Metal Hardness: The Definite Guide (with Hardness Chart)

Hardness refers to the ability of a material to resist local deformation, especially plastic deformation, indentations or scratches.

It is an indicator of the hardness of the material.

Types of hardness

According to the different test methods, there are three types of hardness.

① Scratch hardness

It is mainly used to compare the hardness of different minerals. The method is to choose a stick with a hard end and a soft end, and slide the material to be tested along the rod, and determine the softness and hardness of the material to be tested according to the location of the scratch. Qualitatively speaking, the scratches made by hard objects are long and the scratches made by soft objects are short.

② Indentation hardness

Mainly used for metal materials, the method is to press the specified indenter into the material under test with a certain load, and compare the softness and hardness of the material under test with the local plastic deformation of the material surface. Due to different indenters, loads, and load durations, there are a variety of indentation hardness, mainly Brinell hardness, Rockwell hardness, Vickers hardness, and micro-hardness.

③ Rebound hardness

Mainly used for metal materials. The method is to make a special small hammer drop freely from a certain height to impact the sample of the tested material, and the hardness of the material is determined by the amount of strain energy (measured by the rebound height of the hammer) stored in (and then release) the sample during the impact.

Common HV = HB = HRC hardness comparison table

Hardness comparison table of common ferrous metals

(Approximate conversion of intensity)

Classification of hardness

Tensile strength

N/mm2

Rockwell

Vickers Brinell
HRC HRA HV

HB

17 211 211 710
17.5 214 214 715
18 216 216 725
18.5 218 218 730
19 221 220 735
19.5 223 222 745
20 226 225 750
20.5 229 227 760
21 231 229 765
21.5 234 232 775
22 237 234 785
22.5 240 237 790
23 243 240 800
23.5 246 242 810
24 249 245 820
24.5 252 248 830
25 255 251 835
25.5 258 254 850
26 261 257 860
26.5 264 260 870
27 268 263 880
27.5 271 266 890
28 274 269 900
28.5 278 273 910
29 281 276 920
29.5 285 280 935
30 289 283 950
30.5 292 287 960
31 296 291 970
31.5 300 294 980
32 304 298 995
32.5 308 302 1010
33 312 306 1020
33.5 316 310 1035
34 320 314 1050
34.5 324 318 1065
35 329 323 1080
35.5 333 327 1095
36 338 332 1110
36.5 342 336 1125
37 347 341 1140
37.5 352 345 1160
38 357 350 1175
38.5 362 355 1190
39 70 367 360 1210
39.5 70.3 372 365 1225
40 70.8 382 375 1260
40.5 70.5 377 370 1245
41 71.1 388 380 1280
41.5 71.3 393 385 1300
42 71.6 399 391 1320
42.5 71.8 405 396 1340
43 72.1 411 401 1360
43.5 72.4 417 407 1385
44 72.6 423 413 1405
44.5 72.9 429 418 1430
45 73.2 436 424 1450
45.5 73.4 443 430 1475
46 73.7 449 436 1500
46.5 73.9 456 442 1525
47 74.2 463 449 1550
47.5 74.5 470 455 1575
48 74.7 478 461 1605
48.5 75 485 468 1630
49 75.3 493 474 1660
49.5 75.5 501 481 1690
50 75.8 509 488 1720
50.5 76.1 517 494 1750
51 76.3 525 501 1780
51.5 76.6 534 1815
52 76.9 543 1850
52.5 77.1 551 1885
53 77.4 561 1920
53.5 77.7 570 1955
54 77.9 579 1995
54.5 78.2 589 2035
55 78.5 599 2075
55.5 78.7 609 2115
56 79 620 2160
56.5 79.3 631 2205
57 79.5 642 2250
57.5 79.8 653 2295
58 80.1 664 2345
58.5 80.3 676 2395
59 80.6 688 2450
59.5 80.9 700 2500
60 81.2 713 2555
60.5 81.4 726
61 81.7 739
61.5 82 752
62 82.2 766
62.5 82.5 780
63 82.8 795
63.5 83.1 810
64 83.3 825
64.5 83.6 840
65 83.9 856
65.5 84.1 872
66 84.4 889
66.5 84.7 906
67 85 923
67.5 85.2 941
68 85.5 959
68.5 85.8 978
69 86.1 997
69.5 86.3 1017
70 86.6 1037

> Download above metal hardness chart

HRC / HB approximate conversion tips

  • When the hardness is higher than 20HRC, 1HRC≈10HB,
  • When the hardness is lower than 20HRC, 1HRC≈11.5HB.

Notes: For cutting processing, 1HRC≈10HB can be basically converted (the hardness of the workpiece material has a fluctuation range)

The most common Brinell, Rockwell, and Vickers hardnesses of metal materials are all indentation hardness. The hardness value indicates the ability of the surface of a material to resist plastic deformation caused by the intrusion of another object. When measuring the hardness by the back-jumping method, the hardness value represents the size of the metal’s elastic deformation function.

