Common Problems In Metal Castings And Related Prevention Methods
Measures to prevent pinholes:
(1) It is strictly forbidden to use contaminated cast aluminum alloy materials, organic compounds and materials that are severely oxidized and corroded.
(2) Control the smelting process and strengthen the degassing refining.
(3) Control the thickness of the metal coating, too thick and easy to produce pinholes.
(4) The mold temperature should not be too high, and chilling measures such as copper block or watering should be applied to the thick-walled parts of the casting.
(5) Strictly control the moisture when using the sand type, and use the dry core as much as possible.
Measures to prevent stomata production:
(1) Modify the unreasonable pouring riser system to make the liquid flow stable and avoid gas entrapment.
(2) The mold and core should be preheated beforehand, and then applied to the coating. After the end, it must be dried before use.
(3) Designing molds and cores should consider adequate exhaust measures.
Measures to prevent looseness:
(1) Reasonable riser setting to ensure its solidification and ability to supplement.
(2) Appropriately reduce the working temperature of the metal mold.
(3) Control the thickness of the coating and thin the thick wall.
(4) Adjust the cooling speed of each part of the metal type so that the casting has a large chilling capacity at the thick wall.
Properly reduce the metal casting temperature.
4. Oxidation slag
Measures to prevent oxidative slag inclusion:
(1) Strictly control the smelting process, quickly smelt, reduce oxidation, and thoroughly remove slag.
(2) The Al-Mg alloy must be smelted under a covering agent.
(3) The furnace and tools should be cleaned, and there should be no oxides, and should be preheated. The paint should be dried after use.
(4) The designed gating system must have the ability to stabilize flow, buffer, and slag.
(5) The inclined pouring system is adopted to stabilize the liquid flow without secondary oxidation.
(6) The selected coating has strong adhesion, and does not peel off during the pouring process and enters the casting to form slag inclusions.
5. Hot cracking
Measures to prevent hot cracks:
(1) Local overheating should be avoided and internal stress should be reduced when actually casting the system.
(2) The inclination of the mold and core must be guaranteed above 2°. Once the riser is solidified, the core can be opened and the core can be replaced by a sand core if necessary.
(3) Control the thickness of the paint so that the cooling speed of each part of the casting is consistent.
(4) Select the appropriate mold temperature according to the thickness of the casting.
(5) Refine the alloy structure and improve the thermal cracking ability.
(6) Improve the structure of the casting, eliminate sudden changes in sharp corners and wall thickness, and reduce the tendency of hot cracking.