Steel 718
718 is a nickel-modified P20 plastic mould steel (DIN 1.2738), vacuum-degassed and supplied prehardened to 290–330 HB (30–34 HRC), roughly 880 MPa yield and 1030 MPa tensile with 14 % elongation; the ~1 % Ni addition keeps hardness uniform to the centre of thick plate.
Values for the Prehard condition
718 tempers and conditions
718 is supplied in 6 conditions, soft to hard. Prehard is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
soft-annealed / supply-soft condition | Pick when you intend to rough-machine deep cavities and then quench-and-temper or carburize/nitride yourself. | 450 | 700 | 20 | 215 HB | — |
PrehardDefault Pre-hardened | Standard stock condition: machine the cavity directly, no heat treatment or size-change risk. | 880 | 1,030 | 14 | 32 HRC | — |
vacuum-degassed / ESR premium prehard, improved cleanliness and polishability | Pick for optical/high-gloss cavities and photo-etched textures where inclusion streaks and polish defects are unacceptable. | 880 | 1,030 | 15 | 32 HRC | 7.8 % IACS |
Prehard + gas/plasma nitrided case (surface ~600–750 HV) | Post-machining surface treatment for wear and gas-erosion resistance on slides, gates and glass-filled-resin cavities. | 880 | 1,030 | 12 | 32 HRC | 7.8 % IACS |
pre-hardened high-hardness grade (~34–38 HRC / 330–370 HB) | Choose when the mould runs abrasive filled resins or needs better cavity wear/dent resistance while still machinable prehard. | 1,000 | 1,180 | 12 | 36 HRC | — |
Q&T 38–44 HRC | Used only on small inserts/cores that are re-austenitized (~850 °C, oil) and low-tempered for extra strength; expect distortion and lower toughness. | 1,150 | 1,350 | 10 | 41 HRC | 7.5 % IACS |
What is 718?
718 is a nickel-modified P20 plastic mould steel (DIN 1.2738), vacuum-degassed and supplied prehardened to 290–330 HB (30–34 HRC), roughly 880 MPa yield and 1030 MPa tensile with 14 % elongation; the ~1 % Ni addition keeps hardness uniform to the centre of thick plate. It is cut straight to cavity form with no further heat treatment, polishes and photo-etches well, and accepts repair welding and nitriding, so it is the workhorse for medium and large injection moulds, die-cast mould bases and blow moulds. Corrosion resistance is poor and service is capped near 400 °C by the tempering temperature; for heavily glass-filled resins a harder or stainless mould steel is the better choice. 718 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). 718 has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
What is 718 used for?
- Large injection mould cavity and core plates
- Mould bases and bolster plates
- Mould inserts
- Blow mould bodies
- Die-casting die holders
- Textured cosmetic cavities for automotive interior parts
- Bumper and instrument-panel tooling
Advantages
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- High strength — 880 MPa (128 ksi), better than 89% of steel grades
Limitations
- Limited formability — 15/100, worse than 87% of steel grades
- Poor heat conductor — 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
718 properties
Typical room-temperature values for 718-Prehard; bars are the position among steel grades.
Physical3
718 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
718 has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
718 is rated for continuous service to 400°C (752 °F). It conducts heat at 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades. Thermal expansion is 12.6 µm/m·K (7 µin/in·°F).
Electrical2
718 has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of 718 takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
718's machinability is good (55/100, better than 62% of steel grades); weldability fair (45/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 718 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 718
Is 718 easy to machine?
Machines predictably at 30–34 HRC with coated carbide (≈120–180 m/min milling, rigid setups); use positive geometry and adequate coolant to avoid work-hardened glaze in deep pockets.
Can 718 be welded?
Repair-weldable with matching or low-alloy Ni filler: preheat/interpass 250–325 °C, slow cool, then temper ~30 °C below the original tempering temperature to restore hardness match.
Can 718 be formed, bent or molded?
Supplied as prehard blocks/plate — not a cold-forming product; hot work at 850–1100 °C with slow cooling if reforging is required.
Manufacturability
The process limits FabDigit applies to 718. Every 718 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better55 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
718 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 | 0.35 – 0.45 | 0.4 |
| Si | 0.2 – 0.4 | 0.3 |
| Mn | 1.3 – 1.6 | 1.45 |
| Cr | 1.8 – 2.1 | 1.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| NiNi addition over P20 for through-hardening of thick blocks | 0.9 – 1.2 | 1.05 |
| P | ≤ 0.03 | |
| Smax; some grades add S ~0.05–0.10 for free-machining | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 718?
Excellent mirror-polish and photo-etch response; protect with hard chrome, EN Ni-P or nitriding for wear and rust resistance, and keep cooling channels inhibited.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
How much does 718 cost?
718 is a standard-cost steel ($$), cheaper than about 59% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
718 — frequently asked
What is 718 used for?
718 is typically used for large injection mould cavity and core plates, mould bases and bolster plates, mould inserts, blow mould bodies, die-casting die holders and textured cosmetic cavities for automotive interior parts. In short: workhorse mold-base plate.
What is the yield strength of 718?
718 has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 718 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines predictably at 30–34 HRC with coated carbide (≈120–180 m/min milling, rigid setups); use positive geometry and adequate coolant to avoid work-hardened glaze in deep pockets.
Can 718 be welded?
With care — weldability is rated fair (45/100). Repair-weldable with matching or low-alloy Ni filler: preheat/interpass 250–325 °C, slow cool, then temper ~30 °C below the original tempering temperature to restore hardness match.
What surface finishes work on 718?
Excellent mirror-polish and photo-etch response; protect with hard chrome, EN Ni-P or nitriding for wear and rust resistance, and keep cooling channels inhibited.
Can 718 be formed, bent or molded?
Supplied as prehard blocks/plate — not a cold-forming product; hot work at 850–1100 °C with slow cooling if reforging is required.
What is the maximum service temperature of 718?
718 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 718 cost?
718 is a standard-cost steel ($$), cheaper than about 59% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 718?
Yes — 718 is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- DIN EN ISO 4957 — Tool steels (40CrMnNiMo8-6-4 / 1.2738) — ISO/DIN (2018)
- Uddeholm Impax Supreme (P20+Ni prehardened mould steel) — Uddeholm/ASSAB (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Specialty Handbook: Tool Materials — ASM International (1995)
- GB/T 1299 — Tool and die steels (3Cr2MnNiMo) — SAC (2014)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.