Personal protection, melting safety, die-casting safety
Magnesium alloy melting, magnesium alloy die-casting, well ventilated, fireproof and waterproof
1. The safety in the magnesium alloy die-casting process involves personal protection, smelting safety, and die-casting safety.
The personal protection of the operator is the basic condition for magnesium alloy die-casting. In general, the following protective equipment is the basic protective equipment for magnesium alloy die-casting personnel:
(1) Work clothes
(2) Safety helmet
(3) Protective mask
(4) Thermal insulation asbestos gloves
(5) Fireproof clothes (heat resistance 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. The smelting of magnesium alloy is an important link in the production, and it is also a key link in the safety of magnesium alloy die-casting.
The furnace body is best to have a double-layer structure design. When the inner crucible is broken, the magnesium liquid can flow into the interlayer between the inner and outer layers. At the same time, it alarms to stop heating, so that the molten magnesium liquid will not flow to the outside and cause danger. Always check the furnace for rust, and clean it up if there is rust. The crucible must be inspected by kerosene penetration and X-ray before it is used to prove that it has no defects before it can be used.
The crucible should be hoisted out of the furnace for a comprehensive inspection at least once every six months. When the wall thickness is half of the original, stop using it. Small holes and rust can be repaired after cleaning, but they must be checked. During magnesium die-casting, the magnesium level of the furnace rises and falls a little with the feeding cycle. The upper part of the junction between the liquid level and the crucible wall is eroded and corroded by high temperature magnesium liquid and SF6 protective gas, which is prone to corrosion pits. Pay attention to regular inspections and timely cleaning weld;
Also pay attention to control the concentration of SF6 during operation, too high concentration will cause the crucible to corrode rapidly. Before the magnesium ingot is put into the furnace, it must be preheated to a temperature above 150°C to remove moisture. The spoon and other tools used must also be preheated to a temperature above 150°C. There should be a covered slag box next to the furnace to scoop out the slag from the furnace. Put it in the container and cover it immediately. Generally, a bottle of mixed protective gas should always be kept at the melting site for emergency use in case of sudden power failure or other emergencies.
3. During the magnesium alloy die-casting production process, the most important thing is to keep the site dry and clean.
The mold should be preheated to above 150℃ each time before starting the machine. Do not spray too much paint during spraying to avoid water accumulation in the cavity and cause danger. In addition, the punch and die should not be cooled with water as much as possible. The punch can be cooled by air cooling, and the heating and cooling of the mold can generally use high temperature oil.
The speed of the magnesium alloy die-casting punch is also higher than that of aluminum alloy die-casting. In order to avoid flying material hurting people, sometimes a flying material baffle is added to the parting surface of the mold. The front and rear safety doors must be closed during die casting. Surface.
Waste materials at the production site must be cleaned up in time and can be placed in dry, non-combustible containers. Flying materials and dust should also be cleaned up in time. Judging from the actual fire accidents that occurred in magnesium die-casting plants in various countries, more than 50% of them were caused by magnesium dust and waste disposal such as cleaning and storage problems. Some occurred in the processing link, and about 10% of the accidents occurred in the smelting link. about.
4. The magnesium alloy die-casting workshop requires good ventilation as well as the ordinary die-casting workshop, but also has stricter requirements for fire prevention and waterproofing.
4.1 workshop
The workshop building should be built with non-combustible materials, and the floor material should not absorb water and heat. Do not install the roof exhaust fan near the top of the melting furnace to prevent rain leakage. The die-casting site must be clean, no water, oil, and good ventilation and exhaust conditions are allowed. Magnesium alloy ingots should be stored in a cool, dry and ventilated warehouse, and excessive magnesium ingots should not be stored at the smelting site.
Magnesium alloy nozzle materials and waste materials should also be stored separately in non-combustible containers. The supply of electricity, fuel, cooling water, gas, etc. to the host of the die-casting machine and the furnace should be remotely controlled so that it can be turned off in case of an accident. If the polishing area is set in a workshop, a wet vacuum cleaner is generally required. The workshop should delineate emergency passages and ensure unblocked access at all times.
4.2 Extinguishing
The fire extinguishing agents used for magnesium alloy include dry sand, covering agent, and Class D fire extinguishers. These fire extinguishing equipment should be placed in a conspicuous place and convenient for emergency use on site. Dry sand and covering agent should be stored in a container to prevent moisture and be checked frequently. .
Magnesium alloys may seem terrible due to the dazzling white light and smoke when they burn. But the heat of combustion of magnesium alloys is only half that of gasoline. If there is a small amount of magnesium burning on site, it can be quickly shoveled up, put in the slag box and covered, or transferred to an open place.
If the magnesium liquid is scattered or cannot be shoveled up. Quickly spread dry sand or a covering agent to cover it, and evenly sprinkle it on the burning magnesium. When white smoke is found in the magnesium alloy furnace. The flow of the protective gas SF6 can be increased to clean the oxidized slag on the liquid surface. If it still cannot be stopped, a few preheated magnesium ingots can be put in to quickly reduce the temperature of the magnesium liquid.
When the magnesium liquid surface is found to be burning. The heating system should be shut down quickly, and the flow of the protective gas SF6 should be increased, and a covering agent should be sprinkled on the surface of the magnesium liquid. Class D fire extinguishers should not be used when necessary. Because their expensive and pressurized gas can easily disperse the fire. Magnesium alloy fire outside the furnace is mostly covered with dry sand to extinguish the fire.
