Steel H42
AISI/SAE H42 · UNS T20842
H42 is a molybdenum–tungsten hot-work tool steel (UNS T20842) in the AISI H series, combining tungsten's wear resistance with molybdenum's toughness and lower distortion on hardening.
Reference datasheet — H42 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
H42 tempers and conditions
H42 is supplied in 6 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
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 |
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?
H42 is a molybdenum–tungsten hot-work tool steel (UNS T20842) in the AISI H series, combining tungsten's wear resistance with molybdenum's toughness and lower distortion on hardening. It is stocked as annealed bar and block (223 HB, 830 MPa tensile, 550 MPa yield, 16 % elongation) and heat treated to 50–52, 54–56 or 57–59 HRC, with stress-relieved and nitrided conditions also on file. Maximum service temperature is 400 °C, and with machinability 32 and formability 15 all shaping is done annealed or by grinding and EDM. It has no corrosion resistance; H13 is the tougher, easier-machining alternative. H42 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). H42 has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 71% of steel grades. Elongation at break is 16% and the elastic modulus is 210 GPa (30.5 Msi).
What is H42 used for?
- hot extrusion dies
- die-casting dies
- hot forging inserts
- hot punches
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- High embodied carbon — 3.1 kg CO₂/kg, worse than 92% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
- Poor heat conductor — 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
H42 properties
Typical room-temperature values for H42-ANN; bars are the position among steel grades.
Physical3
H42 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 has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 71% of steel grades. Elongation at break is 16% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
H42 is rated for continuous service to 400°C (752 °F). It conducts heat at 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
H42 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of H42 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's machinability is poor (32/100, worse than 87% of steel grades); weldability poor (25/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. H42 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with H42
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel H42 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T20842
How much does H42 cost?
H42 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
H42 — frequently asked
What is H42 used for?
H42 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?
H42 has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 71% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is H42 easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% 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 be welded?
Not readily — weldability is rated poor (25/100). 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?
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 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?
H42 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 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.
How much does H42 cost?
H42 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.