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Resources/Materials & grades/18CrNiMo7-6

Materials & grades

18CrNiMo7-6 / 1.6587 / 17CrNiMo6 case-hardening steel

18CrNiMo7-6 (1.6587) is a chromium-nickel-molybdenum case-hardening steel with 0.15–0.21% carbon, used for heavily loaded gears and transmission parts. It replaces the older DIN name 17CrNiMo6, and no US, UK or Japanese grade matches it exactly.

Names by standard

What it is called in each region

RegionSystemDesignationNormaMatch
USAAISI/SAE4320Listed against 1.6587 by Total Materia (implicit). Chromium is 0.40–0.60% against 1.50–1.80% for 18CrNiMo7-6, so 4320 is only a loose match.SAE J404Closest equivalent
UKBS 970-3 (1991)822M17Listed against 18CrNiMo7-6 by Total Materia (implicit). DEW prints 822A17, 822H17 and 817M17 instead of 822M17, so check which grade a drawing means.BS 970-3Closest equivalent
BS 970 (1955 EN series)EN355Superseded 1955 name. Roymech and Total Materia map EN355 to 822M17; DEW prints it against 18CrNiMo7-6.—Closest equivalent
EUEN 10027-1 name18CrNiMo7-6EN 10084; EN ISO 683-3Same material
EN 10027-2 number1.6587EN 10084Same material
DIN (legacy)17CrNiMo6Superseded German name for a close predecessor with slightly lower carbon and manganese limits, still seen on older drawings. DEW still quotes its blind-hardened values from DIN 17210.DIN 17210 (superseded)Equivalent
IndieIS 157016Ni6Cr7Mo3IS 1570 (Part 4) footnote 7 states this grade is equivalent to DIN 17CrNiMo6. Carbon tops out at 0.19% and manganese is 0.40–0.60%, so limits differ slightly from the EN grade.IS 1570 (Part 4):1988Equivalent
JapanJIS G 4053SNCM420Nearest JIS nickel-chromium-molybdenum case-hardening steel, but chromium is only 0.40–0.60% and nickel 1.60–2.00%. SNCM815 has 4.00–4.50% nickel and is not a match.JIS G 4053Closest equivalent

On equivalence

  • 17CrNiMo6 is the older German name for this steel and is still quoted against it (Saarstahl titles its sheet "18CrNiMo7-6 (17CrNiMo6)"), but the old DIN limits for carbon and manganese were slightly lower (Atlas, IS 1570). EN 10084 replaced it with 18CrNiMo7-6 (1.6587).
  • India: IS 1570 (Part 4):1988 footnote 7 equates 16Ni6Cr7Mo3 with DIN 17CrNiMo6. The Indian limits are slightly narrower on carbon (0.14–0.19%) and manganese (0.40–0.60%), and IS 1570 (Part 4) sets no phosphorus or sulphur limits.
  • US: 4320 has 0.40–0.60% chromium, against 1.50–1.80% for 18CrNiMo7-6, so it is only a loose match. No SAE grade with 1.5–1.8% chromium and 1.4–1.7% nickel was found in the sources checked.
  • UK: Total Materia and Roymech map EN355 to 822M17 (roughly 2% Ni/Cr/Mo). DEW prints 822A17, 822H17 and 817M17 for the same steel. Roymech lists 817M40 as 1.2% chromium, a different level. The grades are "closest", not confirmed equivalents.
  • Japan: SNCM420 has chromium of 0.40–0.60% and SNCM815 has 4.00–4.50% nickel. Neither matches 18CrNiMo7-6 closely, and Kobelco's cross-reference shows no EN equivalent for either.
  • EN36 (655M13) is a different steel with its own page. 16MnCr5 and 20MnCr5 are nickel-free and are not substitutes.
  • DEW's blind-hardened figures come from the withdrawn DIN 17210 and are guide values. EN 10084 itself gives no diameter-dependent strengths for this grade.

