Steel 43CrMo4 +FP
Heat-treated state
EN 43CrMo4
+FP = treated to ferrite–pearlite structure with specified hardness range
Bar supplied in a controlled hardness window for consistent automatic-lathe machining.
Values for the +FP condition
Other 43CrMo4 tempers and conditions
43CrMo4 is listed in 12 conditions; see the grade overview at 43CrMo4.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Treated for improved cold shearability | Softened/structure-conditioned bar so coils and bars can be cold-sheared into fastener or forging blanks without cracking. | 390 | 620 | 22 | 200 HB | — |
Annealed | Softest supply condition for heavy machining, deep drilling or cold forming before final hardening. | 420 | 660 | 20 | 215 HB | — |
Specified hardenability | Order this when the Jominy end-quench band must be guaranteed for reproducible induction or through hardening of a given section. | 430 | 660 | 18 | 58 HRC | 7.7 % IACS |
+FPThis page Treated to ferrite–pearlite structure with specified hardness range | Bar supplied in a controlled hardness window for consistent automatic-lathe machining. | 450 | 720 | 18 | 17 HRC | 8 % IACS |
Normalized | Refined, uniform ferrite-bainite structure for stock to be re-hardened or for moderate-duty parts. | 530 | 830 | 16 | 24 HRC | — |
Cold drawn | Close-tolerance bright bar for parts machined with minimal stock removal; strength raised by drawing strain. | 680 | 850 | 9 | 24 HRC | 7.5 % IACS |
+QT | Same treatment on larger bar/forging where mass effect lowers core strength. | 720 | 1,000 | 14 | 31 HRC | — |
tempered for toughness | Pick when impact toughness and machinability matter more than peak strength (oilfield, heavy shafts). | 790 | 960 | 16 | 30 HRC | — |
Nitrided / nitrocarburised over Q&T | Low-distortion thin case for wear and fretting resistance with a slight corrosion improvement. | 820 | 1,050 | 10 | 58 HRC | 7.5 % IACS |
+QTDefault Quenched and tempered | Standard high-strength delivery condition for shafts, gears and machine parts in medium sections. | 850 | 1,100 | 13 | 35 HRC | — |
Induction (surface) hardened over Q&T core | The main reason this grade exists — hard 1–5 mm case on journals, splines and tracks with a tough tempered core. | 850 | 1,100 | 12 | 56 HRC | — |
tempered for strength | Higher-strength temper for gears and highly loaded shafts that will not see severe impact. | 1,030 | 1,180 | 12 | 36 HRC | — |
What is 43CrMo4 +FP?
43CrMo4 +FP is 43CrMo4 heat treated to +FP — bar supplied in a controlled hardness window for consistent automatic-lathe machining. 43CrMo4 +FP has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 52% of steel grades. Elongation at break is 18% and the elastic modulus is 210 GPa (30.5 Msi). 43CrMo4 +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). +QT is the default condition FabDigit quotes; +FP is available on request or by drawing note.
Advantages
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
43CrMo4 +FP properties
Typical room-temperature values for 43CrMo4 +FP; 23 are specific to this condition. Other listed values are 43CrMo4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
43CrMo4 +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
43CrMo4 +FP has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 52% of steel grades. Elongation at break is 18% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
43CrMo4 +FP is rated for continuous service to 450°C (842 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
43CrMo4 +FP conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 43CrMo4 +FP takes about 30 MJ of energy and emits 2.1 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 35%.
Manufacturability7
43CrMo4 +FP's machinability is good (60/100, better than 83% of steel grades); weldability fair (45/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 43CrMo4 +FP
Is 43CrMo4 easy to machine?
Machine in +A/+FP (≈200–240 HB) with carbide at 120–180 m/min; in +QT above 300 HB drop speed ~40 % and use rigid setups and coated inserts.
Can 43CrMo4 be welded?
Weldable only with care: preheat 300–350 °C, low-hydrogen consumables, interpass control, and temper/stress relieve at 550–650 °C immediately after welding.
Can 43CrMo4 be formed, bent or molded?
Hot forge 1100→850 °C then slow cool or normalize; cold forming/shearing only in +A or +S condition.
What surface finishes work on 43CrMo4?
No anodizing — protect with black oxide, manganese phosphate, zinc or hard-chrome plating; bake after plating to avoid hydrogen embrittlement; nitriding and induction hardening give the best wear surfaces.
43CrMo4 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 |
|---|---|---|
| Chigher than 42CrMo4 to suit induction hardening | 0.4 – 0.47 | 0.43 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| Slower S (≤0.005) for +QT high-toughness variants | ≤ 0.04 | 0.02 |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual | ≤ 0.4 | 0.15 |
| Curesidual | ≤ 0.3 | 0.15 |
| Fe | balance | — |
43CrMo4 +FP — frequently asked
What is 43CrMo4 +FP used for?
43CrMo4 +FP is typically used for induction-hardened shafts, gears, bearing races, axles and high-strength fasteners. In short: induction-hardening 42CrMo4 variant; deep through-hardening strength; hard surface, tough core.
What is the yield strength of 43CrMo4 +FP?
43CrMo4 +FP has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 43CrMo4 +FP easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machine in +A/+FP (≈200–240 HB) with carbide at 120–180 m/min; in +QT above 300 HB drop speed ~40 % and use rigid setups and coated inserts.
Can 43CrMo4 +FP be welded?
With care — weldability is rated fair (45/100). Weldable only with care: preheat 300–350 °C, low-hydrogen consumables, interpass control, and temper/stress relieve at 550–650 °C immediately after welding.
What surface finishes work on 43CrMo4 +FP?
No anodizing — protect with black oxide, manganese phosphate, zinc or hard-chrome plating; bake after plating to avoid hydrogen embrittlement; nitriding and induction hardening give the best wear surfaces.
Can 43CrMo4 +FP be formed, bent or molded?
Hot forge 1100→850 °C then slow cool or normalize; cold forming/shearing only in +A or +S condition.
What is the maximum service temperature of 43CrMo4 +FP?
43CrMo4 +FP is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 43CrMo4 +QT and 43CrMo4-NIT?
+QT is the default condition — standard high-strength delivery condition for shafts, gears and machine parts in medium sections. NIT: low-distortion thin case for wear and fretting resistance with a slight corrosion improvement. Yield strength is 850 MPa in +QT versus 820 MPa in NIT.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- EN 10084 / EN 10250-3 (bar and open-die forged product conditions) — CEN (2019)
- GB/T 3077 (42CrMo class) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Cr-Mo through-hardening steel bar datasheets (Ovako, Böhler, Saarstahl 42CrMo4/43CrMo4) — various producers (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.