With the continuous development of the industry, there are more and more magnesium alloy die-casting enterprises in Dongguan, and the awareness of the safety of magnesium alloy die-casting is also increasing. The fire safety and precautions in the magnesium alloy die-casting process should be based on safety protection, The machining operation of magnesium alloy ingot preheating to magnesium alloy die casting is described.
1. Preheating before melting of magnesium alloy ingot
Because magnesium alloy ingots always have pores, cracks and surface oxidation, the above characteristics are related to moisture, so due to relative temperature changes during storage and transportation, magnesium alloy ingots will absorb a certain amount of moisture. Therefore, the magnesium alloy ingot is preheated to above 150°C to remove moisture before melting.
Second, security protection
It should be noted that: Magnesium alloy ingots, die-casting parts and surface-treated parts will burn only when they reach the initial melting point. Magnesium alloy burning will emit a dazzling white light, and the flame temperature is 3900℃. Therefore, it is very important to comply with the safety system and fire-fighting regulations and all operators must be trained before they can work.
1. Personal protection is the basic condition for engaging in magnesium alloy operations. In general, the following protective equipment is the basic protective equipment for magnesium alloy die-casting personnel:
(1) Work clothes (2) Safety helmets (3) Protective masks (4) Heat-insulating asbestos gloves (5) Fire-resistant clothes (heat-resistant above 700℃) (6) Safety shoes
Before operating, operators must wear protective equipment according to the above requirements. Personnel who do not wear protective equipment should not approach the work area and cannot perform operations.
2. Avoid storing gas cylinders in areas where magnesium alloy is melted. When necessary, store gas on the floor of fireproof materials.
3. Necessary breathing apparatus should be prepared.
4. Fireproof materials should be used. The floor materials in the melting area should be heat-resistant and non-absorbent. Because ordinary cement will release water when the metal overflows, it is recommended to use refractory bricks and special cement
5. The storage of alloy ingots, scum, processing debris and ground magnesium powder should comply with:
a. The alloy should be stored separately from flammable materials.
b. Due to the danger of heat generation and spontaneous combustion, wet processing scraps should not be dried, and should be placed in a well-ventilated container and air-dried naturally.
c. The means of transportation must be well ventilated.
Three, die casting
Die casting is a better method for the production of magnesium alloys. It can produce complex and thin-walled parts with high productivity and has lower mold loss compared with aluminum alloys. Pay attention to during the die-casting process:
1. Check the punch regularly to prevent water leakage, otherwise it may explode and injure people.
2. The release agent on the mold should be blown dry, otherwise it may cause splashing or injury.
3. Do not spray release agent on the barrel, otherwise it may cause splashing and injury.
Four. Magnesium alloy melting, heat preservation and furnace shutdown
1. All cleaning tools and ladle must be cleaned and completely dried after preheating. Pay attention to slowly put it into the furnace.
2. The surface of the tool must not be surrounded by moisture-absorbing materials.
3. Enter the appropriate flow of shielding gas into the furnace, and the furnace must have good sealing performance, and ensure that the supply of shielding gas cannot be interrupted.
4. To avoid absorbing moisture, do not use too long protective gas delivery pipe.
5. When adding magnesium alloy ingots and other operations, minimize the opening time of the furnace cover window.
6. When the furnace is stopped, the protective gas can be turned off only when the temperature in the crucible is lower than 350℃.
7. The crucible should be inspected regularly to prevent the crucible from cracks and ruptures causing the leakage of magnesium liquid.
Five. Machining
Although die-casting parts can almost meet the accuracy requirements after die-casting, some mechanical processing is usually required. Die-casting magnesium alloy has excellent machinability. Most die casters can perform machining. However, there is a risk of fire when processing machined debris. When processing magnesium alloys, safety regulations must be strictly followed. It is absolutely not allowed to process magnesium alloys on equipment for processing other metals without established safety measures. When machining and handling magnesium alloy chips, the following regulations must be observed:
1. Smoking is strictly prohibited. 2. Keep the cutter sharp and have enough cutting angle. 3. Use a large feed rate to produce thicker debris. 4. Eliminate the fire source of burning debris.
5. Keep the processing place clean to avoid accumulation of excessive debris. 6. Maintain sufficient fire extinguishing agent (dry sand, cast iron filings, D-type fire extinguisher).
7. Use a special inhibitory water/oil emulsifier to reduce the generation of hydrogen and ensure a sufficient supply of emulsifiers. 8. The processing room must be well ventilated.
9. Put the wet crumbs in a well-ventilated steel drum and place them away from machining and die-casting places
With the rise and development of magnesium alloy die-casting, every operator must be trained before taking the job, and the operator must perform the operation according to the instructions. Magnesium alloy die-casting is not difficult.
