Steel 9Cr18
EN 9Cr18 · UNS S44004 · AISI/SAE 440B
9Cr18 is a high-carbon, 17% chromium martensitic stainless bearing steel, roughly equivalent to AISI 440B and cross-referenced to 440A, S44004 and X102CrMo17.
Reference datasheet — 9Cr18 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 A condition
9Cr18 tempers and conditions
9Cr18 is supplied in 7 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard as-supplied bar/ring blank condition: soft enough to turn, drill and cold-form before hardening. | 450 | 760 | 18 | 225 HB | — |
hot rolled and annealed bar/ring blank | Cheapest mill condition for large-diameter bar and forged/rolled bearing ring blanks that will be machined and hardened. | 460 | 780 | 16 | 22 HRC | 2.9 % IACS |
Cold drawn | Choose for close-tolerance small-diameter bar and ball/roller wire feedstock with a bright drawn surface. | 700 | 900 | 10 | 28 HRC | 2.9 % IACS |
Q&T 48–52 HRC | Used for shafts, pump/valve parts and cutlery-type items needing better toughness and stability to ~300 °C, at the cost of hardness and some corrosion resistance. | 1,450 | 1,650 | 5 | 50 HRC | — |
Q&T stabilized | Pick when the bearing or valve part runs continuously at 150–200 °C and must not grow dimensionally. | 1,680 | 1,860 | 4 | 56 HRC | 2.8 % IACS |
Q&T 55–58 HRC | Standard working condition for corrosion-resistant bearing rings, balls, rollers and valve seats. | 1,740 | 1,930 | 3 | 57 HRC | — |
Q&T + sub-zero 58–60 HRC | Maximum hardness and dimensional stability for precision balls and instrument bearings; toughness is lowest. | 1,830 | 2,000 | 2 | 59 HRC | — |
What is 9Cr18?
9Cr18 is a high-carbon, 17% chromium martensitic stainless bearing steel, roughly equivalent to AISI 440B and cross-referenced to 440A, S44004 and X102CrMo17. It is machined in the annealed condition (about 450 MPa yield, 760 MPa tensile, 18% elongation, 225 HB) and then quenched and tempered to 55–60 HRC for corrosion-resistant bearing rings, balls, shafts and valve parts, supplied as bar, tube and forged rings. Corrosion resistance is modest for a stainless (score 38), weldability is poor (score 20) and service is limited to about 400 °C. 9Cr18Mo is the nearest alternative where slightly higher hardness is required. 9Cr18 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 95% of steel grades. It melts at 1,370°C (2,498 °F). 9Cr18 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 52% of steel grades. Elongation at break is 18% and the elastic modulus is 200 GPa (29 Msi).
What is 9Cr18 used for?
- Stainless bearing components
- Pump shafts
- Valve parts
Advantages
- Good corrosion resistance — 38/100, better than 97% of steel grades
Limitations
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
- High embodied carbon — 3.4 kg CO₂/kg, worse than 93% of steel grades
- Poor heat conductor — 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
9Cr18 properties
Typical room-temperature values for 9Cr18-A; bars are the position among steel grades.
Physical3
9Cr18 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 95% of steel grades. It melts at 1,370°C (2,498 °F).
Mechanical15
9Cr18 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 52% of steel grades. Elongation at break is 18% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
9Cr18 is rated for continuous service to 400°C (752 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades. Thermal expansion is 10.4 µm/m·K (5.78 µin/in·°F).
Electrical3
9Cr18 conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is fair (38/100), better than 97% of steel grades.
Sustainability4
Producing a kilogram of 9Cr18 takes about 50 MJ of energy and emits 3.4 kg of CO₂ — more than 93% of steel grades. Typical recycled content is 40%.
Manufacturability8
9Cr18's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (20/100); formability poor (30/100).
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. 9Cr18 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 9Cr18
Is 9Cr18 easy to machine?
