ytior viiU oriaC- Faculty of Engineering
1st year Mining, Petroleum and Metallurgical Engineering,
Materials Science
Mid-Term Exam 2007 Time: 1.5 h
Name:-------------- Dr. Mahmoud M.Tash (Model Answer) ---------No--------------------Part One: Phase Diagrams and heat treatment
1. The eutectoid steel in Fe-C diagram has an austenite phase of composition ….. just below 1140C. (a) 4.3%C (b) 0.8%C
(c) 2%C (d) 0.02%C.
2. The eutectic alloy on the Fe-Fe 3 C Diagram contains (a) 4.3%C (b) 0.8%C (c) 2%C (d) 0.02%C.
3. Annealing is usually performed to (a) Decrease hardness. (b) Increase ductility. (c) Relieve stresses. (d) All of the above.
4. Hardening and tempering produce optimum strength and toughness for (a) Steels of carbon content higher than 0.2%. (b)
Al alloys. (c) Cu alloys. (d) All of the above.
5. Normalizing of steels is (a) Heating to ferrite followed by air cooling. (b) Heating to austenite followed by water cooling.
(c) Heating to austenite followed by air cooling.
6. Full annealing of steels is (a) Heating to ferrite followed by air cooling. (b) Heating to austenite followed by water cooling.
(c) Heating to austenite followed by furnace cooling.
7. Tempering of martensite makes it (a) more brittle (b) tougher (c) harder (d)of higher UTS .
8. The structure of the alloy containing 0.8%C be after quenching in water consists of : (a)Ferrite and pearlite (b) Ferrite and
cementite (c) Martensite (d) None of the above
9. The critical temperature for hypoeutectoid alloys in heat treatment must (a) ensure the alloy is of 2 phases ferrite + austenite
(b) one phase ferrite (c) one phase austenite.
10. Hardening temperature of hypo-eutectoid steels is
(a)30-50 0C above Ac3,
(b)30-50 0C above Ac1,
(c)30-50 0C
0
above Tm, (d) 30-50 C above recrystallization temperature.
11. The 0.5%C steel contains less than 0.02%C in it’s ………. At 750ºC. (a) Austenite (b) Pearlite (c) Ferrite (d) Cementite
12. When the hypoeutectoid steel is heated to the normalizing temperature, the structure obtained is:- (a) Eutectic + Austenite
(b) Pearlite +Fe3C
(c) Fe3C + Austenite
(d) None of the above
13. The amount of phases of alloy contains 0.2% C after equilibrium cooling to room temperature is:- (a) 90% ferrite+ 10%
austenite
(b) 97% ferrite + 3%austenite (c) 97% ferrite + 3% Fe3C
(d) 97% Fe3C + 3% ferrite
14. The amount of phases of alloy contains 0.8% C after equilibrium cooling to room temperature is:- (a)88% austenite +
12%ferrite
(b) 60% ferrite + 40%Fe 3C (c) 88% Fe3C + 12% ferrite
(d) 88% ferrite + 12% Fe3C
15. The stricture of the alloy containing 0.8% C after quenching would contain:- (a)100% pearlite
(b)100%martensite
(c)50%ferrite + 50% Fe3C (d)50%ferrite+ 50% austenite
16. Martensite has a structure of :(a) BCC
(b)FCC (c) BCT
(d) HCP.
17. The amount of phases present in the alloy contains 1.2%C after equilibrium cooling to room temperature is :- (a) 94%
martensite & 6% ferrite (b) 82% ferrite& 18% Fe3C (c) 80% austenite & 20% ferrite
(d) 82 Fe 3C & 18% ferrite
18. As the carbon content changes from 0.2 to 0.8%, the upper critical temperature:- (a) Increases
(b) Decreases
19. The effect of alloying elements on steel like Cr, Mo V, Ti, Si, etc. on heat treatment respond is:-(a)No effect (b) To increase
hardenability (c) Make heat treatment with no effect (d) To decrease hardenability
20. The upper critical temperature for the alloys containing 0.8C is:- (a) 850º C (b) 900º C (c) 773ºC (d) None of the above.
