Stainless Steel N690-SR (Stress relieved)
Heat-treated state
Intermediate step for large mould blocks or long blades to minimise distortion during subsequent hardening.
Values for the SR condition
Other N690 tempers and conditions
N690 is listed in 5 conditions; see the grade overview at N690.
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 | — |
SRThis page 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-SR?
N690-SR is N690 heat treated to SR — intermediate step for large mould blocks or long blades to minimise distortion during subsequent hardening. N690-SR has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 75% of stainless steel grades. Elongation at break is 13% and the elastic modulus is 215 GPa (31.2 Msi). N690-SR 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). Annealed is the default condition FabDigit quotes; SR is available on request or by drawing note.
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
- High strength — 480 MPa (69.6 ksi), better than 75% of stainless steel grades
Limitations
- Difficult to weld — 12/100, worse than 99% of stainless steel grades
- Limited ductility — 13%, worse than 93% of stainless steel grades
- Limited formability — 20/100, worse than 86% 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-SR properties
Typical room-temperature values for N690-SR; 17 are specific to this condition. Other listed values are N690 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
N690-SR 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-SR has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 75% of stainless steel grades. Elongation at break is 13% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
N690-SR 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-SR 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-SR 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-SR's machinability is fair (37/100, better than 57% of stainless steel grades); weldability not recommended (12/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with N690-SR
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.
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.
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 | — |
N690-SR — frequently asked
What is N690-SR used for?
N690-SR 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-SR?
N690-SR has a typical yield strength of 480 MPa (69.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 75% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is N690-SR easy to machine?
Not especially — machinability is rated fair (37/100, better than 57% 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-SR 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-SR?
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-SR 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-SR?
N690-SR 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.