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
0.12-0.18
0.10-0.35
<=0.50
3.80-4.50
1.00-1.40
<=0.050
<=0.050
Mechanical Properties
Tensile Strength
≥1313 MPa (85 tons/sq in, converted)
Elongation
≥12%
Condition
Core, after heat treatment (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.
D
Bright bars in the cold worked condition suitable for machining unless order states otherwise; maximum Brinell hardness may be agreed between purchaser and manufacturer.
Source: BS 970:1955, Part 2, En 39A (page 134)
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
Core, after heat treatment
-
85
-
12
25
-
-
Softened condition
-
-
-
-
-
<=277
-
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 39A (page 135)
Heat treatment
Blank carburise
880/930 C
Refine
850/880 C, cool in air or oil
Harden (oil)
760/780 C
Temper
not exceeding 200 C
Temperatures in degrees C as printed.
Source: BS 970:1955, Part 2, En 39A (page 135)
Notes
Note
See Appendix A for single quench treatment. By arrangement with the purchaser tests may be carried out on samples from which blank carburising has been omitted or modified to a short heating period.
Source: BS 970:1955, Part 2, En 39A
Status in the 1955 edition
Status
Deleted by Amendment 8
Reason
Amendment 8 (Jul 1971): alloy case hardening steels moved to BS 970 Part 3:1971
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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