BS 970 (Part 1):1983 708M40 Steel: Specifications & Listings

Source: BS 970 (Part 1):1983, Table 6

Heat treatment to be given to test bars and to material required in the finally heat treated condition. Note 24: O = oil, W = water. Where oil hardening is specified, either a well-agitated conventional oil or a proven synthetic quenchant may be used. Synthetic quenchants shall not be used for the heat treatment of test bars for material not supplied in the finally heat treated condition. Note 25: suitable for nitriding. Where parts are to be nitrided, the steel shall be hardened and tempered in accordance with Table 7 but the tempering temperature shall be at least 30 deg C above the temperature to be employed for nitriding.

Source: BS 970 (Part 1):1983, Table 7

Condition	Limiting ruling section (mm)	Rm (N/mm2)	Re min (N/mm2)	A min (%)	Izod min (ft lbf)	KCV min (J)	Rp0.2 min (N/mm2), when specifically ordered	HB
Q	250	625-775	450	15	25	28	430	179-229
Q	150	625-775	480	18	15	16	465	179-229
R	250	700-850	495	15	25	28	480	201-255
R	150	700-850	525	17	40	50	510	201-255
S	100	775-925	585	15	40	50	570	223-277
T	63	850-1000	680	13	40	50	665	248-302
U	29	925-1075	755	12	35	42	740	269-331
V	19	1000-1150	850	12	35	42	835	293-352
W (notes 11, 13)	13	1075-1225	940	12	30	35	925	311-375

Values as printed in Table 6 for the limiting ruling section shown. Rp0.2 applies when specifically ordered (note 10). 1 N/mm2 = 1 MPa. Note 11: often ordered in the softened condition for machining and subsequent heat treatment to achieve these specified mechanical properties. Note 13: may not always be obtained by bulk heat treatment, but the properties can be achieved by the appropriate heat treatment of die forgings and components, and also apply to test bars.

Source: BS 970 (Part 1):1983, Table 6

Condition	Heat treatment condition	Size, diameter or across flats (mm)	Rm (N/mm2)	Re min (N/mm2)	A min (%)	Izod min (ft lbf)	KCV min (J)	Rp0.2 min (N/mm2), when specifically ordered	HB
Hardened and tempered + turned or ground	R	over 150 to 250	700-850	495	15	25	28	480	201-255
Hardened and tempered + turned or ground	R	over 63 to 150	700-850	525	17	40	50	510	201-255
Hardened and tempered + turned or ground	S	over 29 to 100	775-925	585	15	40	50	570	223-277
Hardened and tempered + turned or ground	T	6 to 63	850-1000	680	13	40	50	665	248-302
Hardened and tempered + turned or ground	U	6 to 29	925-1075	755	12	35	42	740	269-331
Hardened and tempered + turned or ground	V	6 to 19	1000-1150	850	12	35	42	835	293-352
Hardened and tempered + turned or ground	W (notes 11, 13)	6 to 13	1075-1225	940	12	30	35	925	311-375
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	R	over 63 to 150	700-850	540	12	40	-	525	201-255 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	S	over 29 to 100	775-925	600	11	40	-	585	223-277 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	T	6 to 63	850-1000	700	9	40	-	680	248-302 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	U	6 to 29	925-1075	770	9	35	-	755	269-331 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	V	6 to 19	1000-1150	865	9	35	-	850	293-352 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	W (notes 11, 13)	6 to 13	1075-1225	955	8	30	-	940	311-375 (note 4)
Turned, ground or cold drawn, and finally softened	-	-	-	-	-	-	-	-	248 max

Size is the diameter or across flats. For cold drawn bar of 6 mm or less, all mechanical properties are subject to agreement between purchaser and supplier at the time of enquiry and order (note 8). For normalizing and hardening and tempering treatments see Tables 3 and 7 (note 9). Rp0.2 applies when specifically ordered (note 10). 1 N/mm2 = 1 MPa. Hardness values marked note 4 are for guidance only. Note 11: often ordered in the softened condition for machining and subsequent heat treatment to achieve these specified mechanical properties. Note 13: may not always be obtained by bulk heat treatment, but the properties can be achieved by the appropriate heat treatment of die forgings and components, and also apply to test bars.

Source: BS 970 (Part 1):1983, Table 4 (bright bar)

Appendix D note 47: where a comparison is made the steels are not necessarily equivalent. 'Not listed' means the earlier edition has no entry under this designation.

Source: BS 970 (Part 1):1983, Appendix D