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
Mo
S
P
0.20-0.30
0.10-0.35
0.40-0.65
<=0.40
2.90-3.50
0.40-0.70
<=0.050
<=0.050
Mechanical Properties
Tensile Strength
≥695 MPa (45 tons/sq in, converted)
Yield Strength
≥525 MPa (34 tons/sq in, converted)
Elongation
≥22%
Hardness
201-255 HB
Condition
Hardened and tempered R, ruling section 6 in (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 hardened and tempered unless order states otherwise.
C
Bars for machining hardened and tempered unless order states otherwise.
D
Bright bars finally heat treated, before or after cold work at manufacturer option, unless order states otherwise.
Source: BS 970:1955, Part 2, En 40B (page 136)
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
Hardened and tempered R
6
45
34
22
40
201-255
32
Hardened and tempered S
6
50
38
20
40
223-277
36
Hardened and tempered T
6
55
44
18
40
248-302
41
Hardened and tempered U
6
60
48
17
35
269-321
46
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 40B (page 137)
Heat treatment
Harden (oil)
880/910 C
Temper
suitable temperature between 570 C and 750 C
Stabilise and nitride
When required by the purchaser, followed by a stabilising treatment after rough machining at a temperature not lower than 520 C, and afterwards the parts nitrogen hardened by an approved process. Tests in hardened and tempered condition or, by arrangement, after a stabilising treatment or a blank nitriding treatment.
Temperatures in degrees C as printed.
Source: BS 970:1955, Part 2, En 40B (page 136)
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.
Source: BS 970:1955, Amendment slips 6 to 10
Active BS 970:1955 EN40B Listings on M-EX (For Sale)