Steel SK3
JIS SK3
SK3 is a Japanese water-hardening carbon tool steel at roughly 1.0–1.1 % C, strengthened by quench martensite and fine carbides rather than by alloy additions (JIS carbon tool steel series).
Reference datasheet — SK3 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
SK3 tempers and conditions
SK3 is supplied in 10 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
- Annealed
- Normalized
- Cold Drawn
- Cold Rolled Hard
- Q&T 42-46 HRC
- Q&T 48-52 HRC
- Q&T 55-58 HRC
- Q&T 60-63 HRC
- Q&T 63-65 HRC
- As-Quenched
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault spheroidize annealed (soft, as-supplied) | Standard mill-supplied soft condition for machining, blanking and subsequent hardening. | 400 | 670 | 22 | 195 HB | 48 W/m·K |
austenitized and air cooled | Used to refine coarse or banded structure before spheroidize annealing/hardening; harder and less machinable than annealed. | 520 | 900 | 10 | 27 HRC | 9 % IACS |
cold drawn/ground bar and drill rod (annealed then drawn) | Precision-size bar and drill rod stock for taps, punches and pins that will be hardened after machining. | 600 | 780 | 10 | 20 HRC | 9.2 % IACS |
work-hardened strip (spring/shim temper) | Hard-rolled high-carbon strip for shims, saw and cutter blanks or springs used without further hardening. | 1,000 | 1,150 | 3 | 39 HRC | 9 % IACS |
Tempered ~500 °C | Highest-toughness tempered condition, used for heavy-shock tools and spring components. | 1,250 | 1,400 | 9 | 44 HRC | 9 % IACS |
Tempered ~400 °C | Impact-loaded tooling (hammers, cold chisels, springs) where toughness outranks wear resistance. | 1,450 | 1,650 | 6 | 50 HRC | 8.8 % IACS |
Tempered ~300 °C | Tougher condition for shear blades, chisels and cold punches subject to impact. | 1,650 | 1,900 | 4 | 56 HRC | 8.5 % IACS |
Tempered ~200 °C | General cutting-tool condition: taps, reamers, punches, woodworking blades — good balance of hardness and chipping resistance. | 1,800 | 2,050 | 2 | 61 HRC | — |
Water quenched, tempered ~150–180 °C | Maximum edge hardness for razors, files, engraving tools and scrapers where toughness is not critical. | 1,900 | 2,200 | 1 | 64 HRC | 40 W/m·K |
water/brine quenched, untempered | Intermediate condition only — maximum hardness but very brittle and residually stressed; must be tempered promptly. | 2,000 | 2,400 | 0 | 65 HRC | 7 % IACS |
What is SK3?
SK3 is a Japanese water-hardening carbon tool steel at roughly 1.0–1.1 % C, strengthened by quench martensite and fine carbides rather than by alloy additions (JIS carbon tool steel series). Engineers specify it for cutting edges, taps and dies that must reach 63–65 HRC after quench and temper; it is supplied as spheroidize-annealed bar, flat stock and cold-rolled strip. Annealed values are 400 MPa yield, 670 MPa tensile, 22 % elongation at 195 HB, thermal conductivity 48 W/m·K and a 300 °C service limit, with shallow hardenability. It is effectively unweldable and has no corrosion resistance; SK4 is the tougher, slightly lower-carbon alternative. SK3 has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,400°C (2,552 °F). SK3 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 670 MPa (97.2 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is SK3 used for?
- taps
- dies
- hand tools
- cutting edges
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
SK3 properties
Typical room-temperature values for SK3-Annealed; bars are the position among steel grades.
Physical3
SK3 has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
SK3 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 670 MPa (97.2 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SK3 is rated for continuous service to 300°C (572 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
SK3 conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (9/100), worse than 98% of steel grades.
Sustainability4
Producing a kilogram of SK3 takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
SK3's machinability is fair (45/100, worse than 65% of steel grades); weldability not recommended (12/100); formability fair (40/100).
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. SK3 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SK3
Is SK3 easy to machine?
Machine in the spheroidize-annealed condition (~30 % of AISI 1212) with sharp HSS or coated carbide and generous coolant; after hardening only grinding or EDM is practical.
Can SK3 be welded?
Essentially unweldable for structural use — 1.05 % C causes hard brittle HAZ; if repair welding is unavoidable preheat 300–400 °C, use low-hydrogen or Ni filler and temper immediately.
Can SK3 be formed, bent or molded?
Cold blank, bend and coil only in the spheroidized or lightly rolled strip condition with generous bend radii; hot forge 1050–850 °C then slow cool/anneal to avoid network carbide and cracking.
SK3 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 |
|---|---|---|
| CJIS G4401 SK3 / SK105 | 1 – 1.1 | 1.05 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.1 – 0.5 | 0.3 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Curesidual max | ≤ 0.25 | |
| Niresidual max | ≤ 0.25 | |
| Crresidual max | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on SK3?
Takes a fine mirror polish when hardened; no corrosion resistance, so protect with oil, black oxide, phosphate, chrome/nickel plate or nitride — avoid plating/finishing above ~180 °C on low-tempered tools.
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 SK3 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- W1
How much does SK3 cost?
SK3 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SK3 — frequently asked
What is SK3 used for?
SK3 is typically used for taps, dies, hand tools and cutting edges. In short: hardest of the SK grades; water-hardening, unalloyed; edge retention over toughness.
What is the yield strength of SK3?
SK3 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 670 MPa (97.2 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is SK3 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the spheroidize-annealed condition (~30 % of AISI 1212) with sharp HSS or coated carbide and generous coolant; after hardening only grinding or EDM is practical.
Can SK3 be welded?
Not readily — weldability is rated not recommended (12/100). Essentially unweldable for structural use — 1.05 % C causes hard brittle HAZ; if repair welding is unavoidable preheat 300–400 °C, use low-hydrogen or Ni filler and temper immediately.
What surface finishes work on SK3?
Takes a fine mirror polish when hardened; no corrosion resistance, so protect with oil, black oxide, phosphate, chrome/nickel plate or nitride — avoid plating/finishing above ~180 °C on low-tempered tools.
Can SK3 be formed, bent or molded?
Cold blank, bend and coil only in the spheroidized or lightly rolled strip condition with generous bend radii; hot forge 1050–850 °C then slow cool/anneal to avoid network carbide and cracking.
What is the maximum service temperature of SK3?
SK3 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does SK3 cost?
SK3 is a budget-cost steel ($), cheaper than about 90% 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
- JIS G 4401 Carbon tool steels (SK105 / former SK3) — JSA (2009)
- ASTM A686 Standard Specification for Carbon Tool Steel (W1) — ASTM (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (Water-hardening tool steels) — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating of Tool Steels — ASM International (1991)
- ASM Handbook Vol.16 — Machining (machinability ratings of tool steels) — ASM International (1989)
- GB/T 1298 (T10A equivalent grade) — SAC (2008)
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.