BHN - Brinell Hardness Number

Fully automatic Digital Brinell hardness tester

The Brinell hardness test is commonly used to determine the hardness of materials like metals and alloys.

The test is achieved by applying a known load to the surface of the tested material through a hardened steel ball of known diameter. The diameter of the resulting permanent impression in the tested metal is measured and the Brinell Hardness Number calculated as

BHN = 2 P / (π D (D - (D2 - d2)1/2))                                             (1)

where

BHN = Brinell Hardness Number

P = load on the indenting tool (kg)

D = diameter of steel ball (mm)

d = measure diameter at the rim of the impression (mm)

It is desirable that the test load are limited to a impression diameter in the range of 2.5 to 4.75 mm.

Approximate loads and Brinell Hardness Numbers:

Brinell Hardness Number	Load (kg)
160 - 600	3000
80 - 300	1500
26 - 100	500

Typical Brinell Hardness Numbers for Metals:

Material	Brinell Hardness Number
Soft brass	60
Mild steel	130
Annealed chissel steel	235
White cast iron	415
Nitrided surface	750

Steel Hardness versus Strength:

Brinell		Vickers	Rockwell		Equivalent Rm
Impression  Diameter (mm)	Hardness HB	Hardness HV	Hardness B	Hardness C	(tonf/in2)	(kgf/mm2)	(N/mm2)
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