Abschnitt 1.6 - 1.6 Casting
1.6.1 Sand casting
Moisture in the sand, the core or the coating may lead to an abrupt vaporization of water due to the heat of the molten metal. As a result of this physical explosion, molten magnesium may be ejected.
If the mold is insufficiently degased, (inadequate arrangement of risers or improper feeder) a sudden ejection of molten metal (thermal stroke) is possible.
1.6.2 Die casting
Material deposits at the die halves in the form of thin flash consist of emerged cooled down magnesium alloy. It can be found at the closing edges of the die and the workpiece. These cakings/cast iron residues may lead to leakiness of the die (see DGUV Rule 109-608 "Branche Gießereien", Clause 3.14 "Gießbetrieb Druckgießerei").
The thin flash (e. g. in the deburring area) represents an increased fire load due to the large surface and high flammability.
The unexpected ejection of liquid magnesium as a result of material deposits (e. g. at the closing edges of the die halves or in the area of the filling chamber has already led to accidents with burns to the operating personnel. Furthermore, reactions with moisture and atmospheric oxygen led to fires which damaged system parts (e. g. hydraulic hoses, electric lines).
Due to hairline cracks in the die parts or defective cooling hoses, cooling water may enter into the closed die. As a result of the "shot", the liquid magnesium is abruptly brought into contact with water which inevitably leads to a violent explosion.
Flash with a large surface is highly flammable and, on contact with moisture (e. g. water based release agents), may lead to fire or even to hydrogen generation including explosion hazards.