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Resources/Materials & grades/1055 / C55

Materials & grades

1055 / C55 / S55C medium-high carbon steel: equivalents 55C8, 070M55 (EN9) and C55E

1055 is a plain carbon steel with about 0.55 % carbon and 0.60–0.90 % manganese, used normalized or quenched and tempered where high strength and surface hardness are needed. Its close equivalents are C55 / C55E (1.0535 / 1.1203) in Europe, 070M55 (old EN9) in the UK, 55C8 in India and S55C in Japan.

Names by standard

What it is called in each region

RegionSystemDesignation規格Match
USAAISI/SAE1055Composition limits shown are SAE J403 (P ≤0.030 %). ASTM A29 and older AISI tables give P ≤0.040 %.SAE J403; ASTM A29 / A682Same material
UNSG10550—Same material
UKBS 970070M55Listed against 1055 and C55E by Total Materia, Alan Bright Steel and Zknives. Manganese 0.50–0.90 % against 0.60–0.90 % for 1055. BS 970 has been withdrawn in favour of European standards.BS 970-1Closest equivalent
BS 970 (1955 EN series)EN9Superseded 1955 name for 070M55, with EN9K as a variant (Tachart).—Closest equivalent
EUEN 10027-1 nameC55Carbon 0.52–0.60 %, manganese 0.60–0.90 %.EN ISO 683-1 (formerly EN 10083-2)Equivalent
EN 10027-2 number1.0535Material number of C55.EN ISO 683-1Equivalent
EN 10027-1 nameC55E (1.1203) / C55R (1.1209)Variants with tighter phosphorus and sulphur (E) or a controlled sulphur range (R).EN ISO 683-1Equivalent
DIN (legacy)Ck55 / Cm55Superseded German names for C55E and C55R.—Equivalent
インドIS 157055C8Carbon 0.50–0.60 %, manganese 0.60–0.90 %: the same carbon and manganese as 1055.IS 1570 (Part 2/Sec 1)Equivalent
IS 157055C4Same carbon but a lower manganese range of 0.30–0.60 %.IS 1570 (Part 2/Sec 1)Closest equivalent
IS 1570 (old designation)C55Mn75 (55C8) / C55 (55C4)Superseded Indian names. Old C55 means 55C4, with low manganese, not EN C55.—Closest equivalent
JapanJIS G 4051S55CCarbon 0.52–0.58 %, a narrower range than 1055.JIS G 4051Closest equivalent

On equivalence

  • 1055 and C55 are close equivalents, not the same specification. C55 allows 0.52–0.60 % carbon against 1055's 0.50–0.60 %; manganese is 0.60–0.90 % in both. EN ISO 683-1 also specifies mechanical properties by condition and size.
  • UK 070M55 (old EN9) allows manganese from 0.50 %, while 1055 starts at 0.60 %. Sources differ on the 070M55 manganese maximum (0.80 % at West Yorkshire Steel, 0.90 % at Total Materia and Tachart) and on its phosphorus and sulphur limits.
  • Some tables give 1.1209 for 070M55 and others 1.0535 or 1.1203; 1.1209 is C55R, 1.0535 is C55 and 1.1203 is C55E.
  • Indian 55C8 (Mn 0.60–0.90 %) matches 1055 on carbon and manganese. 55C4 has only 0.30–0.60 % manganese, and its old name C55 is not the same as EN C55.
  • Indian 55C8 under IS 1570 fixes only carbon and manganese; silicon, phosphorus and sulphur come from the product standard ordered.
  • The S55C silicon, manganese, phosphorus and sulphur limits shown here are the common JIS G 4051 limits for the S25C–S58C series, confirmed for S45C and S50C from a reference and a secondary source. The carbon, chromium and chromium-plus-nickel limits are from Total Materia (JIS G 4051:2023).

