Steel 8MoB5-4 +FP
Heat-treated state
EN 8MoB5-4
+FP = treated to ferrite-pearlite structure and hardness range
Best for consistent automatic-lathe machining before carburizing.
Values for the +FP condition
Other 8MoB5-4 tempers and conditions
8MoB5-4 is listed in 10 conditions; see the grade overview at 8MoB5-4.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for the most severe multi-station cold heading and thread rolling (lowest flow stress). | 230 | 390 | 34 | 125 HB | 8.6 % IACS |
+ADefault Annealed | Standard stock condition for cold-heading wire and rod before forming and case hardening. | 255 | 410 | 30 | 135 HB | — |
+FPThis page Treated to ferrite-pearlite structure and hardness range | Best for consistent automatic-lathe machining before carburizing. | 280 | 440 | 27 | 140 HB | 8.6 % IACS |
Treated for shearability | Delivery condition for bar that must be cold sheared into billets without cracking. | 290 | 450 | 26 | 150 HB | 8.6 % IACS |
Hot rolled | Mill as-rolled bar/rod for users who apply their own annealing or direct hot forming. | 300 | 470 | 25 | 150 HB | 8.6 % IACS |
Normalized | Grain refinement and uniform ferrite-pearlite before machining or carburizing. | 300 | 460 | 27 | 145 HB | 8.6 % IACS |
Treated to a specified hardness range | Bar supplied inside an agreed hardness band for stable machining and straightness. | 380 | 560 | 20 | 175 HB | 8.5 % IACS |
Cold drawn | Pick for close tolerance, bright finish and higher as-supplied strength before final heading or machining. | 470 | 560 | 12 | 175 HB | 8.5 % IACS |
Carburized, quenched and low-temperature tempered | Final service condition for case-hardened fasteners, pins and small gears needing a wear-resistant skin with a tough core. | 600 | 850 | 11 | 61 HRC | — |
Quenched and tempered | Used when only core strength is required (e.g. boron-hardened small fasteners without a hard case). | 620 | 780 | 14 | 24 HRC | 8.2 % IACS |
What is 8MoB5-4 +FP?
8MoB5-4 +FP is 8MoB5-4 heat treated to +FP — best for consistent automatic-lathe machining before carburizing. 8MoB5-4 +FP has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 90% of steel grades. Elongation at break is 27% and the elastic modulus is 210 GPa (30.5 Msi). 8MoB5-4 +FP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F). +A is the default condition FabDigit quotes; +FP is available on request or by drawing note.
Advantages
- Forms and bends easily — 82/100, better than 94% of steel grades
- Ductile — tolerates forming and impact — 27%, better than 86% of steel grades
- Tough — resists crack growth — 115 MPa·√m (104.7 ksi·√in), better than 77% of steel grades
- Readily welded — 72/100, better than 75% of steel grades
Limitations
- Low strength — 280 MPa (40.6 ksi), worse than 90% of steel grades
8MoB5-4 +FP properties
Typical room-temperature values for 8MoB5-4 +FP; 22 are specific to this condition. Other listed values are 8MoB5-4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8MoB5-4 +FP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
8MoB5-4 +FP has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 90% of steel grades. Elongation at break is 27% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
8MoB5-4 +FP is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
8MoB5-4 +FP conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 8MoB5-4 +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%.
Manufacturability7
8MoB5-4 +FP's machinability is good (60/100, better than 83% of steel grades); weldability very good (72/100); formability very good (82/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8MoB5-4 +FP
Is 8MoB5-4 easy to machine?
Soft and somewhat gummy in the annealed state — use sharp positive-rake tools, high speed and generous coolant; machine before carburizing, since the 58–63 HRC case needs grinding.
Can 8MoB5-4 be welded?
Low carbon equivalent gives good weldability, but boron and Mo raise HAZ hardenability: use low hydrogen consumables, limit heat input and avoid welding after carburizing.
Can 8MoB5-4 be formed, bent or molded?
Excellent multi-station cold heading and thread rolling in +A/+AC condition; phosphate + soap or polymer lubricant coating on the wire is standard.
What surface finishes work on 8MoB5-4?
No anodizing (ferrous); protect with zinc or zinc-nickel plating (bake to avoid hydrogen embrittlement on hardened parts), zinc-flake coatings, phosphating or black oxide plus oil.
8MoB5-4 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 |
|---|---|---|
| Clow carbon for cold heading | 0.06 – 0.11 | 0.08 |
| Sikept low for cold formability | ≤ 0.3 | 0.15 |
| Mn | 0.3 – 0.7 | 0.5 |
| P | ≤ 0.03 | 0.02 |
| Smax (S-grades higher) | ≤ 0.03 | 0.01 |
| Mocore hardenability, temper-embrittlement resistance | 0.4 – 0.55 | 0.5 |
| Bhardenability booster; requires Ti/Al nitrogen fixing | 8×10⁻⁴ – 0.01 | 0 |
| Tiprotects effective boron by fixing N | 0.02 – 0.06 | 0.04 |
| Algrain refinement / deoxidation | 0.02 – 0.06 | 0.04 |
| Crresidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.25 | 0.1 |
| Fe | balance | — |
8MoB5-4 +FP — frequently asked
What is 8MoB5-4 +FP used for?
8MoB5-4 +FP is typically used for fasteners, pins and small case-hardened parts. In short: excellent cold-heading formability; boron-Mo case-hardening grade; case to 58–63 HRC.
What is the yield strength of 8MoB5-4 +FP?
8MoB5-4 +FP has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 90% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 8MoB5-4 +FP easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Soft and somewhat gummy in the annealed state — use sharp positive-rake tools, high speed and generous coolant; machine before carburizing, since the 58–63 HRC case needs grinding.
Can 8MoB5-4 +FP be welded?
Yes — weldability is rated very good (72/100). Low carbon equivalent gives good weldability, but boron and Mo raise HAZ hardenability: use low hydrogen consumables, limit heat input and avoid welding after carburizing.
What surface finishes work on 8MoB5-4 +FP?
No anodizing (ferrous); protect with zinc or zinc-nickel plating (bake to avoid hydrogen embrittlement on hardened parts), zinc-flake coatings, phosphating or black oxide plus oil.
Can 8MoB5-4 +FP be formed, bent or molded?
Excellent multi-station cold heading and thread rolling in +A/+AC condition; phosphate + soap or polymer lubricant coating on the wire is standard.
What is the maximum service temperature of 8MoB5-4 +FP?
8MoB5-4 +FP is rated for continuous use to about 400°C (752 °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 10263-3/-4 — Steel rod, bars and wire for cold heading and cold extrusion — CEN (2017)
- EN 10027-2 — Numerical designation system (material number 1.5450) — CEN (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing, boron hardenability) — ASM International (2013)
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.