BS 970 (Part 1):1983 905M39: 905M39 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
P
S
Cr
Mo
Al
0.35-0.43
0.40-0.65
<=0.025
<=0.025
1.40-1.80
0.15-0.25
0.90-1.30
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 0.10% (note 23)
Source: BS 970 (Part 1):1983, Table 6
Heat treatment and maximum hardness (through hardening)
Hardening temperature
880-920 deg C
Quenching medium
Oil
Tempering temperature
550-700 deg C
Hardenability test
No hardenability data specified
Maximum hardness HB, softened condition
235
Maximum hardness HB, temper softened condition
255
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
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
35
42
665
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.
Source: BS 970 (Part 1):1983, Table 6
Comparison with earlier editions
BS 970:1970/72 designation
905M39
BS 970:1955 En No.
41B
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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