Hardness (HR Heat Treatment |#1 Annealing Normalizing95 Impact Energy (ft-lb) #2

Question

Hardness (HR Heat Treatment |#1 Annealing Normalizing95 Impact Energy (ft-lb) #2 .9 8.2 #3 1.1 11.7 11.49.16 9.16 #5 Average #2 79 105 100 Average | #1 #4 79 1.6 7.1 15.520.8 19.2 21.7 19.5419.54 20.227.823.7 28.227.52 27.52 35.3 28.4 34.6 36.4 34.34 34.34 79 .5 .94 Polymer Q. 117 123 120 56 Tempered 86 80 83 Water Q. 56 56 Compare the microstructures of the various samples. Describe the structure and the phases that are present. Relate the observed structures to the processing history and the measured properties. 500 Four: Water Ma Figure Two: Normalizing Sample 1500 Magnification) Figure Five: Tempered Sample (500 Magnification)

Explanation / Answer

Fig.1) Alternate layers of ferrite and pearlite phases are observed. Also some peoeutectoid phase is seen. Due to annealing treatment and its furnace cooling nature, grain size is coarser.

Fig2) Due to normalizing, grains are refined and hence hardness of normalized specimen is higher than that of annealed.

Fig. 3&4) Quenching is a heat treatment method where cooling rate is high So that final product is a non equilibrium supersaturated solid solution. Water quenching is the most rapid one. Here austenized steel in cooled in a water medium. Here martensite is formed and its structure us body centred tetragonal shape. So hardness of water quenched is highest when compared with all others.

Fig. 5.) Tempering is heat treatment of quenched specimen to introduce toughness and reduce brittleeness, by heating between 300 to 500 degree Celsius and holding for specified time period. Hence grain size of tempered specimen reduces.

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