Shrinkage Allowance in Materials

Introduction
Shrinkage allowance is the amount of additional material that needs to be added to a casting pattern to compensate for the shrinkage that occurs during the solidification and cooling process. The shrinkage allowance ensures that the final casting dimensions are accurate and match the desired specifications. Different materials have different shrinkage rates, which is why different shrinkage allowances are required for different materials.

Explanation
Among the materials mentioned in the options (Cl, Lead, Brass, and Aluminium alloy), the material with the highest shrinkage allowance is Brass.

Shrinkage Allowance Factors
Several factors influence the shrinkage allowance in a material, including:
1. Cooling rate: Faster cooling rates tend to increase shrinkage.
2. Solidification time: Longer solidification times lead to higher shrinkage.
3. Alloy composition: Different alloy compositions can result in varying shrinkage rates.

Shrinkage Allowance Comparison
Let's analyze the shrinkage allowances for each material:

1. Cl (Chlorine)
Chlorine is not a casting material but a chemical element. Therefore, it does not have a shrinkage allowance.

2. Lead
Lead is a soft and malleable material with a relatively low melting point. It exhibits minimal shrinkage during the cooling process. Therefore, the shrinkage allowance for lead is relatively low compared to other materials.

3. Brass
Brass is an alloy composed of copper and zinc. It has a higher melting point compared to lead. Due to the different thermal properties of copper and zinc, brass experiences a significant amount of shrinkage during cooling. Consequently, a larger shrinkage allowance is required for brass castings.

4. Aluminium Alloy
Aluminium alloys are widely used in various industries due to their lightweight and excellent mechanical properties. They have a relatively low shrinkage rate compared to materials like brass. Therefore, the shrinkage allowance for aluminium alloy castings is lower compared to brass.

Conclusion
Among the materials mentioned in the options, brass has the highest shrinkage allowance. This is because brass, being an alloy of copper and zinc, experiences significant shrinkage during the cooling process. It is important to consider the shrinkage allowance when designing casting patterns to ensure accurate final dimensions in the castings.

LEAD IS HAVING SHRINKAGE ALLOWANCE ABOUT 26MM/M AND BRASS IS AT A RANGE OF 15.5-16MM/M SO LEAD IS CORRECT