Steel S15CK-QT (Quenched and tempered)
Heat-treated state
JIS S15CK
Rarely used for this low-carbon grade; only for thin sections where modest core strength gain is wanted without carburizing.
Values for the QT condition
Other S15CK tempers and conditions
S15CK is listed in 7 conditions; see the grade overview at S15CK.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Wire/bar for cold forging and cold heading of pins, bolts and shafts before carburizing. | 220 | 370 | 38 | 105 HB | 11 % IACS |
Solution annealed | Softest condition; choose for maximum ductility before deep drawing or heavy machining. | 235 | 390 | 36 | 111 HB | 10.8 % IACS |
HRDefault Hot rolled | Standard stock condition for carburizing blanks; machine then case harden. | 255 | 420 | 32 | 121 HB | — |
Normalized | Uniform fine-grain structure before carburizing; reduces distortion and improves machined finish. | 275 | 450 | 32 | 126 HB | 10.8 % IACS |
QTThis page Quenched and tempered | Rarely used for this low-carbon grade; only for thin sections where modest core strength gain is wanted without carburizing. | 350 | 500 | 26 | 160 HB | 10.5 % IACS |
Carburized + quenched & tempered | The functional service condition: hard wear-resistant case (0.3–1.0 mm) over a tough soft core for light-duty pins, bushings and small gears. | 390 | 560 | 25 | 60 HRC | — |
Cold drawn | Pick for close tolerance, bright surface and better chip control on turned pins and shafts. | 440 | 520 | 15 | 149 HB | — |
What is S15CK-QT?
S15CK-QT is S15CK heat treated to QT — rarely used for this low-carbon grade; only for thin sections where modest core strength gain is wanted without carburizing. S15CK-QT has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 74% of steel grades. Elongation at break is 26% and the elastic modulus is 205 GPa (29.7 Msi). S15CK-QT has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 90% of steel grades. It melts at 1,495°C (2,723 °F). HR is the default condition FabDigit quotes; QT is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10.5 % IACS, better than 89% of steel grades
- Conducts heat well — 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades
- Readily welded — 88/100, better than 87% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
S15CK-QT properties
Typical room-temperature values for S15CK-QT; 22 are specific to this condition. Other listed values are S15CK reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
S15CK-QT has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 90% of steel grades. It melts at 1,495°C (2,723 °F).
Mechanical16
S15CK-QT has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 74% of steel grades. Elongation at break is 26% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S15CK-QT is rated for continuous service to 400°C (752 °F). It conducts heat at 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
S15CK-QT conducts electricity at 10.5 % IACS, better than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of S15CK-QT takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
S15CK-QT's machinability is good (55/100, better than 62% of steel grades); weldability excellent (88/100); formability good (62/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S15CK-QT
Is S15CK easy to machine?
Soft and gummy — use sharp positive-rake tools, high speed with coolant and chip-breaking geometry, or specify cold-drawn/normalized stock for cleaner finishes.
Can S15CK be welded?
Excellent weldability by all arc, resistance and gas processes with no preheat; avoid welding after carburizing since the hard case cracks and decarburizes.
Can S15CK be formed, bent or molded?
Very good cold formability — suits cold heading, upsetting, deep drawing and bending; hot forge 1100–1250 °C, then normalize before carburizing.
What surface finishes work on S15CK?
No corrosion resistance in itself: finish with zinc or nickel plating, black oxide, phosphate + oil, or paint; carburized parts should be plated with low-hydrogen processes and baked to avoid embrittlement.
S15CK 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 | 0.13 – 0.18 | 0.16 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| Ptighter than non-K grades | ≤ 0.03 | — |
| Stighter than non-K grades | ≤ 0.03 | — |
| Curesidual | ≤ 0.2 | — |
| Niresidual; Ni+Cr ≤ 0.30 | ≤ 0.2 | — |
| Crresidual; Ni+Cr ≤ 0.30 | ≤ 0.2 | — |
| Fe | balance | — |
S15CK-QT — frequently asked
What is S15CK-QT used for?
S15CK-QT is typically used for pins, light gears and bushings. In short: low-cost carburizing carbon steel; excellent weldability; light-duty case-hardened parts.
What is the yield strength of S15CK-QT?
S15CK-QT has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is S15CK-QT easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Soft and gummy — use sharp positive-rake tools, high speed with coolant and chip-breaking geometry, or specify cold-drawn/normalized stock for cleaner finishes.
Can S15CK-QT be welded?
Yes — weldability is rated excellent (88/100). Excellent weldability by all arc, resistance and gas processes with no preheat; avoid welding after carburizing since the hard case cracks and decarburizes.
What surface finishes work on S15CK-QT?
No corrosion resistance in itself: finish with zinc or nickel plating, black oxide, phosphate + oil, or paint; carburized parts should be plated with low-hydrogen processes and baked to avoid embrittlement.
Can S15CK-QT be formed, bent or molded?
Very good cold formability — suits cold heading, upsetting, deep drawing and bending; hot forge 1100–1250 °C, then normalize before carburizing.
What is the maximum service temperature of S15CK-QT?
S15CK-QT 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 S15CK-HR and S15CK-CD?
HR is the default condition — standard stock condition for carburizing blanks; machine then case harden. CD: pick for close tolerance, bright surface and better chip control on turned pins and shafts. Yield strength is 255 MPa in HR versus 440 MPa in CD.
Sources
- JIS G 4051 — Carbon steels for machine structural use — JISC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- GB/T 699 — Quality carbon structural steels (15 steel) — SAC (2015)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
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.