Stainless Steel 7Cr17 QT-CRYO
Heat-treated state
EN 7Cr17
QT-CRYO = hardened + sub-zero + temper
Adds a −75 °C sub-zero step to convert retained austenite for maximum hardness and dimensional stability.
Values for the QT-CRYO condition
Other 7Cr17 tempers and conditions
7Cr17 is listed in 7 conditions; see the grade overview at 7Cr17.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard supply condition for machining, blanking and blade grinding before hardening. | 415 | 740 | 20 | 220 HB | — |
Hot rolled | Mill supply form for thick bar and plate that will be machined and heat treated by the user. | 430 | 760 | 18 | 20 HRC | 2.9 % IACS |
Cold rolled, half hard strip | Work-hardened strip for stamped blanks and springy parts that will be hardened later. | 750 | 950 | 6 | 30 HRC | 2.9 % IACS |
Q&T ~44–48 HRC | Tougher setting for scissors, shear blades and mechanical parts where chipping must be avoided. | 1,250 | 1,450 | 8 | 46 HRC | — |
Q&T 50–53 HRC | Common kitchen-knife and kitchenware hardness: good balance of edge holding and toughness. | 1,500 | 1,700 | 6 | 52 HRC | — |
Q&T 54–57 HRC | Maximum practical hardness for 7Cr17: best edge retention, lowest toughness and corrosion margin. | 1,650 | 1,850 | 4 | 56 HRC | — |
QT-CRYOThis page Hardened + sub-zero + temper | Adds a −75 °C sub-zero step to convert retained austenite for maximum hardness and dimensional stability. | 1,700 | 1,900 | 3 | 57 HRC | 2.8 % IACS |
What is 7Cr17 QT-CRYO?
7Cr17 QT-CRYO is 7Cr17 heat treated to QT-CRYO — adds a −75 °C sub-zero step to convert retained austenite for maximum hardness and dimensional stability. 7Cr17 QT-CRYO has a yield strength of 1,700 MPa (247 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi). 7Cr17 QT-CRYO 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; QT-CRYO is available on request or by drawing note.
Advantages
- High strength — 1,700 MPa (247 ksi), better than 100% of stainless steel grades
- Low embodied carbon — 3.5 kg CO₂/kg, better than 88% of stainless steel grades
- Conducts heat well — 24 W/m·K (13.9 BTU/hr·ft·°F), better than 81% of stainless steel grades
- High electrical conductivity — 2.8 % IACS, better than 79% of stainless steel grades
Limitations
- Limited ductility — 3%, worse than 100% of stainless steel grades
- Low fracture toughness — 20 MPa·√m (18.2 ksi·√in), worse than 100% of stainless steel grades
- Limited service temperature — 175°C (347 °F), worse than 100% of stainless steel grades
- Difficult to machine — 5/100, worse than 100% of stainless steel grades
- Difficult to weld — 5/100, worse than 100% of stainless steel grades
7Cr17 QT-CRYO properties
Typical room-temperature values for 7Cr17 QT-CRYO; 21 are specific to this condition. Other listed values are 7Cr17 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
7Cr17 QT-CRYO 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
7Cr17 QT-CRYO has a yield strength of 1,700 MPa (247 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
7Cr17 QT-CRYO is rated for continuous service to 175°C (347 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), better than 81% of stainless steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
7Cr17 QT-CRYO conducts electricity at 2.8 % IACS, better than 79% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 78% of stainless steel grades.
Sustainability4
Producing a kilogram of 7Cr17 QT-CRYO takes about 45 MJ of energy and emits 3.5 kg of CO₂ — less than 91% of stainless steel grades. Typical recycled content is 50%.
Manufacturability8
7Cr17 QT-CRYO's machinability is not recommended (5/100, worse than 100% of stainless steel grades); weldability not recommended (5/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 7Cr17 QT-CRYO
Is 7Cr17 easy to machine?
Machine only in the annealed state with sharp carbide tooling, rigid setups and generous coolant; hardened parts require grinding, EDM or CBN.
Can 7Cr17 be welded?
Poor weldability — 0.7 %C martensitic; if unavoidable preheat 200–300 °C, use 309/410NiMo filler and temper immediately after welding.
Can 7Cr17 be formed, bent or molded?
Blank and lightly bend only in the annealed condition with generous radii; harden 1010–1065 °C, oil or air quench, temper below 200 °C or above 550 °C only with corrosion penalty — avoid 400–550 °C.
What surface finishes work on 7Cr17?
Grind, belt and mirror-polish after hardening, then passivate (nitric or citric per ASTM A967); PVD/TiN or chrome plating used on budget cutlery for extra corrosion protection.
7Cr17 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 68Cr17 (old 7Cr17) | 0.6 – 0.75 | 0.68 |
| Si | ≤ 1 | 0.4 |
| Mn | ≤ 1 | 0.5 |
| P | ≤ 0.04 | — |
| S | ≤ 0.03 | — |
| Cr | 16 – 18 | 17 |
| Mooptional residual | ≤ 0.75 | — |
| Niresidual | ≤ 0.6 | — |
| Fe | balance | — |
7Cr17 QT-CRYO — frequently asked
What is 7Cr17 QT-CRYO used for?
7Cr17 QT-CRYO is typically used for kitchen knives, kitchenware, mechanical fittings and shafts. In short: hardenable budget cutlery steel; low-cost 420-type stainless; poor weldability, good hardenability.
What is the yield strength of 7Cr17 QT-CRYO?
7Cr17 QT-CRYO has a typical yield strength of 1,700 MPa (247 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 100% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is 7Cr17 QT-CRYO easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 100% of stainless steel grades). Machine only in the annealed state with sharp carbide tooling, rigid setups and generous coolant; hardened parts require grinding, EDM or CBN.
Can 7Cr17 QT-CRYO be welded?
Not readily — weldability is rated not recommended (5/100). Poor weldability — 0.7 %C martensitic; if unavoidable preheat 200–300 °C, use 309/410NiMo filler and temper immediately after welding.
What surface finishes work on 7Cr17 QT-CRYO?
Grind, belt and mirror-polish after hardening, then passivate (nitric or citric per ASTM A967); PVD/TiN or chrome plating used on budget cutlery for extra corrosion protection.
Can 7Cr17 QT-CRYO be formed, bent or molded?
Blank and lightly bend only in the annealed condition with generous radii; harden 1010–1065 °C, oil or air quench, temper below 200 °C or above 550 °C only with corrosion penalty — avoid 400–550 °C.
What is the maximum service temperature of 7Cr17 QT-CRYO?
7Cr17 QT-CRYO is rated for continuous use to about 175°C (347 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7Cr17-A and 7Cr17 QT-CRYO?
A is the default condition — standard supply condition for machining, blanking and blade grinding before hardening. QT-CRYO: adds a −75 °C sub-zero step to convert retained austenite for maximum hardness and dimensional stability. Yield strength is 415 MPa in A versus 1,700 MPa in QT-CRYO.
Sources
- GB/T 1220 (68Cr17 / 7Cr17) — SAC (2007)
- GB/T 4232 / ASTM A276 martensitic stainless bar — SAC / ASTM (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels (440A) — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating of Stainless Steels — ASM International (1991)
- ASM Handbook Vol.13B — Corrosion of Stainless Steels — ASM International (2005)
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.