Explanation

Mach number is defined as the ratio of the flow velocity to the speed of sound in the medium.

It indicates whether the flow is compressible (high Mach number) or incompressible (low Mach number).

High Mach number → compressibility effects are significant.

Explanation

Cast iron contains graphite flakes that act as lubricants, reducing tool wear during machining.

Its brittle nature allows easy cutting without much deformation.

Cast iron is the easiest to machine among common metals.

Explanation

Molten metal is poured into a reusable metallic mould using gravity, not pressure.

This method produces accurate shapes with smooth surfaces.

It is used for medium production runs.

Permanent mould casting relies on gravity to fill the mould.

Explanation

Steel is forged above its recrystallisation temperature (around 1100 °C) to improve ductility and avoid cracks.

Hot forging refines the grain structure and enhances mechanical properties.

Forging is a hot working process done above recrystallisation temperature.

Explanation

Introducing a shear angle on the cutting tool reduces resistance and spreads the cutting force over a smaller area.

This decreases the required cutting force and improves tool efficiency.

Shear angle is the key factor in reducing cutting force.

Explanation

Hot working is done above the recrystallisation temperature to make metals ductile and easily deformable.

It reduces internal stresses and prevents cracking during shaping.

Hot working must be above recrystallisation temperature for effective deformation.

Explanation

Chromite bricks are highly resistant to both acidic and basic slags, making them ideal for lining furnaces in metallurgical industries.

They can withstand high temperatures and chemical attack during metal processing.

Their high thermal conductivity also helps in efficient heat transfer in industrial furnaces.

Explanation

Slip gauges (or gauge blocks) are generally made of alloy steel for high hardness, wear resistance, and dimensional stability.

They are used for precise measurement and calibration in engineering and machining.

Slip gauges can also be made of ceramic or tungsten carbide for special applications requiring corrosion resistance.

Explanation

Tempering is a heat treatment process used to reduce brittleness and improve toughness in metals, especially steel.

Most materials are tempered at temperatures in the range of 400–500 °C.

The exact tempering temperature is chosen based on the desired balance between hardness and toughness.

Explanation

Tungsten is the strongest metal on Earth.

The melting point of Tungsten is ~ 3,422 °C.

The boiling point of Tungsten is ~ 5,555 °C.