This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Stainless Steels & Other Steels”.
1. Which is the primary element used for making stainless steel alloy?
Explanation: Stainless steels contain iron and a minimum of 10.5% of chromium. This gives it great resistance to corrosion. Therefore, stainless steels are often known as corrosion-resistant steels or chromium-bearing steels.
2. Addition of _______ gives stainless steels an austenitic structure.
Explanation: Nickel is added to stainless steels with a 3.5% to 22% composition to form austenitic structure. This results in the highest corrosion resistance among all stainless steels. They also possess high strength and ductility.
3. Stainless steels with little carbon and no nickel are called ________
a) Ferritic stainless steel
b) Austenitic stainless steel
c) Martensitic stainless steel
d) Duplex stainless steel
Explanation: Ferritic stainless steels are steels containing 12.5% to 17% of chromium. They are nickel¬-free and contain very little carbon making up its composition. They are, therefore, better resistant to corrosion than martensitic stainless steels.
4. Stainless steels with high strength, but low corrosion resistance are known as _______
a) Austenitic stainless steel
b) Ferritic stainless steel
c) Martensitic stainless steel
d) Duplex stainless steel
Explanation: Martensitic stainless steels are made of 12-14% chromium, along with molybdenum, nickel, and carbon. This makes the steels hard and brittle, but poorly resistant to corrosion. Martensitic stainless steels are used in making Swiss army knives.
5. Which of the following are applications of Ferritic stainless steels?
a) Aircraft engine parts, heat exchangers
b) Milk, kettles
c) Oil burner parts, furnace elements
d) Pumps and valve parts
Explanation: Ferritic stainless steels have the ability to be welded, forged, rolled, and machined. They are used for making oil burner parts and furnace elements. Austenitic stainless steel is used to make engine parts, milk cans; Pumps and valve parts are applications of martensitic stainless steels.
6. Which of the following is not a type of oil-hardening steel?
Explanation: Oil hardening steels are a group of cold working tool steels. This group consists of O1 (0.9% C, 1% Mn, 0.5% Cr), O2 type (0.9% C, 1.5% Mn, 0.3% Si), O6 type (1.65% C, 1% Si, 0.25% Mo, and an O7 type.
7. Mushet steel belongs to which group of tool steels?
a) Oil-hardening steels
b) Air-hardening steels
c) High-speed steels
d) Hot-working steels
Explanation: Mushet steel was the first air-hardening tool steel. It belongs to the Cold-working family of tool steels. It was developed by Robert Mushet.
8. What property does the AISI-SAE tool steel grade ‘L’ possess?
c) Plastic mild
d) Special Purpose
Explanation: The steel grade ‘L’ refers to special purpose steel containing low alloy. It consists of elements such as carbon, chromium, manganese, and a few others. The L2 and L6 are the most commonly used steels under this category.
9. The low-carbon, high-alloyed steels which possess high strength and toughness are known as _______
a) Carbon steels
b) Alloy steels
c) Maraging steels
d) Stainless steels
Explanation: Maraging steels are those high strength steels which have tensile strengths up to 1900 MPa. They are composed of 18% Ni, 7% Co, and less than 0.05% C.
10. What do TRIP steels stand for?
a) Transformation Induced Porosity
b) Transformation Induced Plasticity
c) Transformation Induced Pearlite
d) Transformation Induced Property
Explanation: TRIP steels are those steels containing high strength and ductility. They are mainly used for automotive industry needs. The expanded form of TRIP is Transformation Induced Plasticity. It contains an austenite microstructure.
11. What is the maximum allowable temperature at which High-Speed Steels retain good cutting ability?
Explanation: High-speed steels have the ability to remove and cut metal at a much higher rate than carbon steels. They have a good cutting ability even at a temperature as high as 540oC. Above this temperature, they soften and lose their cutting edge.
12. Ultra high-speed steels are made of which of the following elements?
a) Tungsten and molybdenum
b) Chromium and molybdenum
c) Vanadium and cobalt
d) Molybdenum and cobalt
Explanation: Ultra high-speed steels have greater tool lives and greater cutting efficiency. This is due to the addition of vanadium (up to 4%) and cobalt (5% to 12%) along with carbon, chromium, and tungsten.
13. What is the microstructure of Hadfield’s steel?
Explanation: Hadfield’s manganese steels (Mangalloy) possess great strength and toughness. Its austenite structure is obtained by heating it. This also results in high wear resistance, which finds its applications in bulldozers, crushers, etc.
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