Steel SKD1 QT55-58
Hardness band
JIS SKD1 · AISI/SAE D3
QT55-58 = hardened & tempered 55–58 HRC
Higher-temper condition used when dimensional stability or nitriding follow-up matters more than peak hardness.
Values for the QT55-58 condition
Other SKD1 tempers and conditions
SKD1 is listed in 8 conditions; see the grade overview at SKD1.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ESR (electroslag remelted) annealed bar | Premium remelted stock with finer, less banded carbides — pick for large dies, better polish and more isotropic toughness. | 455 | 770 | 14 | 21 HRC | 2.7 % IACS |
ANNDefault Annealed | The as-supplied stock condition for machining dies before hardening. | 460 | 780 | 12 | 22 HRC | — |
Stress relieved | Intermediate step after rough machining of large dies to minimise hardening distortion. | 470 | 790 | 11 | 23 HRC | 2.7 % IACS |
QT55-58This page Hardened & tempered 55–58 HRC | Higher-temper condition used when dimensional stability or nitriding follow-up matters more than peak hardness. | 1,620 | 1,850 | 1 | 57 HRC | 2.6 % IACS |
Hardened & tempered 58–60 HRC | Slightly tougher setting for heavier sections and shock-loaded shear blades. | — | 1,950 | — | 59 HRC | — |
Hardened + deep-freeze (−75 to −196 °C) + tempered, 63–65 HRC | Choose when retained austenite must be removed for maximum hardness and long-term size stability (gauges, precision punches). | 2,000 | 2,300 | 0.5 | 64 HRC | 2.6 % IACS |
Hardened & tempered 60–62 HRC | The usual working hardness for cold-forming, drawing and thread-rolling tools. | — | 2,100 | — | 61 HRC | — |
Hardened & tempered 62–64 HRC | Maximum wear resistance for blanking punches and dies cutting thin, abrasive material — lowest toughness. | — | 2,250 | 0.5 | 63 HRC | — |
What is SKD1 QT55-58?
SKD1 QT55-58 is SKD1 heat treated to QT55-58 — higher-temper condition used when dimensional stability or nitriding follow-up matters more than peak hardness. SKD1 QT55-58 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,850 MPa (268 ksi) — stronger than 98% of steel grades. Elongation at break is 1% and the elastic modulus is 208 GPa (30.2 Msi). SKD1 QT55-58 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 95% of steel grades. It melts at 1,270°C (2,318 °F). ANN is the default condition FabDigit quotes; QT55-58 is available on request or by drawing note.
Advantages
- High strength — 1,620 MPa (235 ksi), better than 98% of steel grades
- Good corrosion resistance — 30/100, better than 95% of steel grades
Limitations
- Low fracture toughness — 14 MPa·√m (12.7 ksi·√in), worse than 100% of steel grades
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 2/100, worse than 100% of steel grades
- Limited ductility — 1%, worse than 99% of steel grades
- Difficult to machine — 10/100, worse than 99% of steel grades
SKD1 QT55-58 properties
Typical room-temperature values for SKD1 QT55-58; 22 are specific to this condition. Other listed values are SKD1 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SKD1 QT55-58 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 95% of steel grades. It melts at 1,270°C (2,318 °F).
Mechanical16
SKD1 QT55-58 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,850 MPa (268 ksi) — stronger than 98% of steel grades. Elongation at break is 1% and the elastic modulus is 208 GPa (30.2 Msi).
Thermal6
SKD1 QT55-58 is rated for continuous service to 350°C (662 °F). It conducts heat at 19 W/m·K (11 BTU/hr·ft·°F), worse than 97% of steel grades. Thermal expansion is 10.8 µm/m·K (6 µin/in·°F).
Electrical3
SKD1 QT55-58 conducts electricity at 2.6 % IACS, worse than 97% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (30/100), better than 95% of steel grades.
Sustainability4
Producing a kilogram of SKD1 QT55-58 takes about 34 MJ of energy and emits 2.6 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 40%.
