Steel S1 · heat-treated state
Steel S1 Q&T
Properties of the Q&T condition, compared with the other S1 tempers.
General working condition; pick the tempering temperature to trade hardness against shock toughness.
What is S1 Q&T?
S1 Q&T is S1 heat treated to Q&T — general working condition; pick the tempering temperature to trade hardness against shock toughness. S1 Q&T has a yield strength of 1,550 MPa (225 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 97% of steel grades. Elongation at break is 6% and the elastic modulus is 207 GPa (30 Msi). S1 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). Annealed is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- High strength — 1,550 MPa (225 ksi), better than 97% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited ductility — 6%, worse than 98% of steel grades
- Poor heat conductor — 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 88% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
S1 Q&T properties
Typical room-temperature values for S1 Q&T — 14 properties are specific to this condition; the rest are grade-level values shared by every S1 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
S1 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
S1 Q&T has a yield strength of 1,550 MPa (225 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 97% of steel grades. Elongation at break is 6% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
S1 Q&T is rated for continuous service to 250°C (482 °F). It conducts heat at 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 88% of steel grades. Thermal expansion is 12.4 µm/m·K (6.89 µin/in·°F).
Electrical3
S1 Q&T conducts electricity at 7.5 % IACS, worse than 68% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of S1 Q&T takes about 34 MJ of energy and emits 2.5 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
S1 Q&T's machinability is not recommended (12/100, worse than 99% of steel grades); weldability not recommended (10/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other S1 tempers and conditions
S1 is also supplied in 5 other conditions. The full side-by-side table is on the S1 overview.
- AnnealedDefaultStandard stocking condition for machining, drilling and forging before hardening.415 MPa yield · 200 HB
- Hardened & TemperedMaximum hardness/wear for punches and shear blades where shock is moderate.1,750 MPa yield · 57 HRC
- H&T 54-56 HRCBalanced hardness/toughness for cold-heading dies, rivet sets and heavy punches.1,600 MPa yield · 55 HRC
- Q&TGeneral working condition; pick the tempering temperature to trade hardness against shock toughness.1,550 MPa yield · 55 HRC
- H&T 50-52 HRCChoose for pneumatic chisels, hot punches and other severe-impact tools where toughness rules.1,400 MPa yield · 51 HRC
Working with S1 Q&T
Is S1 easy to machine?
Machine in the annealed condition (≈55 % of AISI 1212) with rigid setups and sharp carbide or cobalt HSS; hardened parts need grinding or EDM.
Can S1 be welded?
Poor weldability — preheat to 300–400 °C, use matched or low-hydrogen filler, then immediately re-temper; keep welds off high-stress impact faces.
Can S1 be formed, bent or molded?
Forge 1040–1150 °C, stop above ~900 °C and cool slowly, then spheroidize anneal at 760–790 °C; almost no cold forming capability.
What surface finishes work on S1?
Harden from 900–955 °C in oil (protect against decarburisation), temper 205–425 °C to the chosen hardness; finish with black oxide, phosphate or nitriding for wear and light rust protection.
S1 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 – 0.55 | 0.5 |
| Mn | 0.1 – 0.4 | 0.3 |
| Siwide range; Si-rich variants behave like 5CrW2Si | 0.15 – 1.2 | 0.3 |
| Cr | 1 – 1.8 | 1.5 |
| W | 1.5 – 3 | 2.5 |
| VV optional in some heats (max 0.30) | 0.15 – 0.3 | 0.2 |
| Momax per ASTM A681 | ≤ 0.5 | — |
| Niresidual max | ≤ 0.3 | — |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
S1 Q&T — frequently asked
What is S1 Q&T used for?
S1 Q&T is typically used for chisels, rivet sets and punches. In short: shock-resistant tool steel.
What is the yield strength of S1 Q&T?
S1 Q&T has a typical yield strength of 1,550 MPa (225 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is S1 Q&T easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Machine in the annealed condition (≈55 % of AISI 1212) with rigid setups and sharp carbide or cobalt HSS; hardened parts need grinding or EDM.
Can S1 Q&T be welded?
Not readily — weldability is rated not recommended (10/100). Poor weldability — preheat to 300–400 °C, use matched or low-hydrogen filler, then immediately re-temper; keep welds off high-stress impact faces.
What surface finishes work on S1 Q&T?
Harden from 900–955 °C in oil (protect against decarburisation), temper 205–425 °C to the chosen hardness; finish with black oxide, phosphate or nitriding for wear and light rust protection.
Can S1 Q&T be formed, bent or molded?
Forge 1040–1150 °C, stop above ~900 °C and cool slowly, then spheroidize anneal at 760–790 °C; almost no cold forming capability.
What is the maximum service temperature of S1 Q&T?
S1 Q&T is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in S1 Q&T?
Yes — S1 Q&T is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A681 — Alloy Tool Steels — ASTM International (2015)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- GB/T 1299 (5CrW2Si / 6CrW2Si) — SAC (2014)
- Shock-resisting S1 tool steel bar datasheet — tool steel producers/distributors (2023)
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.