Download CWB Welding Inspector Level III Study Guide 2024 Questions & Answers | 100% Correct and more Exams Welding Inspection Technologies in PDF only on Docsity!
CWB Welding Inspector Level III Study
Guide 2024 Questions & Answers | 100%
Correct | Verified
Which of the following metals has the highest thermal conductivity? (a) carbon steel (b) stainless steel (c) aluminum - ✔✔(c) The Ellingham diagram (a) is a plot of thermal conductivity against temperature, (b) shows the free energy of oxide formation against temperature. (c) shows the rate of oxidation of metals against temperature. - ✔✔(b) True or False? A metal with a high negative free energy of oxide formation will generally require greater shielding from the atmosphere during welding. - ✔✔True Electricity can be conducted by: (a) atoms and electrons. (b) electrons and ions. (c) only ions. - ✔✔(b) Which of the following elements is often present in submerged arc fluxes to improve arc stability? (a) copper (b) potassium (c) nickel (d) tungsten - ✔✔(b)
Thoria is added to tunsten electrodes for what purpose? - ✔✔To increase thermionic emission by lowering the work function. True or False? All pure metals have the same crystal structure. - ✔✔False. Metals generally have one of three basic structures. Which crystal structure(s) is (are) composed of close-packed planes? - ✔✔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. - ✔✔(c) Multiplication and subsequent congestion of moving dislocations causes: (a) elastic extension. (b) work or strain hardening. (c) a drop in the yield stress. - ✔✔(b) Which of the following elements are most likely to form interstitial solid solutions? (a) copper (b) nickel (c) carbon - ✔✔(c) If FCC iron has a denser structure than BCC iron, why does it have a higher solubility for carbon? - ✔✔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? - ✔✔One
Why is the temperature range 150°C-400°C usually avoided when forming steels? - ✔✔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 - ✔✔(b) How does yield strength vary with grain size? - ✔✔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 - ✔✔(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. - ✔✔(b) Which of the following alloys would you expect to give the highest risk of hot cracking? (a) Al-0.1%Cu (b) Al-3%Cu (c) Al-8%Cu - ✔✔(b) If centerline solidification cracking is occuring in welding a structural steel what is a likely cause? (a) electrical extension too long (b) arc voltage too high
(c) welding current and speed too high (d) weld too large - ✔✔(c) What is the most likely cause of porosity in aluminum welds? (a) hydrogen (b) nitrogen (c) argon (d) oxygen - ✔✔(a) How can porosity due to nitrogen be controlled in welding nickel? - ✔✔By using filler metal containing titanium. What is the most likely cause of porosity in carbon steel welds? (a) hydrogen from reduction of water (b) nitrogen (c) carbon monoxide from reaction of oxygen with carbon (d) oxygen direct from the air - ✔✔(c) What elements are included in electrodes or fluxes to control porosity in steel welds? (a) silicon, aluminum, manganese (b) copper, nickel, molybdenum (c) sulphur, phosphorus, selenium (d) silica, alumina, magnesia - ✔✔(a) What is thermal conductivity divided by specific heat and specific gravity known as? - ✔✔Thermal diffusivity True or False?
(a) get hotter more quickly. (b) absorb more electrons. (c) have a shorten life. (d) operate at a lower temperature for the same current. (e) emit more ions. - ✔✔(d) The presence of close-packed planes in FCC metals gives many of them the special property of: (a) good high-temperature strength. (b) the ability to undergo extensive plastic deformation. (c) brittleness at low temperatures. (d) complete solubility with all other metals. (e) small grains. - ✔✔(b) Work hardening occurs because of: (a) fine precipitates. (b) a reduction in the number of dislocations making slip more difficult. (c) locking of dislocations by carbon and nitrogen atoms. (d) multiplication and congestion of dislocations. - ✔✔(e) Nickel and copper have complete solid solubility. Copper has a lower melting point then nickel. If a 50/ Cu-Ni alloy is cooled from the liquid what will be the composition of the first solid to form? (a) 50% Cu (b) less than 50% Cu (c) Pure Cu (d) Pure Ni (e) more than 50% Cu - ✔✔(b) A Wide solidification range and rapid growth rate during solidification will encourage: (a) planar growth.
(b) equilibrium conditions. (c) no constitutional supercooling. (d) dendritic growth. (e) eutectic formation. - ✔✔(d) Centerline hot cracking im more likely with: (a) shallow, round welds. (b) short weld pools. (c) wide groove angles. (d) deep, narrow welds. (e) vertical welds. - ✔✔(d) Porosity in welds due to a specific gas is more likely if the: (a) solubility of the gas at the freezing point is much lower than at higher temperatures. (b) solubility of the gas at the freezing point is very high. (c) gas does not dissolve in the liquid. (d) solubility is independent of temperature. (e) gas has a high solubility in the solid. - ✔✔(a) Increasing the initial plate temperature (preheat): (a) has no effect on the cooling rate. (b) reduces the weld heat input. (c) reduces the cooling rate. (d) causes narrower isotherms. (e) improves the arc efficiency. - ✔✔(c)
