BS 970 (Part 1):1983 174H20: 174H20 is a boron case hardening 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
P
S
B
0.17-0.23
1.20-1.50
<=0.060
0.03-0.06
0.0005-0.005
More data from BS 970 (Part 1):1983
From the standard
Other composition limits
Boron
0.0005-0.005 (Table 10)
Source: BS 970 (Part 1):1983, Table 10
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
48
41
3
48
41
5
48
41
7
48
40
9
47
39
11
47
37
13
47
35
15
46
32
20
44
26
25
42
23
30
39
21
35
-
-
40
36
-
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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