Steel P420QH-A (Solution annealed)
Temper
EN P420QH
Occasionally supplied for rough machining of forgings before final quench and temper; not a pressure-retaining delivery condition.
Values for the A condition
Other P420QH tempers and conditions
P420QH is listed in 5 conditions; see the grade overview at P420QH.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AThis page Solution annealed | Occasionally supplied for rough machining of forgings before final quench and temper; not a pressure-retaining delivery condition. | 330 | 500 | 26 | 155 HB | 7.4 % IACS |
QT | Thick forgings and shells; lowest strength class of the grade because of reduced quench severity in the core. | 415 | 550 | 21 | 9 HRC | 7.2 % IACS |
QT | Heavy plate / medium forging section where the specified proof strength steps down with thickness. | 445 | 570 | 22 | 11 HRC | 7.2 % IACS |
Quenched and tempered plus stress relief / simulated PWHT | Order this when vessel fabrication includes post-weld heat treatment; properties are certified after the simulated PWHT cycle. | 450 | 575 | 23 | 190 HB | 7.2 % IACS |
QTDefault Quenched and tempered | Standard as-delivered condition for plate, bar and light forgings; full 420 MPa proof-strength class. | 470 | 590 | 22 | 12 HRC | 7.2 % IACS |
What is P420QH-A?
P420QH-A is P420QH in the A temper — occasionally supplied for rough machining of forgings before final quench and temper; not a pressure-retaining delivery condition. P420QH-A has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). P420QH-A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). QT is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
- Readily welded — 72/100, better than 75% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
P420QH-A properties
Typical room-temperature values for P420QH-A; 22 are specific to this condition. Other listed values are P420QH reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P420QH-A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical17
P420QH-A has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P420QH-A is rated for continuous service to 350°C (662 °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 µm/m·K (6.67 µin/in·°F).
Electrical3
P420QH-A conducts electricity at 7.4 % IACS, worse than 70% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of P420QH-A takes about 29 MJ of energy and emits 2.1 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability7
P420QH-A's machinability is good (56/100, better than 71% of steel grades); weldability very good (72/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P420QH-A
Is P420QH easy to machine?
Machines like a 200 HB Q&T alloy steel — rigid setups, coated carbide, 100–160 m/min turning, generous coolant; avoid heating above the tempering temperature during grinding.
Can P420QH be welded?
Good weldability with low-hydrogen consumables matched to 420 MPa class; preheat roughly 100–150 °C for thick sections, control interpass temperature and heat input, and use PWHT at 530–580 °C when required by code.
Can P420QH be formed, bent or molded?
Cold-form only to moderate radii (≥ 3t) and hot-form below the tempering temperature; any hot forming or normalizing requires re-quench and temper to restore properties.
What surface finishes work on P420QH?
Not anodizable; protect with blast-and-paint, epoxy/zinc-rich primer, metallizing or weld-overlay cladding for corrosive service.
P420QH 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 |
|---|---|---|
| Cladle analysis limit | ≤ 0.18 | 0.14 |
| Si | ≤ 0.5 | 0.3 |
| Mn | 0.8 – 1.7 | 1.3 |
| P | ≤ 0.02 | 0.01 |
| S | ≤ 0.01 | 0 |
| Nimain hardenability/toughness addition | ≤ 1 | 0.5 |
| Cr | ≤ 0.6 | 0.3 |
| Mo | ≤ 0.5 | 0.25 |
| Cu | ≤ 0.3 | 0.1 |
| Vmicro-alloy, sum of Nb+V+Ti limited | ≤ 0.08 | 0.03 |
| Nb | ≤ 0.05 | 0.02 |
| Ti | ≤ 0.03 | 0.01 |
| Altotal Al, grain refinement | ≥ 0.02 | 0.03 |
| N | ≤ 0.02 | 0.01 |
| B | ≤ 5×10⁻⁴ | 2×10⁻⁴ |
| Fe | balance | — |
P420QH-A — frequently asked
What is P420QH-A used for?
P420QH-A is typically used for high-pressure boilers, pressure vessel shells and petrochemical reactors. In short: Q&T pressure-vessel plate; stronger than normalized P420NH; rated to 400 °C.
What is the yield strength of P420QH-A?
P420QH-A has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is P420QH-A easy to machine?
Reasonably — machinability is rated good (56/100, better than 71% of steel grades). Machines like a 200 HB Q&T alloy steel — rigid setups, coated carbide, 100–160 m/min turning, generous coolant; avoid heating above the tempering temperature during grinding.
Can P420QH-A be welded?
Yes — weldability is rated very good (72/100). Good weldability with low-hydrogen consumables matched to 420 MPa class; preheat roughly 100–150 °C for thick sections, control interpass temperature and heat input, and use PWHT at 530–580 °C when required by code.
What surface finishes work on P420QH-A?
Not anodizable; protect with blast-and-paint, epoxy/zinc-rich primer, metallizing or weld-overlay cladding for corrosive service.
Can P420QH-A be formed, bent or molded?
Cold-form only to moderate radii (≥ 3t) and hot-form below the tempering temperature; any hot forming or normalizing requires re-quench and temper to restore properties.
What is the maximum service temperature of P420QH-A?
P420QH-A 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 P420QH-QT and P420QH-A?
QT is the default condition — standard as-delivered condition for plate, bar and light forgings; full 420 MPa proof-strength class. A: occasionally supplied for rough machining of forgings before final quench and temper; not a pressure-retaining delivery condition. Yield strength is 470 MPa in QT versus 330 MPa in A.
Sources
- EN 10028-6 — Flat products for pressure purposes: weldable fine grain steels, quenched and tempered — CEN (2017)
- EN 10222-4 — Steel forgings for pressure purposes: weldable fine grain steels with high proof strength — CEN (2017)
- EN 13445-3 — Unfired pressure vessels: design (physical property data) — CEN (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Quenched and tempered pressure-vessel plate datasheets (Dillinger / Industeel / SSAB type products) — various mills (2023)
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.