The steels with the following compositions are heat treated and the results of microstructures are indicated in Table 2(c). Table 2(c): Heat treated steels and the results of microstructures Steel A 0.35 wt% C Coarse Pearlite Steel B 0.25 wt% C Coarse Pearlite Steel C 0.35 wt% C Fine Pearlite Rank the above steels based on carbon content and microstructures from the highest to the lowest hardness with justification.

The steels with the following compositions are heat treated and the results of microstructures are indicated in Table 2(c). Table 2(c): Heat treated steels and the results of microstructures Steel A 0.35 wt% C Coarse Pearlite Steel B 0.25 wt% C Coarse Pearlite Steel C 0.35 wt% C Fine Pearlite Rank the above steels based on carbon content and microstructures from the highest to the lowest hardness with justification.

Precision Machining Technology (MindTap Course List)

2nd Edition

ISBN:9781285444543

Author:Peter J. Hoffman, Eric S. Hopewell, Brian Janes

Publisher:Peter J. Hoffman, Eric S. Hopewell, Brian Janes

Chapter2: Measurement, Materials, And Safety

Section2.7: Heat Treatment Of Metals

Problem 2RQ: Direct hardening can be performed on steel containing at least________ carbon.

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The TTT diagram for a 1076 eutectoid steel is given: What is the heat treatment process to form 50% Coarse Pearlite + 50% Martensite. 800 A 1400 Eutectoid temperature 700 A 1200 600 1000 500 800 400 A 600 300 M(start) 200 50% 400 M + A M(50%) M(90%) 100 200 10-1 1 10 102 103 104 105 Time (s) Temperature (°C) Temperature (°F)
3.The TTT diagram of a plain carbon steel is given in Fig. 1. Identify whether this steel is a hypoeutectoid, eutectoid or hypereutectoid steel. Explain why the transformation happens slowly at 850°C as well as at 300°C. Determine the microstructures expected in this type of steel after the following heat treatment processes. a) Austenize at 900°C, quench to 400°C and hold for 1000 s and quench to 25°C. b) Austenize at 900°C, quench to 25°C. c) Austenize at 900°C, quench to 675°C and hold for 1 s, quench to 400°C and hold for 900 s and slowly cool to 25°C. 900 Acm Cs 800 A1 FezC + Y 33 Fe3C + pearlite 45 700 Ps 600 ++ Fe3C + pearlite Y+ bainite Bs 500 46 Bainite 400 Yu Bf 300 57 Ms 200 60 Mf Y+ martensite 100 62 Martensite 102 65 103 104 105 106 0.1 1 10 Time (s) Fig. 1 Temperature (°C) Rockwell C hardness
Using the TTT diagram for eutectoid steel, draw the specified cooling path on the diagram. Indicate what phases you expect in the final product with percentage of each phase. Assume the material has been fully austenitized before cooling. a. Water cool to room temperature b. Hot quench in molten salt to 690°C and then cooled isothermally for 2 hours: c. Hot quench to 610°C hold 3 minutes and water quench
phase TÇF Iron -carbon phase diagram 2802°F (1539°C 1600 2912 L+ö 2719°F (1493°C) 1400 2552°F (1400°C) 0.16% Y+L, L+Fe3C 2192 4.3% 2097°F (1147°C) 2.06% 1200 Асм 1832 Аз. 1000 1670°F (910°C) Austețite + cementite+ledeburite Cementite + ledeburite 1472 800 1333°F(723°C) 0.025% 1112 p.83% A2= 1418"F(770°C) 600 752 A1, A2 400 Cementite + pearlite + transformed ledeburite 392 200 FezC 32 3 5 6 6.67% Carbon,% Figure Fe - C phase diagram Perlite+ferite Perlite+cementite
How would the following heat treatment be conducted, quoting approximates temperatures, cooling rate and microstructure of:(i) Normalizing of a plain carbon steel containing 0.8 wt % C, (ii) Quenching of a plain carbon steel containing 0.8 wt % C in water (iii) Quenching of a plain carbon steel containing 0.8 wt % C in oil (iv) full annealing of a plain carbon steel containing 0.8 % C.
13- Copper-rich copper-beryllium alloys are precipitation hardenable. After consulting the portion of the phase diagram shown in the figure below, do the following: (a) Specify the range of compositions over which these alloys may be precipitation hardened. Temperature (°C) (b) Briefly describe the heat-treatment procedures steps (in terms of temperatures) that would be used to precipitation harden an alloy having a composition of 1 wt% Be. 1000 800 600 400 0 (Cu) 0 1 Composition (at% Be) 10 15 a + L 2 α + 1/2 Liquid Composition (wt% Be) 866°C -620°C 3 20 x + 1₁
Question-6 A 0.25% C hypoeutectoid plain-carbon steel is slowly cooled from 950°C to a temperature just slightly below 723°C. (a) Calculate the weight percent proeutectoid ferrite in the steel. (b) Calculate the weight percent eutectoid ferrite and weight percent eutectoid cementite in the steel.
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This equilibrium phase of steel only occurs at temperatures above 723° C: martensite ferrite austenite O cementite
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