21. Fine grain sizes are promoted by certain manufacturing conditions such as:- (a) High cooling rates (b) High amounts of
deformation (c) Certain alloying elements (d) All of the above
22. Parts are furnace annealed to decrease their :-(a)-Brittleness (b)Ductility
(c)Toughness
(d)None of the above
23. The alloy 0.15 %c is designated….. … (a) low C –(b) medium C – (c) high C) steel.
24. The alloy 0.45 %c is designated….. … (a) low C – (b) medium C – (c) high C) steel.
25. The alloy 1.2 %c is designated….. … (a) low C – (b) medium C – (c) high C) steel.
26. The alloy 1 %Cr is designated….. … (a) low – (b) medium -(c) high) Cr alloy steel.
27. The alloy 12 %c is designated….. … (a) low – (b) medium -(c) high) Cr alloy steel.
28. The carbon content in Plain carbon steel 1040 is (a) 0.6%
(b) 0.2%
(c) 0.4%
(d) 0.8%
29. Austenitic stainless steels should have Ni content ≥ 8%
(a) true
(b) false
30. One can produce a huge casting from mealable cast iron (a) true
(b) false
31. One can produce a huge casting from ductile cast iron (a) true
(b) false
32. To produce grey cast iron, (a) fast cooling rate and low content of Si and C,
(b) slow cooling rate and high content of Si
and C
(c) slow cooling rate and low content of Si and C
(d) fast cooling rate and high content of Si and C
33. To produce white cast iron, (a) fast cooling rate and low content of Si and C, (b) slow cooling rate and high content of Si
and C
(c) slow cooling rate and low content of Si and C
(d) fast cooling rate and high content of Si and C
34. To produce Ductile cast iron, (a) fast cooling rate and low content of Si and C,
(b) slow cooling rate and high content
of Si and C + traces of %Mg or Ce%
(c) slow cooling rate and high content of Si and C
35. To produce mealable cast iron,
(a) fast cooling rate and low content of Si and C + heat treatment at 950C,
(b) slow
cooling rate and high content of Si and C
(c) fast cooling rate and low content of Si and C
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ytior viiU oriaC- Faculty of Engineering
1st year Mining, Petroleum and Metallurgical Engineering,
Materials Science
Mid-Term Exam 2007 Time: 1.5 h
36. The main applications for carbon steels are (1)----springs---(2)----rebar-----, for low alloy steels are (1)-----armor steels----(2) automotive----, for tool steels are (1)------Dies------(2)-----cutting tools----and for stainless steels are (1)—corrosion
resistant applications-----(2)—Surgery Tools-----37. The Cr content in the ferritic stainless steels should be more than –11.5%---- and the carbon should be-------- (low , high)
while in the martensitic stainless steels the carbon should be ---------- (low, high)
38. W 50-06 this is –whiteheart - mealable cast iron has a strength of ----500 N/mm2 and elongation of ------6 %
39. B 30-10 this is ---Blackheart mealable cast iron has a strength of --300 N/mm2 and elongation of ----- 10%
40. P 80-04 this is Pearlitic mealable cast iron has a strength of ------- 80 N/mm2 and elongation of ------4%
41. The main applications of cast irons are (1)--Machine Frames and bases -(2)--Pipes------(3)---Milling Balls42. Sketch the cooling curve and microstructure for eutectic alloy.
43. Alloy defects are (1)------point-----(2)---line-----(3)----surface----- and (4)---volume---------------44. Metals have --low---Tm and --low--- modul’s of elasticity (E) while ceramics have -high---Tm and --- high--- E
yoa iaii cttrC
L
L--γ+Fe3C
γ+Fe3C
γ--P (ɑ+Fe3C)
P (ɑ+Fe3C)
+ Fe3C
This lamellar structure could be Pearlite (ɑ + Fe3C) in eutectoid steel at RT and eutectic (γ + Fe3C) in eutectic steel at 727C <T <
1190C
γ
Pearlite (ɑ + Fe3C)
eutectic (γ + Fe3C)
eutectoid (ɑ + Fe3C) + Fe3C
Part Two:
1.
2.
3.
FCC
BCC
Number of atoms per unit cell in BCC is ---- 2 and Number of atoms per unit cell in FCC is -------4
Relationship between the lattice constant and the atomic radius in BCC is --4*r=a*√3 and in FCC is ---- 4*r= a*√2
Atomic packing factor in BCC is 0.68 and Atomic packing factor in FCC is 0.74
Good Luck/ Dr. Mahmoud M. Tash
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