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
Ni
Cr
S
P
0.26-0.34
0.10-0.35
0.40-0.60
3.90-4.30
1.10-1.40
<=0.050
<=0.050
Mechanical Properties
Tensile Strength
≥1544 MPa (100 tons/sq in, converted)
Yield Strength
≥1313 MPa (85 tons/sq in, converted)
Elongation
≥10%
Hardness
444 HB
Condition
Air hardened and tempered (lowest-strength condition of the standard)
More data from BS 970:1955
From the standard
Condition of material on delivery
A
Bars and billets for forging as rolled or forged unless order states otherwise.
B
Forgings and drop-forgings softened unless order states otherwise.
C
Bars for machining softened unless order states otherwise.
Source: BS 970:1955, Part 2, En 30A (page 116)
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
Air hardened and tempered
-
100
85
10
10
444
80
Softened condition
-
-
-
-
-
<=285
-
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 30A (page 117)
Heat treatment
Harden (air, or oil for larger masses) (Air hardening for ruling sections up to 2 1/2 in preferable; oil hardening necessary for larger sizes up to ruling section 6 in)
810/830 C
Temper
if desired, at a suitable temperature not exceeding 250 C
Temperatures in degrees C as printed.
Source: BS 970:1955, Part 2, En 30A (page 116)
Status in the 1955 edition
Status
Deleted by Amendment 7
Reason
Amendment 7 (Sep 1970): direct hardening alloy steels moved to BS 970 Part 2:1970
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.