Engineering Materials MCQ Questions & Answers | Mechanical Engineering

elasticity is the ability of a body to resist a distorting influence and to return to its original size and shape when that influence or force is removed

Cupola is used to melt pig iron to make iron castings in foundry. Charge consists of pig iron, scrap and limestone and coke

Mild steel belongs to the following category of Low carbon steel

The correct option is "Tin and lead".

The usual composition of a soldering alloy is a mixture of tin (Sn) and lead (Pb) in varying proportions, commonly 60% tin and 40% lead or 63% tin and 37% lead (known as eutectic solder).

Tin provides good wettability, which helps the solder spread smoothly over the metal surfaces.

Lead lowers the melting point of the alloy and provides strength and durability to the soldered joint.

This combination creates an alloy with a relatively low melting point, making it ideal for soldering applications in electronics and electrical work.

Why not the others?

"Tin, lead and small percentage of antimony" is used in bearing alloys, not in common solder.

"Tin, lead and silver" forms a type of hard solder, used where stronger joints are required, but it is not the usual composition.

"Tin and copper" is used in lead-free solders (modern alternatives), but traditionally the common solder is tin-lead.

Therefore, the usual composition of a soldering alloy is tin and lead.

The metal suitable for bearings subjected to light loads, is Phosphor bronze

The metal suitable for bearings subjected to heavy loads, is White metal

when Silicon is added to copper it improves the hardness and strength

The addition of nickel to copper improves strength and corrosion resistance while allowing the alloy to remain ductile.

For the allotropic forms of iron, the points of arrest are The points of discontinuity

The principal iron ores are hematite (Fe₂O₃).
Hematite is an iron oxide mineral.
Hematite contains iron about 70%.