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GV SteelsEstablished 2008
Resources/Materials & grades/1040 / C40 / EN8

Materials & grades

1040 / C40 / EN8 (080M40) medium-carbon steel: equivalents 40C8 and S40C

1040, C40, EN8 (080M40), 40C8 and S40C are closely related medium-carbon steels with about 0.40 % carbon, used for shafts, axles, studs and forgings that need more strength than mild steel. They are close equivalents rather than one material: manganese limits and the specified mechanical properties differ by standard.

Names by standard

What it is called in each region

RegionSystemDesignationStandardMatch
USAAISI/SAE1040SAE J403; ASTM A29 / A108Same material
UNSG10400—Same material
UKBS 970080M40Wider manganese range (0.60–1.00 %) than 1040 or C40. BS 970 has been withdrawn in favor of European standards, but 080M40 remains a common UK stock name.BS 970Closest equivalent
BS 970 legacy EN seriesEN8superseded name for 080M40, still the most searched UK name.—Closest equivalent
BS 970080A40Composition-specified (A) variant listed by Saarstahl against C40E.BS 970Closest equivalent
EUEN 10027-1 nameC40Same carbon range as 1040 (0.37–0.44 %) with manganese 0.50–0.80 %.EN ISO 683-1 (formerly EN 10083-2)Equivalent
EN 10027-2 number1.0511Material number of C40.EN ISO 683-1Equivalent
EN 10027-1 nameC40E (1.1186) / C40R (1.1189)Variants with tighter phosphorus and sulfur (E) or a controlled sulfur range for machinability (R).EN ISO 683-1Equivalent
DIN (legacy)Ck40 / Cm40Superseded German names for C40E and C40R.—Equivalent
IndiaIS 157040C8Carbon 0.35–0.45 %, manganese 0.60–0.90 %.IS 1570 (Part 2/Sec 1)Closest equivalent
IS 1570 (old designation)C40Superseded Indian name for 40C8; not the same document as the European C40.—Closest equivalent
JapanJIS G 4051S40CCarbon 0.37–0.43 %, slightly narrower than 1040.JIS G 4051Closest equivalent

On equivalence

  • EN8 is the old BS 970 (original edition) name for 080M40. Its manganese range (0.60–1.00 %) is wider than 1040's (0.60–0.90 %) and C40's (0.50–0.80 %), so EN8 is closest to 1040, not identical.
  • Some UK stockists list C45 and 1045 among EN8 equivalents. EN8's carbon range (0.36–0.44 %) matches 1040 and C40; 1045 and C45 are a step higher in carbon.
  • EN8D (080A42, 0.40–0.45 % C) sits between 1040 and 1045 and is a different grade from EN8.
  • C40, C40E and C40R share carbon, manganese and mechanical requirements; they differ in phosphorus and sulfur limits.
  • Indian 40C8 under IS 1570 fixes only carbon and manganese; phosphorus, sulfur and silicon come from the product standard ordered.
  • S40C (JIS) has a slightly narrower carbon range (0.37–0.43 %). MISUMI's comparison maps S40C to 1039, 1040 and 1042.

Chemical composition

Composition limits, mass %

Element1040USA · SAE J403080M40 (EN8)UK · BS 970C40 (1.0511)EU · EN 10083-2 (now EN ISO 683-1)C40E (1.1186)EU · EN 10083-2 (now EN ISO 683-1)40C8India · IS 1570 (Part 2/Sec 1):1979S40CJapan · JIS G 4051:2023
C0.37–0.440.36–0.440.37–0.440.37–0.440.35–0.450.37–0.43
Si—0.10–0.40≤0.40≤0.40——
Mn0.60–0.900.60–1.000.50–0.800.50–0.800.60–0.90—
P≤0.030≤0.050≤0.045≤0.030——
S≤0.050≤0.050≤0.045≤0.035——
Cr——≤0.40≤0.40—≤0.20
Ni——≤0.40≤0.40——
Mo——≤0.10≤0.10——
Cr+Mo+Ni——≤0.63≤0.63——
Cr+Ni—————≤0.35

