Steel 20NiCrMoS6-4 +FP
Heat-treated state · default condition
EN 20NiCrMoS6-4
+FP = treated to ferrite-pearlite structure and hardness range
Standard gear-blank delivery: uniform ferrite-pearlite microstructure ≤217 HB giving repeatable turning/hobbing and low distortion in carburizing.
Values for the +FP condition
Other 20NiCrMoS6-4 tempers and conditions
20NiCrMoS6-4 is listed in 7 conditions; see the grade overview at 20NiCrMoS6-4.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick for deep drilling, broaching, thread rolling or cold upsetting where the lowest hardness and spheroidal carbides are wanted. | 360 | 600 | 22 | 175 HB | — |
+FPDefaultThis page Treated to ferrite-pearlite structure and hardness range | Standard gear-blank delivery: uniform ferrite-pearlite microstructure ≤217 HB giving repeatable turning/hobbing and low distortion in carburizing. | 420 | 680 | 18 | 200 HB | — |
Treated to hardness range | Ordered when only a guaranteed hardness band (not a specified microstructure) is needed for machining consistency. | 440 | 700 | 16 | 15 HRC | 7.5 % IACS |
Hot rolled | Cheapest bar delivery when the user will do their own normalize/anneal before machining. | 480 | 780 | 14 | 22 HRC | 7.5 % IACS |
Spheroidized annealed and cold drawn | Precision-ground/drawn bar for automatic lathes: tight tolerance, bright surface and higher yield strength before carburizing. | 620 | 760 | 10 | 225 HB | — |
Hardened | Use when the part is quenched (with Jominy-controlled hardenability) and low-temperature tempered to develop a strong, tough core. | 900 | 1,180 | 11 | 37 HRC | — |
Case hardened | Final in-service condition for gears and pinions: hard wear-resistant case with compressive residual stress over a tough Ni-Cr-Mo core. | 950 | 1,250 | 10 | 60 HRC | — |
What is 20NiCrMoS6-4 +FP?
20NiCrMoS6-4 +FP is 20NiCrMoS6-4 heat treated to +FP — standard gear-blank delivery: uniform ferrite-pearlite microstructure ≤217 HB giving repeatable turning/hobbing and low distortion in carburizing. 20NiCrMoS6-4 +FP has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 680 MPa (98.6 ksi) — weaker than 53% of steel grades. Elongation at break is 18% and the elastic modulus is 210 GPa (30.5 Msi). 20NiCrMoS6-4 +FP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- Easy to machine — 62/100, better than 89% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
20NiCrMoS6-4 +FP properties
Typical room-temperature values for 20NiCrMoS6-4 +FP; 16 are specific to this condition. Other listed values are 20NiCrMoS6-4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20NiCrMoS6-4 +FP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
20NiCrMoS6-4 +FP has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 680 MPa (98.6 ksi) — weaker than 53% of steel grades. Elongation at break is 18% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20NiCrMoS6-4 +FP is rated for continuous service to 200°C (392 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
20NiCrMoS6-4 +FP conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 20NiCrMoS6-4 +FP takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability8
20NiCrMoS6-4 +FP's machinability is good (62/100, better than 89% of steel grades); weldability fair (40/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20NiCrMoS6-4 +FP
Is 20NiCrMoS6-4 easy to machine?
Best turned/hobbed in +FP or +AC at 170–217 HB; the 0.03 % S gives short chips and 10–20 % longer tool life than S-free 17NiCrMo6-4 — use coated carbide, 120–200 m/min dry or with MQL.
Can 20NiCrMoS6-4 be welded?
Only conditionally weldable: preheat 200–250 °C, low-hydrogen or matching Ni-Cr-Mo filler, slow cool and temper immediately; the sulfur raises hot-cracking risk, so avoid welding carburized zones entirely.
Can 20NiCrMoS6-4 be formed, bent or molded?
Hot forge 1100–850 °C then normalize/soft anneal; cold heading and thread rolling only from the +AC spheroidized condition — cold formability is reduced by MnS stringers, especially transverse.
What surface finishes work on 20NiCrMoS6-4?
Not anodizable; after carburizing use shot peening for bending fatigue, then oil, phosphate, black oxide or Zn-Ni plate (bake to avoid hydrogen embrittlement) for corrosion protection.
20NiCrMoS6-4 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.17 – 0.23 | 0.2 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| Sdeliberate S addition for machinability (S-grade) | 0.02 – 0.04 | 0.03 |
| Cr | 0.8 – 1.1 | 0.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| Ni | 1.4 – 1.7 | 1.55 |
| Fe | balance | — |
20NiCrMoS6-4 +FP — frequently asked
What is 20NiCrMoS6-4 +FP used for?
20NiCrMoS6-4 +FP is typically used for carburized transmission gears, automotive gearbox shafts, differential pinions and ring gear blanks, splined drive shafts, planetary carriers and pinion pins and hobbed sprockets and gear couplings. In short: free-machining case-hardening steel; 58-62 HRC carburized case; tough Ni-Cr-Mo gear core.
What is the yield strength of 20NiCrMoS6-4 +FP?
20NiCrMoS6-4 +FP has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 680 MPa (98.6 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20NiCrMoS6-4 +FP easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Best turned/hobbed in +FP or +AC at 170–217 HB; the 0.03 % S gives short chips and 10–20 % longer tool life than S-free 17NiCrMo6-4 — use coated carbide, 120–200 m/min dry or with MQL.
Can 20NiCrMoS6-4 +FP be welded?
With care — weldability is rated fair (40/100). Only conditionally weldable: preheat 200–250 °C, low-hydrogen or matching Ni-Cr-Mo filler, slow cool and temper immediately; the sulfur raises hot-cracking risk, so avoid welding carburized zones entirely.
What surface finishes work on 20NiCrMoS6-4 +FP?
Not anodizable; after carburizing use shot peening for bending fatigue, then oil, phosphate, black oxide or Zn-Ni plate (bake to avoid hydrogen embrittlement) for corrosion protection.
Can 20NiCrMoS6-4 +FP be formed, bent or molded?
Hot forge 1100–850 °C then normalize/soft anneal; cold heading and thread rolling only from the +AC spheroidized condition — cold formability is reduced by MnS stringers, especially transverse.
What is the maximum service temperature of 20NiCrMoS6-4 +FP?
20NiCrMoS6-4 +FP is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- EN 10084 — Case hardening steels: technical delivery conditions — CEN (2008)
- EN 10277 — Bright steel products: technical delivery conditions — CEN (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes (carburizing) — ASM International (2013)
- Case-hardening steel bar datasheets (Ni-Cr-Mo gear steels) — Ovako / Böhler / Swiss Steel (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.