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

VickersBrinell
HRCHRAHV

HB

17211211710
17.5214214715
18216216725
18.5218218730
19221220735
19.5223222745
20226225750
20.5229227760
21231229765
21.5234232775
22237234785
22.5240237790
23243240800
23.5246242810
24249245820
24.5252248830
25255251835
25.5258254850
26261257860
26.5264260870
27268263880
27.5271266890
28274269900
28.5278273910
29281276920
29.5285280935
30289283950
30.5292287960
31296291970
31.5300294980
32304298995
32.53083021010
333123061020
33.53163101035
343203141050
34.53243181065
353293231080
35.53333271095
363383321110
36.53423361125
373473411140
37.53523451160
383573501175
38.53623551190
39703673601210
39.570.33723651225
4070.83823751260
40.570.53773701245
4171.13883801280
41.571.33933851300
4271.63993911320
42.571.84053961340
4372.14114011360
43.572.44174071385
4472.64234131405
44.572.94294181430
4573.24364241450
45.573.44434301475
4673.74494361500
46.573.94564421525
4774.24634491550
47.574.54704551575
4874.74784611605
48.5754854681630
4975.34934741660
49.575.55014811690
5075.85094881720
50.576.15174941750
5176.35255011780
51.576.65341815
5276.95431850
52.577.15511885
5377.45611920
53.577.75701955
5477.95791995
54.578.25892035
5578.55992075
55.578.76092115
56796202160
56.579.36312205
5779.56422250
57.579.86532295
5880.16642345
58.580.36762395
5980.66882450
59.580.97002500
6081.27132555
60.581.4726
6181.7739
61.582752
6282.2766
62.582.5780
6382.8795
63.583.1810
6483.3825
64.583.6840
6583.9856
65.584.1872
6684.4889
66.584.7906
6785923
67.585.2941
6885.5959
68.585.8978
6986.1997
69.586.31017
7086.61037

>> 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.

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 symbolIndenter typeTotal test forceF/N(kgf)Hardness rangeApplications
HRA120°diamond cone588.4(60)20~88Hard alloy, carbide, shallow case hardening steel and etc.
HRBØ1.588mm Quenched steel ball980.7(100)20~100Annealed or normalized steel, aluminum alloy, copper alloy, cast iron
HRC120°diamond cone1471(150)20~70Hardened 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.

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 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 unique hardness test in all directions, narrow space and special parts.

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