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INSPECTION

Inspection is principally the domain of the designer and customer. Yet, to some degree, the foundryman will get involved. First, he will inspect the castings for external appearance and dimensions. Microscopic examination will verify the spheroidization and matrix structure. Often this will suffice if the sample is taken according to the wishes of the designer. The frequency of such sampling should also be established.

Some of the routine tests which may be specified, providing these are justified by the anticipated service conditions of the casting, are listed below:

a) Mechanical Property tests:

  1. Determination of ultimate tensile strength, yield strength (proof stress), elongation, hardness
  2. Determination of impact resistance
  3. Determination of dimensional accuracy (possibly with jigs)

Mechanical property tests can be carried out at elevated, room or sub-zero temperatures and particularly in the case of impact resistance, the test temperature should always be specified.

Additionally, the surface and sub-surface conditions of a casting may be assessed by the following:

b) Methods to reveal the presence of surface defects:

  1. Visual inspection
  2. Dye penetrant inspection
  3. Magnetic (fluorescent) particle inspection

c) Methods to reveal the presence of sub-surface defects:

  1. X-Radiography (Gamma Radiography)
  2. Ultrasonic inspection

The integrity of a casting is determined by the production process parameters. Specifying any of the above tests will not improve the integrity of the casting but it will increase the delivered cost. It is reasonable to expect the foundry to exercise basic control of process quality, as previously outlined, and to monitor product quality by measuring hardness, microstructure and to visually inspect casting surface finish. When this basic control and inspection is exercised continuously, the foundryman is well disposed to produce castings which consistently meet specifications.

COURTESY: SIEMPELKAMP, KREFIELD, WEST GERMANY

Ductile Iron casting weighing 85 tons, used for the storage and transportation of spent nuclear fuel element rods. International Atomic Energy Authority (IAEA) controls apply to these castings and they were able to satisfy extremely demanding approval tests.

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