Steel Hardness Conversion Table
  
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Note that hardness conversions are approximate only as the different scales use different methods of testing

Brinell

Brinell

Vickers

Rockwell

Rockwell

Impression

Hardness

hardness

Hardness

Hardness

Equiv Rm

Equiv Rm

Equiv Rm

Dia. mm

HB

HV

B

C

tonf/in˛

kgf/mm˛

N/mm˛

2.50

601

640

-

57.0

-

-

-

2.55

578

615

-

56.0

-

-

-

2.60

555

591

120

54.5

-

-

-

2.65

534

569

119

53.5

-

-

-

2.70

514

547

119

52.0

-

-

-

2.75

495

528

117

51.0

-

-

-

2.80

477

508

117

49.5

-

-

-

2.85

461

491

116

48.5

101

160

1569

2.90

444

474

115

47.0

98

155

1520

2.95

429

455

115

45.5

95

150

1471

3.00

415

440

114

44.5

92

145

1422

3.05

401

425

113

43.0

88

139

1363

3.10

388

410

112

42.0

85

134

1314

3.15

375

396

112

40.5

82

129

1265

3.20

363

383

110

39.0

80

126

1236

3.25

352

372

110

38.0

77

121

1187

3.30

341

360

109

36.5

75

118

1157

3.35

331

350

109

35.5

73

114

1118

3.40

321

339

108

34.5

71

111

1089

3.45

311

328

108

33.0

68

107

1049

3.50

302

319

107

32.0

66

104

1020

3.55

293

309

106

31.0

64

101

990

3.60

285

301

105

30.0

63

99

971

3.65

277

292

104

29.0

61

96

941

3.70

269

284

104

27.5

59

93

912

3.75

262

276

103

26.5

58

91

892

3.80

255

269

102

25.5

56

89

873

3.85

248

261

102

24.0

55

87

853

3.90

241

253

100

23.0

53

84

824

3.95

235

247

99

22.0

51

81

794

4.00

229

241

98

20.5

50

79

775

4.05

223

235

97

-

49

77

755

4.10

217

228

96

-

48

76

745

4.15

212

223

96

-

46

73

716

4.20

207

218

95

-

45

71

696

4.30

197

208

93

-

43

68

667

4.40

187

197

91

-

41

65

637

4.50

179

189

89

-

39

62

608

4.60

170

179

87

-

36

57

559

4.70

163

172

85

-

35

55

539

4.80

156

165

83

-

34

54

530

4.90

149

157

81

-

32

51

500

5.00

143

150

79

-

31

49

481

5.10

137

144

77

-

31

49

481

5.20

131

138

74

-

30

47

461

5.30

126

133

72

-

29

46

451

5.40

121

127

70

-

28

44

431

5.50

116

122

68

-

27

43

422

5.60

111

117

66

-

26

41

402

5.70

107

113

64

-

25

39

382

5.80

103

108

61

-

24

38

373

Links
Hardness Testing

Hardness testing for steel is based upon applying pressure to the steel surface and measuring the depth of the indentation. The three major measurement systems are :-

Brinell  Hardness

The Brinell hardness test consists in indenting the metal surface with a 10-mm-diameter steel ball at a load of 3,000 kg mass (∼29400 N). For soft metals the load is reduced to 500 kg to avoid too deep an impression, and for very hard metals a tungsten carbide ball is used to minimize distortion of the indenter. The load is applied for a standard time, usually 30 s, and the diameter of the indentation is measured with a low-power microscope after removal of the load. The average of two readings of the diameter of the impression at right angles should be made.

Vickers Hardness

The Vickers hardness test uses a square-base diamond pyramid as the indenter. The included angle between opposite faces of the pyramid is 136°. This angle was chosen because it approximates the most desirable ratio of indentation diameter to ball diameter in the Brinell hardness test.

Because of the shape of the indenter, this is frequently called the diamond-pyramid hardness test. The diamond-pyramid hardness number (DPH), or Vickers hardness number (VHN, or VPH), is defined as the load divided by the surface area of the indentation. In practice, this area is calculated from microscopic measurements of the lengths of the diagonals of the impression

Rockwell Hardness Test

The most widely used hardness test is the Rockwell hardness test. Its general acceptance is due to its speed, freedom from personal error, ability to distinguish small hardness differences in hardened steel, and the small size of the indentation, so that finished heat-treated parts can be tested without damage.

This test utilizes the depth of indentation, under constant load, as a measure of hardness. A minor load of 10 kg is first applied to seat the specimen. This minimizes the amount of surface preparation needed and reduces the tendency for ridging or sinking in by the indenter. The major load is then applied, and the depth of indentation is automatically recorded on a dial gage in terms of arbitrary hardness numbers.