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1. Oxidation of slag inclusions
Defect features: Oxidation slag inclusions are mostly distributed on the upper surface of the casting, at the corners of the casting mold that are not ventilated. The fractures are mostly gray-white or yellow, which can be found by X-ray fluoroscopy or mechanical processing, and can also be found in alkali cleaning, acid cleaning or anodizing.
1.1 Reasons:
1.11 The charge is not clean, and the amount of returned charge is too much
1.12 Poor design of gating system
1.13 The slag in the alloy liquid is not cleaned up
1.14 Improper pouring operation, bringing in slag inclusions
1.15 Insufficient standing time after refining and metamorphism
1.2 Prevention method:
1.21 The charge should be sand blown, and the amount of returned charge should be appropriately reduced
1.22 Improve the design of the gating system and improve its slag blocking ability
1.23 Use appropriate flux to remove slag
1.24 When pouring, it should be stable and pay attention to slag blocking
1.25 After refining, the alloy liquid should be left for a certain period of time before pouring
2 air bubbles
Defect characteristics: The pores in the wall of the three castings are generally round or oval, with a smooth surface, usually shiny oxide skin, and sometimes oily yellow. Surface pores and bubbles can be found by sandblasting, and internal pores can be found by X-ray fluoroscopy or mechanical processing. The air bubbles are black on the X-ray film.
2.1 Reasons:
2.11 The casting alloy is not stable and is involved in gas
2.12 type (core) sand mixed with organic impurities (such as coal dust, grass root horse manure, etc.)
2.13 Poor ventilation of mold and sand core
2.14 There are shrinkage holes on the surface of the cold iron
2.15 Poor design of gating system
2.2 Prevention method:
2.21 Correctly grasp the pouring speed and avoid getting involved in the gas.
2.22 type (core) sand shall not be mixed with organic impurities to reduce the gas generation of the molding material
2.23 Improve the exhaust ability of (core) sand
2.24 Correct selection and handling of cold iron
2.25 Improve gating system design
3. Shrinkage
Defect characteristics: shrinkage porosity of aluminum castings generally occurs at the thick part of the root of the fly riser near the inner runner, the thickness transition of the wall, and the thin wall with a large plane. In the as-cast state, the fracture is gray, and the light yellow is gray-white, light-yellow or gray-black after heat treatment. It is cloudy on the X-ray film. Serious filamentous shrinkage can be found by X-ray, fluorescence low-magnification fracture and other inspection methods.
3.1 Reasons:
3.11 Poor feeder effect
3.12 The gas content of the charge is too much
3.13 Overheating near the inner runner
3.14 Too much moisture in the sand mold, and the sand core is not dried
3.15 Coarse grains of alloy
3.16 Improper position of the casting in the mold
3.17 The pouring temperature is too high and the pouring speed is too fast
3.2 Prevention method:
3.21 Refill the molten metal from the riser to improve the design of the riser
3.22 The charge should be clean and free of corrosion
3.23 The riser is set at the shrinkage porosity of the casting, and the cold iron or the cold iron is used in combination with the riser.
3.24 Control sand moisture, and sand core drying
3.25 Take measures to refine grains
3.26 Improve the position of the casting in the mold to reduce the pouring temperature and pouring speed
Xinyuanzhu Group specializes in the production of Ductile iron castings, Pig iron gray iron casting, Steel casting, Brass Casting, Malleable Iron Casting, and undertakes batch casting processing of castings. Welcome guests to cooperate with pictures or samples.