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Resources/Materials & grades/1075 / C75S

Materials & grades

1075 / C75S / 75C6 high-carbon spring steel: equivalents S75C and 070A78

1075 is a plain high-carbon steel with 0.70–0.80 % carbon, used for spring strip, blades and stamped parts after hardening and tempering. Its nearest names are C75S (1.1248) in Europe, 75C6 in India, S75C in Japan and 070A78 in the UK; none is identical.

Names by standard

What it is called in each region

RegionSystemDesignationStandardMatch
USAAISI/SAE1075Plain carbon steel with 0.70–0.80 % C and 0.40–0.70 % Mn.SAE J403; ASTM A29 (bar)Same material
UNSG10750—Same material
AISI/SAE1074Same 0.70–0.80 % C, with 0.50–0.80 % Mn. Nippon Steel lists SAE 1074 and 1075 together against S75C.SAE J403Closest equivalent
UKBS 970070A78Total Materia lists 060A78 and 070A78 against SAE 1075. The 1070 page owns 070A72, the next step down. Limits are not tabulated here.BS 970-1Closest equivalent
EUEN 10027-1 nameC75SCold-rolled strip for springs. Carbon 0.70–0.80 %, with 0.60–0.90 % Mn and tighter P and S than SAE 1075.EN 10132-4Closest equivalent
EN 10027-2 number1.1248EN 10132-4Closest equivalent
DIN (legacy)Ck75Superseded German name for C75S (Matthey sells it as Ck75 (C75E), 1.1248).—Closest equivalent
IndiaIS 157075C6Carbon 0.70–0.80 %, the same as 1075, with 0.50–0.80 % Mn.IS 1570 (Part 2/Sec 1)Closest equivalent
JapanJIS G 4051S75CCarbon 0.70–0.80 %, with 0.60–0.90 % Mn. Nippon Steel Wire and Strip catalogue lists it with SAE 1074 and 1075.JIS G 4051Closest equivalent
JIS G 4401SK75Carbon tool steel with the same 0.70–0.80 % C but only 0.10–0.50 % Mn.JIS G 4401Closest equivalent
JIS G 3506SWRH77A / SWRH77BHard wire rod for drawing, carbon 0.74–0.81 %.JIS G 3506Closest equivalent

On equivalence

  • No European, Indian or Japanese grade matches 1075 exactly. C75S and S75C have the same carbon range but 0.60–0.90 % Mn against 0.40–0.70 % for 1075. 75C6 has 0.50–0.80 % Mn.
  • C75S is a strip grade (EN 10132-4) with phosphorus and sulphur limits of 0.025 % in the Roymech table. thyssenkrupp lists S ≤0.010 % in its product table, so check the supplier's analysis.
  • S75C (JIS G 4051) is offered only as plates, sheets and strips for springs and similar parts. SK75 (JIS G 4401) is a carbon tool steel with much less manganese.
  • 070A78 is the BS 970 name Total Materia lists against 1075. The 1070 page covers 070A72 (0.70–0.75 % C). BS 970 is withdrawn in favour of European standards.
  • 1074 is a separate SAE grade with the same carbon range and 0.50–0.80 % Mn. The two are often treated as one in strip specifications.
  • 1070 and 1080 sit either side of 1075 by carbon; see their pages.

Chemical composition

Composition limits, mass %

Element1075USA · SAE J403 (carbon steels)C75S (1.1248)EU · EN 10132-4:2000 (cold-rolled strip for springs)75C6India · IS 1570 (Part 2/Sec 1):1979S75CJapan · JIS G 4051 (as listed by Nippon Steel for strip)SK75Japan · JIS G 4401 (as listed by Kobelco)
C0.70–0.800.70–0.800.70–0.800.70–0.800.70–0.80
Si—0.15–0.35—0.15–0.350.10–0.35
Mn0.40–0.700.60–0.900.50–0.800.60–0.900.10–0.50
P≤0.030≤0.025—≤0.030≤0.030
S≤0.035≤0.025—≤0.035≤0.030
Cr—≤0.40—≤0.20—
Ni—≤0.40—≤0.20—
Mo—≤0.10———
Cu———≤0.30—

Mechanical properties

Strength and hardness

ConditionTensile strengthYield strengthElongationHardness
Annealed, cold-rolled stripSpecified maximum hardness for S75C / SAE 1074 / SAE 1075 stripNippon Steel, special steel sheet and strip catalogue (U006)———≤200 HV
Annealed, hot-rolled stripSpecified maximum hardness for S75C / SAE 1074 / SAE 1075 stripNippon Steel, special steel sheet and strip catalogue (U006)———≤96 HRB
Annealed, skin passed (EN 10132-4, C75S)Specified; Rp0.2 and Rm are maximums, elongation is a minimumEN 10132-4, as tabulated by Roymech≤640 MPa≤93 ksi≤510 MPa≤74 ksi≥15 %≤200 HV
Cold rolled (EN 10132-4, C75S)Specified maximumsEN 10132-4, as tabulated by Roymech≤1170 MPa≤170 ksi——≤320 HV
Quenched and tempered (EN 10132-4, C75S)Specified range for strip; the source gives one range for all tempering conditionsEN 10132-4, as tabulated by Roymech1200–1900 MPa174–276 ksi——370–580 HV
Oil quenched, as hardenedReference value for strip hardened from 780–840 °C (1435–1545 °F)Nippon Steel, special steel sheet and strip catalogue (U006)———≥57 HRC
Cold-rolled strip, soft temper (Ck75 / C75E)Typical mill range for thin stripLamineries Matthey, Ck75 (C75E) strip datasheet480–600 MPa70–87 ksi——145–175 HV
Cold-rolled strip, hard temper (Ck75 / C75E)Typical mill range for thin stripLamineries Matthey, Ck75 (C75E) strip datasheet840–950 MPa122–138 ksi——250–300 HV
Cold-rolled strip, extra-hard temper (Ck75 / C75E)Typical mill minimum for thin stripLamineries Matthey, Ck75 (C75E) strip datasheet≥930 MPa≥135 ksi——≥290 HV

