Diameter of bar (mm) 25 50 Q4: Using the 2 images below, determine the hardness profile of a cylindirical rod of 8640 steel of diameter 70mm quenched in water, along with a second rod of diameter 30mm quenched in oil. Hardness, HRC 30 40 Cooling rate at 700C (1300F) 490 305 125 56 33 16.3 10 7 5.1 270 170 70 31 18 9 5.6 3.9 2.8 60 L 50 1040 4340 L 3.5 F/s 2 C/s 100 80 50 4140 8640 5140 20 0 10 20 30 40 50 mm Percent martensite 0 1 2 in. Distance from quenched end Cooling rate at 700C (1300F) Cooling rate at 700C (1300F) 305 125 56 33 16.3 10 7 F/s 305 125 56 33 16.3 10 7 F/s 170 70 31 18 9 5.6 3.9 C/s 170 70 31 18 9 5.6 3.9 C/s 100 100 4 4 75 Surface 0 0 10 0 4 R R Center R Center Surface 0 20 30 mm Equivalent distance from quenched end Diameter of bar (in.) Diameter of bar (mm) 25 50 75 Surface R R Center 0 10 20 30 mm 3 1 1 in. 0 4 +4 123 1 1 in. Equivalent distance from quenched end 3 Diameter of bar (in.)