Unit – 6 Heat Treatment Processes
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UNIT – 6 HEAT TREATMENT PROCESSES 01. Salt bath of liquid carburizing contains ____ a) Sodium cyanide, Sodium carbonate, Benzene chloride b) Hydrogen cyanide, Sodium carbonate, Sodium chloride c) Sodium cyanide, Sodium carbonate, Sodium chloride d) None 02. ______ statements is/are false for heat treatment processes. a) Martempering process is designed to overcome limitations of quenching b) Pearlite is obtained as final phase in martempering processes. c) Water is used as quenching medium in Jominy end quench test d) All the above 03. The process which improves machinability of steel, but lowers the hardness is _____ a) Process annealing b) Normalising c) Full annealing d) Spheroidising 04. Carburising is _______. a) Tempering process b) case hardening process c) Annealing process d) None 05. The process of reheating martensitic stainless steel to reduce its brittleness without any significant loss in its hardness is _______. a) Annealing b) Normalising c) Quenching d) Hardening 06. Insufficient hardness after tempering may be due to _______. a) Tempering temperature too low b) Tempering temperature too high c) Oxidising atmosphere in furnace d) Any of the above 07. Spheroidise annealing used to produce speroidal or globular form of ____ from plates of cementite in steel. a) Cementite b) Austenite c) Pearlite d) Ferrite 08. The process of involving the heating of steel above the upper critical temperature and then cooled in furnace is known as _______. a) Annealing b) Normalising c) Tempering d) Hardening 09. A steel is heated at about 875°C where the structure consists of only austenite. It is then cooled suddenly at a temperature of about 250° to 525°. This process of heat treatment is known as a) Annealing b) Normalising c) Martempering d) Austempering 10. Application of batch furnaces are ______. a) Tool making b) In Maintenance shop c) Both a & b d) None 11. Semi-muffle furnace is a type of ______. a) Gas fire furnace b) Oil & Gas fire furnace c) Electric fire furnace d) None 12. Surface of a steel component becomes hard due to phase transformation austenite to martensite in _____ a) Carbonitriding b) Flame hardening c) Both a & b d) None 13. _____ furnace protects the steel from oxidation. a) Full muffle b) Direct fired c) Oil or gas fired d) Semi muffle MEM - Unit 6 Viren Bhirdi - BSIET Page 1 of 7 14. If a sample of steel shows excessive hardness after tempering, the probable cause could be a) Excessive proportion of alloying elements b) Insufficient holding time during tempering c) High temperature during tempering d) Change in volume during cooling 15. _____ property is affected by heat treatment. a) Hardness b) strength c) ductility d) All 16. Nitriding process is carried out in ______. a) Muffle furnace b) Electric furnace c) Gas furnace d) All 17. _____ heat treatment process is used for medium carbon steel. a) Box annealing b) Process annealing c) Bright annealing d) Full annealing 18. _____ are heat treatment processes. a) Annealing b) Normalising c) Tempering d) All 19. Killed steel is ______. a) Steel which has been shaped on a power hammer b) Steel which is deoxidized in the ladle with silicon & aluminum c) Steel with more than normal percentage of carbon d) Steel that has lost its properties due to excessive alloying 20. Austenitic stainless steel contain chromium & nickel in amounts required to assure that even at room temperatures, the steels retain their crystalline structures which are _____ a) HCP b) Diamond cubic c) FCC d) Partly amorphous 21. Flame hardening involves _____ a) heating the surface above the transformation range b) quenching after heating c) minimum case depth 1 mm d) All the above 22. In a hardening process, the hypo eutectoid steel is a) Heated from 30° - 50° above the upper critical temp & then cooled in still air b) Heated from 30° - 50° above the upper critical temp & then cooled slowly in furnace c) Heated from 30° - 50° above the upper critical temp & then cooled suddenly d) Heated below or close to the lower critical temp & then cooled slowly 23. _____ temp range represents the tempering temp for C 30 steel. a) 100° – 150° b) 550° – 660° c) 860° – 890° d) 1400° - 1450° 24. Rapid cooling of austenite results in transformation to a) Pearlite b) Banite c) Martensite d) Ferrite 25. When the steel is normalized, it’s _______. a) Yield point increases b) Ductility decreases c) Ultimate tensile strength increases d) All of these 26. The main objectives of heat treatment is/are ______ a) To relieve internal stresses b) To refine grain structure c) To improve machinability d) All 27. Annealing is done _____. a) To harden the surface b) for surface smoothness