Stainless Steel X108CrMo17-QT56
Hardness band
EN X108CrMo17 · UNS S44004
QT56 = hardened + tempered 200–300 °C, 55–57 HRC
Slightly tougher, more dimensionally stable condition for shafts, valve seats and knife blades.
Values for the QT56 condition
Other X108CrMo17 tempers and conditions
X108CrMo17 is listed in 6 conditions; see the grade overview at X108CrMo17.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stocked bar/wire condition for machining, cold work and subsequent hardening. | 450 | 760 | 14 | 235 HB | — |
cold drawn (annealed then drawn), bright bar/wire | Bright close-tolerance bar and ball/wire feedstock; slightly harder and straighter than +A. | 700 | 900 | 8 | 28 HRC | 2.9 % IACS |
Hardened + tempered 400–500 °C, 50–54 HRC | Used only where higher operating temperature or stress relief matters — corrosion resistance and toughness are reduced by carbide precipitation. | 1,550 | 1,700 | 4 | 52 HRC | — |
QT56This page Hardened + tempered 200–300 °C, 55–57 HRC | Slightly tougher, more dimensionally stable condition for shafts, valve seats and knife blades. | 1,750 | 1,860 | 3 | 56 HRC | — |
Hardened + tempered 150–180 °C, 58–60 HRC | The standard bearing/ball condition: 1010–1070 °C austenitize, oil/gas quench, low temper — max hardness with best corrosion resistance. | 1,900 | 1,970 | 2 | 59 HRC | — |
Hardened + deep-frozen (−80 °C) + tempered, 60–62 HRC | Sub-zero treatment removes retained austenite for maximum hardness and dimensional stability in precision balls and gauges. | 1,950 | 2,030 | 1.5 | 61 HRC | — |
What is X108CrMo17-QT56?
X108CrMo17-QT56 is X108CrMo17 heat treated to QT56 — slightly tougher, more dimensionally stable condition for shafts, valve seats and knife blades. X108CrMo17-QT56 has a yield strength of 1,750 MPa (254 ksi) and a tensile strength of 1,860 MPa (270 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi). X108CrMo17-QT56 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,370°C (2,498 °F). A is the default condition FabDigit quotes; QT56 is available on request or by drawing note.
Advantages
- High strength — 1,750 MPa (254 ksi), better than 100% of stainless steel grades
- Polishes to a fine finish — 85/100, better than 97% of stainless steel grades
- High electrical conductivity — 2.9 % IACS, better than 87% of stainless steel grades
- Conducts heat well — 24.2 W/m·K (14 BTU/hr·ft·°F), better than 83% of stainless steel grades
Limitations
- Limited ductility — 3%, worse than 100% of stainless steel grades
- Difficult to machine — 10/100, worse than 100% of stainless steel grades
- Low fracture toughness — 24 MPa·√m (21.8 ksi·√in), worse than 99% of stainless steel grades
- Difficult to weld — 15/100, worse than 98% of stainless steel grades
- Limited service temperature — 280°C (536 °F), worse than 96% of stainless steel grades
X108CrMo17-QT56 properties
Typical room-temperature values for X108CrMo17-QT56; 11 are specific to this condition. Other listed values are X108CrMo17 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
X108CrMo17-QT56 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical16
X108CrMo17-QT56 has a yield strength of 1,750 MPa (254 ksi) and a tensile strength of 1,860 MPa (270 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
X108CrMo17-QT56 is rated for continuous service to 280°C (536 °F). It conducts heat at 24.2 W/m·K (14 BTU/hr·ft·°F), better than 83% of stainless steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
X108CrMo17-QT56 conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (48/100), worse than 80% of stainless steel grades.
Sustainability4
Producing a kilogram of X108CrMo17-QT56 takes about 58 MJ of energy and emits 5.4 kg of CO₂ — more than 66% of stainless steel grades. Typical recycled content is 45%.
Manufacturability7
X108CrMo17-QT56's machinability is not recommended (10/100, worse than 100% of stainless steel grades); weldability poor (15/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with X108CrMo17-QT56
Is X108CrMo17 easy to machine?
