What kind of crucible should I choose for melting aluminum alloy ?

1.1 Preparation of crucible, ingot mold and smelting tools

1.1.1 Preparation of graphite crucible:

1.1.1.1 Choose a crucible with appropriate capacity according to the amount of melting;

1.1.1.2 Before using a new crucible, it should be slowly heated from room temperature to 900°C for baking to remove the water in the crucible and prevent explosion;

1.1.1.3 Old crucibles (note that the same crucible cannot be used to melt alloys of different grades) should be checked for damage before use, and the surface slag and other dirt should be removed. Preheat it to 250~300℃ before loading.

1.1.2 Iron crucibles generally use ductile iron crucibles, but also cast steel (or steel plate welding) crucibles. In order to improve the service life of the crucible, the outer surface of the crucible can be treated with liquid aluminizing.

1.1.3 Crucibles, ingot molds and smelting tools should be cleaned of residual metal, oxide scale and other debris before use.

1.1.4 New crucibles and old crucibles with rusty dirt should be cleaned by sand blowing or other methods before use, and heated to 700～800℃, kept for 2～4 hours to remove the moisture and other things adsorbed by the crucible. Chemical substances.

1.1.5 The smelting tools of aluminum-magnesium alloys should be cleaned in a solvent such as carnallite before use.

1.1.6 Protective coatings should be applied to crucibles, ingot molds, and smelting tools before use. When the lined insulation crucible is reused, the protective coating may not be applied.

1.1.6.1 The paint composition can be as specified in Table 1:

Table 1 Coatings for crucibles and tools 

1.1.6.2 Preparation of paint: All solid components in the composition of the paint should be ground before preparation, and sieved through 100-140 mesh, and then mixed evenly. When in use, first pour the water glass into hot water at 80-100°C and stir evenly, add the solid components and then stir evenly, and cool it for later use. The parking time of the finished paint is generally no more than 8 hours.

1.1.6.3 Preheat the crucible, ingot mold, and smelting tools to 180-250°C, and coat them with anticorrosive paint.

1.1.7 The welding crucible of carbon steel plate used for heat preservation shall be lined with refractory material on the inner surface. Refractory materials can be as specified in Table 2:

Table 2 Refractory material composition ratio