In practice

Behaviour, heat treatment and uses

Characteristics

  • Carbon is 0.70–0.80 %, so the steel hardens fully by oil quenching and reaches at least 57 HRC as quenched (Nippon Steel, strip hardened from 780–840 °C).
  • Matthey describes Ck75 (C75E) as having very good formability when annealed, high strength and good toughness when hardened and tempered, and lower ductility than Ck60.
  • It is a plain carbon steel with no chromium or vanadium, so hardenability is low. Use it in thin sections such as strip, wire and small blades.
  • SAE J403 allows a boron addition of 0.0005–0.003 % for hardenability; such grades carry a B between the second and third digits (Total Materia).
  • In India the grade is made to carbon and manganese limits only: IS 1570 sets no silicon, phosphorus or sulphur limit for 75C6, which are agreed with the buyer.

Heat treatment

  • Normalizing: 900 °C (1650 °F) (Matthey, Ck75 strip).
  • Soft annealing: 650–720 °C (1200–1330 °F) (Matthey).
  • Hardening: 790–820 °C (1455–1510 °F), water or oil quench (Matthey). Nippon Steel gives 780–840 °C (1435–1545 °F) with oil.
  • Tempering: 350–700 °C (660–1290 °F) for at least 60 minutes, chosen for the hardness required (Matthey). Spring temper strip is typically 370–580 HV after hardening and tempering (EN 10132-4, C75S).

Typical uses

  • Flat springs, clips and spring strip
  • Saw, knife and other blades
  • Stamped and blanked parts that are hardened afterwards
  • Watch, clock and jewellery components (Matthey)
  • Machine parts needing high strength in thin sections

Spring steels

Similar grades compared

GradeC %Mn %Cr %Ni %Tensile, first listed condition
1075 / C75S0.70–0.800.40–0.70≤0.40≤0.40≤640 MPa
5160 / 55Cr30.56–0.640.75–1.000.70–0.90—724 MPa
9254 / 54SiCr60.51–0.590.60–0.800.60–0.80—1450–1750 MPa
A228 music wire0.70–1.000.20–0.70——2400–2650 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.

Questions answered

Common questions

What is the equivalent of 1075 steel?

The closest names are C75S (1.1248) in Europe, 75C6 in India, S75C in Japan and 070A78 in the UK. All have 0.70–0.80 % carbon, but manganese differs slightly, so none is an exact match.

Is 1075 a spring steel?

Yes, in strip and thin sections. It is hardened and tempered to 370–580 HV for spring strip under EN 10132-4 (C75S). For heavy sections, chromium or chromium-vanadium grades such as 5160 or 6150 are used instead.

What is the difference between 1075 and 1074 steel?

Both have 0.70–0.80 % carbon. SAE 1075 limits manganese to 0.40–0.70 % and SAE 1074 allows 0.50–0.80 %. Strip suppliers often treat them as one grade.

What is the Indian equivalent of 1075?

75C6 in IS 1570 (Part 2/Sec 1) is the nearest. It has 0.70–0.80 % carbon and 0.50–0.80 % manganese, with no silicon, phosphorus or sulphur limits.

How hard is 1075 after quenching?

Oil quenched from 780–840 °C, strip reaches at least 57 HRC (Nippon Steel). Tempering at 350–700 °C lowers this to the working hardness, for example 370–580 HV for spring strip.

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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.1080 / 80C61080 is a high-carbon steel with about 0.80 % carbon, used for spring strip, blades, tools and wear parts after hardening and tempering.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.1095 / C100S1095 is a high-carbon steel with about 0.95 % carbon, used for knives, blades, flat springs and hardened wear parts.6150 / 51CrV46150 is a chromium-vanadium alloy steel with about 0.50 % carbon, hardened and tempered for springs, gears, shafts and pinions.5160 / 55Cr35160 is a chromium spring steel with 0.56–0.64 % carbon and 0.70–0.90 % chromium, hardened and tempered for leaf and coil springs.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.NormalizingNormalizing heats steel above its upper critical temperature and lets it cool in still air to give a fine, uniform ferrite–pearlite structure.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. Nippon Steel: special steel sheet and strip catalogue (U006) — S75C, SAE 1074 and SAE 1075 composition, annealed hardness and oil-quench data for strip.
  2. Lamineries Matthey: Ck75 (C75E) strip datasheet — Strip tempers, heat treatment temperatures and use notes.
  3. thyssenkrupp Steel: spring steel strip (EN 10132-4) — C75S composition.
  4. Kobelco: wire rods and bars specification tables — SK75 (JIS G 4401) and SWRH77A/B (JIS G 3506) composition.
  5. IS 1570 (Part 2/Sec 1):1979 Schedules for wrought steels: carbon steels (public copy) — Table 1 carbon and manganese limits for 75C6.
  6. SAE J403: Chemical Compositions of SAE Carbon Steels — Governs the US composition limits.
  7. Roymech: EN 10132 cold rolled narrow steel strip for heat treatment — EN 10132-4 C75S composition and strip properties.
  8. Total Materia: SAE 1075 — SAE J403:2014 carbon and manganese; lists 060A78 and 070A78 as cross-references.

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