Chapter 12, Problem 12.62P

Interpretation Introduction

(a)

Interpretation:

The temperature at which austenite first starts transform on cooling should be calculated.

Concept Introduction:

Austenite is defined as a gamma-phase iron, it is a metallic, non-magnetic iron allotrope or a solid solution of iron, containing an alloying element. Austenite which is known to exist above the eutectoid temperature of 1000K of plain carbon steel. Other alloys of the steel contain different eutectoid temperatures. Austenite can remain stable at room temperature only in the presence of austenite stability elements, e.g. Ni in adequate quantity.

Interpretation Introduction

(b)

Interpretation:

The primary micro-constituents and its forms needs to be explained.

Concept Introduction:

The microconstituent of iron carbide includes austenite ( $\gamma$ ), ferrite, etc. austenite is a solid solution formed from ferrite and iron carbide in gamma iron. It forms when the percentage of carbon in steel is up to 1.8% at 1130 $°$ C. Austenite starts converting into pearlite and ferrite when it cools below 723 $°$ C.

Interpretation Introduction

(c)

Interpretation:

The amount and composition of each phase as 728 $°$ C needs to be determined.

Concept Introduction:

The plain iron-carbon alloys contain the amount of steel between 0.002% and 2.14 % by weight. The values keep on varying depending upon alloying elements like manganese, chromium, tungsten, nickel. Therefore, steel is called as iron-carbon alloy which does not undergo any kind of eutectic reaction. Iron is also able to take two crystalline forms, body-centered cubic structure, and face-centered cubic structure, which depends upon the temperature.

Interpretation Introduction

(d)

Interpretation:

The amount and composition of phases at 726 $°$ C needs to be determined.

Concept Introduction:

The plain iron-carbon alloys contain the amount of steel between 0.002% and 2.14 % by weight. The values keep on varying depending upon alloying elements like manganese, chromium, tungsten, nickel. Therefore, steel is called as iron-carbon alloy which does not undergo any kind of eutectic reaction. Iron is also able to take two crystalline forms, BCC structure, and FCC structure, which depends upon the temperature.

Interpretation Introduction

(e)

Interpretation:

The amount and composition of microconstituent at 726 $°$ C needs to be determined.

Concept Introduction:

The plain iron-carbon alloys contain the amount of steel between 0.002% and 2.14 % by weight. The values keep on varying depending upon alloying elements like manganese, chromium, tungsten, nickel. Therefore, steel is called as iron-carbon alloy which does not undergo any kind of eutectic reaction. Iron is also able to take two crystalline forms, BCC structure, and FCC structure, which depends upon the temperature.