Conversion of Rockwell Hardness (HRC, HRB) to Brinell Hardness (HB or BHN)

Yide Casting a professional iron casting manufacturer & supplier, provides both iron casting made & machining services for decades years. In this article, we will show you the conversion of Rockwell Hardness (HRC, HRB) to Brinell Hardness (HB or BHN).

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, Yide Casting 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 30	HB = 5.970 * HRC + 104.7
From 31 to 40	HB = 8.570 * HRC + 27.6
From 41 to 50	HB = 11.158 * HRC – 79.6
From 51 to 60	HB = 17.515 * HRC – 401

Formula B – Convert HRB into HB

Rockwell B Hardness (HRB)	Brinell Hardness (HB)
From 55 to 69	HB = 1.646 * HRB + 8.7
From 70 to 79	HB = 2.394 * HRB – 42.7
From 80 to 89	HB = 3.297 * HRB – 114
From 90 to 100	HB = 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 Hardness	HB Hardness	HV Hardness	Rm Tensile Strength
Diamond penetrator	Brinell 3000 Kgf	Vickers 30	N / mm2 MPa
20	226	238	760
21	231	243	770
22	237	248	790
23	243	254	810
24	247	260	820
25	253	266	850
26	258	272	860
27	264	279	880
28	271	286	900
29	279	294	930
30	286	302	950
31	294	310	970
32	301	318	1010
33	311	327	1030
34	319	336	1050
35	327	345	1080
36	336	354	1110
37	344	363	1140
38	353	372	1180
39	362	382	1220
40	371	392	1250
41	381	402	1300
42	390	412	1340
43	400	423	1390
44	409	434	1430
45	421	446	1480
46	432	458	1520
47	442	471	1580
48	455	484	1640
49	468	498	1700
50	482	513	1760
51	496	528	1820
52	512	544	1880
53	525	560	1950
54	543	577	2010
55	560	595	2070
56	577	613	2160
57	595	633	2240
58	615	653	2330
59	634	674	2420
60	654	697	–
61	670	720	–
62	688	746	–
63	706	772	–
64	722	800	–
65	739	832	–
66	–	865	–
67	–	900	–
68	–	940	–

Table B – HRB to HB, HV, Rm

HRB Hardness	HB Hardness	HV Hardness	Rm Tensile Strength
Ball 1 / 16 “	Brinell 3000 Kgf	Vickers 30	N / mm2 MPa
49	92	–	320
51	94	–	330
54	–	–	–
55	100	100	340
56	101	101	–
57	103	103	350
58	104	104	–
59	106	106	360
60	107	107	–
61	108	108	–
62	110	110	370
63	112	112	–
64	114	114	–
65	116	116	385
66	117	117	395
67	119	119	400
68	121	121	405
69	123	123	415
70	125	125	420
71	127	127	425
72	130	130	435
73	132	132	440
74	135	135	450
75	137	137	455
76	139	139	460
77	141	141	470
78	144	144	475
79	147	147	485
80	150	150	495
81	153	153	505
82	156	156	530
83	159	159	550
84	162	162	560
85	165	165	565
86	169	169	570
87	172	172	580
88	176	176	590
89	180	180	605
90	185	185	615
91	190	190	620
92	195	195	635
93	200	200	650
94	205	205	675
95	210	210	690
96	216	216	705
97	222	222	715
98	228	228	750
99	234	234	785
100	240	240	800

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.