Common defects and analysis of aluminum castings
Oxidation slag
Defect feature: Oxidized slag is mostly distributed on the upper surface of the casting, at the corner where the mold is not ventilated. Fractures are mostly grey or yellow, found by x-ray or during mechanical processing and can also be found in caustic washing, pickling or anodizing
cause:
1. The charge is not clean, excessive use of returned charge
Poor system design
3. The slag in the alloy liquid is not removed
4. Improper pouring, slag inclusion
5. Insufficient standing time after refining and deterioration
Prevent method:
1. Burden should be blown, and the amount of recycled material should be properly reduced
2. Improve the design of the pouring system and improve its slag blocking capacity
3. Use appropriate flux to remove residue
4. Pouring should be smooth and should pay attention to slag blocking
5. Pre-cast alloy liquid should be left standing for a certain time after refining
Two air bubbles
Defect feature: The three-casting wall pores are generally round or oval, with a smooth surface, usually shiny oxide, and sometimes oily yellow. Surface pores and bubbles can be found by sandblasting. The internal pores can be found by X-ray or mechanical processing. The pores are black on the X-ray film.
cause:
1. Pouring alloy is not smooth and gets involved in gas
2. Type (core) sand mixed with organic impurities (such as coal dust, grass root horse dung, etc.)
3. Poor mold and core ventilation
4. Cold iron surface has shrinkage holes
5. Bad pouring system design
Prevent method:
1. Correctly control the pouring speed and avoid getting caught in gas.
2. No organic impurities can be mixed in the type (core) sand to reduce the amount of gas generated from the molding material
3. Improve the exhaust capacity of (core) sand
4. Correct selection and handling of cold iron
5. Improved pouring system design
Three shrink loose
Defect feature: The aluminum alloy casting shrinkage generally occurs in the vicinity of the inner runner, where the roots of the riser are thick, where the wall is thick and thin, and where there is a large plane. In the as-cast state, the fracture is gray, and the light yellow is grayish yellow or grayish black after heat treatment. The filamentous shrinkage on the x-ray film is severe and the filamentous shrinkage can be found through X-ray, fluorescence low-fold fractures, etc.
cause:
1. Poor feeding effect
2. Too much charge gas
3. Overheating near the sprue
4. Excessive moisture in sand, sand core not dried
5. Alloy grain coarse
6. Improper placement of the casting in the mold
7. Pouring temperature is too high, casting speed is too fast
Prevent method:
1. Refill metal liquid from riser and improve riser design
2. The charge should be clean and free from corrosion
3. Set up the riser at the shrinkage part of the casting, place the cold iron or cold iron together with the riser
4. Control sand moisture, and sand core drying
5. Take measures to refine products
6. Improve the position of the casting in the mold Reduce the pouring temperature and casting speed
Four cracks
Defect features:
1. Cast cracks. Along the grain boundary development, often accompanied by segregation, is a crack that forms at a higher temperature and tends to appear in alloys with larger volume shrinkage and more complex shapes
2. Heat treatment cracks: Due to overheating caused by heat treatment or overheating, cracks often appear through the crystal. Often the alloys that produce stress and have a large thermal expansion coefficient are overdone. Or when there are other metallurgical defects
cause:
1. Casting structure design is irrational, there are sharp corners, the thickness of the wall changes too much
2. Bad sand type (core) conceded
3. Overheated mold
4. Pouring temperature is too high
5. Remove casting prematurely from cast
6. Heat treatment or overheating, excessive cooling rate
Prevent method:
1. Improve casting structure design, avoid sharp corners, wall thickness strives for uniform, smooth transition
2. Take measures to increase the concession of sand type (core)
3. To ensure that all parts of the casting are solidified at the same time or sequentially, improving the design of the pouring system
4. Properly reduce the pouring temperature
5. Control mold cooling time.
6. Thermal correction is used when castings are deformed.
7. Correctly control the heat treatment temperature and reduce the quench cooling rate.
Bolts available from TS Hardware include a comprehensive range of threaded bolts, screws, studs and other essential components used for construction and industrial applications. We manufacture and supply bolts in an extensive selection of sizes, types and materials, including TC Bolts, sheer studs, self drilling screws, and more. We can provide our customers with virtually any type of bolt they need and serve as a one-stop-shop for construction and building components.
Carbon Steel Bolt,High Carbon Steel Bolts,Carbon Steel Nuts,Carbon Steel Wedge Anchor
Taizhou Shuwen Stainless steel Co., Ltd , https://www.shuwengroup.com