Materials & grades
31CrMoV9 / 1.8519 nitriding steel
31CrMoV9 (1.8519) is a chromium-molybdenum-vanadium nitriding steel with 0.27–0.34% carbon and 2.30–2.70% chromium, supplied quenched and tempered and nitrided after machining. Mill data quote a nitrided surface of about 650–800 HV or more, depending on the process.
Names by standard
What it is called in each region
| Region | System | Designation | قياسي | Match |
|---|---|---|---|---|
| USA | AMS (trade name Nitralloy 135 Modified) | AMS 6470No SAE/AISI grade matches 31CrMoV9. AMS 6470 (1.6Cr-0.35Mo-1.13Al, 0.38–0.43C) is the usual US nitriding steel, but it is an aluminium-bearing alloy with less chromium and no vanadium. Match by function only. | SAE AMS 6470 | Closest equivalent |
| EU | EN 10027-1 name | 31CrMoV9 | EN 10085; EN ISO 683-5 | Same material |
| EN 10027-2 number | 1.8519 | EN 10085; EN ISO 683-5 | Same material | |
| Japan | JIS G 4053 | SACM645Japan's nitriding steel, but it carries 0.70–1.20% aluminium, 1.30–1.70% chromium and no vanadium. Kobelco's table pairs it with ISO 41CrAlMo7-4, not 31CrMoV9. Match by function only. | JIS G 4053 | Closest equivalent |
On equivalence
- No SAE/AISI, BS 970 or IS grade is a verified equivalent of 31CrMoV9. The Swiss Steel sheet lists no ASTM, JIS or BS equivalents for 1.8519.
- US: AMS 6470 (Nitralloy 135 Modified, 1.6Cr-0.35Mo-1.13Al, 0.38–0.43C) is the usual US nitriding steel. It is aluminium-bearing and has no vanadium, so it is a match by function only.
- UK: 897M39 (EN40C) is not 31CrMoV9. Total Materia maps it to 40CrMoV13-9 (1.8523) with 3.00–3.50% chromium, and Roymech lists it at about 3.25% alloy. 905M39 (EN41B) is the aluminium type: 0.35–0.43% carbon, 1.40–1.80% chromium and 0.90–1.30% aluminium (West Yorkshire Steel). No UK notation is given.
- India: IS 1570 (Part 4):1988 lists 40Cr7Al10Mo2 (0.35–0.45% C, 1.50–1.80% Cr, 0.10–0.25% Mo, 0.90–1.30% Al) and 40Cr13Mo10V2 (0.35–0.45% C, 3.00–3.50% Cr, 0.90–1.10% Mo, 0.15–0.25% V). Neither matches 31CrMoV9. No Indian notation is given.
- Japan: SACM645 carries aluminium (0.70–1.20%), and Kobelco's cross-reference pairs it with ISO 41CrAlMo7-4. It is the nearest JIS nitriding steel, not an equivalent.
- Vanadium: West Yorkshire Steel gives 0.10–0.25%, while the Swiss Steel sheet gives 0.10–0.20%. The mill value is used here.
- The two mills quote nitrided hardness differently: Swiss Steel gives 650–800 HV 0.5 and Dörrenberg gives at least 800 HV. Hardness depends on nitriding process, temperature and measuring load.
