Hardness knowledge

 

一. Introduction to hardness: Hardness refers to the ability of a material to resist the pressing of hard objects into its surface. It is one of the important performance indicators of metal materials. Generally, the higher the hardness, the better the wear resistance. Commonly used hardness indicators are Brinell hardness, Rockwell hardness and Vickers hardness.

 

1. Brinell hardness (HB) Press a hardened steel ball of a certain size (usually 10mm in diameter) into the surface of the material with a certain load (usually 3000kg) and keep it for a period of time. After the load is removed, the ratio of the load to the indentation area is the Brinell hardness value ( HB), the unit is kilogram force/mm2 (N/mm2).

 

2.Rockwell hardness (HR) When HB>450 or the sample is too small, the Brinell hardness test cannot be used and the Rockwell hardness measurement can be used instead. It uses a diamond cone with an apex angle of 120° or a steel ball with a diameter of 1.59 and 3.18mm, which is pressed into the surface of the material to be tested under a certain load, and the hardness of the material is obtained from the depth of the indentation. According to the hardness of the test material, it can be expressed in three different scales: ·

 

HRA: It is the hardness obtained with a 60kg load and a diamond cone indenter. It is used for extremely hard materials (such as cemented carbide, etc.). ·

HRB: It is the hardness obtained by using a 100kg load and a hardened steel ball with a diameter of 1.58mm, which is used for materials with lower hardness (such as annealed steel, cast iron, etc.). HRC: It is the hardness obtained with a 150kg load and a diamond cone indenter. It is used for materials with high hardness (such as hardened steel, etc.).

 

3 Vickers hardness (HV) With a load of less than 120kg and a diamond square cone indenter with an apex angle of 136°, it is pressed into the surface of the material, and the surface area of the material indentation pit is divided by the load value to obtain the Vickers hardness HV value (kgf/mm2).

 

二. Hardness comparison table: According to the German standard DIN50150, the following is a comparison table of the commonly used ranges of steel tensile strength and Vickers hardness, Brinell hardness, and Rockwell hardness.

抗拉强度 Rm N/mm2	维氏硬度 HV	布氏硬度 HB	洛氏硬度 HRC
250	80	76.0	-
270	85	80.7	-
285	90	85.2	-
305	95	90.2	-
320	100	95.0	-
335	105	99.8	-
350	110	105	-
370	115	109	-
380	120	114	-
400	125	119	-
415	130	124	-
430	135	128	-
450	140	133	-
465	145	138	-
480	150	143	-
490	155	147	-
510	160	152	-
530	165	156	-
545	170	162	-
560	175	166	-
575	180	171	-
595	185	176	-
610	190	181	-
625	195	185	-
640	200	190	-
660	205	195	-
675	210	199	-
690	215	204	-
705	220	209	-
720	225	214	-
740	230	219	-
755	235	223	-
770	240	228	20.3
785	245	233	21.3
800	250	238	22.2
820	255	242	23.1
835	260	247	24.0
850	265	252	24.8
865	270	257	25.6
880	275	261	26.4
900	280	266	27.1
915	285	271	27.8

930	290	276	28.5
950	295	280	29.2
965	300	285	29.8
995	310	295	31.0
1030	320	304	32.2
1060	330	314	33.3
1095	340	323	34.4
1125	350	333	35.5
1115	360	342	36.6
1190	370	352	37.7
1220	380	361	38.8
1255	390	371	39.8
1290	400	380	40.8
1320	410	390	41.8
1350	420	399	42.7
1385	430	409	43.6
1420	440	418	44.5
1455	450	428	45.3
1485	460	437	46.1
1520	470	447	46.9
1555	480	(456)	47.7
1595	490	(466)	48.4
1630	500	(475)	49.1
1665	510	(485)	49.8
1700	520	(494)	50.5
1740	530	(504)	51.1
1775	540	(513)	51.7
1810	550	(523)	52.3
1845	560	(532)	53.0
1880	570	(542)	53.6
1920	580	(551)	54.1
1955	590	(561)	54.7
1995	600	(570)	55.2
2030	610	(580)	55.7
2070	620	(589)	56.3
2105	630	(599)	56.8
2145	640	(608)	57.3
2180	650	(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