Steel H42 HT-NIT
Finish state
AISI/SAE H42 · UNS T20842
HT-NIT = hardened, tempered and gas/plasma nitrided surface
Use for extrusion dies needing a 900–1150 HV case against aluminium wash and abrasive wear; nitride below the tempering temperature.
Values for the HT-NIT condition
Other H42 tempers and conditions
H42 is listed in 6 conditions; see the grade overview at H42.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard as-supplied bar/plate condition for rough machining before hardening. | 550 | 830 | 16 | 223 HB | 26 W/m·K |
Stress relieved | Intermediate step after heavy roughing to minimise distortion during the high-temperature hardening cycle. | 580 | 860 | 15 | 21 HRC | 3.1 % IACS |
Hardened & tempered to 50–52 HRC | Choose for hot forging/extrusion dies where thermal-fatigue cracking dominates over wear. | 1,450 | 1,720 | 8 | 51 HRC | 25 W/m·K |
HT-NITThis page Hardened, tempered and gas/plasma nitrided surface | Use for extrusion dies needing a 900–1150 HV case against aluminium wash and abrasive wear; nitride below the tempering temperature. | 1,600 | 1,900 | 5 | 55 HRC | 2.8 % IACS |
Hardened & tempered to 54–56 HRC | Most common working hardness for hot extrusion dies, mandrels and hot punches. | 1,650 | 1,950 | 6 | 55 HRC | 25 W/m·K |
Hardened & tempered to 57–59 HRC | Pick when abrasive wear or hot-hardness retention outranks impact toughness (hot shear blades, warm-forming punches). | 1,850 | 2,150 | 4 | 58 HRC | 24 W/m·K |
What is H42 HT-NIT?
H42 HT-NIT is H42 supplied in the HT-NIT condition — use for extrusion dies needing a 900–1150 HV case against aluminium wash and abrasive wear; nitride below the tempering temperature. H42 HT-NIT has a yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 98% of steel grades. Elongation at break is 5% and the elastic modulus is 210 GPa (30.5 Msi). H42 HT-NIT has a density of 8.06 g/cm³ (0.291 lb/in³), heavier than 96% of steel grades. It melts at 1,370°C (2,498 °F). ANN is the default condition FabDigit quotes; HT-NIT is available on request or by drawing note.
Advantages
- High strength — 1,600 MPa (232 ksi), better than 98% of steel grades
- High service temperature — 600°C (1,112 °F), better than 98% of steel grades
- Good corrosion resistance — 25/100, better than 92% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 3/100, worse than 100% of steel grades
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 1/100, worse than 100% of steel grades
- Low fracture toughness — 20 MPa·√m (18.2 ksi·√in), worse than 99% of steel grades
- Limited ductility — 5%, worse than 98% of steel grades
H42 HT-NIT properties
Typical room-temperature values for H42 HT-NIT; 22 are specific to this condition. Other listed values are H42 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
H42 HT-NIT has a density of 8.06 g/cm³ (0.291 lb/in³), heavier than 96% of steel grades. It melts at 1,370°C (2,498 °F).
Mechanical16
H42 HT-NIT has a yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 98% of steel grades. Elongation at break is 5% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
H42 HT-NIT is rated for continuous service to 600°C (1,112 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
H42 HT-NIT conducts electricity at 2.8 % IACS, worse than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 92% of steel grades.
Sustainability4
Producing a kilogram of H42 HT-NIT takes about 42 MJ of energy and emits 3.1 kg of CO₂ — more than 92% of steel grades. Typical recycled content is 40%.
Manufacturability7
H42 HT-NIT's machinability is not recommended (3/100, worse than 100% of steel grades); weldability not recommended (5/100); formability not recommended (1/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with H42 HT-NIT
Is H42 easy to machine?
Machine only in the annealed condition with rigid setups, low speeds and cobalt-HSS/carbide tooling; hardened parts need CBN, grinding or EDM (recast layer must be tempered off).
Can H42 be welded?
Repair-weld with matching or H13-type filler at 400–500 °C preheat, interpass hold, then temper 20–30 °C below the last temper; never weld cold.
Can H42 be formed, bent or molded?
Hot work only: forge 1050–1120 °C, stop above 900 °C, slow cool and immediately spheroidize anneal at 870–900 °C; cold forming is not feasible.
What surface finishes work on H42?
Vacuum harden 1150–1200 °C with double or triple temper at 550–650 °C; finish with nitriding, oxide blackening or PVD (CrN/AlTiN) below the tempering temperature — plating with hydrogen risk should be avoided.
H42 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 | 0.55 – 0.7 | 0.62 |
| Mn | 0.15 – 0.4 | 0.28 |
| Sitypical mill practice | 0.15 – 0.4 | 0.3 |
| Cr | 3.75 – 4.5 | 4.1 |
| Mo | 4.5 – 5.5 | 5 |
| W | 5.5 – 6.75 | 6.1 |
| V | 1.75 – 2.2 | 2 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
H42 HT-NIT — frequently asked
What is H42 HT-NIT used for?
H42 HT-NIT is typically used for hot extrusion dies, die-casting dies, hot forging inserts and hot punches. In short: tungsten–molybdenum hot-work hybrid; higher hot wear than H13; low distortion on hardening.
What is the yield strength of H42 HT-NIT?
H42 HT-NIT has a typical yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is H42 HT-NIT easy to machine?
Not especially — machinability is rated not recommended (3/100, worse than 100% of steel grades). Machine only in the annealed condition with rigid setups, low speeds and cobalt-HSS/carbide tooling; hardened parts need CBN, grinding or EDM (recast layer must be tempered off).
Can H42 HT-NIT be welded?
Not readily — weldability is rated not recommended (5/100). Repair-weld with matching or H13-type filler at 400–500 °C preheat, interpass hold, then temper 20–30 °C below the last temper; never weld cold.
What surface finishes work on H42 HT-NIT?
Vacuum harden 1150–1200 °C with double or triple temper at 550–650 °C; finish with nitriding, oxide blackening or PVD (CrN/AlTiN) below the tempering temperature — plating with hydrogen risk should be avoided.
Can H42 HT-NIT be formed, bent or molded?
Hot work only: forge 1050–1120 °C, stop above 900 °C, slow cool and immediately spheroidize anneal at 870–900 °C; cold forming is not feasible.
What is the maximum service temperature of H42 HT-NIT?
H42 HT-NIT is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between H42-ANN and H42 HT-NIT?
ANN is the default condition — standard as-supplied bar/plate condition for rough machining before hardening. HT-NIT: use for extrusion dies needing a 900–1150 HV case against aluminium wash and abrasive wear; nitride below the tempering temperature. Yield strength is 550 MPa in ANN versus 1,600 MPa in HT-NIT.
Sources
- ASTM A681 — Standard Specification for Tool Steels Alloy — ASTM International (2022)
- ASM Handbook Vol. 1: Properties and Selection: Irons, Steels, and High-Performance Alloys — Tool Steels — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
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.