BS 970 (Part 1):1983 826M31: 826M31 is an alloy steel grade specified in BS 970 Part 1:1983 (Table 6, 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
Cr
Mo
Ni
P
S
0.27-0.35
0.45-0.70
0.50-0.80
0.45-0.65
2.30-2.80
<=0.035
<=0.040
More data from BS 970 (Part 1):1983
From the standard
Other composition limits
Phosphorus and sulphur, Z condition
0.025 max each, unless otherwise agreed (note 20)
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
820-850 deg C
Quenching medium
Oil
Tempering temperature
660 deg C max
Hardenability test
No hardenability data specified
Maximum hardness HB, softened condition
255
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 27: tempering between 280 deg C and 500 deg C should be avoided.
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
250
925-1075
740
12
25
28
725
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
X (note 11)
63
1150-1300
1020
10
25
28
1005
341-401
Z (note 11)
63
1550 min
1235
5
8
9
1125
444 min
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
826M31
BS 970:1955 En No.
25
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
Active BS 970 (Part 1):1983 826M31 Listings on M-EX (For Sale)