Mechanical Engineering - Engineering Materials - Discussion

5. 

Which of the following inpurity in cast iron makes it hard and brittle?

[A]. Silicon
[B]. Sulphur
[C]. Manganese
[D]. Phosphorus

Answer: Option B

Explanation:

No answer description available for this question.

Pradeep said: (Oct 30, 2013)  
1. Silicon: It may be present in cast iron upto 4%. It provides the formation of free graphite which makes the iron soft and easily Machinable. It also produces sound castings free from blow-holes, because of its high affinity for oxygen.

2. Sulphur: It makes the cast iron hard and brittle. Since too much sulphur gives unsound casting, therefore, it should be kept well below 0. 1% for most foundry purposes.

3. Manganese: It makes the cast iron white and hard. It is often kept below 0. 75%. It helps to exert a controlling influence over the Harmful effect of sulphur.

4. Phosphorus: It aids fusibility and fluidity in cast iron, but induces brittleness. It is rarely allowed to exceed 1%. Phosphoric irons.

Montu said: (Jul 28, 2017)  
Thank you @Pradeep.

Muthamizh said: (Mar 17, 2018)  
Very useful, thanks @Pradeep.

Sachin said: (Jan 8, 2019)  
Thank you @Pradeep.

Fouzdar said: (Jul 25, 2019)  
Nice explanation. Thanks.

Rohit Raz said: (Aug 3, 2019)  
Thank you @Pradeep.

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