Chemical composition

Composition limits, mass %

Element822M17UK · BS 970-3:1991 (partial, as shown by Total Materia)18CrNiMo7-6 (1.6587)EU · EN 10084 (cast analysis, as printed by DEW)16Ni6Cr7Mo3Indie · IS 1570 (Part 4):1988 (no phosphorus or sulphur limits)
C0.14–0.200.15–0.210.14–0.19
Si—≤0.400.15–0.35
Mn—0.50–0.900.40–0.60
P—≤0.025—
S—≤0.035—
Cr1.30–1.701.50–1.801.50–1.80
Ni—1.40–1.701.40–1.70
Mo—0.25–0.350.25–0.35
Cu≤0.30——

Mechanical properties

Strength and hardness

ConditionTensile strengthYield strengthElongationHardness
Soft annealed (+A)Specified maximum hardnessEN 10084, via DEW and Saarstahl datasheets———≤229 HB
Treated to ferrite-pearlite structure and hardness range (+FP)Specified hardness range for machiningEN 10084, via DEW and Saarstahl datasheets———159–207 HB
Blind hardened, diameter 11 mmGuide values from the withdrawn DIN 17210 as printed by DEW; Z 30%, KV 41 JDEW datasheet, 18CrNiMo7-61180–1420 MPa171–206 ksi835 MPa121 ksi7 %—
Blind hardened, diameter 30 mmGuide values from the withdrawn DIN 17210 as printed by DEW; Z 35%, KV 41 JDEW datasheet, 18CrNiMo7-61080–1320 MPa157–191 ksi785 MPa114 ksi8 %—
Blind hardened, diameter 63 mmGuide values from the withdrawn DIN 17210 as printed by DEW; Z 35%, KV 41 JDEW datasheet, 18CrNiMo7-6980–1270 MPa142–184 ksi685 MPa99 ksi8 %—
Hardened and tempered at 200 °C, diameter ≤16 mmMinimum tensile strength (Saarstahl)Saarstahl datasheet, 18CrNiMo7-6 (17CrNiMo6)≥1200 MPa≥174 ksi———
Hardened and tempered at 200 °C, diameter 16–40 mmMinimum tensile strength (Saarstahl)Saarstahl datasheet, 18CrNiMo7-6 (17CrNiMo6)≥1100 MPa≥160 ksi———
Hardened and tempered at 200 °C, diameter 40–100 mmMinimum tensile strength (Saarstahl)Saarstahl datasheet, 18CrNiMo7-6 (17CrNiMo6)≥900 MPa≥131 ksi———

In practice

Behaviour, heat treatment and uses

Characteristics

  • Chromium (1.50–1.80%), nickel (1.40–1.70%) and molybdenum (0.25–0.35%) give deep hardenability and a tough, high-strength core. Saarstahl quotes a core strength of 1050–1350 MPa.
  • DEW describes good toughness and good machinability, and says the steel is usually weldable.
  • Supplied in hardenability bands +H, +HL and +HH; DEW's Jominy band is tested from 860 °C.
  • Delivery conditions: soft annealed ≤229 HB, spheroidized (+AC) ≤179 HB, ferrite-pearlite (+FP) 159–207 HB, treated for shearability (+S) ≤255 HB, hardness range (+TH) 179–229 HB.
  • Physical properties (DEW): density 7.8 kg/dm³, modulus of elasticity 210 GPa, thermal conductivity 39.8 W/(m·K) at 20 °C. Ac1 730 °C and Ac3 820 °C.

Heat treatment

  • Hot forming: 1100–850 °C (DEW). Saarstahl gives forging or rolling at 1150–850 °C.
  • Normalizing: 850–880 °C, air cool (Saarstahl).
  • Soft annealing: 650–700 °C (DEW, Saarstahl).
  • Carburizing: 880–980 °C (DEW, Saarstahl).
  • Core hardening: 830–870 °C. DEW quenches in oil or polymer; Saarstahl lists water.
  • Case (surface) hardening: 780–820 °C, same quench media as core hardening.
  • Intermediate annealing 630–650 °C (Saarstahl). Tempering: 150–200 °C, air cool (DEW, Saarstahl).

