About P355QH1 steel
P355QH1 is one of thirteen steel grades in EN 10222-4, the European standard for pressure-purpose forgings in weldable fine-grain steels with high proof strength. Its strength comes from grain refinement with aluminium, niobium and vanadium and from quenching and tempering. Carbon is limited to 0.18 % to keep the steel weldable.
Typical uses are pressure vessels, shell-and-tube heat exchangers, chemical tanks and petroleum plant, where parts need strength at elevated temperature and good toughness at low temperature.
Designation
The steel name follows EN 10027-1 and the steel number follows EN 10027-2.
- P
- Steel for pressure purposes
- 355
- Minimum yield strength in MPa for the thinnest section range
- Q
- Quenched and tempered
- H
- Properties specified at elevated (high) temperature
- 1.0571
- Steel number, or Werkstoffnummer
The final 1 is part of the grade name in EN 10222-4 and distinguishes this forging grade from P355QH (1.8867), the quenched and tempered plate grade in EN 10028-6.
Alloy steel or carbon steel
EN 10222-4:2017+A1:2021 classifies P355QH1 as an alloy special steel under EN 10020 (clause 4.1). Older datasheets based on the 1998 edition list it as a non-alloy steel. The current edition also allows more molybdenum (0.25 %) and nickel (0.50 %) than the 1998 limits.
P355QH1 and P355QH
They are different grades. P355QH1 (1.0571) is the forging grade in EN 10222-4 and P355QH (1.8867) is the plate grade in EN 10028-6. Both are quenched and tempered and belong to the 355 MPa strength class, so P355QH1 is the matching forging grade for nozzles, flanges and tube sheets on vessels made from P355QH plate, subject to the design code and the vessel designer.
Ordering from older drawings
Many datasheets still show the 1998 limits for P355QH1, including 0.20 % carbon, 0.015 % sulphur and 0.08 % molybdenum. The current edition sets 0.18 % carbon, 0.010 % sulphur (up to 0.015 % by agreement) and 0.25 % molybdenum. Please state the edition on your purchase order. We melt our own steel and make each heat to the edition specified.
P355QH1 chemical composition
Cast analysis limits in % by mass from EN 10222-4:2017+A1:2021, Table 2. The middle column shows the 1998 values still found in older datasheets. Product analysis may differ from the cast analysis only within the tolerances in Table 3 of the standard.
| Element | EN 10222-4:2017+A1:2021 | Older datasheets, 1998 edition | Effect |
|---|---|---|---|
| Carbon (C) | ≤ 0.18 | ≤ 0.20 | Strength; kept low for weldability |
| Silicon (Si) | ≤ 0.40 | 0.10–0.50 | Deoxidation |
| Manganese (Mn) | 0.90–1.50 | 0.90–1.65 | Main strengthening element; hardenability for the quench |
| Phosphorus (P) | ≤ 0.025 | ≤ 0.025 | Impurity; limited for toughness |
| Sulphur (S) | ≤ 0.010, or up to 0.015 by agreement | ≤ 0.015 | Impurity; limited to protect transverse toughness |
| Aluminium, total (Al) | ≥ 0.020; a maximum of 0.050 should be agreed | 0.020–0.060 | Deoxidation, grain refinement, nitrogen binding |
| Nitrogen (N) | ≤ 0.015 | ≤ 0.020 | Bound by aluminium; Al/N ≥ 2 if aluminium alone binds it |
| Chromium (Cr) | ≤ 0.30 | ≤ 0.30 | Hardenability |
| Copper (Cu) | ≤ 0.30 | ≤ 0.20 | Residual element |
| Molybdenum (Mo) | ≤ 0.25 | ≤ 0.08 | Hardenability and tempering resistance |
| Niobium (Nb) | ≤ 0.05 | ≤ 0.05 | Grain refinement and precipitation strengthening |
| Nickel (Ni) | ≤ 0.50 | ≤ 0.30 | Low-temperature toughness |
| Vanadium (V) | ≤ 0.10 | ≤ 0.10 | Precipitation strengthening |
| Niobium + vanadium | ≤ 0.12 | < 0.12 | Upper limit on combined micro-alloying |
| Titanium (Ti), zirconium (Zr) | Optional: Ti ≤ 0.03, Zr ≤ 0.05 | Not listed | Additional grain refiners |
Elements not listed may not be added intentionally without the purchaser's approval, except for finishing the cast (EN 10222-4, Table 2, note a).
