Hardness is very important for the production of rough metal castings, heat treatment and machining processes. Rockwell hardness (HRC and HRB) and Brinell hardness (HB or BHN) are most commonly used for steel and iron castings.

Although there is no accurate conversion table and formula, Dandong Foundry recommends the following formula and comparison table based on experience and standards.

Formula A – Convert HRC into HB

Rockwell C Hardness (HRC)Brinell Hardness (HB)
From 21 to 30HB = 5.970 * HRC + 104.7
From 31 to 40HB = 8.570 * HRC + 27.6
From 41 to 50HB = 11.158 * HRC – 79.6
From 51 to 60HB = 17.515 * HRC – 401

Formula B – Convert HRB into HB

Rockwell B Hardness (HRB)Brinell Hardness (HB)
From 55 to 69HB = 1.646 * HRB + 8.7
From 70 to 79HB = 2.394 * HRB – 42.7
From 80 to 89HB = 3.297 * HRB – 114
From 90 to 100HB = 5.582 * HRB – 319

The following two conversion tables are from the standard ASTM A370. Table A is the comparison between Rockwell C hardness, Brinell hardness, Vickers hardness and tensile strength (Rm). Table B is a comparison between HRB, BH, HV and Rm.

Table A – HRC to HB, HV, Rm

HRC HardnessHB HardnessHV HardnessRm Tensile Strength
Diamond penetratorBrinell 3000 KgfVickers 30N / mm2 MPa
20226238760
21231243770
22237248790
23243254810
24247260820
25253266850
26258272860
27264279880
28271286900
29279294930
30286302950
31294310970
323013181010
333113271030
343193361050
353273451080
363363541110
373443631140
383533721180
393623821220
403713921250
413814021300
423904121340
434004231390
444094341430
454214461480
464324581520
474424711580
484554841640
494684981700
504825131760
514965281820
525125441880
535255601950
545435772010
555605952070
565776132160
575956332240
586156532330
596346742420
60654697 –
61670720 –
62688746 –
63706772 –
64722800 –
65739832 –
66 –865 –
67 –900 –
68 –940 –

Table B – HRB to HB, HV, Rm

HRB HardnessHB HardnessHV HardnessRm Tensile Strength
Ball 1 / 16 “Brinell 3000 KgfVickers 30N / mm2 MPa
4992 –320
5194 –330
54 – – –
55100100340
56101101 –
57103103350
58104104 –
59106106360
60107107 –
61108108 –
62110110370
63112112 –
64114114 –
65116116385
66117117395
67119119400
68121121405
69123123415
70125125420
71127127425
72130130435
73132132440
74135135450
75137137455
76139139460
77141141470
78144144475
79147147485
80150150495
81153153505
82156156530
83159159550
84162162560
85165165565
86169169570
87172172580
88176176590
89180180605
90185185615
91190190620
92195195635
93200200650
94205205675
95210210690
96216216705
97222222715
98228228750
99234234785
100240240800

HRC – diamond penetrator 120°, load 1470 N (150 kgf) duration 30 seconds.
HRB – ball 1/16’’, load 980 N (100 kgf) duration 30 seconds.
HB – ball 10 mm, load 29,400N (3000 kgf) durata 15 seconds.
BHN – Brinell Hardness Number, which is the same meaning as HB.
HV – diamond penetrator 136°, load 294 N (30 kgf) duration 15 seconds.

 

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