Steel SUP13 QT+SP
Finish state
GB SUP13
QT+SP = q&T 44–48 HRC + shot peened
Standard production route for automotive leaf/coil springs — peening compressive layer raises fatigue life several-fold.
Values for the QT+SP condition
Other SUP13 tempers and conditions
SUP13 is listed in 9 conditions; see the grade overview at SUP13.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize Annealed | Softest, most machinable condition — used before heavy cold upsetting or deep machining of torsion-bar ends. | 450 | 740 | 22 | 210 HB | 8 % IACS |
Solution annealed | Pick for machining, cold forming or coiling of heavy sections before hardening. | 500 | 800 | 18 | 230 HB | — |
Normalized | Uniform fine pearlitic structure for stock preparation before hardening, or for lightly loaded parts. | 600 | 960 | 14 | 29 HRC | 7.8 % IACS |
Hot rolled | Mill supply condition for bars and flats that will be formed and then quench-and-tempered by the spring maker. | 620 | 1,000 | 12 | 31 HRC | — |
Cold drawn | Close-tolerance, bright bar or wire for small springs and pins that will be hardened after forming. | 900 | 1,050 | 8 | 33 HRC | 7.5 % IACS |
Q&T 40–44 HRC (oil quenched, high temper) | Tougher, lower-strength spring temper for very thick leaf springs, stabilizer bars and impact-loaded parts. | 1,200 | 1,330 | 11 | 42 HRC | — |
QT 44-48 HRCDefault Q&T 44–48 HRC (standard spring temper) | The standard service condition for SUP13 leaf and heavy coil springs — best balance of fatigue strength and toughness. | 1,420 | 1,570 | 9 | 46 HRC | — |
QT+SPThis page Q&T 44–48 HRC + shot peened | Standard production route for automotive leaf/coil springs — peening compressive layer raises fatigue life several-fold. | 1,420 | 1,570 | 9 | 47 HRC | 7.2 % IACS |
Q&T 48–52 HRC (high-strength temper) | Maximum stress capability for torsion bars and highly stressed coil springs; accept lower toughness and higher notch/hydrogen sensitivity. | 1,620 | 1,800 | 6 | 50 HRC | — |
What is SUP13 QT+SP?
SUP13 QT+SP is SUP13 supplied in the QT+SP condition — standard production route for automotive leaf/coil springs — peening compressive layer raises fatigue life several-fold. SUP13 QT+SP has a yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,570 MPa (228 ksi) — stronger than 96% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi). SUP13 QT+SP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). QT 44-48 HRC is the default condition FabDigit quotes; QT+SP is available on request or by drawing note.
Advantages
- High strength — 1,420 MPa (206 ksi), better than 96% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
SUP13 QT+SP properties
Typical room-temperature values for SUP13 QT+SP; 22 are specific to this condition. Other listed values are SUP13 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SUP13 QT+SP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
SUP13 QT+SP has a yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,570 MPa (228 ksi) — stronger than 96% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SUP13 QT+SP is rated for continuous service to 230°C (446 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
SUP13 QT+SP conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of SUP13 QT+SP takes about 30 MJ of energy and emits 2.1 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability7
SUP13 QT+SP's machinability is not recommended (12/100, worse than 99% of steel grades); weldability poor (15/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUP13 QT+SP
Is SUP13 easy to machine?
Machine in the annealed or spheroidized state (≤260 HB) with rigid setups and coated carbide; at 44–52 HRC only grinding, hard turning with CBN or EDM are practical.
Can SUP13 be welded?
Effectively unweldable in service condition (0.60 %C): if unavoidable, preheat 300–350 °C, low-hydrogen consumables, immediate PWHT/temper — avoid welding on spring-active surfaces.
Can SUP13 be formed, bent or molded?
Hot form or coil at 850–950 °C, or cold form annealed stock; then austenitize ~840–870 °C, oil quench (Mo gives good through-hardening in thick sections) and temper 400–500 °C to target hardness, followed by shot peening.
What surface finishes work on SUP13?
No natural corrosion resistance — use phosphate + oil, zinc-rich or epoxy paint, or powder coat; if electroplating, bake at 190–200 °C to avoid hydrogen embrittlement, and never grind/decarburize the peened surface.
SUP13 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 | 0.56 – 0.64 | 0.6 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.7 – 1 | 0.85 |
| Cr | 0.7 – 0.9 | 0.8 |
| Mo | 0.25 – 0.35 | 0.3 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Curesidual, max | ≤ 0.3 | — |
| Fe | balance | — |
SUP13 QT+SP — frequently asked
What is SUP13 QT+SP used for?
SUP13 QT+SP is typically used for heavy coil springs, railway suspension springs, rail bogie helical springs, large-section torsion bars, mining and crushing equipment springs and off-highway suspension springs. In short: deep-hardening spring steel; for large-section springs; high toughness spring grade.
What is the yield strength of SUP13 QT+SP?
SUP13 QT+SP has a typical yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,570 MPa (228 ksi) — stronger than 96% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is SUP13 QT+SP easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Machine in the annealed or spheroidized state (≤260 HB) with rigid setups and coated carbide; at 44–52 HRC only grinding, hard turning with CBN or EDM are practical.
Can SUP13 QT+SP be welded?
Not readily — weldability is rated poor (15/100). Effectively unweldable in service condition (0.60 %C): if unavoidable, preheat 300–350 °C, low-hydrogen consumables, immediate PWHT/temper — avoid welding on spring-active surfaces.
What surface finishes work on SUP13 QT+SP?
No natural corrosion resistance — use phosphate + oil, zinc-rich or epoxy paint, or powder coat; if electroplating, bake at 190–200 °C to avoid hydrogen embrittlement, and never grind/decarburize the peened surface.
Can SUP13 QT+SP be formed, bent or molded?
Hot form or coil at 850–950 °C, or cold form annealed stock; then austenitize ~840–870 °C, oil quench (Mo gives good through-hardening in thick sections) and temper 400–500 °C to target hardness, followed by shot peening.
What is the maximum service temperature of SUP13 QT+SP?
SUP13 QT+SP is rated for continuous use to about 230°C (446 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUP13 QT 44-48 HRC and SUP13-SA?
QT 44-48 HRC is the default condition — the standard service condition for SUP13 leaf and heavy coil springs — best balance of fatigue strength and toughness. SA: softest, most machinable condition — used before heavy cold upsetting or deep machining of torsion-bar ends. Yield strength is 1,420 MPa in QT 44-48 HRC versus 450 MPa in SA.
Sources
- JIS G 4801 — Spring steels — Japanese Industrial Standards Committee (2011)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (4161 / Cr-Mo spring steels) — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture (spring steel fatigue and shot peening) — ASM International (1996)
- SAE J404 / J1268 — Chemical compositions and hardenability of alloy steels (4161) — SAE International (2019)
- JIS B 2704 — Helical compression and extension springs, design — JISC (2018)
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.