There is no unified standard value for the melting temperature of aluminum alloys, and a reasonable control range needs to be determined based on the composition characteristics of the alloy, liquidus temperature, elemental characteristics, and product quality requirements. At the same time, the smelting process is divided into three core stages: melting, refining, and static casting. The temperature control objectives for each stage are different, and differentiated temperature standards need to be implemented.

Deformed aluminum alloy is the main raw material for industrial extrusion and rolling products, and its melting temperature control needs to balance composition stability and casting quality. The reference temperature range for each alloy system is as follows.

The melting point of 1-series pure aluminum (such as 1060, 1070, 1100) is about 657-660 ℃, with extremely low alloy element content, low risk of element burnout, and relatively wide temperature control range. Melting temperature: 700~750 ℃, the melting rate can be appropriately accelerated; Refining temperature: 720~740 ℃, ensuring the effectiveness of refining and degassing; Static casting temperature: 690~730 ℃, adjusted according to the specifications of the ingot. It should be noted that pure aluminum has good thermal conductivity and fast hydrogen absorption rate at high temperatures. Therefore, the maximum melting temperature should not exceed 760 ℃, and the high-temperature insulation time should be shortened as much as possible.

The 3-series alloys (such as 3003 and 3004) are mainly composed of manganese as the alloying element. Manganese has a high melting point and low burning loss. The liquidus temperature of the alloy is about 650-655 ℃, and the process window is wide. Melting temperature: 710~760 ℃; Refining temperature: 720~745 ℃; Static casting temperature: 700~735 ℃. This alloy has low thermal sensitivity, but temperatures exceeding 770 ℃ can still lead to increased oxidation and hydrogen absorption, and the upper limit needs to be controlled.

5 series alloys (such as 5052, 5083, 5A06) have high magnesium content and are prone to oxidation and volatilization, making them one of the most temperature controlled alloy systems. Melting temperature: 700~740 ℃, over temperature melting is strictly prohibited; Refining temperature: 710~730 ℃, using low-temperature refining to reduce magnesium loss; Static casting temperature: 690~720 ℃. The maximum melt temperature in production must not exceed 750 ℃, otherwise it will cause a large amount of magnesium element burning and excessive magnesium oxide inclusions, while significantly increasing the hydrogen absorption capacity.

6-series alloys (such as 6061, 6063, 6082) are currently the most widely used deformed aluminum alloys, with low total magnesium and silicon content and strong process adaptability. Melting temperature: 720~760 ℃; Refining temperature: 730~750 ℃; Static casting temperature: 710~740 ℃. The temperature control of 6063 alloy for ordinary building profiles can be appropriately relaxed, but for high-end industrial profiles and 6061 alloy for forging, overheating must be strictly controlled, with a maximum temperature not exceeding 770 ℃, to avoid coarse grains.

The alloy elements of 2-series hard aluminum (2024, 2A12) and 7-series ultra hard aluminum (7075, 7050) are complex, with a high tendency to crack and strong sensitivity to overheating, requiring extremely high precision in temperature control. Melting temperature: 720~750 ℃, slowly increase the temperature to melt; Refining temperature: 730-745 ℃, with temperature fluctuations controlled within ± 5 ℃; Static casting temperature: 30-60 ℃ above the liquidus line, precisely set according to the specifications of the ingot. This type of alloy is strictly prohibited from overheating at high temperatures. Once it exceeds the solidus line temperature and overheats, the material will be completely scrapped.

Aluminum alloy casting is commonly used for die-casting and sand casting, and its composition is mainly eutectic alloys, such as A356 and ZL101 of Al Si series. The eutectic temperature is low and the flowability requirement is high. Melting temperature: 730-780 ℃, ensuring sufficient melting of silicon phase and alloy elements; Metamorphic treatment temperature: 730~750 ℃, ensuring the effectiveness of the metamorphic agent; Refining and pouring temperature: 710~760 ℃, adjusted according to the casting wall thickness and structure. Although slightly higher melting temperatures are allowed for casting aluminum alloys, long-term temperatures exceeding 780 ℃ can still lead to an increase in pinhole defects, failure of modifiers, and a decrease in mechanical properties. Therefore, it is also necessary to control the upper temperature limit.

On the basis of the above standard range, dynamic adjustments need to be made according to specific working conditions in actual production:

When the proportion of recycled materials is high, the inherent inclusions and hydrogen content in the melt are relatively high. Therefore, the upper limit of the melting temperature should be appropriately lowered to reduce the combined effect of oxidation and gas absorption;

Large sized ingots have a high risk of cracking, and the casting temperature should be set to the lower limit to avoid high temperatures exacerbating the tendency towards hot cracking; Small sized ingots can be heated appropriately to ensure smooth filling;

In rainy season and high humidity environments, the hydrogen absorption rate of the melt is fast. Therefore, the melting temperature should be lowered by 10-15 ℃ to reduce the hydrogen solubility base;

For products with high requirements for anodized surface quality, low-temperature melting should be strictly controlled to reduce oxidation inclusions and avoid subsequent surface defects.