Question

Refractory metals are used in the construction of furnaces because
(A) They can withstand high temperatures
(B) They are chemically inert
(C) Their melting point is high
(D) None of the above

Answer 1

Hint: A category of metallic elements known as refractory metals are extremely heat-and wear-resistant. Of the most common of the refractory metals, tungsten has the highest density and melting point. The melting point of tungsten is so high that it is very difficult to convert it into liquid. It is often used in conditions where there are high temperatures, strength is required, and high density is not a problem.

Complete Step by Step Answer:
Refractory metals are used in the construction of furnaces because they can withstand high temperatures, are chemically inert, and their melting points are high. There are five refractory metals. These are niobium ($Nb$), molybdenum ($Mo$), tantalum ($Ta$), tungsten ($W$), and rhenium ($\operatorname{Re}$).

They all have characteristics in common, such as great hardness at room temperature and a melting point over${{2000}^{o}}C$. Refractory metals are resistant to creep deformation at extremely high temperatures because of their high melting points.
Hence, the correct options are (A), (B), and (C).

Note: The main function of the refractory material used within a marine boiler is to minimise heat losses from the furnace and to contain the heat produced by the fuel being burned there. Therefore, it is essential that these materials have the capacity to tolerate high temperatures and have insulating qualities.