This set of Foundry Multiple Choice Questions & Answers (MCQs) focuses on “Casting Defects”.
1. ______________ is a defect caused by loose dowels.
a) Mould Shift
d) Blow holes
Explanation: Mould shift produces a casting which does not match at the parting line. There is mismatching of the top and bottom parts of the casting at the mould joint due to worn out, loose, bent or ill-fitting of the clamping pins.
2. Variation in wall thickness occurs due to _________ core boxes.
c) Surface finished
d) Worn out
Explanation: Worn out core boxes give oversize core dimensions. Worn out core prints allowing a core to float or move. Inadequate core print areas permit lifting of the core due to the buoyancy of molten metal. Hence the variation in wall thickness occurs.
3. __________ usually occurs at the parting line and results in excess of metal.
d) All of the mentioned
Explanation: The fins, fash and strain all occur due to the same reason. They occur at the parting line. Straining or movement of the mould makes a casting appreciably thicker than the pattern. Hence, at the parting line excess metal is accumulated which is to be grounded off.
4. Patterns having insufficient taper result in __________
b) Blow holes
Explanation: Fins at the mold joint occur when bottom boards are too flexible or if the pattern plates are not sufficiently rigid to keep straight during ramming. Thus the pattern having insufficient taper require excessive rapping for the withdrawal from sand which results in fins at joint.
5. _______________ occurs in the casting due to the quality variation.
Explanation: Under normal conditions, like all the metallurgical products, castings also contain certain imperfections which contribute to a normal quality variation. Such imperfections are taken as defects or flaws.
6. Defective casting account normally for the higher losses than any other losses incurred by foundry industry.
Explanation: The defects such as blowholes, scab etc result in degenerated castings which make them unsuitable to perform the functions they are supposed to perform. That makes the entire casting to be scrapped off. Hence, it is the greatest loss to the industry.
7. Defects by ____________ are discovered by mechanical testing.
Explanation: The material used for the making of the castings has several mechanical properties such as tensile strength, compressive strength etc which are expected in the castings. These material defects are defects in mechanical properties (tensile, bending, impact, etc) of the casting.
8. Surface defects are discovered by radiography.
Explanation: The defects in the castings which exist under the surface are not able to be discovered by conventional methods. Hence they are revealed by processes such as machining, sectioning or radiography.
9. The best defense against the defects in castings is visual examination and machining.
Explanation: Visual examination and machining take time for the dispatch of the manufactured castings. Instead, close control and standardization of all the aspects of manufacturing technique offer the best defense against the occurrence of defects in castings.
10. ________________ is the displacement of the mould while closing a mould.
d) Mould Shift
Explanation: A crush allows itself as an irregular sandy depression in the casting. It occurs due to an excessive weighting of the green sand mould. Hence, it is the displacement of sand while closing a mold, thereby deforming mold surfaces.
Sanfoundry Global Education & Learning Series – Foundry and Forging.
To practice all areas of Foundry and Forging, here is complete set of 1000+ Multiple Choice Questions and Answers.