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
0.30-0.40
0.10-0.35
1.30-1.70
<=0.050
<=0.050
Mechanical Properties
Tensile Strength
≥618 MPa (40 tons/sq in, converted)
Yield Strength
≥432 MPa (28 tons/sq in, converted)
Elongation
≥22%
Hardness
179-229 HB
Condition
Hardened and tempered Q, ruling section 6 in (lowest-strength condition of the standard)
Typical Available Sizes
Round Bar
16mm–250mm dia
Flat Bar
20×8mm–150×40mm
Sizes are indicative. Contact seller for exact availability.
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 finally heat treated unless order states otherwise.
C
Bars for machining finally heat treated 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 15 (page 76)
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 Q
6
40
28
22
25
179-229
-
Hardened and tempered Q
4
40
28
22
35
179-229
26
Hardened and tempered R
2 1/2
45
34
20
30
201-255
32
Hardened and tempered S
7/8
50
38
20
30
223-277
36
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 15 (page 77)
Heat treatment
Harden (oil)
840/870 C
Temper
suitable temperature between 550 C and 660 C
Temperatures in degrees C as printed.
Source: BS 970:1955, Part 2, En 15 (page 76)
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.