Chemical composition

Composition limits, mass %

Element1055USA · SAE J403070M55UK · BS 970C55 (1.0535)EU · EN 10083-2 / EN ISO 683-1C55E (1.1203)EU · EN 10083-2 / EN ISO 683-155C8インド · IS 1570 (Part 2/Sec 1):197955C4インド · IS 1570 (Part 2/Sec 1):1979S55CJapan · JIS G 4051
C0.50–0.600.50–0.600.52–0.600.52–0.600.50–0.600.50–0.600.52–0.58
Si——≤0.40≤0.40——0.15–0.35
Mn0.60–0.900.50–0.900.60–0.900.60–0.900.60–0.900.30–0.600.60–0.90
P≤0.030—≤0.045≤0.030——≤0.030
S≤0.050—≤0.045≤0.035——≤0.035
Cr—≤0.30≤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 (1055)Estimated minimum, bars about 19–32 mm (3/4–1-1/4 in), SAE J1397 basisSAE J1397 estimates as published by ICAST; AZoM lists 660 / 560 MPa, 10 %, 197 HB for cold-drawn bar650 MPa94 ksi360 MPa52 ksi12 %192 HB
Normalized +N (C55 / C55E)Specified minimum, d 16–100 mmEN 10083-2 as tabulated by Roymech≥640 MPa≥93 ksi≥330 MPa≥48 ksi12 %—
Quenched and tempered +QT (C55 / C55E)Specified, d 16–40 mmEN 10083-2 as tabulated by Roymech750–900 MPa109–131 ksi≥490 MPa≥71 ksi14 %—
Hot rolled or normalized (55C8)Specified minimum, ruling sections up to 150 mmIS 1570 (Part 2/Sec 1):1979, Table 2≥720 MPa≥104 ksi—13 %—
Hardened and tempered (55C8), lower rangeSpecified, limiting ruling section 63 mmIS 1570 (Part 2/Sec 1):1979, Table 4700–850 MPa102–123 ksi≥460 MPa≥67 ksi15 %—
Hardened and tempered (55C8), higher rangeSpecified, limiting ruling section 30 mmIS 1570 (Part 2/Sec 1):1979, Table 4800–950 MPa116–138 ksi≥540 MPa≥78 ksi13 %—
Normalized (S55C)JIS G 4051 reference minimums; the standard gives these for guidance, not as acceptance valuesJIS G 4051 reference values (minimums), as reproduced by toishi.info, materialmechanics.work and hayamihyou.net; normalized tensile agrees with Total Materia≥650 MPa≥94 ksi≥390 MPa≥56 ksi≥15 %183–255 HB
Quenched and tempered (S55C)JIS G 4051 reference minimums; the standard gives these for guidance, not as acceptance valuesJIS G 4051 reference values (minimums), as reproduced by toishi.info, materialmechanics.work and hayamihyou.net; normalized tensile agrees with Total Materia≥780 MPa≥113 ksi≥590 MPa≥85 ksi≥14 %229–285 HB

In practice

Behaviour, heat treatment and uses

Characteristics

  • High strength and surface hardness for a plain carbon steel, with lower ductility than 1045 or 1050.
  • Easily flame hardened. AZoM's plain-carbon steel article notes that steels in this carbon range harden readily and can reach high tensile strength where low ductility is acceptable.
  • Weldability is poor. Careful preheat and post-weld heat treatment are needed, and in most cases a lower-carbon grade is the better choice.
  • Machinability is lower than for 1030 to 1045: AZoM rates 1055 at 55 on the scale where 1212 is 100.
  • Usually machined in the annealed or normalized condition and hardened afterwards.

Heat treatment

  • Normalizing: about 800–850 °C (1470–1560 °F) for S55C (Total Materia). Cool in air.
  • Hardening: about 800–850 °C (1470–1560 °F) with a water quench for S55C (Total Materia).
  • Tempering: about 550–650 °C (1020–1200 °F) for S55C (Total Materia). Lower temperatures give higher hardness and less toughness.
  • Quenching and tempering is limited by hardenability. IS 1570 gives 63 mm (lower strength range) and 30 mm (higher range) as limiting ruling sections for 55C8.

