BS 970 (Part 1):1983 170H20: 170H20 is a boron 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
B
P
S
0.17-0.23
0.80-1.10
0.0005-0.005
<=0.035
<=0.040
More data from BS 970 (Part 1):1983
From the standard
Other composition limits
Boron
Soluble boron 0.0005-0.005; total boron may be determined provided the hardenability values are realized (note 18)
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)
Preheat treatment temperature (hardenability test)
910-930 deg C
Austenitizing temperature (hardenability test)
905 deg C
Softened condition
Not usually supplied in the softened condition; no mechanical properties specified
Source: BS 970 (Part 1):1983, Table 7
Hardenability requirements (end quench test)
Distance from quenched end (mm)
HRC max
HRC min
1.5
48
41
3
48
40
5
47
36
7
46
25
9
43
-
11
39
-
13
32
-
15
26
-
20
20
-
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 9
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
Active BS 970 (Part 1):1983 170H20 Listings on M-EX (For Sale)