(This standard is now obsolete)

STRENGTH GRADE DESIGNATION		TENSILE RANGE Kg/ mm2	TENSILE RANGE Tons/ Sq in	TENSILE RANGE N/ mm2	HARD- NESS HB	HARD- NESS HV	HARD-NESS ROCKWELL B	HARD-NESS ROCKWELL C
4.6-4.8	Min	40	25.40	392	110	110	62	-
	Max	55	34.90	539	170	170	68	-
5.6-5.8	Min	50	31.75	490	140	140	77	-
	Max	70	44.45	686	215	215	97	-
6.6-6.8	Min	60	38.10	588	170	170	88	-
	Max	80	50.80	785	245	245	102	-
8.8	Min	80	50.80	785	225	225	-	18
	Max	100	63.50	981	300	300	-	31
10.9	Min	100	63.50	981	280	280	-	27
	Max	120	76.20	1177	365	370	-	38
12.9	Min	120	76.20	1177	330	330	-	34
	Max	140	88.90	1373	425	440	-	44
14.9	Min	140	88.90	1373	390	400	-	40
	Max	160	101.00	1569	-	510	-	49

Note:-

The strength grade designation consists of two figures, the first representing one tenth of the minimum tensile strength in Kgf/mm2, and the second represents one tenth of the ratio between the minimum yield stress and the minimum tensile strength; expressed as a percentage.

i.e. Strength grade 8.8 is thus:-

1. 1/10 minimum tensile strength of 80kgf/mm2 gives the first figure 8.

2. 1/10 ratio
(Stress at permanent set limit / minimum tensile strength)% = 1/10 x 64/80 x 100/1 = 8 the second figure.

3. Multiply these two figures together will give the stress at permanent set limit
(or the yield stress)

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