Steel S20C · heat-treated state
Steel S20C-QT
Properties of the QT condition, compared with the other S20C tempers.
Only worth it on small sections — low carbon limits hardenability, giving modest strength gains over normalizing.
What is S20C-QT?
S20C-QT is S20C heat treated to QT — only worth it on small sections — low carbon limits hardenability, giving modest strength gains over normalizing. S20C-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 53% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi). S20C-QT has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 89% of steel grades. It melts at 1,490°C (2,714 °F). CD is the default condition FabDigit quotes; QT is available on request or by drawing note.
Advantages
- Conducts heat well — 51.9 W/m·K (30 BTU/hr·ft·°F), better than 96% of steel grades
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Readily welded — 92/100, better than 93% of steel grades
S20C-QT properties
Typical room-temperature values for S20C-QT — 10 properties are specific to this condition; the rest are grade-level values shared by every S20C temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
S20C-QT has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 89% of steel grades. It melts at 1,490°C (2,714 °F).
Mechanical16
S20C-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 53% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S20C-QT is rated for continuous service to 400°C (752 °F). It conducts heat at 51.9 W/m·K (30 BTU/hr·ft·°F), better than 96% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
S20C-QT conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of S20C-QT takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability8
S20C-QT's machinability is fair (48/100, worse than 57% of steel grades); weldability excellent (92/100); formability good (60/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other S20C tempers and conditions
S20C is also supplied in 6 other conditions. The full side-by-side table is on the S20C overview.
- CDDefaultDefault stocked form: higher strength, tight tolerance and good surface for shafts, pins and turned parts.400 MPa yield · 143 HB
- QTOnly worth it on small sections — low carbon limits hardenability, giving modest strength gains over normalizing.420 MPa yield · 170 HB
- CARBChoose for wear surfaces (gears, pins, bushings): hard 0.5–1.2 mm case on a tough, low-strength core.400 MPa yield · 60 HRC
- CD-SRUse when machined parts must stay straight — residual stress removed at ~550–650 °C with only small strength loss.350 MPa yield · 137 HB
- NUniform fine grain and predictable properties — the condition JIS specifies minimum strengths against (≥402 MPa UTS).280 MPa yield · 131 HB
- HRCheapest form for welded structures and parts to be fully machined or later heat treated.260 MPa yield · 121 HB
- ASoftest, most ductile state — pick for deep drawing, severe cold bending or before carburizing.240 MPa yield · 111 HB
Working with S20C-QT
Is S20C easy to machine?
Free machining at moderate speeds but gummy in the annealed state — cold-drawn bar, positive rake and sharp tooling give the best finish; expect burrs.
Can S20C be welded?
Excellent weldability by all arc processes with no preheat up to ~25 mm; carbon equivalent ≈ 0.3, use E70xx/ER70S-x filler.
Can S20C be formed, bent or molded?
Bends, headers and stamps readily when annealed or hot rolled; cold-drawn bar needs generous bend radii or intermediate anneal.
What surface finishes work on S20C?
Not anodizable — protect by zinc plating, black oxide, phosphate + oil, nitrocarburizing or paint; carburize and grind where wear resistance is needed.
S20C 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 | 0.18 – 0.23 | 0.2 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| P | ≤ 0.03 | — |
| S | ≤ 0.04 | — |
| Curesidual, max | ≤ 0.3 | — |
| Niresidual, max | ≤ 0.2 | — |
| Crresidual, max; Ni+Cr ≤ 0.35 | ≤ 0.2 | — |
| Fe | balance | — |
S20C-QT — frequently asked
What is S20C-QT used for?
S20C-QT is typically used for general fabrication, brackets and welded plate. In short: cold-drawn machining bar.
What is the yield strength of S20C-QT?
S20C-QT has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is S20C-QT easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Free machining at moderate speeds but gummy in the annealed state — cold-drawn bar, positive rake and sharp tooling give the best finish; expect burrs.
Can S20C-QT be welded?
Yes — weldability is rated excellent (92/100). Excellent weldability by all arc processes with no preheat up to ~25 mm; carbon equivalent ≈ 0.3, use E70xx/ER70S-x filler.
What surface finishes work on S20C-QT?
Not anodizable — protect by zinc plating, black oxide, phosphate + oil, nitrocarburizing or paint; carburize and grind where wear resistance is needed.
Can S20C-QT be formed, bent or molded?
Bends, headers and stamps readily when annealed or hot rolled; cold-drawn bar needs generous bend radii or intermediate anneal.
What is the maximum service temperature of S20C-QT?
S20C-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 S20C-CD and S20C-A?
CD is the default condition — default stocked form: higher strength, tight tolerance and good surface for shafts, pins and turned parts. A: softest, most ductile state — pick for deep drawing, severe cold bending or before carburizing. Yield strength is 400 MPa in CD versus 240 MPa in A.
Can FabDigit make parts in S20C-QT?
Yes — S20C-QT is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G 4051 — Carbon steels for machine structural use — JISC (2016)
- GB/T 699 — Quality carbon structural steels (20 steel) — SAC (2015)
- ASTM A108 / SAE J403 (1020) — ASTM / SAE (2018)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- worldsteel LCI data for steel bar — World Steel Association (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.