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231.

During heat treatment, deformation and volume changes can be minimised by

A.	slowly cooling in the martensitic range	B.	using surface hardening when possible
C.	using alloy steels least prone to such changes	D.	Any of the above

232.

Quenching cracks during heat treatment can be minimised:

A.	by avoiding sharp projections and sudden transitions from thick to thin sections	B.	articles should be free from stress before heat treatment
C.	heat to minimum stable temperature for hardening	D.	Any of the above

233.

Formation of thick layer of scale on the surface of steel articles can be minimised by

A.	heating in furnaces with reducing neutral or protective atmosphere	B.	heating in boxes with used carburising agent or cast iron chips
C.	heating in molten salt bath	D.	Any of the above

234.

Which of the following furnace is used for steel only?

A.	Cupola	B.	Air furnace
C.	Open hearth furnace	D.	Indirect arc furnace

235.

During heat treatment the formation of thick layer of scale on the surface of steel articles is mainly due to

A.	excessive hardness	B.	oxidation
C.	reduction	D.	coarse grain structure

236.

During heat treatment quenching cracks occur due to

A.	irregular martensitic transformation within the article	B.	oxidising atmosphere within the fumace
C.	heating at higher temperatures for longer durations	D.	All of the above

237.

Which metal has the highest melting point?

A.	Antimony	B.	Chromium
C.	Gold	D.	Stainless steel

238.

Which colour of heat represents the highest temperature?

A.	Blood red	B.	Salmon
C.	Dry cherry	D.	White

239.

Which of the following furnace is used to convert liquid pig iron into steel?

A.	Cupola	B.	Open hearth furnace
C.	Converter	D.	Induction arc furnace

240.

Which of the following can be used as fuel in open hearth furnace?

A.	Liquid fuels	B.	Coke oven gas
C.	Producer gas	D.	Any of the above