Chemical composition
Composition limits, mass %
| Element | 31CrMoV9 (1.8519)EU · EN ISO 683-5 (cast analysis, as printed by Swiss Steel) | SACM645Japan · JIS G 4053 (as tabulated by Kobelco; function-only match) |
|---|---|---|
| C | 0.27–0.34 | 0.40–0.50 |
| Si | ≤0.40 | 0.15–0.50 |
| Mn | 0.40–0.70 | ≤0.60 |
| P | ≤0.025 | ≤0.030 |
| S | ≤0.035 | ≤0.030 |
| Cr | 2.30–2.70 | 1.30–1.70 |
| Ni | — | ≤0.25 |
| Mo | 0.15–0.25 | 0.15–0.30 |
| V | 0.10–0.20 | — |
| Al | — | 0.70–1.20 |
Mechanical properties
Strength and hardness
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Soft annealedSpecified maximum hardnessDörrenberg datasheet, 1.8519 | — | — | — | ≤248 HB |
| Quenched and tempered (+QT)Diameter 16–40 mm; yield and elongation are minimums; Z ≥35%, KV ≥25 J at room temperature (Swiss Steel)EN ISO 683-5, via Dörrenberg and Swiss Steel datasheets | 1100–1300 MPa160–189 ksi | ≥900 MPa≥131 ksi | ≥9 % | — |
| Quenched and tempered (+QT)Diameter 40–100 mm; yield and elongation are minimums; Z ≥40%, KV ≥30 J at room temperature (Swiss Steel quotes 40–80 mm)EN ISO 683-5, via Dörrenberg and Swiss Steel datasheets | 1000–1200 MPa145–174 ksi | ≥800 MPa≥116 ksi | ≥10 % | — |
| Quenched and tempered (+QT)Diameter 100–160 mm; yield and elongation are minimums; KV ≥35 JEN ISO 683-5:2021, via Dörrenberg datasheet | 900–1100 MPa131–160 ksi | ≥700 MPa≥102 ksi | ≥11 % | — |
| Quenched and tempered (+QT)Diameter 160–250 mm; yield and elongation are minimums; KV ≥40 JEN ISO 683-5:2021, via Dörrenberg datasheet | 850–1050 MPa123–152 ksi | ≥650 MPa≥94 ksi | ≥12 % | — |
| Nitrided, gas nitridingSurface hardness; Swiss Steel quotes 650–800 HV 0.5 depending on nitriding temperature (typical, not guaranteed)Swiss Steel Group technical datasheet, 31CrMoV9+QT+SH | — | — | — | 650–800 HV 0.5 |
| NitridedSurface hardness; Dörrenberg states a minimum after nitridingDörrenberg datasheet, 1.8519 | — | — | — | ≥800 HV |
In practice
Behaviour, heat treatment and uses
Characteristics
- An aluminium-free nitriding steel alloyed with chromium, molybdenum and vanadium (Dörrenberg: CrMoV-alloyed nitriding steel).
- Swiss Steel says it is used for gears, connecting rods and shafts that are nitrided because of high wear and dynamic loads.
- Delivered quenched and tempered: Swiss Steel bright bar is quenched and tempered and peeled, with a grain size above 5 (ASTM E112).
- Swiss Steel estimates bending fatigue strength at about half the tensile strength, about 500 MPa at a tensile strength near 1100 MPa (calculated).
- Swiss Steel quotes a density of 7.73 kg/dm³ and a modulus of elasticity of 210 GPa. Its individual bar hardening process covers diameters of 15–80 mm.
- Nitriding case depth, nitriding temperature and time were not given by the mills read. Take them from the heat treater's process data.
Heat treatment
- Soft annealing: 680–720 °C with furnace cooling, 248 HB maximum (Dörrenberg).
- Normalizing: 870–900 °C, air cool (Dörrenberg). West Yorkshire Steel gives 860–900 °C.
- Hardening: 840–880 °C in oil or water (Dörrenberg). Temper from the supplier's tempering diagram; West Yorkshire Steel quotes 540–680 °C.
- Nitriding follows hardening and tempering, after machining. Swiss Steel quotes gas nitriding with a surface hardness of 650–800 HV 0.5 depending on the nitriding temperature.
- Hot working (West Yorkshire Steel): begin forging at 1050 °C and do not forge below 930 °C. Cool very slowly after forging.
