Is magnesium easy to catch fire?

Magnesium alloy will not burn when placed at room temperature. However, attention must be paid to fire prevention during cutting.

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Fire hazard of magnesium alloy cutting process

1 Magnesium chips are lively in nature and are easily combustible at high temperatures. In the magnesium alloy cutting process, most of the magnesium chip incision is unoxidized magnesium and magnesium alloy.

 Because metallic magnesium is a first-class flammable product when wet, its ignition point and minimum ignition energy are low, and the chips are thin and small, and the specific surface area is large, so it is very easy to burn in the air under high temperature environment.
 

2 High temperature will be generated during high-speed cutting, which will ignite magnesium chips. During machining, in order to give full play to the cutting performance of the tool and improve the production efficiency and the quality of the workpiece, a higher cutting speed is generally required. 

The high-speed cutting often makes the temperature of metal chips as high as 700°C~1,000°C. When there is no effective supply of coolant, the high temperature will be enough to ignite the magnesium chips and catch fire.
 

3 The burning temperature of magnesium chips is high, the fire spreads quickly, and it is difficult to fight the fire. Once a fire occurs, magnesium has a combustion temperature of up to 3,000°C and a combustion heat value of up to 25 121 kJ/kg. When magnesium chips are in powder form, they can explode when mixed with air and exposed to fire. 

In addition, because magnesium can react chemically to release hydrogen when it meets with water at high temperature, water, foam, carbon tetrachloride and other extinguishing agents are restricted in metal magnesium fires, and the extinguishing effects of dry powder and halogenated alkane extinguishing agents are not obvious, making it difficult to put out the fire. Big.
 

Magnesium alloy cutting process fire prevention

1 Control the cutting speed. The generation of cutting heat increases in the same proportion as the cutting speed, so the cutting speed has a great influence on the cutting temperature. In actual work, we found that the cutting heat generated by different cutting speeds will change the color of the surface oxide film of the chips. Therefore, the safe lathe spindle speed can be estimated through the color of the magnesium alloy cutting oxide film at different cutting speeds.

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Source: @joe   Author: @cyanbat

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