gas for rotor degassing is 8-12 L/min, and the degassing time is 8-12 minutes; After degassing, the hydrogen content is controlled to be ≤ 0.2ml/100g Al, and the automotive parts are strictly controlled to be ≤ 0.15ml/100g Al.
The refining agent should be added at a weight of 0.2-0.4% of the aluminum liquid. After refining, it must be left to stand and immediately put into operation if it cannot be completely degassed.
The crucible liquid level is continuously covered with insulation flux to reduce the contact between aluminum liquid and air, and to reduce oxidation and slagging; Thoroughly remove the slag, and the sediment at the bottom of the furnace cannot be sucked into the riser.
3、 Differences in aluminum liquid control among overseas customers
The temperature measurement frequency of Southeast Asian factories is low, relying on visual inspection of aluminum liquid brightness and not detecting hydrogen content. They accept infiltration and repair of pores.
Tier 1 in North America, each furnace of aluminum liquid comes with a spectrum and hydrogen content detection report, and temperature and degassing records are included in PPAP. If the hydrogen content exceeds the standard, the entire furnace is prohibited.
European customers continuously measure hydrogen online, with closed-loop control of aluminum liquid temperature. Once the hydrogen content exceeds the standard, production will be automatically suspended to avoid batch defects.
The environment temperature in the Middle East workshop is high, and the heat dissipation of the crucible is slow. The insulation temperature should be set at a lower limit of 700-710 ℃ to prevent long-term high-temperature suction.
4、 Abnormal temperature defect chain of aluminum liquid
Long term overheating of aluminum liquid>730 ℃ → intensified hydrogen absorption and oxidation → porosity, slag inclusion, coarse grain size, and decreased mechanical properties;
Aluminum liquid temperature is too low<695 ℃ → insufficient fluidity → thin-walled cold insulation, flow lines, insufficient pouring;
After refining and degassing, it is not allowed to stand still → bubbles and oxidized slag are suspended in the aluminum liquid → intermittent slag inclusion pores, sometimes good and sometimes bad;
There is too much sediment at the bottom of the furnace, and the rising pipe sucks in the sediment → the casting contains large particles of slag, which is directly judged as waste by X-ray.
5、 Long tail traffic layout ideas
The temperature, degassing, and hydrogen content of aluminum liquid belong to the special topic of smelting process, which is targeted at smelting supervisors, process engineers, and quality personnel.
keywords LPDC aluminum melt temperature control、hydrogen degassing for A356 low pressure casting；
Problem class: A356 melt temperature window for LPDC;
Comparative category: hydrogen content standard automotive aluminum casting.
Suitable for smelting matching and quality control special pages.
6、 Common misconceptions in the industry
Misconception 1: Aluminum liquid has high temperature and good fluidity. High temperature will absorb a large amount of hydrogen and oxidize, causing pores and mechanical properties to deteriorate, which is not worth the loss.
Misconception 2: Directly producing after degassing and stirring, bubbles and slag still remain suspended, defects intermittently erupt, and troubleshooting is extremely difficult.
Misconception 3: Only looking at the temperature measurement of the crucible, ignoring the cooling of the injection, there is a temperature drop from the furnace to the crucible, and many production lines ignore this temperature difference.
FAQ
Q: What is the working temperature for A356 crucible insulation?
A: 700-720 ℃.
Q: Recommended temperature for baking?
A: 720-740 ℃.
Q: What are the hydrogen content control targets for automotive parts?
A：≤0.15ml/100g Al。
Q: How long should it be left to stand after degassing?
A: 15-25 minutes, let the slag and gas float up.
Q: What is the minimum temperature at the forefront of aluminum liquid?
A: Not lower than 660 ℃ to prevent cold insulation.
Q: What are the main hazards of aluminum liquid overheating?
A: Hydrogen absorption oxidation leads to enlarged pores, coarse grains, and mechanical deterioration.
Q: North American aluminum liquid control requirements?
A: Spectral+hydrogen content detection, with traceable records.
Q: What is the flow rate of argon gas for rotor degassing?
A：8–12L/min， Remove air for 8-12 minutes.