Common ferrous metal hardness comparison table (approximate strength conversion)
Hardness classification				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
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	70.5	382	375	1260
40.5	70.8	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	77.4	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	-	-
64.4	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	-	-

HRC/HB approximate conversion tips
Hardness is higher than 20HRC, 1HRC≈10HB,
Hardness is lower than 20HRC, 1HRC≈11.5HB.
Remarks: For cutting processing, 1HRC≈10HB can basically be converted uniformly (hardness of workpiece material has a fluctuation range)

Hardness refers to ability of a material to resist localized deformation, especially plastic deformation, indentation or scratching. It is a measure of softness and hardness of a material.
According to different test methods, hardness is divided into three types.
① Scratch hardness. It is mainly used to compare degree of softness and hardness of different minerals. Method is to select a rod with one end hard and one soft at the other, and scratch tested material along rod, determine softness and hardness of tested material according to position of scratch. Qualitatively speaking, scratches made by hard objects are longer, and scratches made by soft objects are shorter.
② Press-fit hardness. Mainly used for metal materials, method is to press specified indenter into tested material with a certain load, and compare hardness of tested material with size of local plastic deformation on the surface of material. Due to difference of indenter, load and load duration, there are many kinds of indentation hardness, mainly Brinell hardness, Rockwell hardness, Vickers hardness and microhardness.
③ Rebound hardness. Mainly used for metal materials, method is to make a special small hammer fall freely from a certain height to impact sample of material to be tested, and use amount of strain energy stored (and then released) by sample during impact process (through return of small hammer). jump height determination) to determine hardness of material.
The most common Brinell hardness, Rockwell hardness and Vickers hardness of metal materials belong to indentation hardness, and hardness value indicates ability of material surface to resist plastic deformation caused by indentation of another object; rebound method (Shore, Leeb) measures hardness, and hardness value represents size of elastic deformation function of metal.

Use a quenched steel ball or cemented carbide ball with a diameter of D as an indenter, press it into surface of test piece with a corresponding test force F, and remove test force after a specified holding time to obtain an indentation with a diameter of d. Divide test force by surface area of indentation, obtained value is Brinell hardness value, and symbol is represented by HBS or HBW.

 

Difference between HBS and HBW is difference in pressure head. HBS means that indenter is a hardened steel ball, which is used to measure materials with a Brinell hardness value below 450, such as mild steel, gray cast iron and non-ferrous metals. HBW indicates that indenter is cemented carbide and is used to measure materials with a Brinell hardness value below 650.
Same test block, when other test conditions are exactly same, the two test results are different, HBW value is often greater than HBS value, and there is no quantitative rule to follow.
After 2003, my country has adopted the international standard equivalently, cancelled steel ball indenter, and all used carbide ball head. Therefore, HBS was discontinued, and all Brinell hardness symbols were represented by HBW. In many cases, Brinell hardness is only expressed in HB, which refers to HBW. However, HBS is still seen in literature papers from time to time.
Brinell hardness measurement method is suitable for cast iron, non-ferrous alloys, various annealed, quenched and tempered steels.

Use a diamond cone with a cone apex angle of 120° or a hardened steel ball of Ø1.588mm and Ø3.176mm as indenter and load, press down under initial load of 10kgf and the total force of 60, 100 or 150kgf (ie initial load plus main load) successively. After the total load was applied, hardness was expressed by difference between indentation depth when main load was removed, main load was retained and indentation depth under initial load.

 

Rockwell hardness test uses three test forces and three indenters, which have a total of 9 combinations, corresponding to 9 scales of Rockwell hardness. 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.
Commonly used Rockwell hardness test specification table

Use range of HRC scale is 20~70HRC. When hardness value is less than 20HRC, because conical part of indenter is pressed too much and sensitivity is reduced, HRB scale should be used instead; Life of indenter will be greatly shortened, so HRA scale should generally be used instead.
Rockwell hardness test is simple, rapid, and small indentation, can test surface of finished product, hard and thin workpiece. Due to small indentation, for materials with uneven structure and hardness, hardness value fluctuates greatly, and accuracy is not as high as Brinell hardness. Rockwell hardness is used to measure hardness of steel, non-ferrous metals, cemented carbide, etc.

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

 

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

Impact body with a certain quality of tungsten carbide ball head is used to impact surface of specimen under action of a certain force, and then rebound. Due to different hardness of material, rebound speed after impact is also different. A permanent magnet material is installed on impact device. When impact body moves up and down, its peripheral coil induces an electromagnetic signal proportional to speed, which is then converted into a Leeb hardness value through an electronic circuit, and symbol is marked HL.
Leeb hardness tester does not require a workbench, and its hardness sensor is as small as a pen, which can be directly operated by hand. It can easily detect whether it is a large, heavy workpiece or a workpiece with complex geometric dimensions.
Another advantage of Leeb hardness is that damage to surface of product is very light, and sometimes it can be used as a non-destructive test; it is unique for hardness testing in all directions, narrow spaces and special parts.