Stainless Steel N690
N690 is an Austrian (Böhler-Uddeholm) cobalt-alloyed martensitic stainless steel of the 440C type (UNS S44004), supplied as annealed strip and flat bar and also available stress-relieved.
Reference datasheet — N690 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
N690 tempers and conditions
N690 is supplied in 5 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault soft annealed bar/plate/strip (≤250 HB) | Stock condition for blade blanks and mould blocks: machine, grind and profile before hardening. | 460 | 780 | 14 | 235 HB | — |
Stress relieved | Intermediate step for large mould blocks or long blades to minimise distortion during subsequent hardening. | 480 | 800 | 13 | 22 HRC | — |
Hardened & tempered to 56–58 HRC | Tougher setting for thick blades, choppers and tools where chipping resistance matters more than edge retention. | 1,700 | 1,950 | 2 | 57 HRC | — |
Hardened & tempered to 58–60 HRC | Default finished-blade condition: best balance of edge retention, toughness and stain resistance. | 1,850 | 2,100 | 1.5 | 59 HRC | — |
Hardened + deep-freeze (cryo) + tempered, 60–62 HRC | Maximum hardness/edge retention with retained austenite transformed; choose for slicing edges and wear parts, accepting lower toughness. | 1,950 | 2,200 | 1 | 61 HRC | — |
What is N690?
N690 is an Austrian (Böhler-Uddeholm) cobalt-alloyed martensitic stainless steel of the 440C type (UNS S44004), supplied as annealed strip and flat bar and also available stress-relieved. It is chosen for added toughness at 440C-level hardness, reaching 56-58, 58-60 or 60-62 HRC with a cryogenic cycle, and it holds a 48 corrosion rating that suits marine blade work. Annealed values are 460 MPa yield, 780 MPa tensile, 14 % elongation and 235 HB; formability rates 22, machinability 38, service is capped near 400 °C and it is essentially not weldable. 154CM is the closest alternative. N690 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,380°C (2,516 °F). N690 has a yield strength of 460 MPa (66.7 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 73% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 215 GPa (31.2 Msi).
What is N690 used for?
- premium knife blades
- diving knives
- cutlery
Advantages
- Polishes to a fine finish — 85/100, better than 97% of stainless steel grades
- High electrical conductivity — 2.7 % IACS, better than 78% of stainless steel grades
Limitations
- Difficult to weld — 12/100, worse than 99% of stainless steel grades
- Limited ductility — 14%, worse than 91% of stainless steel grades
- Limited formability — 22/100, worse than 82% of stainless steel grades
- Needs corrosion protection — 48/100, worse than 80% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
N690 properties
Typical room-temperature values for N690-Annealed; bars are the position among stainless steel grades.
Physical3
N690 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,380°C (2,516 °F).
Mechanical15
N690 has a yield strength of 460 MPa (66.7 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 73% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
N690 is rated for continuous service to 400°C (752 °F). It conducts heat at 16 W/m·K (9.24 BTU/hr·ft·°F), better than 58% of stainless steel grades. Thermal expansion is 10.4 µm/m·K (5.78 µin/in·°F).
Electrical3
N690 conducts electricity at 2.7 % IACS, better than 78% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (48/100), worse than 80% of stainless steel grades.
Sustainability4
Producing a kilogram of N690 takes about 55 MJ of energy and emits 4.5 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 45%.
Manufacturability7
N690's machinability is fair (38/100, better than 63% of stainless steel grades); weldability not recommended (12/100); formability poor (22/100).
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 stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. N690 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with N690
Is N690 easy to machine?
Machine only in the annealed state with rigid setups, sharp carbide or coated carbide and moderate speeds; after hardening use grinding, EDM or CBN only.
Can N690 be welded?
Essentially not weldable for structural purposes — high carbon causes brittle martensite and cracking; if unavoidable, preheat 250–350 °C, matching/austenitic filler and immediate temper.
Can N690 be formed, bent or molded?
Hot form 1050–850 °C with slow cooling and immediate soft anneal; cold forming limited to gentle bends of thin annealed strip.
N690 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 | 1.01 – 1.12 | 1.07 |
| Si | 0.25 – 0.55 | 0.4 |
| Mn | 0.25 – 0.55 | 0.4 |
| Cr | 16.5 – 17.5 | 17.3 |
| Moimproves pitting resistance and secondary carbide fineness | 0.9 – 1.3 | 1.1 |
| Vgrain refinement | 0.07 – 0.15 | 0.1 |
| Coraises matrix strength and tempering stability | 1.3 – 1.7 | 1.5 |
| Pimpurity | ≤ 0.03 | |
| Simpurity | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on N690?
Takes an excellent mirror polish after hardening; passivate or electropolish for best stain resistance, and PVD/DLC coatings must run below the tempering temperature.
Surface treatments FabDigit runs on stainless 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).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel N690 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- S44004
How much does N690 cost?
N690 is a high-cost stainless steel ($$$$), pricier than about 78% 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.
N690 — frequently asked
What is N690 used for?
N690 is typically used for premium knife blades, diving knives and cutlery. In short: cobalt-alloyed 440C alternative; tougher than standard 440C; marine-grade blade steel.
What is the yield strength of N690?
N690 has a typical yield strength of 460 MPa (66.7 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 73% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is N690 easy to machine?
Not especially — machinability is rated fair (38/100, better than 63% of stainless steel grades). Machine only in the annealed state with rigid setups, sharp carbide or coated carbide and moderate speeds; after hardening use grinding, EDM or CBN only.
Can N690 be welded?
Not readily — weldability is rated not recommended (12/100). Essentially not weldable for structural purposes — high carbon causes brittle martensite and cracking; if unavoidable, preheat 250–350 °C, matching/austenitic filler and immediate temper.
What surface finishes work on N690?
Takes an excellent mirror polish after hardening; passivate or electropolish for best stain resistance, and PVD/DLC coatings must run below the tempering temperature.
Can N690 be formed, bent or molded?
Hot form 1050–850 °C with slow cooling and immediate soft anneal; cold forming limited to gentle bends of thin annealed strip.
What is the maximum service temperature of N690?
N690 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.
What is the difference between N690 Annealed and N690-SR?
Annealed is the default condition — stock condition for blade blanks and mould blocks: machine, grind and profile before hardening. SR: intermediate step for large mould blocks or long blades to minimise distortion during subsequent hardening. Yield strength is 460 MPa in Annealed versus 480 MPa in SR.
How much does N690 cost?
N690 is a high-cost stainless steel ($$$$), pricier than about 78% 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.
Sources
- BÖHLER N690 Corrosion-resistant knife and tool steel — voestalpine BÖHLER Edelstahl (2021)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys (440C data) — ASM International (1990)
- ASTM A276 / A756 — Stainless Steel Bars and Shapes (Type 440C reference) — ASTM (2017)
- GB/T 1220 (9Cr18MoV comparison grade) — SAC (2007)
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.