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C45 / C45E (Ck45) — 1.0503 / 1.1191

The medium-carbon quenched and tempered steel C45 and its variants C45E (formerly Ck45) and C45R: designations and equivalents, chemical composition, strength in the normalized and quenched-and-tempered condition, hardness, heat treatment, weldability and cutting data.

LiveUpdated 11 October 20264 min read

C45 / C45E1.0503 / 1.1191, EN ISO 683-1 (% by mass)6C0.42–0.5014Si0.10–0.4025Mn0.50–0.8024Cr≤ 0.40quenched and tempered shaft (+QT)keywayhardened rimsofter core

C45: composition limits, EN ISO 683-1

Carbon content, EN ISO 683-1
0.42–0.50% C
Tensile strength, quenched and tempered, d ≤ 16 mm
700–850MPa
Maximum hardness, soft annealed (+A)
207HB
Approximate AISI and JIS equivalents
1045 / S45C

C45 is a non-alloy, medium-carbon steel for quenching and tempering: more strength than a structural steel, without alloying elements. It is supplied normalized, soft-annealed, treated for shearability or quenched and tempered.

Designations

NameNumberNote
C451.0503Base grade
C45E1.1191Lower maximum P and S; formerly Ck45 (DIN 17200)
C45R1.1201Specified sulphur range 0.020–0.040 %; formerly Cm45

Approximate equivalents: AISI/SAE 1045, JIS S45C. Equivalent grades are never identical; check the composition and the properties of the standard you buy to.

The governing standard is EN ISO 683-1:2018, which replaced EN 10083-1 and EN 10083-2 (2006). Many mill data sheets still cite EN 10083.

Chemical composition

Heat analysis, % by mass, EN ISO 683-1:

CSiMnP maxS maxCr maxMo maxNi maxCr+Mo+Ni maxCu max
0.42–0.500.10–0.400.50–0.800.045 (C45) · 0.025 (C45E)0.045 (C45) · 0.035 (C45E)0.400.100.400.630.30

C45R has S 0.020–0.040 %. The old EN 10083-2 gave silicon as max 0.40 % without a minimum; the 0.10 % minimum comes with EN ISO 683-1. For the maximum P of C45E, Lucefin prints 0.020 %, against 0.025 % in the other sheets.

Mechanical properties

Normalized (+N), minimum values:

Diameter d (mm)ReH (MPa)Rm (MPa)A (%)
≤ 1634062014
16 < d ≤ 10030558016
100 < d ≤ 25027556016

Quenched and tempered (+QT):

Diameter d (mm)Re min (MPa)Rm (MPa)A min (%)Z min (%)
≤ 16490700–8501435
16 < d ≤ 40430650–8001640
40 < d ≤ 100370630–7801745

For C45E and C45R, Saarstahl, Deutsche Edelstahlwerke and thyssenkrupp give a minimum impact energy KV of 25 J in all three bands; Lucefin prints 15 J. The diameter is that of the heat-treated section, and strength falls as the bar gets thicker because C45 hardens only to a limited depth. Its hardenability band for C45E (thyssenkrupp, Lucefin) shows how fast: 55–62 HRC at 1.5 mm from the quenched end, 28–57 HRC at 5 mm, 22–32 HRC at 11 mm.

quenched endend-quenched test bar20304050600246810121416HRCdistance from the quenched end (mm)55–621.528–57522–3211
The hardenability band of C45E at the three distances quoted above: the hardness range a bar may show after quenching from one end. Within 11 mm of the quenched end the minimum falls from 55 to 22 HRC. Only the three quoted points are drawn.
020040060080010001200140001640100160250Strength (MPa)d (mm)42CrMo4C45020040060080010001200140001640100160250Strength (MPa)d (mm)
Quenched and tempered (+QT): minimum yield strength Re (line) and tensile strength range Rm (band) against the diameter of the heat-treated section, from the EN ISO 683-1 and EN ISO 683-2 values in the tables. C45 is listed only up to 100 mm. Hover a step to read it.

Hardness: soft-annealed (+A) max 207 HB; treated for shearability (+S) max 255 HB.

Heat treatment

Temperatures in °C, as given by the steel makers:

TreatmentRangeNotes
Normalizing840–880DEW and Ovako give 840–870
Soft annealing650–710Saarstahl 680–710; DEW and Ovako 650–700
Hardening820–860Water or oil (Saarstahl). Lower in water than in oil: DEW 820–850 in water, 830–860 in oil; Ovako 820–850 and 840–870. thyssenkrupp gives 840–880
Tempering550–660For the +QT strengths above
500600700800900Temperature (°C)Normalizing840–880DEW, Ovako 840–870Soft annealing650–710Saarstahl 680–710DEW, Ovako 650–700Hardening820–860DEW, water 820–850DEW, oil 830–860Ovako, water 820–850Ovako, oil 840–870thyssenkrupp 840–880Tempering550–660500600700800900Temperature (°C)Normalizing840–880DEW, Ovako 840–870Soft annealing650–710Saarstahl 680–710DEW, Ovako 650–700Hardening820–860DEW, water 820–850DEW, oil 830–860Ovako, water 820–850Ovako, oil 840–870thyssenkrupp 840–880Tempering550–660
Heat treatment temperatures from the table above. The thick bar is the range this page uses; thin bars are the values individual makers print. Hover a bar to read it.

Weldability

Deutsche Edelstahlwerke describes C45E and C45R as difficult to weld and advises against using them in welded structures. Lucefin, if welding cannot be avoided, gives a preheat of 250 °C and stress relieving at 550 °C after welding.

Machining

C45 is a P-group material in ISO 513. For cutting-force calculations, ISCAR places annealed C45 in its group 2 (190 HB, kc1.1 = 1500 N/mm², mc = 0.22) and Seco uses C45E as the reference material of its group P4 (kc1.1 = 2000 N/mm², mc = 0.15). The two sets differ; read cutting forces before mixing them. Ovako offers a calcium-treated “M-Steel” version intended to reduce tool wear and improve chip control.

Sources (12)

Every value and quotation on this page comes from the documents below.

  1. EN ISO 683-1:2018, Heat-treatable steels — Part 1: Non-alloy steels for quenching and tempering (SIS catalogue page)
  2. DIN EN ISO 683-1:2018-09 (DIN Media; replaces EN 10083-1 and -2)
  3. Saarstahl, Werkstoffdatenblatt C45 (1.0503)
  4. Saarstahl, Werkstoffdatenblatt C45E / C45R
  5. Deutsche Edelstahlwerke, Werkstoffdatenblatt 1.1191 / 1.1201 (C45E / C45R), 2011
  6. thyssenkrupp Materials Schweiz, THYROQUENCH 1191 (C45E), 2021
  7. Swiss Steel, C45E / C45R data sheet (EN ISO 683-1:2018)
  8. Lucefin, technical card C45E (ISO 683-1:2018), 2024
  9. Ovako, Steel Navigator: C45
  10. MISUMI, material comparison table (JIS / AISI / DIN), for reference only
  11. ISCAR, "Materials and Grades according to DIN/ISO 513 and VDI 3323" (material groups, kc1.1)
  12. Seco Tools, Milling catalogue 2025, "Workpiece materials — Classification" (distributor copy)