Machine only in the annealed condition with sharp carbide tools, rigid setups, low-to-moderate speed and heavy coolant; hardened parts (55–60 HRC) must be ground, EDM'd or hard-turned with CBN.
Can 9Cr18 be welded?
Not recommended for structural joints — high carbon gives hard, crack-prone martensite; if unavoidable, preheat 200–300 °C, use matching or 309/310 filler and immediately anneal or temper.
Can 9Cr18 be formed, bent or molded?
Only light cold forming/bending in the annealed state (large radii, no sharp bends); hot work 1100→900 °C with slow cooling and mandatory post-forging anneal to avoid quench cracking.
9Cr18 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 |
|---|---|---|
| CGB/T 1220 / GB/T 3086 | 0.9 – 1 | 0.95 |
| Si | ≤ 0.8 | 0.4 |
| Mn | ≤ 0.8 | 0.45 |
| Cr | 17 – 19 | 18 |
| Niresidual | ≤ 0.6 | 0.25 |
| Moresidual only; the Mo-alloyed version is 9Cr18Mo (0.40–0.70 Mo) | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.3 | |
| P | ≤ 0.04 | |
| Sbearing quality often ≤0.020 | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 9Cr18?
Passivate per ASTM A967 (nitric or citric) after grinding to restore the chromium oxide film; takes a mirror polish at 57 HRC and accepts hard chrome, black oxide or PVD coatings (keep bake/coating temperature below the tempering temperature).
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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 9Cr18 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S44004
- AISI / SAE
- 440B
- Similar grades
- 440AX102CrMo17
How much does 9Cr18 cost?
9Cr18 is a premium-cost steel ($$$), cheaper than about 51% 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.
9Cr18 — frequently asked
What is 9Cr18 used for?
9Cr18 is typically used for stainless bearing components, pump shafts and valve parts. In short: stainless bearing grade; hardens to 55–60 HRC; 440B-class corrosion resistance.
What is the yield strength of 9Cr18?
9Cr18 has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 9Cr18 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine only in the annealed condition with sharp carbide tools, rigid setups, low-to-moderate speed and heavy coolant; hardened parts (55–60 HRC) must be ground, EDM'd or hard-turned with CBN.
Can 9Cr18 be welded?
Not readily — weldability is rated poor (20/100). Not recommended for structural joints — high carbon gives hard, crack-prone martensite; if unavoidable, preheat 200–300 °C, use matching or 309/310 filler and immediately anneal or temper.
What surface finishes work on 9Cr18?
Passivate per ASTM A967 (nitric or citric) after grinding to restore the chromium oxide film; takes a mirror polish at 57 HRC and accepts hard chrome, black oxide or PVD coatings (keep bake/coating temperature below the tempering temperature).
Can 9Cr18 be formed, bent or molded?
Only light cold forming/bending in the annealed state (large radii, no sharp bends); hot work 1100→900 °C with slow cooling and mandatory post-forging anneal to avoid quench cracking.
What is the maximum service temperature of 9Cr18?
9Cr18 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 9Cr18-A and 9Cr18 QT58-60?
A is the default condition — standard as-supplied bar/ring blank condition: soft enough to turn, drill and cold-form before hardening. QT58-60: maximum hardness and dimensional stability for precision balls and instrument bearings; toughness is lowest. Yield strength is 450 MPa in A versus 1,830 MPa in QT58-60.
How much does 9Cr18 cost?
9Cr18 is a premium-cost steel ($$$), cheaper than about 51% 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
- GB/T 1220 Stainless steel bars — SAC (China) (2007)
- GB/T 3086 High carbon chromium stainless bearing steel — SAC (China) (2019)
- ASTM A276 / UNS S44003–S44004 stainless bars and shapes — ASTM (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (440A/B/C) — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials (martensitic stainless steels) — ASM International (2005)
- ASM Handbook Vol.16 — Machining (machinability ratings of stainless steels) — ASM International (1989)
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.