P355QH1 heat treatment
EN 10222-4 requires P355QH1 forgings to be delivered quenched and tempered. The forging is austenitized at 860–940 °C, quenched in water, polymer or oil, and tempered at 600–700 °C. Unlike P460QH, P460QL1 and P460QL2, P355QH1 has no option in the standard for delivery in the normalized condition.
We heat treat P355QH1 in our own heat treatment shop, which has 14 furnaces. The largest car-bottom furnaces measure 8,000 × 2,000 × 2,000 mm and 6,000 × 3,500 × 2,300 mm, and two 15 m well-type furnaces are used to quench long shafts vertically.
| Stage | Temperature | Cooling | Purpose |
|---|---|---|---|
| Austenitizing | 860–940 °C | Water, polymer or oil quench | Transforms the section to austenite so the quench can harden it |
| Tempering | 600–700 °C | Not specified | Restores toughness and relieves quenching stresses |
If the 0.2 % proof strength at elevated temperature is to be verified, the test temperature is agreed at enquiry; otherwise EN 10222-4 sets it at 300 °C (clause 6.4).
P355QH1 mechanical properties
Minimum values for quenched and tempered P355QH1 forgings with ruling sections from 70 to 400 mm, typical for heavy forgings such as tube sheets, girth flanges and shells. Ruling sections of 70 mm and below have higher minimum yield strengths, up to 355 MPa (EN 10222-4, Table 4).
Tensile properties at room temperature
| Ruling section t | Yield strength ReH, min. | Tensile strength Rm | Elongation A, longitudinal, min. | Elongation A, transverse, min. |
|---|---|---|---|---|
| 70 < t ≤ 100 mm | 315 MPa | 470–630 MPa | 21 % | 19 % |
| 100 < t ≤ 250 mm | 295 MPa | 470–630 MPa | 21 % | 19 % |
| 250 < t ≤ 400 mm | 275 MPa | 470–630 MPa | 21 % | 19 % |
Impact energy, Charpy V-notch KV2
| Test temperature | Longitudinal, min. | Transverse, min. |
|---|---|---|
| +20 °C | 63 J | 40 J |
| 0 °C | 55 J | 34 J |
| −20 °C | 47 J | 27 J |
| −40 °C | 34 J | Not specified |
A different test temperature or different minimum values can be agreed at enquiry (options 6 and 7 of EN 10222-4). Our laboratory runs Charpy impact tests down to −60 °C.
0.2 % proof strength at elevated temperature
The H in the grade name means that proof strength values at elevated temperature are specified. They are used in the design of pressure equipment that operates above room temperature.
| Temperature | 70 < t ≤ 100 mm | 100 < t ≤ 250 mm | 250 < t ≤ 400 mm |
|---|---|---|---|
| 50 °C | 305 | 285 | 266 |
| 100 °C | 287 | 268 | 250 |
| 150 °C | 265 | 249 | 232 |
| 200 °C | 244 | 228 | 213 |
| 250 °C | 224 | 209 | 195 |
| 300 °C | 206 | 192 | 179 |
| 350 °C | 190 | 178 | 166 |
| 400 °C | 179 | 167 | 156 |
For weight estimates use a density of 7.85 g/cm³, typical of carbon-manganese steels. EN 10222-4 does not specify physical properties.
