Metallurgical Processes

Submerged Arc Welding (SAW) is extensively used for heavy fabrication including pipes, penstocks, LPG pressure vessels, and bridge girders. Its high deposition rate and deep penetration make it ideal for the long welds and thick materials used in these structures, so the statement is false.

Copper conducts heat better, and this helps in faster cooking.

Galvanisation is the process of applying a protective zinc coating to iron or steel to prevent rusting. Zinc acts as a sacrificial anode, oxidizing preferentially to iron, and also forms a protective layer of zinc carbonate that prevents atmospheric corrosion.

When iron rusts, it combines with oxygen from air to form iron oxide (Fe2O3). Since oxygen atoms add to the iron, the total mass increases. This follows the law of conservation of mass - the nail's weight increases by the mass of oxygen atoms that bond with iron.

Hemochromatosis results in iron overload, which is typically treated by phlebotomy.

Correct. The option correctly uses 'differ from' instead of 'different from'. The uses of 'these metals' removes any ambiguity about what is stronger yet lighter. 'Stronger yet lighter' correctly contrasts the two qualities of the metals.

A. Mild steel contains 0.15% to 0.30% of carbon. Medium steel has 0.30% to 0.60% of carbon. B. Promoted iron is used as the catalyst in the Haber-Bosch process for the making of NH₃. C. Mild steel is malleable and can be bent or machined. This is hardened (tempered) by heating to red heat and quenched by plunging into water or oil.

P. The Parkes process, patented in 1850 uses zinc to form a material which the silver enters. This floats on the lead and can be skimmed off.
Q. The Pattinson process was patented by its inventor, Hugh Lee Pattinson, in 1833. It depended on well-known material properties; essentially that lead and silver melt at different temperatures. The equipment consisted of a row of about 8-9 iron pots, which could be heated from below. Argentiferous lead was charged to the central pot and melted. This was then allowed to cool, as the lead solidified, it was skimmed off and moved to the next pot in one direction, and the remaining metal was then transferred to the next pot in the opposite direction. The process was repeated in the pots successively, and resulted in lead accumulating in the pot at one end and silver on the other end. R. Fire process- The initial product of copper smelting was impure black copper, which was then repeatedly melted to purify it, alternately oxidising and reducing it. In one of the melting stages, lead was added. Gold and silver preferentially dissolved in this, thus providing a means of recovering these precious metals. To produce purer copper suitable for making copper plates or hollow-ware, further melting processes were undertaken, using charcoal as fuel. The repeated application of such fire-refining processes was capable of producing copper that was 99.25% pure.

It usually contains less than 0.1 percent carbon and 1 or 2 percent slag. So, it is the purest form of iron.

Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case hardened surface.

Iron loses its activity when dipped in conc. nitric acid and becomes chemically inert.

The temperature here is 1500 - 1600 degree celsius.

Steel iron rod becomes hard and brittle on immersing in water.

A bi-metal rod bends when heated because the two metals have different coefficients of linear expansion. One metal expands more than the other for the same temperature increase, causing the composite rod to curve toward the side with less expansion. This principle is used in thermostats and temperature-control devices.

Gold's low chemical reactivity makes it ideal for jewellery because it doesn't tarnish, corrode, or react with skin and atmospheric elements. Highly reactive metals would corrode quickly, and while gold does have high density (not low as option C suggests), its primary advantage for jewellery is its inertness. This property of being noble and unreactive is why gold has been used for jewellery for millennia.