c) for relieving stresses d) to improve microstructure for good surface finish MEM - Unit 6 Viren Bhirdi - BSIET Page 2 of 7 28. ______ is the last phase obtained after completing heat treatment cycle in patenting process a) Bainite b) Martensite c) Pearlite d) None 29. Advantage of liquid carburizing ______ a) salt bath offer rapid & uniform heating b) Low distortion c) Negligible surface distortion d) All 30. Cracks of vertical nature & dark coloured fissures in a sample of hardened steel indicates that a) steel contains excessive alloying elements b) steel has been burned c) steel has been properly hardened d) hardness accordance with the carbon percentage 31. The temperature range of the solid carburizing in degree celsius ____ a) 750 – 850 b) 721 – 800 c) 925 – 950 d) 550 – 650 32. Soaking time _____ with increase in section thickness and the amount of alloying elements a) decreases b) remains same c) increases d) none 33. In normalizing, one of the following statements is not correct. a) it relieves internal stresses b) it produces a uniform structure c) the rate of cooling is moderately high d) the rate of cooling is slow 34. Solid carburizing is also called as ______. a) Open carburizing b) Hidden carburizing c) Quick C d) Pack C 35. The process of decomposition martensite structure, by heating martensitic steel below its critical temperature is called as _____ a) Austenitizing b) Quenching c) Tempering d) None 36. Annealing of steel is done to impart which one of the following property on steel? a) Hardness b) toughness c) ductility d) brittleness 37. Quenching operation is usually followed by ______. a) Annealing b) Normalising c) Tempering d) None 38. Steel can be hardened quickly by the process of ______. a) Induction hardening b) Cyaniding c) Nitriding d) Carburising 39. The hardness of steel increases if it contains _____. a) Pearlite b) Ferrite c) Cementite d) Martensite 40. Austenite in steel is transformed into “fine pearlite structure” by ______. a) Annealing b) Normalising c) Tempering d) Hardening 41. During heat treatment, the formation of thick layer of scale on the surface of steel articles is mainly due to a) Excessive hardness b) Oxidation c) Reduction d) Coarse grain structure 42. In flame hardening oxy-acetylene flame is used. a) True b) False 43. _____ can be used as fuel in open hearth furnace. a) Liquid fuels b) coke oven gas c) producer gas d) any of the above MEM - Unit 6 Viren Bhirdi - BSIET Page 3 of 7 44. Induction hardening is basically ______. a) carburizing process b) surface hardening process c) core hardening process d) None of these 45. One of the following is not the purpose of full annealing a) Refine grains b) induces softness c) remove strain and stresses d) produces hardest material 46. _____ furnace is used for steel only. a) Cupola b) Open hearth c) Indirect arc furnace d) All 47. One of the following structure is least hard. a) Pearlite b) Martensite c) Austenite d) Sorbite 48. Case depth of gas carburizing is up to ______ a) 0.2-0.5 mm b) 0.4-0.6 mm c) 0.7-0.8 mm d) 0.9-1.0 mm 49. A modified quenching procedure used to minimize distortion & cracking that may develop during uneven cooling the heat treated material is _____ a) Austempering b) Martempering c) Tempering d) All 50. Insufficient hardness after tempering may be due to ______ a) Tempering temp too low b) Tempering temp too high c) oxidizing atmosphere in the furnace d) any of the above 51. Full muffle type furnaces protect the steel from oxidation by ____ a) circulating the gases around the chamber containing steel b) circulating the gases in the chamber containing steel c) Both a & b d) None of these 52. ______°C temperature range represents the tempering temperature for C30 steel. a) 100-150 b) 550-660 c) 860-890 d) 1400-1450 53. Annealing of steel is done to impart which one of the following property on steel? a) Hardness b) Toughness c) Ductility d) Brittleness 54. During hardening soft spots can be avoided by ______. a) using a more effective cooling medium b) protecting against decarburization in heating c) obtaining a more homogeneous structure employing annealing or normalizing before hardening d) All the above 55. _____ is/are heat treatment processes. a) Annealing b) Normalising c) Tempering d) All 56. Defect in steel due to heat treatment ______. a) Black fracture b) Warping c) Soft spot d) All 57. In normalising process, the hypo-eutectiod steel is heated from 30° C to 50° C above the upper critical temperature and then cooled in still air. a) True b) False 58. The alloying element which can replace tungsten in high speed steels is ____ a) nickel b) vanadium c) cobalt d) molybdenum MEM - Unit 6 Viren Bhirdi - BSIET Page 4 of 7 59. In induction hardening ____ is high.