BS 970 (Part 1):1983 070M55: 070M55 is a carbon steel grade specified in BS 970 Part 1:1983 (Table 6, category 1). Section three of the standard advises that category 1 steels be used for new designs and established designs whenever possible.
Matched by chemical composition and mechanical properties, not a formal equivalence claim. Always verify against the applicable standard before substitution.
Chemical Composition (%)
C
Mn
P
S
0.50-0.60
0.50-0.90
<=0.050
<=0.050
More data from BS 970 (Part 1):1983
From the standard
Other composition limits
Phosphorus and sulphur
Each 0.050 max (clause 1.7.2.1, carbon and carbon manganese steels)
Residual elements: see clause 1.7.3.
Source: BS 970 (Part 1):1983, Table 6
Heat treatment and maximum hardness (through hardening)
Hardening temperature
810-840 deg C
Quenching medium
Oil
Tempering temperature
550-660 deg C
Softened condition
Not usually supplied in the softened condition
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.
Source: BS 970 (Part 1):1983, Table 7
Mechanical properties by heat treatment condition
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
R
100
700-850
415
14
-
-
385
201-255
S
63
775-925
480
14
-
-
450
223-277
T (note 13)
19
850-1000
570
12
-
-
555
248-302
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 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.
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground
R
over 29 to 100
700-850
475
10
-
-
435
201-255 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground
R
over 13 to 29
700-850
510
10
-
-
475
201-255 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground
S
6 to 63
775-925
525
10
-
-
485
223-277 (note 4)
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground
T (note 13)
6 to 19
850-1000
595
9
-
-
550
248-302 (note 4)
Turned, ground or cold drawn and finally softened
-
-
-
-
-
-
-
-
201 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 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.
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
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