Matched by chemical composition and mechanical properties, not a formal equivalence claim. Always verify against the applicable standard before substitution.
Chemical Composition (%)
C
Si
Mn
S
P
0.50-0.60
0.05-0.35
0.50-0.80
<=0.050
<=0.050
Mechanical Properties
Tensile Strength
≥695 MPa (45 tons/sq in, converted)
Yield Strength
≥355 MPa (23 tons/sq in, converted)
Elongation
≥18%
Hardness
201-255 HB
Condition
Normalised, ruling section 4 in (lowest-strength condition of the standard)
More data from BS 970:1955
From the standard
Mechanical properties
Condition
Ruling section or size (in)
Tensile strength (tons/sq in)
Yield stress (tons/sq in)
Elongation (%)
Izod impact (ft lb)
Brinell (HB)
Proof stress 0.2% (tons/sq in), when requested
Normalised
4
45
23
18
-
201-255
-
Hardened and tempered R
2
45
30
18
-
201-255
28
Hardened and tempered S
1 1/8
50
33
18
-
223-277
31
Hardened and tempered T
1 1/8
55
36
15
-
248-302
34
Values as printed in BS 970:1955; tensile strength, yield stress and proof stress in tons/sq in, Izod in ft lb. Minimum unless a range is shown.
Source: BS 970:1955, Part 2, En 9K (page 62)
Heat treatment
Normalise
810/840 C
Harden (oil)
810/840 C
Temper
550/660 C
Temperatures in degrees C as printed.
Source: BS 970:1955, Part 2, En 9K (page 61)
Status in the 1955 edition
Status
Deleted by Amendment 9
Reason
Amendment 9 (Feb 1972): carbon and carbon-manganese steels moved to BS 970 Part 1:1972
BS 970:1955 was amended up to Amendment 10 (June 1972); steels were moved to the revised Parts 1 to 5 and deleted from this edition.
Source: BS 970:1955, Amendment slips 6 to 10
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