Mechanical properties

Strength and hardness

ConditionTensile strengthYield strengthElongationHardness
Hot rolled (1040)Estimated minimum, bars 19–32 mm (3/4–1-1/4 in), SAE J1397 basisSAE J1397 estimates as published by Guanyu and ICAST76 ksi (524 MPa)42 ksi (290 MPa)18 %149 HB
Cold drawn (1040)Estimated minimum, bars 19–32 mm (3/4–1-1/4 in), SAE J1397 basisSAE J1397 estimates as published by Guanyu and ICAST85 ksi (586 MPa)71 ksi (490 MPa)12 %170 HB
Normalized (EN8 / 080M40)Specified minimum as published by a UK supplier; section size not statedTachart 080M40≥79.8 ksi (≥550 MPa)≥40.6 ksi (≥280 MPa)16 %152–207 HB
Hardened and tempered, 'R' condition (EN8 / 080M40)Limiting ruling section up to 19 mmSmiths Metal Centres EN8 datasheet102–123 ksi (700–850 MPa)≥67 ksi (≥465 MPa)16 %201–255 HB
Normalized +N (C40 / C40E)Specified minimum, d 16–100 mmEN 10083-2 as tabulated by Roymech and Saarstahl≥79.8 ksi (≥550 MPa)≥42 ksi (≥290 MPa)17 %—
Quenched and tempered +QT (C40 / C40E)Specified, d 16–40 mmEN 10083-2 as tabulated by Roymech and Saarstahl91–113 ksi (630–780 MPa)≥58 ksi (≥400 MPa)18 %—
Hot rolled or normalized (40C8)Specified range, ruling sections up to 150 mmIS 1570 (Part 2/Sec 1):1979, Table 284–99 ksi (580–680 MPa)—18 %—
Hardened and tempered (40C8)Specified, limiting ruling section 30 mmIS 1570 (Part 2/Sec 1):1979, Table 4102–123 ksi (700–850 MPa)≥69.6 ksi (≥480 MPa)17 %—

In practice

Behavior, heat treatment and uses

Characteristics

  • Medium carbon gives noticeably higher strength and wear resistance than mild steel, with moderate toughness.
  • Limited hardenability: only fairly small sections harden through when quenched; larger sections harden at the surface only.
  • Responds well to flame or induction hardening for a hard surface over a normalized core.
  • Weldable with care: preheat, low-hydrogen consumables and post-weld stress relief are recommended, and welding of hardened material is avoided.
  • Machines well in the normalized or hot-rolled condition.

Heat treatment

  • Normalizing: about 850–890 °C (1560–1630 °F), cool in air (Saarstahl, C40E); AZoM gives about 900 °C (1650 °F) for 1040.
  • Soft annealing: about 680–710 °C (1255–1310 °F), furnace cool (Saarstahl, C40E).
  • Hardening: about 830–870 °C (1525–1600 °F), quench in water or oil (Saarstahl, C40E); AZoM gives 844–899 °C (1550–1650 °F) with a water quench for 1040.
  • Tempering: about 550–660 °C (1020–1220 °F) for quenched-and-tempered (+QT) properties (Saarstahl); lower tempering temperatures give higher strength.
  • Stress relieving: about 594 °C (1100 °F) for 1040 (AZoM).

Typical uses

  • Shafts, axles and spindles
  • Studs, bolts and pins
  • Connecting rods, couplings and crankshafts
  • Gears and sprockets that are flame or induction hardened
  • General forgings and machined parts

Carbon steels

Similar grades compared

GradeC %Mn %Cr %Ni %Tensile strength, first listed condition
1040 / C40 / EN80.37–0.440.60–0.90≤0.40≤0.4076 ksi (524 MPa)
1030 / C300.28–0.340.60–0.90≤0.40≤0.4068 ksi (470 MPa)
1035 / C350.32–0.380.60–0.90≤0.40≤0.4073 ksi (500 MPa)
1045 / C450.43–0.500.60–0.90≤0.40≤0.4082 ksi (565 MPa)
1050 / C500.48–0.550.60–0.90≤0.40≤0.4090 ksi (620 MPa)
1055 / C550.50–0.600.60–0.90≤0.40≤0.4094 ksi (650 MPa)
1008≤0.100.30–0.50——44 ksi (303 MPa)
1010 / C10E0.08–0.130.30–0.60≤0.30—46 ksi (320 MPa)
1015 / C15E0.13–0.180.30–0.60≤0.30—49 ksi (340 MPa)
10180.15–0.200.60–0.90≤0.20—58 ksi (400 MPa)

Composition from the US standard where one exists, otherwise the first standard listed on each grade's page. Strength conditions differ between grades; open a grade's page for its full table.

Questions answered

Common questions

What is the equivalent of EN8 steel?

EN8 is the old British name for 080M40. Its closest equivalents are AISI/SAE 1040, European C40 (1.0511), Indian 40C8 and Japanese S40C. They are close equivalents, not identical: EN8 allows up to 1.00 % manganese.

Is EN8 the same as C45 or 1045?

No. EN8 has 0.36–0.44 % carbon, which matches 1040 and C40. C45 and 1045 have 0.42–0.50 % and 0.43–0.50 % carbon, so they are slightly stronger and harden more readily. Some suppliers list them as substitutes, but they are different grades.

