环亚AG国际厅

Industry information

Position:Home > News Center > Industry information

  • Common defects of aluminum castings and their causes analysis and prevention methods
  • Editor:Hangzhou Hongcheng Pml Precision Mechanism LtdDate:2018-01-22 09:37 Click:
1. Stomata
1. Stomata
Features: 1. the surface of the hole wall is generally smooth with metallic luster. 2. single or group or subsurface of the castings. 3. oil and smoke blowholes are oil yellow.
Features: 1. hole wall surface is generally smooth, with metallic luster. 2. single or.
 
Cause analysis: 1. when molten metal is poured, the gas that is involved in the solidification of alloy fluid is in the form of pores in the casting. 2. the subcutaneous pores formed on the surface of the casting after the reaction of metal and mold. 3. the inclusion gas on the alloy liquid or the oxide gas attached to the oxide scale is mixed into the alloy solution to form pores.
Reason analysis: 1. the gas involved in the pouring of liquid metal is. Or the gas attached to the oxide skin is mixed into mixed
 
Prevention method: prevent air from getting involved in 1. pouring. 2. the alloy fluid is filtered through the filter before entering the cavity to remove slag, oxide scale and air bubbles in the alloy solution. 3. replace casting material or coating to prevent alloy fluid from casting. 4. repair welding is allowed after cleaning up the defects in the repair welding area.
Prevention method: prevent air from getting involved in 1. pouring. The 2. alloy liquid. ROM reacting with the mold. 4. when the defects are cleaned and cleaned
 
Two, pinhole
Two, pinhole
Features: 1. evenly distributed small holes in the entire section of the casting (less than 1 mm in diameter). 2. the quicker parts of solidification are smaller pores and smaller amounts of pores. 3. a circular hole in the eutectic alloy and a long hole in the alloy with a wide interval of solidification. 4. the small black spots on the X optical negative appear a discontinuous milky white concave spot on the fracture surface.
Features: 1. small holes are distributed evenly in the entire section of the. Y with wide solidification interval. In 4. X optical film on a on
 
Cause analysis: the gas (mainly hydrogen) in the liquid state of the alloy in the liquid state, which precipitates from the alloy during the solidification of the alloy.
The reason analysis is that the molten gas (mainly hydrogen) of, mainly, ",", "
 
Prevention method: 1. alloy thoroughly refining and degassing in liquid state. 2. increase solidification speed during solidification and prevent dissolved gas from precipitation in the alloy. 3. casting is solidified under pressure to prevent the dissolution of gas from the alloy. 4. the furnace materials, auxiliary materials and tools should be dry.
Prevention method: 1. alloy liquid state thoroughly degassing.   2. the solidification rate is. Es from the alloy.   4. the furnace materials, auxiliary materials and, auxiliary
 
Three, loose
Three, looseness
Features: 1.. It is not a tight tissue with sponge like shape. The surface of the 2. hole is rough and the grain is large. 3. the fracture is gray or yellowish, and is gray, pale yellow or black after heat treatment. More than 4. is produced at the hot spot. 5. densely small bright spots were detected on the X light negative.
Characteristics: 1. is a sponge like non tight tissue, in serious case of. Ght spot was found on the X photo film with cloud - cloud -
 
Cause analysis: 1. alloy liquid degasification is not clean, forming gas porosity. 2. the final solidifying part is insufficient. 3. mold overheating, excessive moisture and poor exhaust.
Reason analysis: 1. alloy liquid degassing is not clean to form a gas.
 
Prevention methods: 1. maintain reasonable solidification sequence and shrinkage. 2. the furnace is clean. 3. the cold iron is placed in the loose parts. 4. the defective parts can be cleaned up and repaired after welding parts are allowed.
Prevention methods: 1. maintain a reasonable order of solidification and recontract. 2. charge of.
 
Four, mixed with
Four, inclusion
The particles on the surface or inside of the casting formed by mixing the coating, molding material and refractory material into the alloy liquid.
The surface or inner parts of the castings formed by mixing mixing,
 
Cause analysis: 1. foreign matter mixed with liquid alloy and poured into casting mold. 2. the refining effect is bad. 3. exfoliate or molding material on the inner surface of the mold is spalling off.
The reasons are as follows: 1. foreign materials are mixed into the liquid.
 
Prevention method: 1. refine carefully and pay attention to slagging. 2. the coating layer of the melting tool should be firmly attached. 3. the pouring system and the cavity should be cleaned up. 4. the furnace should be kept clean. 5. the surface inclusions can be removed by grinding, and repair welding is necessary if necessary.
Prevention method: 1. refine carefully and pay attention to slagging. 2. the coating layer. Welding can be made when necessary.
 
Five, slag
Five, slag inclusion
Characteristics: 1. oxidation slag inclusions exist in the internal parts of castings, and the fracture is yellow or gray. 2. the slag is dark brown and spotted, and the hole is smooth after the slag is removed. After exposure to air for a period of time, corrosion characteristics sometimes occur.
Characteristics: 1. oxidizing slag is formed in the castings, and the fracture is. Cs.
 
Cause analysis: 1. after refining metamorphic treatment, slag is not clean. 2. after refining, the static time is not enough. 3. the gating system is unreasonable and the two oxide scale is involved in the alloy solution. 4. after refining, the alloy liquid is stirred or polluted.
The reasons are as follows: 1. the slag is not clean after refining. 2..
 
Methods of prevention: 1. strictly carry out the requirements of refining modification casting process. 2. when pouring, the metal liquid flow should be injected smoothly into the mold. 3. the burden should be kept clean. The treatment and usage of the recycled material should strictly abide by the process regulations.
Prevention methods: 1. strictly enforce the requirements of refining and casting process. The 2.
 
Six. Crack
Six. Crack
Characteristic: 1. the crack is straight or irregular curve. 2. the hot crack surface is characterized by oxidation. There is no metallic luster. It occurs mostly in the inner corner of the hot section, and at the intersection of thick and thin sections. 3. the surface of the broken metal is clean.
Characteristic: 1. the crack is straight or irregular curve. The 2. hot crack section. Tic. 3. the surface of the broken metal is clean.
 
Cause analysis: 1. the cooling of the parts of the casting is not uniform. 2. the solidification and cooling process of castings can not be contracted freely due to external resistance, and the internal stress exceeds the alloy strength and produces cracks.
Cause analysis: 1. the cooling of the parts of the casting is not.
 
Prevention methods: 1. as far as possible, sequentially solidify or solidify at the same time, reduce internal stress. 2. refine the alloy structure. 3. select the appropriate pouring temperature. 4. increase the concession of the mold.
Prevention methods: 1. as much as possible to maintain order to solidify or.
 
Seven. Segregation of
Seven, segregation
Features: 1.. The chemical composition of the bottom and upper part of the crucible is uneven during the smelting process.