APPROXIMATE ROCKWELL HARDNESS CONVERSION NUMBERS FOR
AUSTENITIC SHEET STEEL
A,B

Rockwell Hardness Number

Rockwell Superficial Hardness Number

C Scale, 150-kgf
Diamond Penetrator
(HRC)
A Scale, 60-kgf
Diamond Penetrator
(HRA)
15-N Scale, 15-kgf
Superficial
Diamond Penetrator
(HR 15-N)
30-N Scale, 30-kgf
Superficial
Diamond Penetrator
(HR 30-N)
45-N Scale, 45-kgf
Superficial
Diamond Penetrator
(HR 45-N)
48 74.4 84.1 66.2 52.1
47 73.9 83.6 65.3 50.9
46 73.4 83.1 64.5 49.8
45 72.9 82.6 63.6 48.7
44 72.4 82.1 62.7 47.5
43 71.9 81.6 61.8 46.4
42 71.4 81.0 61.0 45.2
41 70.9 80.5 60.1 44.1
40 70.4 80.0 59.2 43.0
39 69.9 79.5 58.4 41.8
38 69.3 79.0 57.5 40.7
37 68.8 78.5 56.6 39.6
36 68.3 78.0 55.7 38.4
35 67.8 77.5 54.9 37.3
34 67.3 77.0 54.0 36.1
33 66.8 76.5 53.1 35.0
32 66.3 75.9 52.3 33.9
31 65.8 75.4 51.4 32.7
30 65.3 74.9 50.5 31.6
29 64.8 74.4 49.6 30.4
28 64.3 73.9 48.8 29.3
27 63.8 73.4 47.9 28.2
26 63.3 72.9 47.0 27.0
25 62.8 72.4 46.2 25.9
24 62.3 71.9 45.3 24.8
23 61.8 71.3 44.4 23.6
22 61.3 70.8 43.5 22.5
21 60.8 70.3 42.7 21.3
20 60.3 69.8 41.8 20.2
 
B Scale, 100-kgf,
1/16 in (1.588 mm) ball
(HRB)
A Scale, 60-kgf,
Diamond Penetrator
(HRA)
15-T Scale, 15-kgf,
1/16 in (1.588 mm) ball
(HR 15-T)
30-T Scale, 30-kgf,
1/16 in (1.588 mm) ball
(HR 30-T)
45-T Scale, 45-kgf,
1/16 in (1.588 mm) ball
(HR 45-T)
100 61.5 91.5 80.4 70.2
99 60.9 91.2 79.7 69.2
98 60.3 90.8 79.0 68.2
97 59.7 90.4 78.3 67.2
96 59.1 90.1 77.7 66.1
95 58.5 89.7 77.0 65.1
94 58.0 89.3 76.3 64.1
93 57.4 88.9 75.6 63.1
92 56.8 88.6 74.9 62.1
91 56.2 88.2 74.2 61.1
90 55.6 87.8 73.5 60.1
89 55.0 87.5 72.8 59.0
88 54.5 87.1 72.1 58.0
87 53.9 86.7 71.4 57.0
86 53.3 86.4 70.7 56.0
85 52.7 86.0 70.0 55.0
84 52.1 85.6 69.3 54.0
83 51.5 85.2 68.6 52.9
82 50.9 84.9 67.9 51.9
81 50.4 84.5 67.2 50.9
80 49.8 84.1 66.5 49.9
79 49.2 83.8 65.8 48.9
78 48.6 83.4 65.1 47.9
77 48.0 83.0 64.4 46.8
76 47.4 82.6 63.7 45.8
75 46.9 82.3 63.0 44.8
74 46.3 81.9 62.4 43.8
73 45.7 81.5 61.7 42.6
72 45.1 81.2 61.0 41.8
71 44.5 80.8 60.3 40.7
70 43.9 80.4 59.6 39.7
69 43.3 80.1 58.9 38.7
68 42.8 79.7 58.2 37.7
67 42.2 79.3 57.5 36.7
66 41.6 78.9 56.8 35.7
65 41.0 78.6 56.1 34.7
64 40.4 78.2 55.4 33.6
63 39.8 77.8 54.7 32.6
62 39.3 77.5 54.0 31.6
61 38.7 77.1 53.3 30.6
60 38.1 76.7 52.6 29.6
Standard deviation D 1.44 2.29 1.67 1.57

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