P355QH1 forgings we produce
Jiangyin Jiangnan Metal Co., Ltd. was founded in 1997 and is located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We have 460 employees, melt our own steel and hold CCS, BV, DNV, LR and NK approvals. Open-die forging suits single parts, small batches and parts too large for closed dies, such as tube sheets, girth flanges and nozzles for individual vessels.
| Product family | P355QH1 parts | Used in |
|---|---|---|
| Tube sheets and discs | Tube sheets (tube plates), channel covers, blind covers, forged discs | Shell-and-tube heat exchangers, pressure vessels |
| Forged flanges | Girth flanges, body flanges, cover flanges, blind flanges, long weld neck nozzles, self-reinforced nozzles | Pressure vessels, reactors, heat exchangers |
| Seamless rolled rings | Flange rings, girth-flange blanks, ring forgings for vessel connections | Pressure vessels, heat exchangers |
| Forged rings | Rings punched and expanded over a saddle mandrel | Flanged joints and vessel connections |
| Forged cylinders and pipes | Shells, nozzle necks, sleeves, bushes, barrels, casings, hollow bars | Vessel shells, nozzles, housings |
| Valve parts | Valve bodies, bonnets, closures, seat rings, stems | Pressure-retaining valves |
| Forged bars and blocks | Round bars, blocks, hubs, housings, shafts | Machined pressure-retaining parts |
Size range for P355QH1 forgings
We forge on 6,300 t, 4,000 t and 2,000 t hydraulic presses and roll rings on 6 m, 3 m and 1 m ring rolling mills. Steel is melted on site in heats of up to 60 t.
| Product | Size limit | Equipment |
|---|---|---|
| Seamless rolled rings | Up to 6,000 mm outside diameter | 6 m ring rolling mill |
| Discs, tube sheets, blocks | Up to Ø5,000 mm machined | Ø5,000 mm vertical turning lathe |
| Forged shafts | Up to Ø1,600 × 14,000 mm turned | Horizontal lathe; 15 m well-type furnaces for vertical quenching |
| Bored cylinders, hollow shafts | Up to Ø1,600 × 10,000 mm | CNC deep-hole drilling machine |
| Single-piece weight | Up to 30,000 kg | 6,300 t press; 60 t maximum heat |
Thicker sections cool more slowly during quenching, so EN 10222-4 sets a lower minimum yield strength for each heavier thickness band. Please give the ruling section in your enquiry so the property requirements can be agreed before forging.
Production route
All eight stages take place at our works, so every P355QH1 forging can be traced back to its melt number.
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Melting and ladle refining
Steel is melted in the electric arc furnace and refined in the ladle furnace, where sulphur is taken down and aluminium, niobium and vanadium are trimmed to the ordered edition of EN 10222-4. Where tight nitrogen control is needed, the heat is also decarburised under vacuum (VOD). The melt number assigned here stays on every record through to shipment.
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Chemistry check at the furnace
Cast analysis is verified at the furnace by optical emission spectrometry to ASTM E415 and infrared carbon–sulphur analysis to ASTM E1019, rather than taken from a supplier certificate.
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Open-die forging and ring rolling
The steel is cast into ingot, reheated and forged on the 6,300 t, 4,000 t or 2,000 t hydraulic press, targeting a forging ratio of at least 3:1 for sound, refined grain through the section. Hollow parts are punched and expanded over a saddle mandrel, and ring blanks continue to the 6 m, 3 m or 1 m ring rolling mill.
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Quenching and tempering
The forging is austenitized at 860–940 °C, quenched in water, polymer or oil, and tempered at 600–700 °C in the on-site heat-treatment shop.
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Mechanical testing
Test pieces are tensile tested on 600 kN and 300 kN machines to ISO 6892 and ASTM A370, and Charpy impact tested at the temperatures the order specifies. EN 10222-4 sets P355QH1 impact minimums down to −40 °C, and the laboratory tests down to −60 °C.
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Proof machining and ultrasonic testing
The forging is rough machined to a proof-machined condition and examined ultrasonically to EN 10228-3, or to ASTM A388 where specified. Magnetic particle testing to ASTM E709 is available for surface examination.
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Dimensional inspection and marking
Dimensions are checked against the drawing and recorded in a dimensional report, and the forging is marked for traceability to its melt number.