Manufacturability8
SKD1 QT55-58's machinability is not recommended (10/100, worse than 99% of steel grades); weldability not recommended (5/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SKD1 QT55-58
Is SKD1 easy to machine?
Machine only in the annealed state with rigid setups, sharp carbide or coated-carbide tooling, moderate speeds and generous coolant; hardened SKD1 must be ground or EDM'd, and stress-relieve rough-machined dies before hardening.
Can SKD1 be welded?
Essentially a repair-only operation: preheat to 300–400 °C, use matched high-Cr tool-steel electrodes, keep interpass hot and temper immediately — cold-cracking risk is high.
Can SKD1 be formed, bent or molded?
No cold forming; hot work between about 1050 and 900 °C with slow furnace cooling followed by spheroidize annealing at 850–870 °C.
What surface finishes work on SKD1?
Harden 950–980 °C, oil or pressurised-gas quench, temper twice at 150–250 °C (deep-freeze if size stability is critical); finish with grinding, then nitriding, PVD TiN/CrN or black oxide for wear and light corrosion protection.
SKD1 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 |
|---|---|---|
| CAISI D3 range is 2.00–2.35 | 1.8 – 2.4 | 2.1 |
| Si | ≤ 0.4 | 0.3 |
| Mn | ≤ 0.6 | 0.35 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Crsome JIS/vendor tables quote up to 15 %; D3 is 11.00–13.50 | 11 – 13 | 12 |
| Monot intentionally added; residual/optional | ≤ 0.6 | — |
| Voptional in D3 | ≤ 1 | — |
| Woptional in D3 | ≤ 1 | — |
| Niresidual | ≤ 0.5 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
SKD1 QT55-58 — frequently asked
What is SKD1 QT55-58 used for?
SKD1 QT55-58 is typically used for cold forming dies, thread rolling dies and blanking punches. In short: highest wear resistance, cold-work; D3 equivalent, oil/air hardening; low toughness and machinability.
What is the yield strength of SKD1 QT55-58?
SKD1 QT55-58 has a typical yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,850 MPa (268 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SKD1 QT55-58 easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine only in the annealed state with rigid setups, sharp carbide or coated-carbide tooling, moderate speeds and generous coolant; hardened SKD1 must be ground or EDM'd, and stress-relieve rough-machined dies before hardening.
Can SKD1 QT55-58 be welded?
Not readily — weldability is rated not recommended (5/100). Essentially a repair-only operation: preheat to 300–400 °C, use matched high-Cr tool-steel electrodes, keep interpass hot and temper immediately — cold-cracking risk is high.
What surface finishes work on SKD1 QT55-58?
Harden 950–980 °C, oil or pressurised-gas quench, temper twice at 150–250 °C (deep-freeze if size stability is critical); finish with grinding, then nitriding, PVD TiN/CrN or black oxide for wear and light corrosion protection.
Can SKD1 QT55-58 be formed, bent or molded?
No cold forming; hot work between about 1050 and 900 °C with slow furnace cooling followed by spheroidize annealing at 850–870 °C.
What is the maximum service temperature of SKD1 QT55-58?
SKD1 QT55-58 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SKD1-ANN and SKD1 QT-CRYO?
ANN is the default condition — the as-supplied stock condition for machining dies before hardening. QT-CRYO: choose when retained austenite must be removed for maximum hardness and long-term size stability (gauges, precision punches). Yield strength is 460 MPa in ANN versus 2,000 MPa in QT-CRYO.
Sources
- JIS G 4404 — Alloy tool steels — Japanese Standards Association (2015)
- ASTM A681 — Standard Specification for Tool Steels Alloy (Type D3) — ASTM International (2015)
- GB/T 1299 — (Cr12) — SAC (2014)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys (Cold-Work Tool Steels) — ASM International (1990)
- ASM Handbook Vol.16: Machining (machinability ratings of tool steels) — ASM International (1989)
- 1.2080 / D3 cold-work tool steel datasheet — Böhler / Daido / Hitachi Metals equivalents (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.