With the demand for Ductile Iron Castings ever rising, foundries
have cropped up by the dozens to cater to this need. It becomes
very important then to ensure that the Ductile Iron, that one is
purchasing, is of the best quality. Even the foundries
themselves keep inspecting their products, to ensure their
survival in the market.
Following are the Inspection Methods for Ductile Iron Castings:
Metallographic Inspection: In this method, the samples of
the Ductile Iron material are taken and scrutinized under the
microscope. The structure and nature of the graphite in the
Ductile Iron material are then analyzed. The graphite in Ductile
Iron Castings has nodular or spherical shapes which bring out
the full potential of the matrix. The nodularity is taken as a
measurement of the quality of the material.
Chemical Analysis: Chemical analysis is used to ascertain
the content of chemicals. Specialized chemical analysis
instruments like DF100 Direct Reading Spectrometer are used for
Tests based on the Mechanical Properties: Ductile Iron is
the hardest and has the highest Tensile strength among the Iron
alloys. Thus, tests which evaluate these Mechanical Properties
are done to ascertain the quality of the Ductile Iron Castings.
Since the Tensile Test is not feasible every time, the hardness
test is preferred most of the times. Usually, a force of 3000kg
and a pressure ball of 10mm diameter are considered as ideal for
a proper test.
Surface Inspection: There are 3 methods of Surface
(a) Ductile Iron when cut produces chips and strips. On the
other hand, Grey Iron tends to be powdery in nature
(b) The sound which a body made of Ductile Iron makes when hit,
is pleasant and creates sound waves in harmonic motion. The
sound which a body made of Grey Iron will make on the other hand
is more like a thud
(c) The surface of the Ductile Iron can be checked for any
defects like cracks, air holes, slag inclusion etc.
Magnetic Particle Inspection: Ductile Iron Castings can
also be subjected to Magnetic Particle Inspection to check for
any defects, especially in the casting head areas.
Ultrasonic Testing: Ultrasonic Testing can not only
reveal any dents or holes on the surface of the Ductile Iron but
also show cracks and other defects on the inside of the
material. However, care has to be taken while analyzing the
results of the Ultrasonic Tests. The complex structure of the
Ductile Iron Casting raises the possibility of wrong judgments.
Foundries put the Ductile Iron Casting through the above
mentioned Inspection Methods to make sure that the material
which leave the foundries are of high quality.
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