Steel S4
AISI/SAE S4 · UNS T41904
S4 is a silicon-manganese shock-resisting tool steel (T41904) from the AISI S group; roughly 2 % Si provides the high toughness the family is used for, and annealed bar runs 210 HB with 430 MPa yield, 720 MPa tensile and 25 % elongation.
Reference datasheet — S4 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
S4 tempers and conditions
S4 is supplied in 7 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault spheroidize annealed bar/plate, machinable condition | Stock condition for machining, forming and drilling before hardening. | 430 | 720 | 25 | 210 HB | — |
Hot rolled | Mill-supplied stock for forging shops that will anneal or heat treat in-house. | 620 | 950 | 15 | 29 HRC | — |
Normalized | Used to refine forged structure prior to spheroidize annealing; not a finished tool condition. | 700 | 1,100 | 12 | 34 HRC | 3 % IACS |
Hardened & tempered ~425 °C | Maximum-toughness condition for heavy shock work such as jackhammer and chipping tools. | 1,420 | 1,700 | 10 | 50 HRC | — |
Hardened & tempered ~315 °C | Balanced hardness/toughness for rivet sets, shear blades and pneumatic tool bits. | 1,550 | 1,900 | 7 | 55 HRC | — |
Hardened & tempered ~205 °C | Maximum hardness/wear condition for chisels and punch tips where edge retention outweighs toughness. | 1,750 | 2,100 | 4 | 58 HRC | — |
As-quenched | Untempered martensite; must be tempered immediately — brittle and crack-prone in this state. | 1,900 | 2,200 | 1 | 62 HRC | 2.7 % IACS |
What is S4?
S4 is a silicon-manganese shock-resisting tool steel (T41904) from the AISI S group; roughly 2 % Si provides the high toughness the family is used for, and annealed bar runs 210 HB with 430 MPa yield, 720 MPa tensile and 25 % elongation. It is hardened to about 50, 55 or 58 HRC for tools that absorb repeated impact, and is stocked mainly as hot-rolled bar and flats. Limits are modest wear resistance, poor weldability, no corrosion resistance and a 400 °C service ceiling; S7 is the usual alternative when air hardening or deeper sections are needed. S4 has a density of 7.79 g/cm³ (0.281 lb/in³), lighter than 90% of steel grades. It melts at 1,420°C (2,588 °F). S4 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 51% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
What is S4 used for?
- Shear blades
- Rivet sets
- Punches
- Chisels
Advantages
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Low electrical conductivity — 3.1 % IACS, worse than 89% 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 — 22/100, worse than 81% of steel grades
S4 properties
Typical room-temperature values for S4-Annealed; bars are the position among steel grades.
Physical3
S4 has a density of 7.79 g/cm³ (0.281 lb/in³), lighter than 90% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical13
S4 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 51% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
S4 is rated for continuous service to 400°C (752 °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
S4 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of S4 takes about 33 MJ of energy and emits 2.4 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 35%.
Manufacturability7
S4's machinability is fair (48/100, worse than 57% of steel grades); weldability poor (22/100); formability fair (35/100).
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. S4 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S4
Is S4 easy to machine?
Machine only in the annealed (≤235 HB) condition with sharp carbide or cobalt HSS; the ~2 % Si is abrasive, so use rigid setups, generous coolant and finish-grind after hardening.
Can S4 be welded?
Poor weldability — preheat 260–320 °C, use matched or low-hydrogen filler, weld with minimum heat input and temper immediately at the tool's tempering temperature to avoid quench cracks.
Can S4 be formed, bent or molded?
Forge 1040–1150 °C, stop above 900 °C and cool slowly, then spheroidize anneal at ~790 °C; cold forming is limited to mild bending of annealed stock.
S4 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 | 0.5 – 0.65 | 0.57 |
| Sihigh Si gives temper resistance and hardenability | 1.75 – 2.25 | 2 |
| Mn | 0.6 – 0.95 | 0.8 |
| Crresidual/optional in ASTM A681 | ≤ 0.35 | 0.2 |
| Voptional grain refiner | ≤ 0.35 | 0.2 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on S4?
Protect against decarburization during austenitizing (neutral salt, vacuum or stop-off paint), then finish by grinding and apply oil, black oxide, phosphate or nitriding for corrosion and galling resistance.
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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel S4 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T41904
How much does S4 cost?
S4 is a premium-cost steel ($$$), cheaper than about 51% 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.
S4 — frequently asked
What is S4 used for?
S4 is typically used for shear blades, rivet sets, punches and chisels. In short: high-toughness impact steel; high-silicon S grade; not a wear grade.
What is the yield strength of S4?
S4 has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 51% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is S4 easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Machine only in the annealed (≤235 HB) condition with sharp carbide or cobalt HSS; the ~2 % Si is abrasive, so use rigid setups, generous coolant and finish-grind after hardening.
Can S4 be welded?
Not readily — weldability is rated poor (22/100). Poor weldability — preheat 260–320 °C, use matched or low-hydrogen filler, weld with minimum heat input and temper immediately at the tool's tempering temperature to avoid quench cracks.
What surface finishes work on S4?
Protect against decarburization during austenitizing (neutral salt, vacuum or stop-off paint), then finish by grinding and apply oil, black oxide, phosphate or nitriding for corrosion and galling resistance.
Can S4 be formed, bent or molded?
Forge 1040–1150 °C, stop above 900 °C and cool slowly, then spheroidize anneal at ~790 °C; cold forming is limited to mild bending of annealed stock.
What is the maximum service temperature of S4?
S4 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S4 Annealed and S4-AQ?
Annealed is the default condition — stock condition for machining, forming and drilling before hardening. AQ: untempered martensite; must be tempered immediately — brittle and crack-prone in this state. Yield strength is 430 MPa in Annealed versus 1,900 MPa in AQ.
How much does S4 cost?
S4 is a premium-cost steel ($$$), cheaper than about 51% 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.
Sources
- ASTM A681 Standard Specification for Tool Steels Alloy — ASTM International (2022)
- SAE J437/J438 Tool and Die Steels — SAE International (2007)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- ASM Specialty Handbook: Tool Materials — ASM International (1995)
- ASM Handbook Vol.16: Machining (tool steel machinability ratings) — ASM International (1989)
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.