CWB Module 22 Latest Update Graded A

CWB Module 22 Latest Update Graded A Complete the following: a) Chromium stabilizes the _____ form of iron b) Nickel stabilizes the _____ form of iron a) bcc b) fcc If a straight chromium steel of 18% Cr and < 0.1 % C is heated to 1000°C will it transform to austenite or remain as ferrite? remain as ferrite What is the predominant structure of an 18% Cr, 8% Ni steel at room temperature? austenite The chromium content of a stainless steel is 20%. Is it likely this is a martensitic grade? No, Martensitic grade is 18% to 11.5% Cr A 14% Cr martensitic steel heated to 1000°C and air cooled produces a) ferrite b) aus1enite c) martensite c) martensite Does an austenitic stainless steel have a greater or lesser work hardening rate than carbon steel? greater A carbon steel component operates satisfactorily at 500°C under a stress of 50MPa. If 304 stainless were substituted, up to what level could the temperature be raised? 600°C, 20% more then carbon The loss of corrosion resistance due to carbide formation and chromium depletion is known as: a) sigma formation b) sensitization c) stabilization b) sensitization What maximum carbon level is usually specified to ensure freedom from sensitization during welding? a) 0.03% b) 0.003% C) 0.3% a) 0.03% The presence of residual delta ferrite in the weld metal indicates that primary solidification was? a) ferrite b) austenite a) ferrite A method of controlling weld metal fissuring is to always use a stabilized weld metal to ensure primary solidification is austenite: a) is to always use a stabilized weld metal b) to ensure primary solidification is austenite c) to ensure there is a small amount of residual delta ferrite in the weld metal c) to ensure there is a small amount of residual delta ferrite in the weld metal True or false: "Welds in austenitic stainless steels are always preheated to prevent hydrogen induced cracking False When a two layer overlay of stainless on carbon steel is made it is common practice to use E308 for the second layer and E _____for the first layer (E309) on top of the carbon and then E308 Weld metal containing large amounts of ferrite and is exposed to high temperature service may: a) suffer embrittlement due to sigma formation b) have improved ductility due to ferri1e growth c) become air hardening a) suffer embrittlement due to sigma formation Preheat is usually required when welding martensitic stainless steels: a) to prevent cracking b) to soften the HAZ c) to promote ferrite a) to prevent cracking Why would 650°C be a better temperature to specify for a PWHT of a welded martensitic stainless steel than 550°C To avoid temper embrittlement True or false: "Ferritic stainless steels are very tolerant of contamination during welding because of their very high ductility" False True or false? "Conventional flame cutting with oxy-acetylene cannot be used on stainless steels" True Which of the following actions might reduce the risk of carbon contamination in welding stainless steels? a} use aluminum oxide grinding wheels reserved for stainless steel b) use cellulosic type electrodes c} carefully clean off grease and dirt before welding d) use stainless steel cleaning brushes e} use C02 for back shielding the weld a} use aluminum oxide grinding wheels reserved for stainless steel c} carefully clean off grease and dirt before welding d) use stainless steel cleaning brushes If a buttering technique is used to weld 304 stainless to mild steel what should be used for the butter layer? a) E48018 (mild steel) b) E308 c) E309 c) E309 The presence of chromium in iron will stabilize which crystal structure? (a) hcp (b) cementite (c) fcc (d) austenite (e) bcc (e) bcc A straight chromium S1eel with <0.1 % carbon and 18% chromium when heated to 1000°c will: (a) remain ferritic (b) form martensite (c) transform to austenite (d) cause grain refinement (e) precipitate sigma phase (a) remain ferritic Stabilized austenitic stainless steels such as 347 do not become sensitized in welding because: (a) they have very low carbon that avoids carbide precipitation (b) they contain elements such as niobium (columbium) that tie up the carbon (c) they have higher than average chromium (d) they have a small percentage of ferrite present (e) they are always supplied in the solution annealed condition (b) they contain elements such as niobium (columbium) that tie up the carbon If a plate of austenitic stainless steel is cold formed it experiences: (a) zero work hardening (b) discontinuous yielding (c) grain growth (d) strain aging (e) a greater spring-back than a comparable plate of carbon steel (e) a greater spring-back than a comparable plate of carbon steel Weld decay is caused by? (a) excessive grain growth in the HAZ (b) chromium depletion at the grain boundaries due to carbide precipitation (c) loss of chromium during transfer in the arc (d) precipitation of niobium (columbium) carbide at the grain boundaries (b) chromium depletion at the grain boundaries due to carbide precipitation There is an increased risk of weld metal fissuring when- (a) the steel is not stabilized (b) no preheat is applied (c) the ferrite content is too high (d) the primary solid to form on solidification is austenite (e) chromium depletion occurs on solidification (d) the primary solid to form on solidification is austenite On the Delong diagram the amount of ferrite is indicated by? (a) the percent ferrite (b) the nickel equivalent (c) the ferrite number (d) the chromium equivalent (e) it is not indicated on the Delong diagram (c) the ferrite number Which of the following is likely to result in cracking due to martensrte formation? (a) E309 deposited over E308 weld metal (b) E308 deposited over E309 weld metal (c) E48018 (mild steel) weld metal deposited over E308 weld metal (d) E309 deposited over E4B018 weld metal (C) E48018 (mild steel) weld metal deposited over E308 weld metal Which of the following processes would not be recommended for welding type 304 stainless steel? (a) GTAW with argon shielding (b) SMAW with EXX-15 electrodes (c) GTAW with helium shielding (d) GMAW with co2 shielding (d) GMAW with co2 shielding An unstabilized stainless steel with 0.15% carbon has been welded. What heat treatment could be applied to prevent weld decay in service? (a)stress relief at 650°C followed by a furnace cool (b)stress relief at 650°C followed by a quench (c)solution treatment at 1100°C followed by a furnace cool (d)austenitize at 910°c followed by a furnace cool (e)solution treatment at 1100°C followed by a rapid cool (e)solution treatment at 1100°C followed by a rapid cool