Engineering Materials - Study Mode

[#331] According to Indian standard specifications, SG 400/15 means
Correct Answer

(B) Spheroidal graphite cast iron with minimum tensile strength 400 MPa and 15 percent elongation

Explanation

Solution: S. G. Iron (Spheroidal Graphite Iron) is a type of cast iron that has been treated while molten with an element such as magnesium or cerium to induce the formation of free graphite as nodules or spherulites. This imparts a measurable degree of ductility (easily manipulated) to the cast metal. According to Indian standard specifications, SG 400/15 means Spheroidal graphite cast iron with minimum tensile strength 400 MPa and 15 percent elongation.

[#332] Paramagnetic alpha iron changes to gamma iron at
Correct Answer

(B) 912°C

Explanation

Solution: Below 912°C (1,674°F) iron again adopts the BCC structure characteristic of α-iron, also called ferrite. The substance assumes a paramagnetic property and it changes into gamma iron.

[#333] Pure iron is the structure of
Correct Answer

(A) Ferrite

Explanation

Solution: iron with a bcc structure is called ferrite. Another name for ferrite is alpha iron. ferrite is shown in figure

[#334] Gun metal contains
Correct Answer

(C) 85 - 92% copper and rest tin with little lead and nickel

Explanation

Solution: Gun metal , also known as red brass , is a type of bronze that is commonly used in casting and for making items like valves, gears, and bearings due to its resistance to corrosion and high strength. It typically contains 85% to 92% copper , and the remainder is made up of tin , with small amounts of lead and sometimes nickel to improve its machinability and corrosion resistance. Now let's look at why the other options are incorrect: Option A: 70% copper and 30% zinc — This composition is closer to brass , not gun metal. Option B: 90% copper and 10% tin — This is a typical composition of standard bronze , not gun metal specifically. Option D: 70 - 78% copper and rest tin — This composition does not accurately reflect gun metal and lacks the small additions of lead and nickel that characterize gun metal. Conclusion: The correct composition of gun metal is 85 - 92% copper , with the remainder being tin and small amounts of lead and nickel . Hence, the correct answer is Option C .

[#335] Which is the false statement about wrought iron? It has
Correct Answer

(D) Uniform strength in all directions

Explanation

Solution: Physical properties of wrought iron are listed below: Soft and Tough Ductile Hight tensile Strength High compressive strength Easily forged and weldable