Metallic Materials and Alloying Elements

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Questions and Answers

What is the impact of silicon on the critical temperature of a material?

Silicon increases the critical temperature only in low carbon compositions.

Silicon has no effect on the critical temperature.

Silicon increases the critical temperature, with variations based on carbon content. (correct)

Silicon decreases the critical temperature in all compositions.

What phenomenon occurs when austenitic stainless steel is heated to between 500 to 850°C?

Improvement of mechanical properties.

Sensitization due to loss of corrosion resistance. (correct)

Formation of additional carbide structures.

Increased hardness due to phase transformation.

What happens to the sensitization of austenitic stainless steel when it is quenched from temperatures above 1000°C?

Sensitization increases due to thermal mismatch.

Sensitization does not change and remains active.

Sensitization can only be reversed by cooling down naturally.

Sensitization disappears. (correct)

What is the main cause of grain boundary corrosion in stainless steel?

Improper heat treatment leading to chromium carbide precipitation. Signup and view all the answers

At what temperature does sensitization in ferritic stainless steel occur following quenching from high temperature?

900°C Signup and view all the answers

What is one reason for adding alloying elements to steels?

To improve mechanical properties Signup and view all the answers

How does boron affect the hardenability of steel?

It is ineffective when carbon content increases Signup and view all the answers

Which type of steel is NOT categorized as alloy steel?

Low-Carbon Steel Signup and view all the answers

What effect does increasing carbon content have on boron-treated steels?

It diminishes boron's effectiveness Signup and view all the answers

Which property of alloy steels is typically improved by adding alloying elements?

Magnetic permeability Signup and view all the answers

In what proportion is boron typically added to boron-treated steels?

0.0005–0.003% Signup and view all the answers

Which characteristic does NOT influence the addition of alloying elements?

Surface aesthetics Signup and view all the answers

Which type of cast iron is characterized by its good wear resistance and workability?

Malleable Cast Iron Signup and view all the answers

What is the effect of manganese on hardenability in steel alloys?

Increases hardenability by promoting deep hardening Signup and view all the answers

How does nickel influence austenite transformation in steel?

It depresses the Ac and Ar critical temperatures Signup and view all the answers

What role does chromium play in steel structures?

Forms complex carbide structures and increases hardenability Signup and view all the answers

Which statement accurately describes the effect of vanadium in steel?

Promotes finer grain size and increases hardness at elevated temperatures Signup and view all the answers

What unique characteristic does molybdenum contribute to steel alloys?

Forms complex carbide structures and enhances depth of hardening Signup and view all the answers

Which of the following correctly describes the properties of nickel combined with chromium in steel?

Increases hardenability, impact strength, and fatigue resistance Signup and view all the answers

What is the primary effect of using manganese in constructional steel alloys?

To facilitate deep hardening by increasing the hardenability Signup and view all the answers

Which effect of chromium in steel is NOT correctly stated?

It decreases resistance to oxidation and corrosion Signup and view all the answers

Study Notes

Metallic Materials

Steels are alloys of iron and carbon with various alloying elements to enhance properties.
Alloying elements affect steel properties by controlling hardenability, temperature resistance, chemical resistance, and influencing special properties like magnetic permeability.

Effect of Alloying Elements

Boron (B) increases hardenability, particularly effective with low-carbon alloy steels, but less effective with higher carbon contents.
Manganese (Mn) acts as a carbide former, increasing hardenability and facilitating deep hardening in constructional steel alloys.
Nickel (Ni) increases hardenability by decreasing the critical cooling rate and depressing critical temperatures, resulting in greater hardenability, higher impact strength, and fatigue resistance.
** Chromium (Cr)** is a strong carbide former, increasing hardenability and improving oxidation and corrosion resistance.
Vanadium (V) is a strong carbide-forming element, increasing hardenability, promoting finer grain size, and enhancing hardness at elevated temperatures.
Molybdenum (Mo) forms complex carbide structures, increases hardenability, and is often used in conjunction with nickel and/or chromium.
Silicon (Si) increases the critical temperature, requiring higher austenitizing temperatures, but it is not a carbide former.

Stainless Steel Issues

Sensitization occurs when stainless steel experiences grain boundary corrosion or stress corrosion cracking, caused by the deterioration of corrosion resistance near grain boundaries due to chromium carbide precipitation.
Sensitization is a dynamic phenomenon that occurs faster at higher temperatures.
Austenite stainless steel sensitization occurs between 500-850°C, while ferritic stainless steel sensitization happens above 900°C.
Sensitization can be reversed by quenching austenite from above 1000°C or annealing ferritic steel around 800°C.

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Description

Explore the fascinating world of metallic materials, focusing on steel alloys and their properties. Understand how various alloying elements such as Boron, Manganese, Nickel, Chromium, and Vanadium enhance hardenability and other characteristics of steel. This quiz will challenge your knowledge about the science behind these materials.