Function and application of magnesium alloy furnace


In magnesium alloy smelting process, metal oxidation reaction should be avoided to prevent metal combustion. To achieve this effect, we usually sprinkle some flux on the metal melt. Sometimes, we can also use fluxless processes. The common flux is beryllium metal, and the common flux free process is flux free melting. The melting process of magnesium alloy is mainly flux melting. The flux removes impurities from the magnesium and forms a protective film on the surface of the magnesium alloy melt to isolate air. However, the effect of flux film on air isolation is not very ideal, and the magnesium loss caused by oxidation combustion in smelting process is relatively large.

In magnesium alloy smelting process, metal oxidation reaction should be avoided to prevent metal combustion. To achieve this effect, we usually sprinkle some flux on the metal melt. Sometimes, we can also use fluxless processes. The common flux is beryllium metal, and the common flux free process is flux free melting. The melting process of magnesium alloy is mainly flux melting. The flux removes impurities from the magnesium and forms a protective film on the surface of the magnesium alloy melt to isolate air. However, the effect of flux film on air isolation is not very ideal, and the magnesium loss caused by oxidation combustion in smelting process is relatively large.

In addition, there are still some problems in the melting process of flux in magnesium alloy smelters. On the one hand, it is easy to produce flux inclusion, which leads to the decrease of mechanical properties and corrosion resistance of castings, and limits the application of magnesium alloys. On the other hand, the flux reacts with the magnesium alloy liquid to produce corrosive smoke, which damages the smelting equipment and deteriorates the working environment. In order to improve the safety of smelting process, the oxidation of magnesium alloy liquid is reduced. For fluxless melting processes, a mixture of sulfur hexafluoride (SF6) and nitrogen (N2) protective gas or dry air is used in the furnace to avoid liquid level contact with air. The SF6 content of the gas mixture should be carefully selected. If the SF6 content is too high, it will corrode the crucible and reduce its service life. If the content is too low, the melt cannot be effectively protected. In general, both flux melting and flux free melting can produce high quality cast magnesium alloys if done properly. At present, magnesium alloy smelters mainly include AZ91D, AM60B, AM50A, AS41B and so on. AZ91D magnesium alloy is commonly used. The general specification of magnesium alloy ingot is 4-12kg/ ingot. Taking 7kg AZ91D die-cast magnesium alloy ingot as an example, a new charging method is introduced in this paper.

1. Take 30 pieces of dried magnesium alloy ingot, among which 15 pieces are cut at 1/3 and 2/3 ratio, and the other 15 pieces are cut at 1/2 ratio. Clean foreign matter (oil, water, magnesium, etc.) on the ingot surface.

2. The crucible of the furnace should be clean, free from rust, oil, water and foreign matter.

3. First smooth the bottom of the crucible with the whole material.

4. Discharge 2/3 materials one by one along the furnace wall.

5. The small gap between materials or between the pot and the boiler wall should be filled with 1/2 material and 1/3 material. It is important to place alloy blocks to reduce clearance and to make sufficient contact with the furnace wall to ensure heat transfer.

6. After installation, clean the foreign bodies on the furnace cover, cover the furnace, clean the foreign bodies on the furnace surface, and keep the furnace surface clean.

Preheating of magnesium alloy:

The heating power ratio of 0 ~ 200℃ is 11%. The heating power ratio from 200℃ to 300℃ is 14%; The heating power ratio from 300℃ to 350℃ is 17%; It takes 18 hours for magnesium alloy to rise from room temperature to 350℃.

Magnesium alloy smelt adding protective gas: When the temperature reaches 350℃, the smelt automatically supplies protective gas, including SF6 and N2. Magnesium alloy furnace slag cleaning: at the end of each shift, furnace slag cleaning steps: clean the surface of the slag removal tool, and preheat the furnace for 10 minutes; Waste slag collection box should be dry, no combustible materials; Before cleaning the furnace, the value of N2 flowmeter should be maintained at 100. The value of SF6 flowmeter should be adjusted to 20. The value of the mixed gas flowmeter is maintained at 80. After 5 minutes of ventilation at this flow rate, slag removal can begin. Wear protective clothing, cover and hot gloves to open the furnace cover, and use a shovel to remove and collect waste around the crucible, charging pot and heat probe protective sleeve. This operation must be completed within 3 minutes. If it cannot be completed within 3 minutes, the furnace cover must be closed; Close the stove cover and wait about 10-15 minutes.

 

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Function and application of magnesium alloy furnace

In magnesium alloy smelting process, metal oxidation reaction should be avoided to prevent metal combustion. To achieve this effect, we usually sprinkle some flux on the metal melt. Sometimes, we can also use fluxless processes. The common flux is beryllium metal, and the common flux free process is flux free melting. The melting process of magnesium alloy is mainly flux melting. The flux removes impurities from the magnesium and forms a protective film on the surface of the magnesium alloy melt to isolate air. However, the effect of flux film on air isolation is not very ideal, and the magnesium loss caused by oxidation combustion in smelting process is relatively large.