National Metallurgical Laboratory Senior Research Fellow Interview Questions and Answers

Heat treatment processes differ in temperature, time, and cooling rate to achieve desired material properties.

• Annealing: heating and slowly cooling to reduce hardness and increase ductility

• Quenching: rapid cooling to increase hardness and strength

• Tempering: heating and cooling to increase toughness and reduce brittleness

• Normalizing: heating and cooling to refine grain structure and improve machinability

• Hardening: heati...read more

The diameter of the DI pipes continuously casted at NML was 100mm.

• DI pipes were continuously casted at NML

• The diameter of the pipes was 100mm

Cryogenic process of heat treatment involves cooling materials to extremely low temperatures to improve their properties.

• Materials are cooled to temperatures below -150°C using liquid nitrogen or helium.

• This process improves the wear resistance, toughness, and dimensional stability of materials.

• Common applications include treating tool steels, aerospace alloys, and superconducting materials.

• The process can also be used...read more

The temperature range for various heat treatments in metallurgy varies depending on the specific process.

• Annealing temperature range: 300-1200°C

• Quenching temperature range: Room temperature to 200°C

• Normalizing temperature range: 800-950°C

• Austempering temperature range: 250-450°C

• Other heat treatments have their own specific temperature ranges

• Temperature ranges can also vary depending on the type of metal being treated

Strength and hardness are related but not the same. Strength is the ability to withstand force while hardness is resistance to deformation.

• Strength refers to the ability of a material to withstand an applied force without breaking or deforming.

• Hardness refers to the resistance of a material to deformation, scratching, or abrasion.

• A material can be strong but not hard, such as rubber, or hard but not strong, such as gla...read more

Continuous cooling curves show the cooling behavior of a material during solidification.

• Continuous cooling curves are used to determine the cooling rate required for a material to achieve a desired microstructure.

• They are plotted by cooling a sample at a constant rate and measuring its temperature as a function of time.

• The curves can be used to predict the formation of different phases and microstructures in the materi...read more

Fe-C diagram shows the phases of iron-carbon alloys at different temperatures and carbon concentrations.

• The diagram is also known as the iron-carbon phase diagram.

• It is used to understand the behavior of steel and cast iron.

• The diagram shows the different phases of iron and carbon at different temperatures and carbon concentrations.

• The diagram has three main regions: austenite, ferrite, and cementite.

• The eutectoid poin...read more

Heat treatments include annealing, tempering, quenching, and case hardening. Each process has unique properties and uses.

• Annealing involves heating and slowly cooling to soften metal and improve ductility.

• Tempering involves heating and cooling to increase toughness and reduce brittleness.

• Quenching involves rapid cooling to increase hardness and strength.

• Case hardening involves adding a hard outer layer to a softer meta...read more

The diameter of DI pipes used during the continuous casting process varies depending on the specific application.

• The diameter of DI pipes used in continuous casting can range from 100mm to 1000mm or more.

• The diameter is determined by factors such as the size of the casting machine, the type of metal being cast, and the desired output.

• For example, a smaller diameter pipe may be used for casting smaller products like rod...read more

Fe-C diagram with peritectic or eutectic lines

• Fe-C diagram shows the phases of iron-carbon alloys at different temperatures and carbon concentrations

• Peritectic line separates the liquid and solid phases during cooling

• Eutectic line separates the two-phase region from the three-phase region

• Peritectic reaction occurs when a solid phase reacts with a liquid phase to form a new solid phase

• Eutectic reaction occurs when a liq...read more

Hardness and strength are related but not the same. Hardness is a measure of resistance to indentation while strength is a measure of resistance to deformation.

• Hardness is a measure of a material's ability to resist scratching, cutting, or penetration.

• Strength is a measure of a material's ability to resist deformation or fracture under an applied load.

• Hardness and strength are related because materials that are harder ...read more

Heat treatment includes annealing, tempering, quenching, and normalizing.

• Annealing involves heating the material to a specific temperature and then cooling it slowly.

• Tempering involves heating the material to a specific temperature and then cooling it quickly.

• Quenching involves heating the material to a specific temperature and then cooling it rapidly.

• Normalizing involves heating the material to a specific temperature ...read more