Mechanical Engineering - Workshop Technology - Discussion

The correct answer is: chills, chaplets, and padding.

Directional solidification in casting refers to the controlled solidification of molten metal to achieve a specific grain structure and orientation. This can be improved by using:

- Chills: Metal inserts that absorb heat and promote solidification in a specific direction.
- Chaplets: Small metal pieces that support the sand mould and help to direct solidification.
- Padding: A layer of insulating material (e.g., sand, graphite) that slows down solidification in certain areas.

Using a combination of chills, chaplets, and padding can help to:

- Control the rate of solidification
- Prevent porosity and shrinkage defects
- Achieve a more uniform grain structure
- Improve the overall quality of the casting

The other options are incorrect because:

- Chills and chaplets alone may not provide sufficient control over solidification.
- Chills and padding alone may not provide adequate support for the sand mould.
- Chaplets and padding alone may not effectively control the direction of solidification.

The specific combination and arrangement of chills, chaplets, and padding will depend on the casting design, material, and process requirements.

The two thick portions of the casting have been provided with risers. The cooling of this casting will initiate from thin section and move towards the heavier sections.

For the production of a sound casting, the temperature gradients should be such that no part of the casting remains without metal during the full solidification cycle.

For this, the thinner section should be tapered towards heavier sections to change the progressive solidification to directional solidification.

This tapering of thinner section towards thicker section is known as 'padding'. However, this will require extra material. If padding is not provided, centre line shrinkage or porosity will result in the thinner section.

Chaplets are used to support the core and also doing the function of directional solidification. I think the answer D.

Chaplets are used for supporting cores while chills are used for used for increasing directional solidification.

Chill= chill are used to increase the cooling rate.

Padding= it safe restless defect or penetration defect.

Padding on which chills rests and used to transmit the cooling effect to bottom of the casting.

The correct answer is Option B. I agree with the given answer.

Ref: R.S. KHURMI.

The correct answer is Option B.

Refer: R. S. KHURMI.

D is the answer. All improve solidification.

Be aware cheplets only support the core.