169. An important precaution to produce a good soldered joint is that
A.The soldering iron bit must first be made red hot
B.The joint area must be clean and close-fitting
C.Aluminium wire must be placed along the joint
D.A thin film of lubricating oil must be applied to the joint edges

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170. The following flux is used for brazing aluminium and magnesium
A.Mixture of boric acid, borax and wetting agent
B.Boric acid, borax, or fluoride with a wetting agent
C.Chlorides and fluorides mixed with water
D.Any of the above

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171. Post cleaning is necessary at brazed joint in order to avoid
A.Scaling
B.Slagging
C.Oxidation
D.Corrosion

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172. The purpose of using borax in brazing is to
A.Replace flux
B.Dissolve oxides when heating the work
C.Accelerate the formation of oxides on the work
D.Prevent the speller from melting too quickly

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173. The commonly used flux for brazing is
A.Resin
B.NH4CL
C.Borax
D.Soft iron

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174. The brazing process is carried in the temperature range of
A.150°C to 250°C
B.250°C to 450°C
C.500°C to 700°C
D.700°C to 900°C

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175. Which of the following is not a heat treatment process
A.Austempering
B.Martempering
C.Parkerising
D.Cyaniding

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