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Certification
An EN 10204 3.1 inspection certificate is issued as standard. An EN 10204 3.2 certificate witnessed by BV, DNV, LR, SGS, TÜV or the customer's own inspector is available on request. Heat-treatment charts, NDT reports, dimensional reports and PMI records are available as supporting records.
Applicable standards
| Standard | Title | Role for P355QH1 forgings |
|---|---|---|
| EN 10222-4:2017+A1:2021 | Steel forgings for pressure purposes, Part 4: Weldable fine grain steels with high proof strength | Defines the grade, chemistry, heat treatment and mechanical properties |
| EN 10222-1:2017 | Steel forgings for pressure purposes, Part 1: General requirements for open die forgings | Steelmaking, inspection, sampling, test methods, retests and marking |
| Directive 2014/68/EU | Pressure Equipment Directive (PED) | EN 10222-4 supports its essential safety requirements for material data (Annex ZA) |
| EN 10204 | Metallic products, types of inspection documents | 3.1 certificate as standard; 3.2 with a third-party witness |
| EN 10228-3 | Non-destructive testing of steel forgings, Part 3: Ultrasonic testing of ferritic or martensitic steel forgings | Internal soundness examination |
| EN 10229 | Evaluation of resistance of steel products to hydrogen induced cracking (HIC) | Optional test for sour (wet H₂S) service, agreed at order |
| EN 10027-1 and EN 10027-2 | Designation systems for steels: steel names and numerical system | The name P355QH1 and the number 1.0571 |
| EN 10020 | Definition and classification of grades of steel | Classifies P355QH1 as an alloy special steel |
| EN 10028-6 | Flat products made of steels for pressure purposes, Part 6: Weldable fine grain steels, quenched and tempered | Covers the plate counterpart P355QH (1.8867) |
P355QH1 vs P355NH and P285QH
Comparison with two related grades, based on Tables 1 and 2 of EN 10222-4:2017+A1:2021.
| Property | P355QH1 | P355NH | P285QH |
|---|---|---|---|
| Steel number | 1.0571 | 1.0565 | 1.0478 |
| EN 10020 class | Alloy special steel | Non-alloy quality steel | Non-alloy quality steel |
| Delivery condition | Quenched and tempered (+QT) | Normalized (+N) | Quenched and tempered (+QT) |
| Austenitizing or normalizing | 860–940 °C; water, polymer or oil | 880–960 °C; air | 860–940 °C; water, polymer or oil |
| Tempering | 600–700 °C | None | 600–700 °C |
| Thickness limit in Table 1 | None stated | Equivalent thickness below 40 mm | None stated |
| Carbon, max. | 0.18 % | 0.18 % | 0.18 % |
| Manganese | 0.90–1.50 % | 1.10–1.70 % | 0.80–1.50 % |
| Molybdenum, max. | 0.25 % | 0.08 % | 0.08 % |
| Nickel, max. | 0.50 % | 0.50 % | 0.30 % |
| Niobium + vanadium, max. | 0.12 % | 0.12 % | 0.05 % |
| Strength class | 355 MPa | 355 MPa | 285 MPa |
EN 10222-4 limits the normalized grades P355NH, P355NL1, P355NL2 and P420NH to an equivalent thickness below 40 mm, so heavier forgings in the 355 MPa class call for a quenched and tempered grade such as P355QH1. P285QH is the lower strength option. For low temperature service, the standard also includes the quenched and tempered grades P355QL1 (1.8868) and P355QL2 (1.8869).
Related datasheets: P355NH forgings, P355NL2 forgings and ASTM A350 LF2 forgings.
