BS 970 (Part 3):1991 070M55 Steel: Specifications & Listings

Maximum unless a range is stated.

Source: BS 970 (Part 3):1991, Table 13

Condition	Reference symbol	Size (mm)	Tensile strength Rm (MPa)	Yield Re, min (MPa)	Elongation, min (%)	Impact Izod, min (J)	Impact KCV, min (J)	Rp0.2, min (MPa)	Hardness HB	Notes
Normalized + turned or ground		≥ 6 ≤ 63	700 min.	355	12	—	—	—	201-255
Normalized + turned or ground		> 63 ≤ 250	600 min.	310	13			—	170-223
Normalized + cold drawn or normalized + cold drawn + ground		≥ 6 ≤ 13	760 min.	610	6	—	—	570
Normalized + cold drawn or normalized + cold drawn + ground		> 13 ≤ 16	750 min.	600	7	—	—	560
Normalized + cold drawn or normalized + cold drawn + ground		> 16 ≤ 40	710 min.	575	7	—	—	495
Normalized + cold drawn or normalized + cold drawn + ground		> 40 ≤ 63	700 min.	545	8	—	—	440
Normalized + cold drawn or normalized + cold drawn + ground		> 63 ≤ 76	670 min.	530	9	—	—	420
Hardened and tempered + turned or ground	R	> 13 ≤ 100	700-850	415	14	—	—	385	201-255
Hardened and tempered + turned or ground	S	≥ 6 ≤ 63	775-925	480	14	—	—	450	223-277
Hardened and tempered + turned or ground	T	≥ 6 ≤ 19	850-1000	570	12	—	—	555	248-302	(4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	R	> 29 ≤ 100	700-850	475	10	—	—	435	201-255
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	R	> 13 ≤ 29	700-850	510	10	—	—	475	201-255
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	S	≥ 6 ≤ 63	775-925	525	10	—	—	485	223-277
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground	T	> 6 ≤ 19	850-1000	595	9	—	—	550	248-302	(4)
Turned, ground or cold drawn and finally softened		—	—	—	—	—	—	—	201 max.

Condition letters P to Z are the tensile strength ranges of Table 29. Rp0.2 applies when specifically ordered (note 3). Hardness HB is for guidance only except in the softened condition (note 13). Impact: Izod, or KCV when the standard impact test is not required (option A.3). Note 4: These properties cannot always be obtained by bulk heat treatment of bar but can be achieved by the appropriate heat treatment of components by the purchaser. Note 4: These properties cannot always be obtained by bulk heat treatment of bar but can be achieved by the appropriate heat treatment of components by the purchaser.

Source: BS 970 (Part 3):1991, Table 20

Normalizing, hardening and tempering temperatures as given in Tables 27 and 28 (clause 4.2); Table 22 hardening temperatures for case hardening steels.

Source: BS 970 (Part 3):1991, Table 27 and Table 28