Steel S1
AISI/SAE S1 · UNS T41901 · GB 4CrW2Si, 6CrW2Si
S1 (UNS T41901) is a water/oil-hardening chromium–tungsten shock-resisting tool steel with roughly 0.50 % C, 1.5 % Cr and 2.5 % W, giving high impact toughness at working hardnesses of 50–58 HRC.
Values for the Annealed condition
S1 tempers and conditions
S1 is supplied in 5 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault soft, as-supplied bar/flat condition | Standard stocking condition for machining, drilling and forging before hardening. | 415 | 690 | 25 | 200 HB | — |
Hot Rolled / as-forged (unannealed bar) | Mill condition on larger forged sections; normally spheroidize-annealed before machining. | 720 | 1,050 | 10 | 34 HRC | 7.5 % IACS |
Tempered ~425 °C for maximum shock resistance | Choose for pneumatic chisels, hot punches and other severe-impact tools where toughness rules. | 1,400 | 1,700 | 9 | 51 HRC | — |
Quenched and tempered | General working condition; pick the tempering temperature to trade hardness against shock toughness. | 1,550 | 1,900 | 6 | 55 HRC | — |
Tempered ~315 °C | Balanced hardness/toughness for cold-heading dies, rivet sets and heavy punches. | 1,600 | 1,950 | 6 | 55 HRC | — |
What is S1?
S1 (UNS T41901) is a water/oil-hardening chromium–tungsten shock-resisting tool steel with roughly 0.50 % C, 1.5 % Cr and 2.5 % W, giving high impact toughness at working hardnesses of 50–58 HRC. It is the classic choice for pneumatic chisels, rivet sets, punches, shear blades, cold-heading and hot-punching tooling where the tool sees heavy shock rather than pure abrasion. Limits are modest wear resistance and hot hardness compared with D- or H-series steels, poor corrosion resistance, and considerable size change/decarburisation risk during heat treatment. S1 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). S1 has a yield strength of 415 MPa (60.2 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 56% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
What is S1 used for?
- Chisels
- Rivet sets
- Punches
Advantages
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Poor heat conductor — 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 88% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
S1 properties
Typical room-temperature values for S1-Annealed; bars are the position among steel grades.
Physical3
S1 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 has a yield strength of 415 MPa (60.2 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 56% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
S1 is rated for continuous service to 200°C (392 °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 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of S1 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's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (20/100); formability poor (25/100).
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. S1 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S1
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.
Manufacturability
The process limits FabDigit applies to S1. Every S1 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair45 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
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 |
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.
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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel S1 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T41901
- GB (China)
- 4CrW2Si6CrW2Si
- Similar grades
- 1.2542
How much does S1 cost?
S1 is a premium-cost steel ($$$), pricier than about 57% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
S1 — frequently asked
What is S1 used for?
S1 is typically used for chisels, rivet sets and punches. In short: shock-resistant tool steel.
What is the yield strength of S1?
S1 has a typical yield strength of 415 MPa (60.2 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 56% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is S1 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed condition (≈55 % of AISI 1212) with rigid setups and sharp carbide or cobalt HSS; hardened parts need grinding or EDM.
Can S1 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — preheat to 300–400 °C, use matched or low-hydrogen filler, then immediately re-temper; keep welds off high-stress impact faces.
What surface finishes work on S1?
Harden from 900–955 °C in oil (protect against decarburisation), temper 205–425 °C to the chosen hardness; finish with black oxide, phosphate or nitriding for wear and light rust protection.
Can S1 be formed, bent or molded?
Forge 1040–1150 °C, stop above ~900 °C and cool slowly, then spheroidize anneal at 760–790 °C; almost no cold forming capability.
What is the maximum service temperature of S1?
S1 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does S1 cost?
S1 is a premium-cost steel ($$$), pricier than about 57% 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.
Can FabDigit make parts in S1?
Yes — S1 is available for CNC machining; every part is priced by an engineer rather than instantly. 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; 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.