CWB Level 3 Module 21 Welding Metallurgy of Steels fully solved graded A+ 2023/2024

CWB Level 3 Module 21 Welding Metallurgy of SteelsWhat forms the largest group of commercially important alloys? - correct answer Steel Steels are alloys of iron with less than ____ % of carbon plus a wide range of other elements - correct answer 2 % Elements which form interstitial solutions with iron - correct answer Carbon, nitrogen, boron and hydrogen Elements which from substitutional solutions with iron - correct answer Manganese and Silicon Below 910 C, Iron is in _________ structure - correct answer BCC B/w 910 C and 1390 C iron takes____ structure - correct answer FCC Above 1390 Cand upto the melting point 1534 C , its ______ structure - correct answer BCC What are allotropic forms of iron ? - correct answer BCC, FCC structures at different temperatures True stable form of carbon in iron is ____ - correct answer graphite Eutectic is formed at ________ wt of Carbon - correct answer 4.3% Austenite / gamma phase in iron dissolves up to ______ % of Carbon - correct answer 2% With no carbon present, austenite starts to form at which temperature? - correct answer 910 C With 0.8% wt carbon, austenite starts to form at which temperature? - correct answer 723 C The region where the carbon is dissolved in BCC iron is very narrow? - correct answer Ferrite phase / Alpha What is the amount of carbon in Ferrite region? - correct answer 0.02 wt % at 723 C Ferrite cannot be considered as __________ - correct answer Pure iron At what % of carbon and temperature does eutectoid forms? - correct answer 0.8% C and 723 C Eutectoid occurs in which state? - correct answer soild Steel of eutectoid composition will, wen cooled from the austenitic region, transforms at 723 C to from a two solid phase called ________ - correct answer Ferrite and Cementite (Fe3C) or Pearlite Pearlite is made of - correct answer Ferrite and cementite Hardness of cementite is - correct answer 1150 HV Wht is the %wt and temp for delta ferrite? - correct answer 0.1 % wt and 1493 C What is the appearance of peritectic on iron carbon diagram? - correct answer inverted eutectoid What is the percentage of carbon in peritectic phase? - correct answer 0.16% What chemical reaction happens in peritectic region ? - correct answer a two phase mixture of delta ferrite and liquid transform on cooling to a single phase solid of austenite Peritectic phase is used to explain what phenomena in welding? - correct answer Hot cracking Pearlite is made of two phases ,which are .. - correct answer Ferrite and cementite Ferrite contains very less carbon where as cementite contains ___ % of carbon - correct answer 6.7% A faster growth of cementite plates results in ........... - correct answer Finer pearlite What causes the austenite grain growth? - correct answer Heating to higher temperatures than those necessary to get complete transformation to austenite. The grain grow to ____________ the surface energy - correct answer lower What are fine grain steels? - correct answer Some steels contain small precipitates ,such as Al and nitrides ,which pin the austenite grain boundaries and retain small grains upto high temperatures Fine grain steels are used when ____ - correct answer toughness is a consideration Coarse grain steels are used when....... - correct answer high temp creep resistance is important