Metallurgical Processes

Due to electroplating, a brand new bicycle has shining handlebar and wheel rims.

Hot rolling is a metalworking process that occurs above the recrystallization temperature of the material. After the grains deform during processing, they recrystallize, which maintains an equiaxed microstructure and prevents the metal from work hardening.

Quenching is the rapid cooling of a workpiece to obtain certain material properties. 

The puddling furnace is a metalmaking technology used to make wrought iron or steel from the pig iron produced in a blast furnace. The furnace is constructed to pull the hot air over the iron without it coming into direct contact with the fuel. The major advantage of this system is keeping the impurities of the fuel separated from the charge.

Pyrometallurgy is a branch of extractive metallurgy. It consists of the thermal treatment of minerals and metallurgical ores and concentrates to bring about physical and chemical transformations in the materials to enable recovery of valuable metals.

Calcining is thermal decomposition of a material. Examples include decomposition of hydrates such as ferric hydroxide in to ferric oxide and water vapour, or decomposition of calcium carbonate in to calcium oxide and carbon dioxide and or of iron carbonate in to iron oxide.

This is the correct option. Hydrochloric acid is used for removing oxide film from steel objects.

Boron trichloride, BCl₃ is a valuable reagent in organic synthesis. It is a starting material for the production of elemental boron. It is also used in the refining of aluminium, magnesium, zinc and copper alloys to remove nitrides, carbides, and oxides from molten metal.

Kinks in rails can form due to various defects: loose packing at joints allows movement, gauge/alignment defects cause stress concentrations, and cross-level issues at joints create irregularities. All three factors (options A, B, C) can contribute to kink formation, making option D the comprehensive correct answer.

Cathodic modification is the retardation of anodic reaction as the result of an increase in the ability of an alloy to be passivated by the introduction of an active cathode into the alloy e.g., the alloying of stainless steel and titanium with platinum group metals

Bethanization is a process to protect steel from corrosion by plating it with zinc.

In the context of corrosion, passivation is the spontaneous formation of a hard non-reactive surface film that inhibits further corrosion. This layer is usually an oxide or nitride that is a few nanometers thick.

The Hall-Héroult process is the major industrial process for the production of aluminium. It involves dissolving alumina in molten cryolite, and electrolysing the molten salt bath to obtain pure aluminium metal.

A number of metals such as silver, gold and platinum, have been obtained in colloidal state by treating the aqueous solution of their salts, with a suitable reducing agent such as formaldehyde, phenyl hydrazine, hydrogen peroxide, stannous chloride etc.

This option is correct because the finely powdered colemanite ore is usually boiled with sodium carbonate to obtain sodium borax and sodium metaborate.