Casting

The low permeability in sand can cause which of the following defects in casting

• Rough surface

• Blow holes

• Hot Tears

• Drop

The distortion in casting cannot be prevented by

• modification of casting design

• modification of casting design

• providing sufficient machining allowance to cover the distortion effect

• providing proper shrinkage allowance

Which of the following is true in case of directional solidification?

• all parts of a casting do not cool at the same time due to varying cross sections

• The rate of heat loss varies to adjoining mould walls

• The thinnest section solidify first and the riser solidify last

Which of the following is true about riser?

• It permits the molten metal to rise above the highest point in the casting.

• Filling up of mould cavity can be visually checked from it.

• The casting solidifies directionally towards the riser

Which of the following is not a casting defect?

• Swell

• Hot Tears

• Shrinkage

• Hot Cracks

Which of the following is true for sand castings?

• They cannot be used for pressure tight vessels

• They are stronger than wrought products

• They have lower density and poor strength

• They have poor ductility

According to their use, which of the following is not a type of moulding sand?

• Green Sand

• Dry Sand

• Loam Sand

• Wet Sand

The function of cores in casting is to

• form extended parts

• form internal cavities

• used for directional solidification

• none of the above

In permanent mould casting, the molten metal is poured

• under external pressure

• under gravity

• partially under gravity and partially under external

  pressure

• none of the above

Which of the true? In permanent mould casting, the moulds are usually coated with a refractory wash and then lamp black to

• Reduce chilling effect

• To prevent shrinkage

• Facilitates the removal of casting