BS 970 (Part 1):1983 720M32: 720M32 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
0.28-0.35
0.40-0.70
2.80-3.30
0.40-0.60
<=0.035
<=0.040
More data from BS 970 (Part 1):1983
From the standard
Other composition limits
Phosphorus and sulphur
P 0.035 max, S 0.040 max, alloy steels (clause 1.7.2.1)
Residual elements: see clause 1.7.3.
Source: BS 970 (Part 1):1983, clause 1.7.2.1
Heat treatment and maximum hardness (through hardening)
Hardening temperature
880-910 deg C
Quenching medium
Oil
Tempering temperature
550-700 deg C
Maximum hardness HB, softened condition
248
Maximum hardness HB, temper softened condition
277
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
U
250
925-1075
755
12
30
35
740
269-331
U
150
925-1075
755
12
35
42
740
269-331
V
150
1000-1150
850
12
35
42
835
293-352
W (note 11)
100
1075-1225
940
11
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.
Source: BS 970 (Part 1):1983, Table 6
Comparison with earlier editions
BS 970:1970/72 designation
Not listed
BS 970:1955 En No.
None
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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