CWB Welding Inspector Level III Study Guide Questions and Verified Answers_ 100% Correct_ Graded A

CWB Welding Inspector Level III Study Guide Questions and Verified Answers_ 100% Correct_ Graded A Which of the following elements is often present in submerged arc fluxes to improve arc stability? (a) copper (b) potassium (c) nickel (d) tungsten - ANSWER -(b) Thoria is added to tunsten electrodes for what purpose? - ANSWER -To increase thermionic emission by lowering the work function. True or False? All pure metals have the same crystal structure. - ANSWER -False. Metals generally have one of three basic structures. Which crystal structure(s) is (are) composed of close-packed planes? - ANSWER -FCC and HCP The real strength of metals is lower than the theoretical value because: (a) real crystals always fracture along specific crystal planes. (b) grain boundary sliding occurs. (c) the presence of dislocations facilitates slip. - ANSWER -(c) Multiplication and subsequent congestion of moving dislocations causes: (a) elastic extension. (b) work or strain hardening. (c) a drop in the yield stress. - ANSWER -(b) Which of the following elements are most likely to form interstitial solid solutions? (a) copper (b) nickel (c) carbon - ANSWER -(c) If FCC iron has a denser structure than BCC iron, why does it have a higher solubility for carbon? - ANSWER -The preferred site for carbon in BCC iron is smaller than that in FCC iron. If two metals have complete mutual solid solubility how many phases are formed in the solid- one or two? - ANSWER -One How many phases are there in a eutectic- one or two? - ANSWER -Two Without referring to the text, draw the phase diagram for a eutectic system with limited mutual solid solubility of the two components. - ANSWER -Refer to Figure 6.6(Module 20-2014, page 18) Using the portion of the iron-carbon phase diagram in Figure 6.10(Module 20- 2014, page 21), use the lever rule to determine the precentage of ferrite and eutectoid pearlite present in a slowly cooled 0.2% carbon steel. - ANSWER - About 25% pearlite and 75% ferrite. Here the tie line begins at 0.0%C (α ferrite) and ends at 0.08%C (pearlite). The fulcrum for the lever rule is at 0.2%C % pearlite = (0.2%C - 0.0%C)/).8%C - 0.0%C) x 100% % pearlite = (0.2/0.8) x 100% % pearlite = 25% Which of the following metals has the highest work hardening coefficient? (a) 70/30 brass (b) aluminum (c) copper (d) low carbon steel - ANSWER -(a) True or False? Recrystallization always involves the formation of a new phase. - ANSWER - False To get recovery and recrystallization the metal must have been previously (a) quenched. (b) heated. (c) cold worked. - ANSWER -(c) Can strain aging in low carbon steels take place at room temperature? - ANSWER -Yes Why is the temperature range 150°C-400°C usually avoided when forming steels? - ANSWER -Because of "blue brittleness", i.e., lower ductility due to dynamic strain aging. Which of the following is a condition for an alloy to show precipitation hardening? (a) there must be a eutectoid system (b) the solubility of one component must rise with increasing temperature (c) there must be complete solid solubility - ANSWER -(b) How does yield strength vary with grain size? - ANSWER -Inversely as the square root of the grain size. Which of the following factors increases the degree of constitutional supercooling? (a) very slow solidification rate (b) an alloy with a very narrow solidification range (c) an alloy with a wide solidification range - ANSWER -(c) Hot Cracking during welding is more likely in: (a) pure metals. (b) alloys with a wide solidification range. (c) alloys with a very high alloy content. - ANSWER -(b)