BS 970 (Part 1):1983 722M24: 722M24 is an alloy 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
Cr
Mo
P
S
0.20-0.28
0.45-0.70
3.00-3.50
0.45-0.65
<=0.035
<=0.040
More data from BS 970 (Part 1):1983
From the standard
Other composition limits
Suitable for nitriding
When so ordered by the purchaser, in which case 4 x P plus Sn must not exceed 0.12% (note 22)
Phosphorus and sulphur
P 0.035 max, S 0.040 max, alloy steels (clause 1.7.2.1)
Source: BS 970 (Part 1):1983, Table 6
Heat treatment and maximum hardness (through hardening)
Hardening temperature
880-910 deg C
Quenching medium
Oil
Tempering temperature
570-700 deg C
Maximum hardness HB, softened condition
241
Maximum hardness HB, temper softened condition
269
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
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
T
250
850-1000
650
13
30
35
635
248-302
T
150
850-1000
680
13
40
50
665
248-302
U
150
925-1075
755
12
35
42
740
269-331
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.
Source: BS 970 (Part 1):1983, Table 6
Mechanical properties, bright bar
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
T
over 150 to 250
850-1000
650
13
30
35
635
248-302
Hardened and tempered + turned or ground
T
6 to 150
850-1000
680
13
40
50
665
248-302
Hardened and tempered + turned or ground
U
6 to 150
925-1075
755
12
35
42
740
269-331
Hardened and tempered + cold drawn or hardened and tempered + cold drawn + ground
T
6 to 150
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 150
925-1075
770
9
35
-
755
269-331 (note 4)
Turned, ground or cold drawn, and finally softened
-
-
-
-
-
-
-
-
269 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.
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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