استخدامات نموذجية
- Gears, connecting rods and shafts that need nitrided wear resistance (Swiss Steel)
- Spindles loaded to high pressure, screws, control parts, bolts and crankshafts (Dörrenberg)
- Machined tools pre-hardened and then nitrided to about 800 HV (West Yorkshire Steel)
Alloy and case-hardening steels
Similar grades compared
| الدرجة | C % | Mn % | Cr % | Ni % | Tensile, first listed condition |
|---|---|---|---|---|---|
| 31CrMoV9 | 0.27–0.34 | 0.40–0.70 | 2.30–2.70 | ≤0.25 | 1100–1300 MPa |
| 4130 / 25CrMo4 | 0.28–0.33 | 0.40–0.60 | 0.80–1.10 | ≤0.25 | 590–760 MPa |
| 4135 / 34CrMo4 | 0.33–0.38 | 0.70–0.90 | 0.80–1.10 | ≤0.25 | 1000–1200 MPa |
| 4140 / 42CrMo4 | 0.38–0.43 | 0.75–1.00 | 0.80–1.10 | ≤0.25 | 655 MPa |
| 4145 | 0.43–0.48 | 0.75–1.00 | 0.80–1.10 | ≤0.25 | ≥965 MPa |
| 4150 / 50CrMo4 | 0.48–0.53 | 0.75–1.00 | 0.80–1.10 | ≤0.25 | 731 MPa |
| 4340 / EN24 | 0.38–0.43 | 0.60–0.80 | 0.70–0.90 | 1.65–2.00 | 745 MPa |
| 5140 / 41Cr4 | 0.38–0.43 | 0.70–0.90 | 0.70–0.90 | ≤0.25 | 570 MPa |
| 6150 / 51CrV4 | 0.48–0.53 | 0.70–0.90 | 0.80–1.10 | ≤0.40 | 670 MPa |
| 8640 / SNCM240 | 0.38–0.43 | 0.75–1.00 | 0.40–0.60 | 0.40–0.70 | 1000–1413 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.
أسئلة وأجوبة
Common questions
What is 31CrMoV9?
31CrMoV9 (1.8519) is a nitriding steel with 0.27–0.34% carbon, 2.30–2.70% chromium, 0.15–0.25% molybdenum and 0.10–0.20% vanadium. It is bought quenched and tempered, machined and then nitrided to harden the surface.
What is the equivalent of 31CrMoV9?
No standard names a verified equivalent in the USA, UK, India or Japan. SACM645 in Japan and AMS 6470 (Nitralloy 135 Modified) in the USA are nitriding steels, but they contain aluminium and differ in chromium and vanadium.
What hardness does 31CrMoV9 reach after nitriding?
Swiss Steel quotes 650–800 HV 0.5 by gas nitriding, depending on the nitriding temperature. Dörrenberg states a minimum of 800 HV after nitriding. Hardness depends on the process, so ask the heat treater for the case profile.
Is 31CrMoV9 the same as EN40C or 897M39?
No. 897M39 (EN40C) is listed as 40CrMoV13-9 (1.8523) with 3.00–3.50% chromium, which is a different steel. 905M39 (EN41B) is an aluminium nitriding steel.
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Related references
References
Sources
- Swiss Steel Group, technical datasheet Nitriding Steel 31CrMoV9+QT+SH — Composition per EN ISO 683-5, QT properties, nitrided surface hardness, delivery condition, physical properties.
- Dörrenberg Edelstahl, datasheet 1.8519 / 31CrMoV9 — Typical analysis, QT properties by diameter (EN ISO 683-5:2021), heat treatment, minimum nitrided hardness.
- 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.
- 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.
- West Yorkshire Steel, 31CrMoV9 — Composition, forging, normalizing, hardening and tempering ranges.
- West Yorkshire Steel, 905M39 nitriding steel — Composition of the aluminium nitriding grade 905M39.
- SAE AMS6470P: Steel, nitriding, 1.6Cr-0.35Mo-1.13Al (0.38–0.43C) (135 Mod) — Standard title only; the specification text was not read.
- Total Materia, B.S. 897 M 39 — 897M39 equals EN40C and 40CrMoV13-9; partial composition.
- Total Materia, DIN 31 CrMoV 9 — Composition and equivalence list (no JIS, IS or SAE entries visible).
- Roymech, sample BS 970 steels — EN40C mapped to 897M39.
Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.