Unraveling the Mystery: Rockwell (HRC) vs Brinell (HB) Hardness Conversion

1. Hardness

Hardness is a performance indicator used to gauge the softness or hardness of materials. There are many methods of hardness testing, each with different principles, resulting in hardness values and meanings that are not exactly alike.

The most common is the static load indentation hardness test, namely, Brinell Hardness (HB), Rockwell Hardness (HRA, HRB, HRC), Vickers Hardness (HV), and the hardness of rubber plastic Shore Hardness (HA, HD) among others. These hardness values represent the material’s surface resistance to being indented by a hard object.

The most popular Leeb Hardness (HL) and Shore Hardness (HS) belong to the rebound hardness test, their values representing the magnitude of the metal’s elastic deformation work.

Therefore, hardness is not a pure physical quantity, but a comprehensive performance indicator reflecting the elasticity, plasticity, strength, and toughness of the material.

2. Types of Hardness

Hardness of Steel

The code for metal hardness (Hardness) is H. Depending on the hardness test method,

it is typically represented as Brinell (HB), Rockwell (HRC), Vickers (HV), Leeb (HL) hardness, etc., with HB and HRC being the most commonly used.
HB has a broad application range, while HRC is suitable for materials with high surface hardness, such as heat-treated hardness. The difference between the two lies in the different heads of the hardness testers, with the Brinell hardness tester using a steel ball and the Rockwell hardness tester using a diamond.
HV is suitable for microscopic analysis. Vickers Hardness (HV) uses a load of up to 120kg and a diamond square cone indenter with a top angle of 136° pressed into the material’s surface. The Vickers Hardness value (HV) is calculated by dividing the surface area of the indentation in the material by the load value.
HL Portable hardness tester, easy to measure, uses a bouncing ball head to impact the hardness surface, producing a bounce. Using the ratio of the rebound speed of the impact head at 1mm from the sample surface to the impact speed to calculate the hardness. The formula is: Leeb Hardness HL = 1000 × VB (Rebound speed) / VA (Impact speed).
The most commonly used portable Leeb hardness tester can be converted into: Brinell (HB), Rockwell (HRC), Vickers (HV), Shore (HS) hardness after Leeb (HL) measurement. Or the hardness value is directly measured by Brinell (HB), Rockwell (HRC), Vickers (HV), Leeb (HL), Shore (HS) using the Leeb principle.

HB – Brinell Hardness:

Brinell Hardness (HB) is generally used when the material is softer, such as non-ferrous metals, or steel before heat treatment or after annealing. Rockwell Hardness (HRC) is generally used for materials with higher hardness, such as post-heat treatment hardness.

Brinell Hardness (HB) uses a certain test load to press a hardened steel ball or hard alloy ball of a certain diameter into the metal surface to be tested, hold it for a specified time, then unload, and measure the diameter of the indentation on the tested surface.

The Brinell hardness value is the quotient obtained by dividing the load by the spherical surface area of the indentation.

It is typically: using a certain load (generally 3000kg) to press a certain size (usually 10mm in diameter) hardened steel ball into the material surface, maintain it for a while, unload, and the ratio of the load to its indentation area is the Brinell Hardness value (HB), unit is kgf/mm2 (N/mm²).

HR – Rockwell Hardness

Rockwell Hardness (HR-) uses indentation plastic deformation depth to determine the hardness value index. A hardness unit is 0.002mm.

When HB > 450 or the sample is too small, Brinell hardness test cannot be used and Rockwell hardness measurement should be adopted instead.

It uses a diamond cone with a 120° apex angle or a steel ball with a diameter of 1.59, 3.18mm, under a certain load, to press into the material surface to be tested, and the material’s hardness is calculated from the depth of the indentation.

According to the different hardness of the test material, it is expressed in three different scales:

HRA: Hardness obtained using a 60kg load and a diamond cone indenter, used for extremely hard materials (such as cemented carbides).
HRB: Hardness obtained using a 100kg load and a hardened steel ball of 1.59mm diameter, used for lower hardness materials (such as annealed steel, cast iron, etc.).
HRC: Hardness obtained using a 150kg load and a diamond cone indenter, used for very high hardness materials (such as quenched steel).

