BS 970 (Part 1):1983 708H20: 708H20 is a case hardening alloy steel grade supplied to hardenability (H) requirements, specified in BS 970 Part 1:1983 (Table 10, category 1).
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
0.17-0.23
0.60-0.90
0.85-1.15
0.15-0.25
<=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
Preheat treatment temperature (hardenability test)
930-950 deg C
Austenitizing temperature (hardenability test)
925 deg C
Table 12 gives no maximum hardness for this steel.
Source: BS 970 (Part 1):1983, Table 12
Hardenability requirements (end quench test)
Distance from quenched end (mm)
HRC max
HRC min
1.5
47
39
3
47
38
5
46
35
7
44
32
9
41
29
11
39
26
13
36
22
15
35
22
20
33
20
25
31
-
30
30
-
35
29
-
40
28
-
45
28
-
Rockwell C hardness at the stated distance from the quenched end in the end quench hardenability test. A dash means no value is specified. Preheat and austenitizing temperatures: see the heat treatment block.
Source: BS 970 (Part 1):1983, Table 10
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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