Steel SK5 Q&T (Quenched and tempered)
Heat-treated state
JIS SK5
Working condition for cutting edges, saw teeth, scrapers and wear plates where maximum hardness matters more than toughness.
Values for the Q&T condition
Other SK5 tempers and conditions
SK5 is listed in 6 conditions; see the grade overview at SK5.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
spheroidize/full annealed (≤ 217 HB) | Softest, most machinable and most formable condition; the standard delivery state for tool-steel bar prior to hardening. | 380 | 640 | 20 | 185 HB | — |
HRDefault Hot rolled | Cheapest starting stock for parts that will be re-annealed, machined or hardened afterwards. | 400 | 710 | 12 | 200 HB | — |
Cold rolled | Pick for blanking, stamping and forming operations followed by hardening; good gauge tolerance and surface. | 430 | 720 | 10 | 210 HB | — |
austenitized ~900 °C, air cooled (fine pearlite) | Use to refine grain and homogenize forgings/hot-rolled stock before hardening, or where medium strength without quenching is enough. | 525 | 1,010 | 11 | 31 HRC | — |
Blue-tempered / hardened-and-tempered spring strip, 44–50 HRC | Ready-to-use spring/shim strip: high elastic limit with enough toughness to bend and coil without re-heat-treating. | 1,350 | 1,550 | 4 | 47 HRC | — |
Q&TThis page Quenched and tempered | Working condition for cutting edges, saw teeth, scrapers and wear plates where maximum hardness matters more than toughness. | 1,650 | 2,000 | 2 | 60 HRC | — |
What is SK5 Q&T?
SK5 Q&T is SK5 heat treated to Q&T — working condition for cutting edges, saw teeth, scrapers and wear plates where maximum hardness matters more than toughness. SK5 Q&T has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 205 GPa (29.7 Msi). SK5 Q&T has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- High strength — 1,650 MPa (239 ksi), better than 99% of steel grades
- 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 machine — 8/100, worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- Low fracture toughness — 20 MPa·√m (18.2 ksi·√in), worse than 99% of steel grades
- Difficult to weld — 8/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
SK5 Q&T properties
Typical room-temperature values for SK5 Q&T; 16 are specific to this condition. Other listed values are SK5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SK5 Q&T has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
SK5 Q&T has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SK5 Q&T is rated for continuous service to 180°C (356 °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
SK5 Q&T conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SK5 Q&T takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability8
SK5 Q&T's machinability is not recommended (8/100, worse than 100% of steel grades); weldability not recommended (8/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SK5 Q&T
Is SK5 easy to machine?
Machine only in the annealed condition (≈45% of 1212) with sharp carbide or coated HSS tooling; once hardened above ~50 HRC, switch to grinding, EDM or hard turning with CBN.
Can SK5 be welded?
Poor weldability at 0.85% C — expect martensite and quench cracks; if unavoidable, preheat 250–350 °C, use low-hydrogen/austenitic filler and post-weld temper immediately.
Can SK5 be formed, bent or molded?
Blank, bend and coil in the soft/annealed temper with generous radii (≥2t) and well-lubricated tooling; blue-tempered strip forms only to spring-type radii, then stress-relieve at 200–260 °C.
What surface finishes work on SK5?
Not anodizable — protect with oil, phosphate/black oxide, electroless nickel, zinc or hard chrome; polish easily to a bright edge but keep humidity off unprotected surfaces.
SK5 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 G 4401 SK5 / SK85 | 0.8 – 0.9 | 0.85 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.1 – 0.5 | 0.35 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Curesidual max | ≤ 0.25 | |
| Niresidual max; Ni+Cr ≤ 0.35 | ≤ 0.25 | |
| Crresidual max | ≤ 0.3 | |
| Fe | balance |
SK5 Q&T — frequently asked
What is SK5 Q&T used for?
SK5 Q&T is typically used for hand tools, cold cutting knives, saw blades, doctor and scraper blades, spring clips and retainers and shims and feeler strip. In short: spring carbon steel sheet.
What is the yield strength of SK5 Q&T?
SK5 Q&T has a typical yield strength of 1,650 MPa (239 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is SK5 Q&T easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine only in the annealed condition (≈45% of 1212) with sharp carbide or coated HSS tooling; once hardened above ~50 HRC, switch to grinding, EDM or hard turning with CBN.
Can SK5 Q&T be welded?
Not readily — weldability is rated not recommended (8/100). Poor weldability at 0.85% C — expect martensite and quench cracks; if unavoidable, preheat 250–350 °C, use low-hydrogen/austenitic filler and post-weld temper immediately.
What surface finishes work on SK5 Q&T?
Not anodizable — protect with oil, phosphate/black oxide, electroless nickel, zinc or hard chrome; polish easily to a bright edge but keep humidity off unprotected surfaces.
Can SK5 Q&T be formed, bent or molded?
Blank, bend and coil in the soft/annealed temper with generous radii (≥2t) and well-lubricated tooling; blue-tempered strip forms only to spring-type radii, then stress-relieve at 200–260 °C.
What is the maximum service temperature of SK5 Q&T?
SK5 Q&T is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SK5-HR and SK5-BT?
HR is the default condition — cheapest starting stock for parts that will be re-annealed, machined or hardened afterwards. BT: ready-to-use spring/shim strip: high elastic limit with enough toughness to bend and coil without re-heat-treating. Yield strength is 400 MPa in HR versus 1,350 MPa in BT.
Can FabDigit make parts in SK5 Q&T?
Yes — SK5 Q&T is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G 4401 Carbon tool steels (SK85/SK5) — JISC (2009)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (AISI 1080 data) — ASM International (1990)
- ASM Specialty Handbook — Tool Materials — ASM International (1995)
- GB/T 1298 (T8A/T9A comparison) — SAC (2008)
- Hardened & tempered / blue-tempered carbon spring strip datasheets — strip mill producers (e.g. Sandvik, Nippon Steel strip) (2022)
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.