Furthermore:

(1)HRC refers to the Rockwell C scale.

(2)HRC and HB are widely used in production.

(3)The HRC range is HRC 20–67, equivalent to HB225–650.

If the hardness is higher than this range, Rockwell hardness A scale HRA is used. If the hardness is lower than this range, Rockwell hardness B scale HRB is used. The upper limit of Brinell hardness is HB650, it cannot exceed this value.

(4)The indenter of the Rockwell hardness tester C scale is a 120° diamond cone, and the test load is a fixed value, the Chinese standard is 150 kgf.

The indenter of the Brinell hardness tester is a hardened steel ball (HBS) or a hard alloy ball (HBW), and the test load varies with the ball diameter, ranging from 3000 to 31.25 kgf.

(5)Rockwell hardness has small indentations, the measured value is local, the average value should be obtained by measuring several points, suitable for finished products and thin plates, belonging to the category of non-destructive testing.

The indentation of Brinell hardness is larger, the measured value is accurate, not suitable for finished products and thin plates, generally not belonging to the category of non-destructive testing.

(6)Rockwell hardness value is a nameless number, without a unit. (Therefore, it is incorrect to refer to Rockwell hardness in terms of degrees.)

Brinell hardness has a unit, and it has a certain approximate relationship with tensile strength.

(7)Rockwell hardness is directly displayed on the dial or can be displayed digitally, it is convenient to operate, fast, intuitive, suitable for mass production.

Brinell hardness requires measuring the diameter of the indentation with a microscope, then looking up the table or calculating, the operation is more complicated.

(8)Under certain conditions, HB and HRC can be converted by looking up the table. The mental calculation formula can be approximately remembered as: 1HRC≈1/10HB.

3. Comparison table of tensile strength with Vickers hardness, Brinell hardness, and Rockwell hardness

According to the German standard DIN50150, below is the comparison table of tensile strength with Vickers Hardness, Brinell Hardness, and Rockwell Hardness for commonly used range of steel materials:

Tensile Strength Rm N/mm²	HV	HB	HRC
250	80	76.0	–
270	85	80.7	–
285	90	85.2	–
305	95	90.2	–
320	100	95.0	–
335	105	99.8	–
350	110	105	–
370	115	109	–
380	120	114	–
400	125	119	–
415	130	124	–
430	135	128	–
450	140	133	–
465	145	138	–
480	150	143	–
490	155	147	–
510	160	152	–
530	165	156	–
545	170	162	–
560	175	166	–
575	180	171	–
595	185	176	–
610	190	181	–
625	195	185	–
640	200	190	–
660	205	195	–
675	210	199	–
690	215	204	–
705	220	209	–
720	225	214	–
740	230	219	–
755	235	223	–
770	240	228	20.3
785	245	233	21.3
800	250	238	22.2
820	255	242	23.1
835	260	247	24.0
850	265	252	24.8
865	270	257	25.6
880	275	261	26.4
900	280	266	27.1
915	285	271	27.8
930	290	276	28.5
950	295	280	29.2
965	300	285	29.8
995	310	295	31.0
1030	320	304	32.2
1060	330	314	33.3
1095	340	323	34.4
1125	350	333	35.5
1115	360	342	36.6
1190	370	352	37.7
1220	380	361	38.8
1255	390	371	39.8
1290	400	380	40.8
1320	410	390	41.8
1350	420	399	42.7
1385	430	409	43.6
1420	440	418	44.5
1455	450	428	45.3
1485	460	437	46.1
1520	470	447	46.9
1555	480	(456)	47.7
1595	490	(466)	48.4
1630	500	(475)	49.1
1665	510	(485)	49.8
1700	520	(494)	50.5
1740	530	(504)	51.1
1775	540	(513)	51.7
1810	550	(523)	52.3
1845	560	(532)	53.0
1880	570	(542)	53.6
1920	580	(551)	54.1
1955	590	(561)	54.7
1995	600	(570)	55.2
2030	610	(580)	55.7
2070	620	(589)	56.3
2105	630	(599)	56.8
2145	640	(608)	57.3
2180	650	(618)	57.8
	660		58.3
	670		58.8
	680		59.2
	690		59.7
	700		60.1
	720		61.0
	740		61.8
	760		62.5
	780		63.3
	800		64.0
	820		64.7
	840		65.3
	860		65.9
	880		66.4
	900		67.0
	920		67.5
	940		68.0

