BS 970 (Part 1):1983 665M20: 665M20 is a case hardening alloy steel grade specified in BS 970 Part 1:1983 (Table 11, category 2). 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
Mo
Ni
P
S
0.17-0.23
0.35-0.75
0.20-0.30
1.50-2.00
<=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
Mechanical properties, test bar
Test bar diameter (mm)
Rm min (N/mm2)
A min (%)
Izod min (ft lbf)
KCV min (J)
19
850
11
20
22
Values as printed in Table 11 for the test bar diameter shown. 1 N/mm2 = 1 MPa.
Source: BS 970 (Part 1):1983, Table 11
Heat treatment and maximum hardness
Hardening temperature
820-840 deg C
Maximum hardness HB, bars and billets for forging
207
Maximum hardness HB, forgings and bars for machining, normalized
207
Maximum hardness values apply when specified on the order, in the condition of delivery. Quantities not limited in Table 12 are not shown.
Source: BS 970 (Part 1):1983, Table 12
Comparison with earlier editions
BS 970:1970/72 designation
665M20
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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