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Casting Defects Analyze

Writer:Lian DequanSource:Henan Metals Number of visits: Date:2014-1-2
Analysis for the five types of defects in casting
1.Casting shrinkage causes and countermeasures. 
The main reasons: when the alloys solidification shrinkage,it led to casting shrinkage,and when the alloys melting,the internal of casting absorb a lot of oxygen, nitrogen, etc.,so the casting shrinkage caused by gases released during the alloys solidification. 
2, The reason of casting surface roughness is not smooth
Cavity surface roughness and the chemistry between the molten metal and the cavity surface, mainly reflecting the following situations.
a, coarse particles embedded in the material , not delicate stirring .
b, after solidification of the embedding material directly into the muffle furnace roasting, too much water.
c, with burning heat up too fast, the expansions produced in the difference positions of cavity,make cavity interior surface spalling.
d, the highest temperature of roasting or baking time is too long, make the cavity inside is too dry, etc.
e, The melting temperature of metals or cast ring firing temperature is too high,the metals react with the cavity,  the casting surface burning and stick of embedded material.
f, The backing mold is not sufficient, when the molten metal pouring into the mold, causing the decomposition of the embedding material,and occurrence of more gas,make many pitting on the casting surface.
g,After the molten metal into the casting,resulting in a local high temperature in the cavity , the local surface roughness of the casting . 
3, About cracks in the casting,there are two major reasons:
One is usually due to its metal solidification too fast, produce the casting defects (joint);
Second is cracking due to the high temperature.
a, For the metal solidification too fast to produce the casting joint,it can be by controlling the casting and coagulation time to solve.
-The related factors for Casting pour time: the shape of the wax type.
-The thickness and number of casting.
-Casting Pressure (Casting machine).
-The permeability of the embedding material.
-The related factors of coagulation time : the shape of the wax type.
-The highest roasting temperature of casting ring.
-The type of the embedding materials.
-The type of metals.
-The temperature of the castings.
b, The cracks caused by the high temperature,the mechanical properties of embedding materials & metals are related.
-Easy to produce cracks in the following circumstances: pouring into the mold easy to get the cracks when the molten metal stated high temperature.
-High strength of the embedding material cracks easily;
-Extensibility small flipping alloy of nickel and cobalt flipping alloys are prone to cracking.
C, The causes and countermeasures of spherical protrusions
Mainly the embedding material mixed residual air (bubble) stay on the surface of wax type and cause.
D, How the casting flash is formed
Mainly for casting ring crack, the molten metal run into the cracks of cavity.

TypeInfo: Industry Info

Keywords for the information:Defects  Casting Defects 


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