Is 1040 the same as C40?

They are close equivalents with the same carbon range (0.37–0.44 %). C40 has lower manganese (0.50–0.80 % against 0.60–0.90 %), and EN ISO 683-1 specifies mechanical properties by condition and size, which SAE J403 does not.

What is the difference between EN8 and EN8D?

EN8 is 080M40 (0.36–0.44 % C). EN8D is 080A42, a separate grade with 0.40–0.45 % carbon and 0.70–0.90 % manganese, so it is slightly higher in carbon.

Can EN8 be hardened?

Yes. It can be quenched and tempered, but through-hardening is limited to small sections. For wear surfaces it is usually flame or induction hardened.

From the GV Steels range

Products listed with 1040 / C40 / EN8

Stakes & pins

Rebar Stakes

Diameter: 5/8-1 in / 16-25 mm · Length: 16-56 in / 300-1400 mm

Specifications
Formwork & reinforcement

Formwork Pins

Diameter: 5/8-1 in / 16-25 mm · Length: 12-56 in / 300-1400 mm

Specifications
Bars & rods

Cut Bars / Dowel Bars

Diameter (Round): 1/4-1 in / 6-25 mm · Size (Square): 5/8, 3/4, 7/8 in / 16, 18, 20 mm

Specifications
Request a quote

Keep reading

1045 / C451045 is a medium-carbon steel with about 0.45 % carbon, supplied hot rolled, normalized or quenched and tempered for shafts, pins, gears and forgings.10181018 is a low-carbon, non-alloy steel with 0.15–0.20 % carbon and 0.60–0.90 % manganese, widely used as cold-drawn bar for machined and case-hardened parts.4140 / 42CrMo4AISI 4140 is a medium-carbon chromium-molybdenum alloy steel, normally used hardened and tempered for shafts, gears and high-strength bolts.NormalizingNormalizing heats steel above its upper critical temperature and lets it cool in still air to give a fine, uniform ferrite–pearlite structure.Quenching and temperingQuenching and tempering hardens steel by cooling it rapidly from the austenite range to form martensite, then reheats it below Ac1 to trade some hardness for toughness.AnnealingAnnealing heats steel to a set temperature, holds it and cools it slowly to make it softer, more ductile and easier to machine or cold form.SAE / AISI numbersA four-digit SAE/AISI number such as 1045 or 4140 names a carbon or alloy steel by its chemistry: the first two digits identify the steel family and the last two give the nominal carbon content in hundredths of a percent.EN 10027 names and numbersEuropean steels carry two identifiers under EN 10027: a steel name (Part 1) such as S235JR, C45 or 42CrMo4 that describes the steel's use or chemistry, and a material number (Part 2) such as 1.0503 or 1.7225.BS 970 and the EN seriesBS 970 names steels with a six-character code such as 080M40, in which the first three digits give the steel type, the letter says how the steel is specified and the last two digits give the carbon content.IS 1570 and Indian designationsIndian steel names follow the letter-symbol code in IS 1762 (Part 1), which the IS 1570 schedules use: 45C8 means about 0.45% carbon, C for carbon steel and about 0.8% manganese, while alloy names such as 40Cr4Mo3 list each element with a multiplied content figure.JIS steel designationsJapanese JIS steel symbols start with S for steel and add letters for the steel family or its use, but the number means different things in different standards.

References

Sources

  1. ICAST: SAE J403 / SAE J1397 UNS G10400, Hot Rolled — SAE J403 composition and J1397 estimated properties.
  2. ICAST: SAE J403 / SAE J1397 UNS G10400, Cold Drawn
  3. Guanyu: Mechanical properties of steel (hot rolled and cold drawn estimated minimums)
  4. AZoM: AISI 1040 Carbon Steel (UNS G10400) — UNS number, heat-treatment temperatures and uses.
  5. Interlloy: 1040 bright carbon steel bar — Relates 1040 to BS 970 080M40 (EN8).
  6. Smiths Metal Centres: EN8 technical datasheet — 080M40 composition and 'R' condition properties.
  7. Tachart: 080M40
  8. Roymech: EN 10083 steels for quenching and tempering — C40 / C40E composition and +N / +QT properties.
  9. Saarstahl material data sheet: C40E (Ck40), 1.1186 — Heat-treatment temperatures; lists BS 080M40, 080A40, 060A40 and SAE 1040.
  10. IS 1570 (Part 2/Sec 1):1979 Schedules for wrought steels: carbon steels (public copy)
  11. Total Materia: JIS S40C (JIS G 4051:2023)
  12. MISUMI: JIS and foreign standards comparison for machine structural steels
  13. Macsteel: Bright bar 080A42 (EN8D)

Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.