4. Rough Relationship Table of Various Hardness

Barcol	Brinell	Vickers	Webster	Rockwell
GYZJ	10mm	5kg	B	Rockwell
934-1	500kg			B	E	F	H
35		21					32
36		22					35
37		23					37
38		24					40
39		25					42
40	25	26					45
41	25	27					47
42	26	28					49
43	27	29					51
44	27	30					54
45	28	30					56
46	29	31					58
47	30	32			23		60
48	30	33	0.7		26		62
49	31	34	1.3		28		64
50	32	35	1.9		31		66
51	33	36	2.5		34		68
52	34	38	3.1		36		70
53	35	39	3.6		39	30	72
54	37	40	4.2		41	34	73
55	38	41	4.7		44	37	75
56	39	43	5.3		46	40	77
57	40	44	5.8		48	43	78
58	42	45	6.3		50	46	80
59	43	47	6.8		53	48	82
60	45	49	7.3		55	51	83
61	46	50	7.8		57	54	85
62	48	52	8.3		59	56	86
63	50	54	8.8		61	59	88
64	51	56	9.2		63	61	89
65	53	58	9.7		65	63	90
66	55	60	10.1		67	66	92
67	57	62	10.6		69	68	93

Barcol		Vickers	Webster	Rockwell
GYZJ	10mm	5kg	B	Rockwell
934-1	500kg			B	E	F	H
68	60	65	11		71	70	94
69	62	67	11.4		73	72	95
70	64	70	11.8	17	75	74	97
71	67	72	12.2	23	76	75	98
72	69	75	12.6	28	78	77	99
73	72	78	12.9	33	80	79	100
74	75	81	13.3	38	81	80	101
75	78	85	13.7	42	83	82	102
76	80	88	14	47	84	83	103
77	84	92	14.3	51	86	85	104
78	87	95	14.7	55	87	86	105
79	90	99	15	59	89	88	106
80	94	103	15.3	63	90	89	106
81	97	108	15.6	66	91	90	107
82	101	112	15.9	70	92	91	108
83	105	117	16.2	73	94	92	109
84	109	121	16.4	76	95	93	109
85	113	126	16.7	79	96	94	110
86	117	131	16.9	81	97	95	111
87	121	137	17.2	84	98	96	111
88	126	142	17.4	86	99	97	112
89	130		17.6	88	100	98	112
90	135		17.8	90	101	98	113
91	140		18		102	99	114
92	145		18.2		103	100
93			18.4		103	100
94			18.6		104	101
95			18.7		105	102
96			18.9		106	102
97			19		106	103
98			19.2		107
98			19.3		107
100			19.4		108

5. The Approximate Conversion Value of Steel’s Brinell Hardness

HB		HV	HRA	HRB	HRC	HRD	HS	Tensile Strength MPa
Standard Sphere	Tungsten Carbide Sphere	HV	HRA	HRB	HRC	HRD	HS	Tensile Strength MPa
–	–	940	85.6	–	68	76.9	97	–
–	–	920	85.3	–	67.5	76.5	96	–
–	–	900	85	–	67	76.1	95	–
–	-767	880	84.7	–	66.4	75.7	93	–
–	-757	860	84.4	–	65.9	75.3	92	–

–	-745	840	84.1	–	65.3	74.8	91	–
–	-733	820	83.8	–	64.7	74.3	90	–
–	-722	800	83.4	–	64	73.8	88	–
–	-712	–	–	–	–	–	–	–
–	-710	780	83	–	63.3	73.3	87	–
–	-698	760	82.6	–	62.5	72.6	86	–

–	-684	740	82.2	–	61.8	72.1	–	–
–	-682	737	82.2	–	61.7	72	84	–
–	-670	720	81.8	–	61	71.5	83	–
–	-656	700	81.3	–	60.1	70.8	–	–
–	-653	697	81.2	–	60	70.7	81	–

–	-647	690	81.1	–	59.7	70.5	–	–
–	-638	680	80.8	–	59.2	70.1	80	–
–	630	670	80.6	–	58.8	69.8	–	–
–	627	667	80.5	–	58.7	69.7	79	–

