4. Spherical protrusion defects
Mainly caused by the air (bubbles) remaining after the embedding material is mixed and stayed on the surface of the wax type.
(1) The real air conditioner and the embedding material are better after being vacuum-embedded.
(2) Spraying a surfactant on the surface of the wax type before embedding (for example, a castmate of Nisshin Co., Ltd.).
(3) First apply the embedding material to the wax type.
(4) The bubble is extruded by a method of pressure embedding.
(5) Pay attention to the direction of the wax type when embedding, and do not have any depression below the joint between the wax type and the casting path.
(6) Prevent the air bubbles from being mixed in the embedding, and the casting ring and the casting seat and the buffer paper should be closely adhered; the embedding material should be poured along the inner wall of the casting ring (using the vibration machine).
(7) Do not oscillate after filling the casting ring.
5. The flash edge defect of the casting
Mainly due to the cracking of the casting ring, the molten metal flows into the crack of the cavity.
(1) Changing the embedding conditions: using a higher strength embedding material. Gypsum-based embedding materials have lower strength than phosphate-based embedding materials, so care should be taken when using them. Try to use a circle casting. When the ring is not cast, the casting ring is prone to cracking, so it is necessary to note.
(2) Conditions for calcination: Do not directly calcine after the embedding material is solidified (should be calcined after several hours). It should be slowly warmed up. Cast immediately after roasting, do not repeat the roasting of the cast ring.