Typické použití

  • Heavily loaded transmission parts such as crown wheels and drive pinions (DEW)
  • Gears for heavy-duty, high-stress service where core toughness matters (DEW, Saarstahl)

Alloy and case-hardening steels

Similar grades compared

JakostC %Mn %Cr %Ni %Tensile, first listed condition
18CrNiMo7-60.15–0.210.50–0.901.50–1.801.40–1.701180–1420 MPa
16MnCr50.13–0.180.70–0.900.70–0.90≤0.25≥1000 MPa
20MnCr50.17–0.220.70–0.900.70–0.90≤0.25≥1200 MPa
655M13 / EN36A0.08–0.130.45–0.651.00–1.403.00–3.50700–770 MPa
815M17 / EN3530.14–0.200.60–0.900.80–1.201.20–1.50≥1200 MPa
4320 / SNCM4200.17–0.220.45–0.650.40–0.601.65–2.00580 MPa
8620 / 20NiCrMo2-20.18–0.230.70–0.900.40–0.600.40–0.70530 MPa
93100.08–0.130.45–0.651.00–1.403.00–3.501289 MPa
4130 / 25CrMo40.28–0.330.40–0.600.80–1.10≤0.25590–760 MPa
4135 / 34CrMo40.33–0.380.70–0.900.80–1.10≤0.251000–1200 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.

Odpovědi na Vaše otázky

Common questions

What is 17CrNiMo6?

17CrNiMo6 is the older German name for 18CrNiMo7-6 (1.6587), the same case-hardening steel. EN 10084 uses 18CrNiMo7-6, but suppliers and drawings still quote 17CrNiMo6.

What is the equivalent of 18CrNiMo7-6?

In India, IS 1570 (Part 4) lists 16Ni6Cr7Mo3 as equivalent to DIN 17CrNiMo6. In the UK the usual name is 822M17 (EN355). No US or Japanese grade matches it exactly; 4320 and SNCM420 are only loose matches.

What is 18CrNiMo7-6 used for?

Heavily loaded gears and transmission parts, such as crown wheels and drive pinions. The steel is carburized and hardened to give a hard case over a core of roughly 1050–1350 MPa.

Is 18CrNiMo7-6 weldable?

DEW states that the steel is usually weldable. Welding after carburizing or hardening changes the case and core, so weld in the soft condition where possible and follow a qualified procedure.

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Keep reading

4320 / SNCM420SAE 4320 is a nickel-chromium-molybdenum case-hardening steel with 0.17–0.22% carbon and 1.65–2.00% nickel, carburized to give a hard case over a tough core.815M17 / EN353815M17 (formerly EN353) is a nickel-chromium-molybdenum case-hardening steel with 0.14–0.20% carbon, still ordered by its BS 970 name.655M13 / EN36A655M13, formerly EN36A, is a UK case-hardening steel with about 3.25 % nickel and 0.8 % chromium, used for heavily loaded gears and shafts in large sections.8620 / 20NiCrMo2-28620 is a low-alloy nickel-chromium-molybdenum steel with about 0.20 % carbon, supplied for carburizing to give a hard case over a tough core in gears, shafts and pins.93109310 is a nickel-chromium-molybdenum carburizing steel with about 0.10 % carbon and 3.25 % nickel, used for highly stressed aerospace gears and shafts.16MnCr516MnCr5 (1.7131) is a manganese-chromium case-hardening steel with 0.14–0.19 % carbon, used for gears, shafts and camshafts that are carburized and hardened.20MnCr520MnCr5 (1.7147) is a manganese-chromium case-hardening steel with 0.17–0.22 % carbon and a higher core strength than 16MnCr5, used for gears, shafts and cam parts.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.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. Deutsche Edelstahlwerke (Swiss Steel Group), Werkstoffdatenblatt Carbodur 6587 / 18CrNiMo7-6 (1.6587) — EN 10084 composition, BS designations (EN355, 822A17, 822H17, 817M17), delivery hardness, blind-hardened values, heat treatment.
  2. Saarstahl, Werkstoff-Datenblatt 18CrNiMo7-6 (17CrNiMo6) — Typical analysis, core strength, tensile after hardening and tempering, heat treatment.
  3. IS 1570 (Part 4):1988 Schedules for wrought steels, alloy steels (public copy) — Table 1 composition limits and the footnote cross-references to AISI and DIN grades.
  4. Kobelco: wire rod and bar specification tables (JIS G 4053 alloy steels for machine structure, revision of 20 Nov 2008; JIS G 4107 bolting steels) — JIS composition tables and the JIS-to-ISO/AISI cross-reference table.
  5. Total Materia, B.S. 822 M 17 — Partial composition and equivalents (EN355, 18CrNiMo7-6, SAE 4320 implicit).
  6. Roymech, sample BS 970 steels — 1955 EN number to BS 970 name table.

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