主な用途

  • Shafts, gears and cams that are flame or induction hardened
  • Wear parts, rollers and forged tooling
  • Agricultural tools and blades
  • Forgings needing more strength than 1045 or 1050

Carbon steels

Similar grades compared

グレードC %Mn %Cr %Ni %Tensile, first listed condition
1055 / C550.50–0.600.60–0.90≤0.40≤0.40650 MPa
1030 / C300.28–0.340.60–0.90≤0.40≤0.40470 MPa
1035 / C350.32–0.380.60–0.90≤0.40≤0.40500 MPa
1040 / C40 / EN80.37–0.440.60–0.90≤0.40≤0.40524 MPa
1045 / C450.43–0.500.60–0.90≤0.40≤0.40565 MPa
1050 / C500.48–0.550.60–0.90≤0.40≤0.40620 MPa
1008≤0.100.30–0.50——303 MPa
1010 / C10E0.08–0.130.30–0.60≤0.30—320 MPa
1015 / C15E0.13–0.180.30–0.60≤0.30—340 MPa
10180.15–0.200.60–0.90≤0.20—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 for its full table.

よくあるご質問

Common questions

What is the equivalent of 1055 steel?

C55 / C55E (1.0535 / 1.1203) in Europe, 070M55 in the UK, 55C8 in India and S55C in Japan. They are close equivalents with slightly different composition limits, not identical specifications.

What is EN9 steel?

EN9 is the old 1955 British name for 070M55, a plain carbon steel with 0.50–0.60 % carbon. It is superseded; the current European equivalent is C55E (1.1203).

Is 1055 the same as C55?

No, but they are close. C55 has 0.52–0.60 % carbon and 0.60–0.90 % manganese. 1055 has 0.50–0.60 % carbon and 0.60–0.90 % manganese.

Is 1055 steel weldable?

Only with difficulty. At about 0.55 % carbon it forms hard, brittle martensite in the heat-affected zone, so it needs preheat and post-weld heat treatment. A lower-carbon grade is usually the better choice for welded parts.

Is S55C equivalent to 1055?

Yes, as a close equivalent. S55C (JIS G 4051) has 0.52–0.58 % carbon and 0.60–0.90 % manganese, which falls inside the 1055 limits.

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1050 / C501050 is a plain medium-carbon steel with about 0.50 % carbon and 0.60–0.90 % manganese, used normalized or quenched and tempered for shafts, gears and parts that are flame or induction hardened.1060 / C601060 is a high-carbon steel with about 0.60 % carbon, supplied hot rolled, annealed or normalized for parts that need a hard, wear-resistant surface or a spring-like temper.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.1070 / 070A721070 is a high-carbon steel with about 0.70 % carbon, used for springs, spring wire, blades and wear parts after hardening and tempering.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. IS 1570 (Part 2/Sec 1):1979 Schedules for wrought steels: carbon steels (public copy) — 55C8 and 55C4 composition, hot-rolled and hardened-and-tempered properties.
  2. Roymech: EN 10083 steels for quenching and tempering — C55 / C55E composition and +N / +QT properties.
  3. AZoM: AISI 1055 Carbon Steel (UNS G10550) — Composition, properties and machinability rating.
  4. AZoM: Steels, plain carbon steels — General behaviour of medium-high carbon steels.
  5. ICAST: SAE J403 / SAE J1397 UNS G10550, Hot Rolled — SAE J403 composition and J1397 estimated properties.
  6. Total Materia: B.S. 070 M 55 — 070M55 carbon, manganese and chromium limits; cross-references to En9, C55E and S55C.
  7. Tachart: 070M55 — Aliases En9, En9K, C55E and 1.1203.
  8. West Yorkshire Steel: 070M55 carbon steel — Lists a narrower manganese range of 0.50–0.80 %.
  9. Alan Bright Steel: comparison of world steel standards — BS 970 1955 / 1983 / 1991 to AISI cross-reference (070M55 as EN9).
  10. Total Materia: JIS S55C (JIS G 4051:2023) — C, Cr and Cr+Ni limits, tensile, hardness, heat treatment.
  11. ASM Alloy Digest: S50C and S53C (JIS G 4051 composition) — Si, Mn, P, S limits common to the JIS S-C series.
  12. MISUMI: JIS and foreign standards comparison for machine structural steels — S55C against 1055, C55, 070M55.
  13. toishi.info — JIS S-C carbon steel mechanical properties (normalized and quenched-and-tempered) — S30C, S35C, S50C and S55C pages, read by the independent checker
  14. materialmechanics.work — JIS G 4051 S-C mechanical properties

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