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Hardness Conversion Charts

Tensile Strength and Hardness Conversions for Steels

Brinell Dia of Impression mm Brinell Hardness Number HB Vickers Hardness Number HV Rockwell C Scale Hardness Number HRC Equiv. Rm tonf/in2 Equiv. Rmkgf/mm2 Equiv. Rm N/mm2
    832 65      
    800 64      
    772 63      
    746 62      
    697 60      
    674 59      
    653 58      
2.50 (601) 633 57      
2.55 (578) 615 56      
2.60 (555) 591 54.5      
2.65 (534) 569 53.5      
2.70 (514) 547 52      
2.75 (495) 528 51      
2.80 (477) 508 49.5      
2.85 (461) 491 48.5 101 160 1569
2.90 444 474 47 98 155 1520
2.95 429 455 45.5 95 150 1471
3.00 415 440 44.5 92 145 1422
3.05 401 425 43 88 139 1363
3.10 388 410 42 85 134 1314
3.15 375 396 40.5 82 129 1265
3.20 363 383 39 80 126 1236
3.25 352 372 38 77 121 1187
3.30 341 360 36.5 75 118 1157
3.35 331 350 35.5 73 114 1118
3.40 321 339 34.5 71 111 1089
3.45 311 328 33 68 107 1049
3.50 302 319 32 66 104 1020
3.55 293 309 31 64 101 990
3.60 285 301 30 63 99 971
3.65 277 392 29 61 96 941
3.70 269 284 27.5 59 93 912
3.75 262 276 26.5 58 91 892
3.80 255 269 25.5 56 89 873
3.85 248 261 24 55 87 853
3.90 241 253 23 53 84 824
3.95 235 247 22 51 81 794
4.00 229 241 20.5 50 79 775
4.05 223 235 (20) 49 77 755
4.10 217 228 (19) 48 76 745
4.15 212 223 (18) 46 73 716
4.20 207 218 (17) 45 71 696
4.30 197 208 (14) 43 68 667
4.40 187 197 (12) 41 65 637
4.50 179 189 (10) 39 62 608
4.60 170 176 - 36 57 559
4.70 163 172 - 35 55 539
4.80 156 165 - 34 54 530
4.90 149 157 - 32 51 500
5.00 143 150 - 31 49 481
5.10 137 144 - 31 49 481
5.20 131 138 - 30 47 461
5.30 126 133 - 29 46 451
5.40 121 127 - 28 44 431
5.50 116 122 - 27 43 422
5.60 111 117 - 26 41 402
5.70 107 113 - 25 39 382
5.80 103 108 - 24 38 373

The figures in brackets (over 450) require a tungsten Carbide ball (BS240 - 1986).

HB to HV and HV to HRC conversions are based on A.S.T.M.E. 140.

Rockwell C. scale and tonf/in2 figures in brackets are for guidance only.

Tensile Strength Ranges
P = 35 - 40 ton/in2 = 163 - 207 HB
Q = 40 - 50 = 197 - 229  
R = 45 - 55 = 207 - 248  
S = 50 - 60 = 229 - 277  
T = 55 - 65 = 248 - 302  
U = 60 - 70 = 277 - 321  
V = 65 - 75 = 302 - 341  
W = 70 - 80 = 321 - 363  
X = 75 - 85 = 341 - 388  
Y = 80 - 90 = 363 - 401  
Z = 100 +   = 461 +    

Based on BS970 Pt. 1 (1970)

Fastener Tensile Ranges
3.6 = 300-420 N/mm2 = 27 ton/in2 max 116 HB max.
4.6/4.8 = 400-520 = 26-34 ton in2 111-156 HB
5.6/5.8 = 500-660 = 32-43 149-197
6.6/6.8 = 600-740 = 39-48 179-217
8.8 = 800-980 = 51-64 235-293
9.8 = 900-1025 = 58-66 262-302
10.9 = 1000-1150 = 65-75 293-341
12.9 = 1200 - 1375 = 77-88 352-401

Based on ISO 898-1 (1988)

Over Equivalents

N/mm2=MN/M2=MPa

Kgf=mm2=Kp/mm2

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