Cast iron is a common method to prevent casting
Features: casting, there will be some good casting surface crack shape of silk straight or curved shape first.
Two kinds of hot crack and cold crack.
The rupture of cracking takes the twists and turns and irregular shape, its fracture was dark surface, has the deep oxidation color.
Cold crack fissure is straight, casting fracture surface with metallic luster and relatively clean, sometimes mild oxidation color.
Crack is the main reason of the formation of castings, cooling solidification contraction have been hampered by the internal stress, when the internal stress is greater than the strength of the metal material, the casting crack formation of cracks.
Foundry prevention measures: (
Strictly control the chemical composition of molten iron.
With sulfur high-energy 'hot shortness' formation of castings, the cracking, w (in gray cast iron
12%, but also cannot too low,
Should not be lower than 0.
, sulfur is too low to affect the inoculation effect, the most suitable w (
05% ~ 0.
Phosphorus are high-energy produce castings' cold brittleness, cold crack, w (in gray cast iron
W (in 15%, ductile iron
Adjust the cooling rate of the casting parts, to avoid local overheating, casting on the casting or hot section of heavy section, put cold iron runner in scattered appropriately, make each part of the casting temperature tends to uniform.
After casting gating, open type don't too early, do not use cold water irrigation, high temperature casting within the open type time is suitable for casting temperature below 600 ℃.
When conditions permit, changing the structure of the castings, preventing casting crack.
Such as set up the stiffener, two section transition parts by rectangular rounded corners, to reduce stress concentration.
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