Question

Grossman’s critical diameter method is adopted to determine:

• A. Case depth in carburising methods
• B. Percentage of ductility
• C. Percentage of carbon in steel
• D. Hardenability of steel

Hint:

The \textbf{Grossman method} uses the \textbf{critical diameter} to quantify the \textbf{hardenability} of steel, essential in heat treatment design.

Answer 1

The Correct Option is D

Step 1: Understanding Hardenability
Hardenability refers to the ability of steel to harden in depth under a given set of conditions — it is not the same as hardness. High hardenability means a larger portion of the material can transform to martensite upon quenching. Step 2: Grossman’s Critical Diameter Method
This method determines the critical diameter (D\textsubscript{c}): - D\textsubscript{c} is the diameter of a round bar that just fully hardens to 50% martensite at its center upon quenching. - It is used to compare and classify steels based on their hardenability. Step 3: Key Concept
- A larger critical diameter indicates higher hardenability. - The method considers the cooling rate and alloying elements affecting transformation. Step 4: Elimination of Other Options
- (A) relates to case hardening, not bulk hardenability.
- (B) and (C) are mechanical or compositional properties not evaluated by this method. Conclusion: Grossman’s critical diameter method is a standard approach to evaluating the hardenability of steel.