Question

The connecting rods and gear shafts are commonly made using

• A. Low carbon steels
• B. Medium carbon steels
• C. High carbon steels
• D. Stainless steels

Hint:

Components subjected to repeated mechanical loads usually require materials with a balance of strength and toughness, which is why medium carbon steels are preferred.

Answer 1

The Correct Option is B

Step 1: Understanding the application of connecting rods and gear shafts.
Connecting rods and gear shafts are machine components that are subjected to repeated cyclic loads, torsion, and bending stresses during operation. Therefore, the material used must possess good strength, toughness, and wear resistance.
Step 2: Properties of medium carbon steels.
Medium carbon steels contain approximately 0.3%–0.6% carbon. This composition provides a good balance between strength and ductility. They can also be heat-treated to improve hardness and fatigue strength, making them suitable for dynamically loaded components.
Step 3: Eliminating other options.
(A) Low carbon steels: These have high ductility but low strength, making them unsuitable for high-stress components.
(C) High carbon steels: These are very hard and brittle, increasing the risk of fracture under cyclic loads.
(D) Stainless steels: These are mainly used for corrosion resistance and are not commonly selected due to higher cost.
Step 4: Final conclusion.
Medium carbon steels best satisfy the mechanical requirements of connecting rods and gear shafts.