Rockwell (HRC) vs Brinell (HB) Hardness Conversion

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 
HVHBHRC
2508076.0
2708580.7
2859085.2
3059590.2
32010095.0
33510599.8
350110105
370115109
380120114
400125119
415130124
430135128
450140133
465145138
480150143
490155147
510160152
530165156
545170162
560175166
575180171
595185176
610190181
625195185
640200190
660205195
675210199
690215204
705220209
720225214
740230219
755235223
77024022820.3
78524523321.3
80025023822.2
82025524223.1
83526024724.0
85026525224.8
86527025725.6
88027526126.4
90028026627.1
91528527127.8
93029027628.5
95029528029.2
96530028529.8
99531029531.0
103032030432.2
106033031433.3
109534032334.4
112535033335.5
111536034236.6
119037035237.7
122038036138.8
125539037139.8
129040038040.8
132041039041.8
135042039942.7
138543040943.6
142044041844.5
145545042845.3
148546043746.1
152047044746.9
1555480(456)47.7
1595490(466)48.4
1630500(475)49.1
1665510(485)49.8
1700520(494)50.5
1740530(504)51.1
1775540(513)51.7
1810550(523)52.3
1845560(532)53.0
1880570(542)53.6
1920580(551)54.1
1955590(561)54.7
1995600(570)55.2
2030610(580)55.7
2070620(589)56.3
2105630(599)56.8
2145640(608)57.3
2180650(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

BarcolBrinellVickersWebsterRockwell
GYZJ10mm5kgB
934-1500kgBEFH
352132
362235
372337
382440
392542
40252645
41252747
42262849
43272951
44273054
45283056
46293158
4730322360
4830330.72662
4931341.32864
5032351.93166
5133362.53468
5234383.13670
5335393.6393072
5437404.2413473
5538414.7443775
5639435.3464077
5740445.8484378
5842456.3504680
5943476.8534882
6045497.3555183
6146507.8575485
6248528.3595686
6350548.8615988
6451569.2636189
6553589.7656390
66556010.1676692
67576210.6696893
BarcolVickersWebsterRockwell
GYZJ10mm5kgB
934-1500kgBEFH
68606511717094
69626711.4737295
70647011.817757497
71677212.223767598
72697512.628787799
73727812.9338079100
74758113.3388180101
75788513.7428382102
76808814478483103
77849214.3518685104
78879514.7558786105
79909915598988106
809410315.3639089106
819710815.6669190107
8210111215.9709291108
8310511716.2739492109
8410912116.4769593109
8511312616.7799694110
8611713116.9819795111
8712113717.2849896111
8812614217.4869997112
8913017.68810098112
9013517.89010198113
911401810299114
9214518.2103100
9318.4103100
9418.6104101
9518.7105102
9618.9106102
9719106103
9819.2107
9819.3107
10019.4108

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

HBHVHRAHRBHRCHRDHSTensile Strength
MPa
Standard SphereTungsten Carbide Sphere
94085.66876.997
92085.367.576.596
900856776.195
-76788084.766.475.793
-75786084.465.975.392
-74584084.165.374.891
-73382083.864.774.390
-72280083.46473.888
-712
-7107808363.373.387
-69876082.662.572.686
-68474082.261.872.1
-68273782.261.77284
-67072081.86171.583
-65670081.360.170.8
-65369781.26070.781
-64769081.159.770.5
-63868080.859.270.180
63067080.658.869.8
62766780.558.769.779
67780.759.170
60164079.857.368.777
64079.857.368.7
57861579.15667.775
60778.855.667.4
55559178.454.766.7732055
579785466.12015
53456977.853.565.8711985
53377.152.5651915
51454776.952.164.7701890
-49553976.751.664.31855
53076.451.163.91825
49552876.35163.8681820
-47751675.950.363.21780
50875.649.662.71740
47750875.649.662.7661740
-46149575.148.861.91680
49174.948.561.71670
46149174.948.561.7651670
44447474.347.2611595
47274.247.160.81585
44447274.247.160.8631585
42942945573.445.759.7611510
41541544072.844.558.8591460
4014014257243.157.8581390
38838841071.441.856.8561330
37537539670.640.455.7541270
3633633837039.154.6521220
35235237269.3-11037.953.8511180
34134136068.7-10936.652.8501130
33133135068.1-108.535.551.9481095
32132133967.5-10834.351471060
31131132866.9-107.533.150461025
30230231966.3-10732.149.3451005
29329330965.7-10630.948.343970
28528530165.3-105.529.947.6950
27727729264.6-104.528.846.741925
26926928464.1-10427.645.940895
26226227663.6-10326.64539875
25525526963-10225.444.238850
24824826162.5-10124.243.237825
24124125361.810022.84236800
  
23523524761.49921.741.435785
22922924160.898.220.540.534765
22322323497.3-18.8
21721722896.4-17.533725
21221222295.5-16705
20720721894.6-15.232690
20120121293.8-13.831675
19719720792.8-12.730655
19219220291.9-11.529640
18718719690.7-10620
18318319290-928615
17917918889-827600
17417418287.8-6.4585
17017017886.8-5.426570
16716717586-4.4560
16316317185-3.325545
15615616382.9-0.9525
14914915680.823505
14314315078.722490
13713714376.421460
13113113774450
1261261327220435
12112112769.819415
11611612267.618400
11111111765.715385
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Shane
Author

Shane

Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

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