Steel H12-QT52
Hardness band
AISI/SAE H12 · UNS T20812 · GB 4Cr5MoWVSi
QT52 = hardened & tempered to 51–54 HRC
Use for punches, dummy blocks and mandrels where abrasion at temperature dominates and shock loads are low.
Values for the QT52 condition
Other H12 tempers and conditions
H12 is listed in 7 conditions; see the grade overview at H12.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ESR (electroslag remelted) premium quality, annealed | Specify for large die blocks and polished cavities needing low inclusion content, tighter isotropy and better transverse toughness. | 495 | 750 | 26 | 205 HB | 3.3 % IACS |
ANNDefault Annealed | Standard mill supply condition for bar and plate; machine the die cavity here, then harden and temper. | 500 | 760 | 24 | 210 HB | — |
Hot rolled | Low-cost oversize stock for roughing; must be annealed or hardened before use — hardness and structure are non-uniform. | 800 | 1,000 | 12 | 32 HRC | 28 W/m·K |
Hardened & tempered to 44–46 HRC | Choose for large forging dies and extrusion tooling where thermal-fatigue cracking, not wear, governs life. | 1,250 | 1,450 | 11 | 45 HRC | 27 W/m·K |
Hardened, tempered + gas/plasma nitrided case | Surface treatment for extrusion dies and die-casting inserts to resist soldering and abrasion; keep the case thin to avoid heat-check initiation. | 1,300 | 1,560 | 9 | 48 HRC | 3.2 % IACS |
Hardened & tempered to 47–49 HRC | Balanced hardness/toughness setting used for most hot-forging, die-casting and extrusion tooling. | 1,400 | 1,600 | 9 | 48 HRC | 27 W/m·K |
QT52This page Hardened & tempered to 51–54 HRC | Use for punches, dummy blocks and mandrels where abrasion at temperature dominates and shock loads are low. | 1,600 | 1,850 | 6 | 53 HRC | — |
What is H12-QT52?
H12-QT52 is H12 heat treated to QT52 — use for punches, dummy blocks and mandrels where abrasion at temperature dominates and shock loads are low. H12-QT52 has a yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,850 MPa (268 ksi) — stronger than 98% of steel grades. Elongation at break is 6% and the elastic modulus is 210 GPa (30.5 Msi). H12-QT52 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,425°C (2,597 °F). ANN is the default condition FabDigit quotes; QT52 is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 85/100, better than 99% of steel grades
- High strength — 1,600 MPa (232 ksi), better than 98% of steel grades
- High service temperature — 480°C (896 °F), better than 88% of steel grades
Limitations
- Difficult to machine — 10/100, worse than 99% of steel grades
- Limited ductility — 6%, worse than 97% of steel grades
- Low electrical conductivity — 3.3 % IACS, worse than 86% of steel grades
- Poor heat conductor — 29 W/m·K (16.8 BTU/hr·ft·°F), worse than 84% of steel grades
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
H12-QT52 properties
Typical room-temperature values for H12-QT52; 15 are specific to this condition. Other listed values are H12 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
H12-QT52 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
H12-QT52 has a yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,850 MPa (268 ksi) — stronger than 98% of steel grades. Elongation at break is 6% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
H12-QT52 is rated for continuous service to 480°C (896 °F). It conducts heat at 29 W/m·K (16.8 BTU/hr·ft·°F), worse than 84% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
H12-QT52 conducts electricity at 3.3 % IACS, worse than 86% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of H12-QT52 takes about 33 MJ of energy and emits 2.5 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 40%.
Manufacturability8
H12-QT52's machinability is not recommended (10/100, worse than 99% of steel grades); weldability poor (25/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with H12-QT52
Is H12 easy to machine?
Machine fully in the annealed condition (≈60 % of 1212) with rigid setups and coated carbide; above ~45 HRC use hard-milling or EDM plus stress relief.
Can H12 be welded?
Weldable for die repair only: preheat/interpass 350–400 °C, matching 5 % Cr filler, slow cool and immediately re-temper 15–20 °C below the last tempering temperature.
Can H12 be formed, bent or molded?
Hot work at 1050–1120 °C with slow cooling to 850 °C and immediate annealing at 845–900 °C; cold forming is not practical.
What surface finishes work on H12?
Takes a good mirror polish (best in ESR quality); protect with nitriding, PVD (CrN/AlTiN), phosphating or oil — do not anodize, and avoid decarburized skin before polishing.
H12 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 |
|---|---|---|
| CASTM A681 / GB/T 1299 4Cr5MoWVSi | 0.3 – 0.4 | 0.35 |
| Si | 0.8 – 1.2 | 1 |
| Mn | 0.2 – 0.5 | 0.35 |
| Cr | 4.75 – 5.5 | 5.1 |
| Mo | 1.25 – 1.75 | 1.5 |
| Wdistinguishes H12 from H13 | 1 – 1.7 | 1.4 |
| V | 0.2 – 0.5 | 0.4 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
H12-QT52 — frequently asked
What is H12-QT52 used for?
H12-QT52 is typically used for extrusion dies, die-casting dies, hot forging dies and mandrels. In short: tungsten-bearing 5 % Cr grade; good hot hardness; reduced heat-check resistance.
What is the yield strength of H12-QT52?
H12-QT52 has a typical yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,850 MPa (268 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is H12-QT52 easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine fully in the annealed condition (≈60 % of 1212) with rigid setups and coated carbide; above ~45 HRC use hard-milling or EDM plus stress relief.
Can H12-QT52 be welded?
Not readily — weldability is rated poor (25/100). Weldable for die repair only: preheat/interpass 350–400 °C, matching 5 % Cr filler, slow cool and immediately re-temper 15–20 °C below the last tempering temperature.
What surface finishes work on H12-QT52?
Takes a good mirror polish (best in ESR quality); protect with nitriding, PVD (CrN/AlTiN), phosphating or oil — do not anodize, and avoid decarburized skin before polishing.
Can H12-QT52 be formed, bent or molded?
Hot work at 1050–1120 °C with slow cooling to 850 °C and immediate annealing at 845–900 °C; cold forming is not practical.
What is the maximum service temperature of H12-QT52?
H12-QT52 is rated for continuous use to about 480°C (896 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between H12-ANN and H12-QT52?
ANN is the default condition — standard mill supply condition for bar and plate; machine the die cavity here, then harden and temper. QT52: use for punches, dummy blocks and mandrels where abrasion at temperature dominates and shock loads are low. Yield strength is 500 MPa in ANN versus 1,600 MPa in QT52.
Sources
- ASTM A681 Standard Specification for Tool Steels Alloy — ASTM International (2022)
- GB/T 1299 (4Cr5MoWVSi) — SAC (2014)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. — ASM International (1998)
- Hot-work tool steel datasheets (5 % Cr class, W-alloyed) — Böhler / voestalpine (2022)
- (H12/4Cr5MoWVSi ) (2025)
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.