–	–	677	80.7	–	59.1	70	–	–
–	601	640	79.8	–	57.3	68.7	77	–

–	–	640	79.8	–	57.3	68.7	–	–
–	578	615	79.1	–	56	67.7	75	–

–	–	607	78.8	–	55.6	67.4	–	–
–	555	591	78.4	–	54.7	66.7	73	2055

–	–	579	78	–	54	66.1	–	2015
–	534	569	77.8	–	53.5	65.8	71	1985

–	–	533	77.1	–	52.5	65	–	1915
–	514	547	76.9	–	52.1	64.7	70	1890

-495	–	539	76.7	–	51.6	64.3	–	1855
–	–	530	76.4	–	51.1	63.9	–	1825
–	495	528	76.3	–	51	63.8	68	1820

-477	–	516	75.9	–	50.3	63.2	–	1780
–	–	508	75.6	–	49.6	62.7	–	1740
–	477	508	75.6	–	49.6	62.7	66	1740

-461	–	495	75.1	–	48.8	61.9	–	1680
–	–	491	74.9	–	48.5	61.7	–	1670
–	461	491	74.9	–	48.5	61.7	65	1670

444	–	474	74.3	–	47.2	61	–	1595
–	–	472	74.2	–	47.1	60.8	–	1585
–	444	472	74.2	–	47.1	60.8	63	1585

429	429	455	73.4	–	45.7	59.7	61	1510
415	415	440	72.8	–	44.5	58.8	59	1460
401	401	425	72	–	43.1	57.8	58	1390
388	388	410	71.4	–	41.8	56.8	56	1330
375	375	396	70.6	–	40.4	55.7	54	1270

363	363	383	70	–	39.1	54.6	52	1220
352	352	372	69.3	-110	37.9	53.8	51	1180
341	341	360	68.7	-109	36.6	52.8	50	1130
331	331	350	68.1	-108.5	35.5	51.9	48	1095
321	321	339	67.5	-108	34.3	51	47	1060

311	311	328	66.9	-107.5	33.1	50	46	1025
302	302	319	66.3	-107	32.1	49.3	45	1005
293	293	309	65.7	-106	30.9	48.3	43	970
285	285	301	65.3	-105.5	29.9	47.6	–	950
277	277	292	64.6	-104.5	28.8	46.7	41	925

269	269	284	64.1	-104	27.6	45.9	40	895
262	262	276	63.6	-103	26.6	45	39	875
255	255	269	63	-102	25.4	44.2	38	850
248	248	261	62.5	-101	24.2	43.2	37	825
241	241	253	61.8	100	22.8	42	36	800

235	235	247	61.4	99	21.7	41.4	35	785
229	229	241	60.8	98.2	20.5	40.5	34	765
223	223	234	–	97.3	-18.8	–	–
217	217	228	–	96.4	-17.5	–	33	725
212	212	222	–	95.5	-16	–	–	705

207	207	218	–	94.6	-15.2	–	32	690
201	201	212	–	93.8	-13.8	–	31	675
197	197	207	–	92.8	-12.7	–	30	655
192	192	202	–	91.9	-11.5	–	29	640
187	187	196	–	90.7	-10	–	–	620

183	183	192	–	90	-9	–	28	615
179	179	188	–	89	-8	–	27	600
174	174	182	–	87.8	-6.4	–	–	585
170	170	178	–	86.8	-5.4	–	26	570
167	167	175	–	86	-4.4	–	–	560

163	163	171	–	85	-3.3	–	25	545
156	156	163	–	82.9	-0.9	–	–	525
149	149	156	–	80.8	–	–	23	505
143	143	150	–	78.7	–	–	22	490
137	137	143	–	76.4	–	–	21	460

131	131	137	–	74	–	–	–	450
126	126	132	–	72	–	–	20	435
121	121	127	–	69.8	–	–	19	415
116	116	122	–	67.6	–	–	18	400
111	111	117	–	65.7	–	–	15	385

READ NEXT:

Unraveling the Mystery: Rockwell (HRC) vs Brinell (HB) Hardness Conversion

1. Hardness