National Metallurgical Laboratory Interview Questions, Process, and Tips

Minerals are naturally occurring inorganic substances with a definite chemical composition, while metals are a type of mineral that have high electrical conductivity and luster.

• Minerals are inorganic substances found in nature, while metals are a subset of minerals with specific properties.

• Metals have high electrical conductivity, malleability, and luster, distinguishing them from other minerals.

• Examples of metals incl...read more

Sponge iron is a metallic product produced through the direct reduction of iron ore in the form of lumps, pellets, or fines.

• Sponge iron is also known as direct reduced iron (DRI).

• It is produced by removing oxygen from iron ore through a chemical reaction using natural gas or coal as a reducing agent.

• Sponge iron is used as a raw material in the production of steel through the electric arc furnace (EAF) or basic oxygen f

WHRB in rotary kiln stands for Waste Heat Recovery Boiler, which is used to recover heat from the exhaust gases of the kiln.

• WHRB is a type of boiler that captures and reuses the heat energy from the exhaust gases of a rotary kiln.

• It helps in improving the overall energy efficiency of the kiln operation.

• The recovered heat can be used for various purposes such as preheating combustion air or generating steam for power ge...read more

Iron smelting process is a method of extracting iron from its ore using heat and reducing agents.

• Iron ore is heated in a blast furnace with coke (carbon) and limestone as reducing agents.

• The coke burns to produce carbon monoxide, which reacts with the iron ore to release the iron metal.

• The limestone helps to remove impurities from the iron ore, forming slag as a byproduct.

• The molten iron is then collected at the bottom...read more

The Iron-Carbon Diagram is a graphical representation of the phases of iron and carbon at different temperatures.

• Shows the phases of iron and carbon at different temperatures

• Consists of regions such as austenite, ferrite, cementite, and pearlite

• Helps in understanding the microstructure of steel

• Used in heat treatment processes to control the properties of steel

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