4 Commonly used hardness

Brinell Hardness

A hardened steel ball or hard alloy ball with a diameter of D is used as the indenter, and the corresponding test force F is pressed into the surface of the test piece. After the prescribed holding time, the test force is removed to obtain an indentation of diameter d. Divide the test force by the indentation surface area. The value obtained is the Brinell hardness value, and the symbol is expressed by HBS or HBW.

Brinell Hardness

The difference between HBS and HBW is the indenter. HBS indicates that the indenter is a hardened steel ball, which is used to determine materials with a Brinell hardness value below 450, such as mild steel, gray cast iron and non-ferrous metals.

HBW indicates that the indenter is a hard alloy, which is used to measure materials with a Brinell hardness value below 650.

The same test block, when the other experimental conditions are exactly the same, the results of the two tests are different, the HBW value is often greater than the HBS value, and there is no quantitative law to follow.

HBW Formula

After 2003, China has adopted international standards equivalently, eliminating steel ball indenters and using hard alloy ball heads.

Therefore, HBS was discontinued, and all Brinell hardness symbols were represented by HBW.

Many times Brinell hardness is only expressed by HB, which means HBW. However, HBS is still seen in the literature.

The Brinell hardness measurement method is suitable for cast iron, non-ferrous alloys, various annealed as well as quenched and tempered steels. It is not suitable to measure samples or workpieces that are too hard, too small, too thin, and do not allow large indentations on the surface.

Rockwell Hardness

A diamond cone with a cone apex angle of 120 ° or Ø1.588mm and Ø3.176mm hardened steel ball is used as the indenter and used in conjunction with the load. Under the initial load of 10kgf and the total load (that is, the initial load plus main load) of 60, 100 or 150kgf force, press the sample. After the total load, the hardness is expressed by the difference between the indentation depth when the main load is removed while the main load is retained and the indentation depth under the initial load.

Rockwell Hardness

The Rockwell hardness test uses three test forces and three indenters, which have a total of nine combinations, corresponding to nine scales of Rockwell hardness. The application of these 9 rulers covers almost all commonly used metal materials.

There are three commonly used HRA, HRB and HRC, of which HRC is the most widely used.

Table of commonly used Rockwell hardness test specifications

Hardness symbol Indenter type Total test forceF/N(kgf) Hardness range Applications
HRA 120°diamond cone 588.4(60) 20~88 Hard alloy, carbide, shallow case hardening steel and etc.
HRB Ø1.588mm Quenched steel ball 980.7(100) 20~100 Annealed or normalized steel, aluminum alloy, copper alloy, cast iron
HRC 120°diamond cone 1471(150) 20~70 Hardened steel, quenched and tempered steel, deep case hardening steel

The use range of HRC scale is 20 ~ 70HRC. 

When the hardness value is less than 20HRC, because the conical part of the indenter is pressed too much, the sensitivity is reduced, and the HRB scale should be used instead. When the hardness of the sample is greater than 67HRC, the pressure on the tip of the indenter is too large, the diamond is easily damaged, and the life of the indenter will be greatly shortened. Therefore, the HRA scale should be used instead.

The Rockwell hardness test is simple, fast, and has small indentation. It can test the surface of finished products and harder and thinner work pieces. Because the indentation is small, the hardness value fluctuates greatly for materials with uneven structure and hardness, and the accuracy is not as high as the Brinell hardness.

Rockwell hardness is used to determine the hardness of steel, non-ferrous metals, cemented carbide, and the like.

Vickers Hardness

Vickers Hardness

The Vickers hardness measurement principle is similar to Brinell hardness. A diamond quadrangular pyramid indenter with an opposite angle of 136 ° was used to press the surface of the material with a specified test force F. The test force is removed after holding for a specified time, and the hardness value is expressed by the average pressure on the unit surface area of the regular quadrangular pyramid indentation, and the symbol is HV.

HV Formula

The Vickers hardness measurement range is large, and it can measure materials with a hardness in the range of 10 ~ 1000HV, and the indentation is small. It is generally used to measure thin materials and surface hardened layers with carburizing and nitriding.

Leeb Hardness

A certain mass of impact body equipped with tungsten carbide ball head is used to impact the surface of the test piece under a certain force, and then rebound. Due to different material hardness, the rebound speed after impact is also different. Permanent magnetic material is installed on the impact device. When the impact body moves up and down, its peripheral coil will induce an electromagnetic signal proportional to the speed. Then it is converted into Leeb hardness value by the electronic circuit, and the symbol is HL.

The Leeb hardness tester does not require a workbench. Its hardness sensor is as small as a pen and can be directly operated by hand. Whether it is large, heavy or complex geometries, it can be easily inspected.

Another advantage of Leeb hardness is that the surface of the product is lightly damaged and sometimes used for a non-destructive test. It has a unique hardness test in all directions, narrow space and special parts.

Hardness testers

  1. Micro Vickers hardness testing machine

HM series:

Micro Vickers hardness testing machine

  1. Vickers hardness testing machine
    HV series:

Vickers hardness testing machine

  1. Rockwell hardness testing machine
    HR series:

Rockwell hardness testing machine

  1. Portable Leeb hardness tester
    HH series:

Portable Leeb hardness tester

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