Machine only in the soft-annealed condition with rigid setups, sharp carbide tooling and generous coolant (~40 % of 1212); after hardening to 58–60 HRC only grinding, honing, lapping or EDM are practical.
Can X108CrMo17 be welded?
Effectively non-weldable for structural joints — if unavoidable, preheat 250–300 °C, use a matching or 309/312 filler and full post-weld anneal or re-hardening to avoid martensite cracking.
Can X108CrMo17 be formed, bent or molded?
Cold forming is limited to gentle operations on annealed stock; hot forge at 1050–1150 °C, finish above 900 °C and cool slowly in furnace, then spheroidize anneal at 850–900 °C to ≤255 HB.
What surface finishes work on X108CrMo17?
Harden at 1010–1070 °C with oil/gas quench, optional −80 °C sub-zero, temper 150–180 °C; passivate in nitric or citric acid after machining, and mirror-polish or superfinish for bearing and ball surfaces (hard chrome or PVD for extra wear).
X108CrMo17 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 |
|---|---|---|
| Chigh carbon gives primary Cr-carbides and ~60 HRC | 0.95 – 1.2 | 1.08 |
| Si | ≤ 1 | 0.4 |
| Mn | ≤ 1 | 0.45 |
| Pbearing quality often ≤0.025 | ≤ 0.04 | — |
| Sbearing quality often ≤0.015 | ≤ 0.03 | — |
| Cr | 16 – 18 | 17 |
| Mo | 0.4 – 0.8 | 0.55 |
| Niresidual | ≤ 0.5 | — |
| Fe | balance | — |
X108CrMo17-QT56 — frequently asked
What is X108CrMo17-QT56 used for?
X108CrMo17-QT56 is typically used for stainless bearings, ball/roller elements and pump and valve wear parts. In short: european 440C equivalent; highest-hardness stainless bearing steel; grind or EDM after hardening.
What is the yield strength of X108CrMo17-QT56?
X108CrMo17-QT56 has a typical yield strength of 1,750 MPa (254 ksi) and a tensile strength of 1,860 MPa (270 ksi) — stronger than 100% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is X108CrMo17-QT56 easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 100% of stainless steel grades). Machine only in the soft-annealed condition with rigid setups, sharp carbide tooling and generous coolant (~40 % of 1212); after hardening to 58–60 HRC only grinding, honing, lapping or EDM are practical.
Can X108CrMo17-QT56 be welded?
Not readily — weldability is rated poor (15/100). Effectively non-weldable for structural joints — if unavoidable, preheat 250–300 °C, use a matching or 309/312 filler and full post-weld anneal or re-hardening to avoid martensite cracking.
What surface finishes work on X108CrMo17-QT56?
Harden at 1010–1070 °C with oil/gas quench, optional −80 °C sub-zero, temper 150–180 °C; passivate in nitric or citric acid after machining, and mirror-polish or superfinish for bearing and ball surfaces (hard chrome or PVD for extra wear).
Can X108CrMo17-QT56 be formed, bent or molded?
Cold forming is limited to gentle operations on annealed stock; hot forge at 1050–1150 °C, finish above 900 °C and cool slowly in furnace, then spheroidize anneal at 850–900 °C to ≤255 HB.
What is the maximum service temperature of X108CrMo17-QT56?
X108CrMo17-QT56 is rated for continuous use to about 280°C (536 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between X108CrMo17-A and X108CrMo17 DCT60?
A is the default condition — standard stocked bar/wire condition for machining, cold work and subsequent hardening. DCT60: sub-zero treatment removes retained austenite for maximum hardness and dimensional stability in precision balls and gauges. Yield strength is 450 MPa in A versus 1,950 MPa in DCT60.
Sources
- ISO 683-17 Heat-treatable steels — Ball and roller bearing steels — ISO (2014)
- DIN 17230 Wälzlagerstähle (X108CrMo17, 1.3543) — DIN (1980)
- ASTM A276 / A756 / UNS S44004 (AISI 440C) — ASTM (2017)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Martensitic stainless bearing steel 1.3543/440C datasheet — Ovako / Böhler / Sandvik (2022)
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.