Stainless Steel SUH1 QT-HS
Heat-treated state
JIS SUH1
QT-HS = hardened + low-side temper 690–720 °C
Pick when valve-stem/fastener strength and wear matter more than toughness and service stays below ~650 °C.
Values for the QT-HS condition
Other SUH1 tempers and conditions
SUH1 is listed in 6 conditions; see the grade overview at SUH1.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick for bar stock that must be machined, upset or forged before final hardening. | 450 | 760 | 22 | 20 HRC | — |
Hot rolled | Mill-supplied hot-worked bar or forged valve blanks intended for later hardening and tempering. | 600 | 900 | 16 | 31 HRC | 2.3 % IACS |
Cold drawn | Choose for close-tolerance, bright-surface bar for automatic machining before heat treatment. | 620 | 860 | 14 | 26 HRC | 2.5 % IACS |
QTDefault Quenched and tempered | Standard as-delivered valve-steel condition: best balance of hot strength, hardness and scaling resistance. | 760 | 1,000 | 18 | 31 HRC | — |
QT + Nitrided | Use for valve stems and guides needing high surface wear and scuff resistance over a tempered martensitic core. | 760 | 1,000 | 16 | 31 HRC | 2.2 % IACS |
QT-HSThis page Hardened + low-side temper 690–720 °C | Pick when valve-stem/fastener strength and wear matter more than toughness and service stays below ~650 °C. | 880 | 1,120 | 13 | 36 HRC | — |
What is SUH1 QT-HS?
SUH1 QT-HS is SUH1 heat treated to QT-HS — pick when valve-stem/fastener strength and wear matter more than toughness and service stays below ~650 °C. SUH1 QT-HS has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,120 MPa (162 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 13% and the elastic modulus is 215 GPa (31.2 Msi). SUH1 QT-HS has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,420°C (2,588 °F). QT is the default condition FabDigit quotes; QT-HS is available on request or by drawing note.
Advantages
- High strength — 880 MPa (128 ksi), better than 98% of stainless steel grades
- Low embodied carbon — 3.5 kg CO₂/kg, better than 88% of stainless steel grades
- Conducts heat well — 21 W/m·K (12.1 BTU/hr·ft·°F), better than 76% of stainless steel grades
Limitations
- Low fracture toughness — 32 MPa·√m (29.1 ksi·√in), worse than 99% of stainless steel grades
- Difficult to weld — 22/100, worse than 94% of stainless steel grades
- Limited ductility — 13%, worse than 93% of stainless steel grades
- Needs corrosion protection — 42/100, worse than 90% of stainless steel grades
- Limited formability — 18/100, worse than 89% of stainless steel grades
SUH1 QT-HS properties
Typical room-temperature values for SUH1 QT-HS; 12 are specific to this condition. Other listed values are SUH1 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
SUH1 QT-HS has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
SUH1 QT-HS has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,120 MPa (162 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 13% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
SUH1 QT-HS is rated for continuous service to 650°C (1,202 °F). It conducts heat at 21 W/m·K (12.1 BTU/hr·ft·°F), better than 76% of stainless steel grades. Thermal expansion is 11 µm/m·K (6.11 µin/in·°F).
Electrical3
SUH1 QT-HS conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 90% of stainless steel grades.
Sustainability4
Producing a kilogram of SUH1 QT-HS takes about 52 MJ of energy and emits 3.5 kg of CO₂ — less than 76% of stainless steel grades. Typical recycled content is 60%.
Manufacturability8
SUH1 QT-HS's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability poor (22/100); formability poor (18/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUH1 QT-HS
Is SUH1 easy to machine?
Machine in the annealed condition with sharp carbide tooling, rigid setups and generous coolant — the high-Si matrix work-hardens and is abrasive; grinding is normal for finished valve stems.
Can SUH1 be welded?
Poor weldability: 0.45 %C martensitic steel needs 300–400 °C preheat, matching or austenitic filler, and immediate 730–780 °C temper; friction welding to an austenitic head is the production route for bimetal valves.
Can SUH1 be formed, bent or molded?
Hot forge/upset at 1050–1150 °C and cool slowly to avoid quench cracks; cold bending or heading is not practical.
What surface finishes work on SUH1?
No anodizing; use nitriding or chromizing/aluminizing for wear and hot-gas protection, or phosphate/oil for storage — the 9 %Cr matrix will rust in damp storage.
SUH1 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 | 0.4 – 0.5 | 0.45 |
| Sihigh Si gives the scaling resistance | 3 – 3.5 | 3.25 |
| Mn | ≤ 0.6 | 0.35 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Ni | ≤ 0.6 | — |
| Cr | 8 – 10 | 9 |
| Fe | balance | — |
SUH1 QT-HS — frequently asked
What is SUH1 QT-HS used for?
SUH1 QT-HS is typically used for engine exhaust valves, high-temperature fasteners and furnace parts. In short: 750 °C valve steel; si-modified 410 martensitic; hardness retained hot.
What is the yield strength of SUH1 QT-HS?
SUH1 QT-HS has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 1,120 MPa (162 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is SUH1 QT-HS easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Machine in the annealed condition with sharp carbide tooling, rigid setups and generous coolant — the high-Si matrix work-hardens and is abrasive; grinding is normal for finished valve stems.
Can SUH1 QT-HS be welded?
Not readily — weldability is rated poor (22/100). Poor weldability: 0.45 %C martensitic steel needs 300–400 °C preheat, matching or austenitic filler, and immediate 730–780 °C temper; friction welding to an austenitic head is the production route for bimetal valves.
What surface finishes work on SUH1 QT-HS?
No anodizing; use nitriding or chromizing/aluminizing for wear and hot-gas protection, or phosphate/oil for storage — the 9 %Cr matrix will rust in damp storage.
Can SUH1 QT-HS be formed, bent or molded?
Hot forge/upset at 1050–1150 °C and cool slowly to avoid quench cracks; cold bending or heading is not practical.
What is the maximum service temperature of SUH1 QT-HS?
SUH1 QT-HS is rated for continuous use to about 650°C (1,202 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUH1-QT and SUH1-A?
QT is the default condition — standard as-delivered valve-steel condition: best balance of hot strength, hardness and scaling resistance. A: pick for bar stock that must be machined, upset or forged before final hardening. Yield strength is 760 MPa in QT versus 450 MPa in A.
Sources
- JIS G 4311 — Heat-resisting steel bars — Japanese Standards Association (2019)
- GB/T 1221 — Heat-resisting steel bars (4Cr9Si2) — SAC (2007)
- EN 10090 — Valve steels and alloys for internal combustion engines (X45CrSi9-3, 1.4718) — CEN (1998)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- X45CrSi9-3 / 1.4718 valve steel datasheet — European special steel producer (2021)
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.