Cast Steel Defects of Sand Casting
Steel castings made by
sand casting process always
have some casting defects,
such as shrinkage, sand inclusion, blowhole, porosity and cracks
etc.
In China, most of steel foundries,
including Dandong Foundry, produce steel castings by manual method,
and the cast sand needs better air permeability, and moreover, cast
steel has larger shrink rate than cast
iron. These factors cause cast steel has more defects.
Cast steel shrinkage, porosity
Shrinkage normally happens at the positions of gating system. Mainly
because the hot liquid steel cools too quick, there is no enough
steel water to compensate the shrink areas. Shrinkage have some
different types, large shrinkage looks like irregular air holes,
small shrinkage has many small pin holes, so this kind of shrinkage
is also called as porosity.
Cast steel sand inclusion, sand hole
Sand inclusion is also
very common defect. Sand grain easily fall off because of the flush
of hot liquid steel during pouring process.
Cast steel blowhole
Cast steel materials have some steel scraps, which has some aluminum
components, so after chemical reaction, the generated gas will be
held on the surfaces or inside.
Cast steel crack
There are some different types of cracks, such as cold cracking, hot
cracking, shrinkage crack, craze cracks, and heat treatment cracks.
Cracks are fatal defects for steel castings, because they could
seriously reduce the tensile strength of cast steel.
The above cast steel defects on the surfaces of castings could be
repaired by electric welding and cast steel repairing adhesive if
they do not affect the application. The inside defects could be
inspected by NDT testing methods, such as ultrasonic testing (UT) or
magnetic particle test. However, the inside defects almost can not
be repaired.
For more metal casting defects and pictures, please refer to "Metal Casting Defects".
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