Enquiry checklist
We quote from a drawing or a written specification. If the enquiry is complete, we usually send a price within two working days.
| Item | Why we need it |
|---|---|
| Standard and edition | The 1998 and 2017+A1:2021 editions differ for carbon, silicon, manganese, sulphur, aluminium, nitrogen, copper, molybdenum and nickel |
| Drawing or dimensions, with the ruling section | The ruling section selects the minimum yield-strength band |
| Quantity and delivery date | Sets furnace batching and lead time |
| Delivery condition | As-forged, proof machined or finish machined to drawing |
| EN 10222-4 options | Elevated-temperature tensile test temperature, Charpy test temperature or values, aluminium maximum, sulphur up to 0.015 %, HIC test to EN 10229 |
| Ultrasonic testing | EN 10228-3 quality class, or ASTM A388 acceptance criteria |
| Inspection document | EN 10204 3.1, or 3.2 with the named inspection body |
| Destination | Port or delivery address for packing and shipping |
Minimum order is 10 kg, with no minimum number of pieces. Lead time is normally 20 to 60 days. P355QH1 does not need remelting, so it is usually at the lower end of that range. If third-party inspection is required, please mention it in the enquiry so it can be scheduled before shipment.
P355QH1 FAQ
What is P355QH1 steel?
P355QH1 (1.0571) is a quenched and tempered, weldable fine-grain steel for pressure equipment forgings, covered by EN 10222-4. Its tensile strength is 470–630 MPa and it has specified proof strength at elevated temperature. Common parts are tube sheets, girth flanges, nozzles, rings and shells for pressure vessels and heat exchangers.
What does P355QH1 stand for, and what is its material number?
Under the EN 10027-1 naming system, P means a steel for pressure purposes, 355 is the minimum yield strength in MPa for the thinnest section range, Q means quenched and tempered, and H means properties are specified at elevated temperature. The steel number, or Werkstoffnummer, is 1.0571.
Is P355QH1 an alloy steel or a carbon steel?
EN 10222-4:2017+A1:2021 classifies P355QH1 as an alloy special steel under EN 10020. Older datasheets based on the 1998 edition list it as a non-alloy steel. Its carbon is limited to 0.18 %, with 0.90–1.50 % manganese and small allowances for molybdenum, nickel, niobium and vanadium.
What is the difference between P355QH1 and P355NH?
Both are 355 MPa grades in EN 10222-4. P355NH (1.0565) is normalized at 880–960 °C and cooled in air, while P355QH1 (1.0571) is quenched from 860–940 °C and tempered at 600–700 °C. EN 10222-4 limits P355NH to an equivalent thickness below 40 mm, so heavier forgings in this strength class call for P355QH1. P355QH1 also allows up to 0.25 % molybdenum, against 0.08 % for P355NH.
Is P355QH1 the same as P355QH?
No. P355QH1 (1.0571) is the forging grade of EN 10222-4, while P355QH (1.8867) is the quenched-and-tempered plate grade of EN 10028-6. They share the 355 MPa strength class and the quenched-and-tempered condition, but their chemistry limits and testing follow different standards.
Is there an ASTM equivalent to P355QH1?
There is no direct ASTM or ASME equivalent. ASTM A350 LF2 and ASTM A105 are sometimes cross-referenced, but their chemistry limits, heat treatment, impact requirements and elevated-temperature design data differ from EN 10222-4. Substituting one for the other needs approval from the purchaser and the equipment designer.
What heat treatment does P355QH1 require?
P355QH1 forgings must be delivered quenched and tempered. EN 10222-4 sets austenitizing at 860–940 °C, quenching in water, polymer or oil, and tempering at 600–700 °C. The standard gives no normalized delivery option for this grade.
What impact energy must P355QH1 reach at −40 °C?
EN 10222-4 requires at least 34 J Charpy V-notch impact energy (KV2) at −40 °C on longitudinal test pieces. The other longitudinal minimums are 63 J at +20 °C, 55 J at 0 °C and 47 J at −20 °C. Transverse minimums are 40 J, 34 J and 27 J at the same three temperatures.
What changed for P355QH1 in EN 10222-4:2017+A1:2021?
Compared with the 1998-edition values in many datasheets, the current edition lowers maximum carbon from 0.20 % to 0.18 %, sulphur from 0.015 % to 0.010 % and nitrogen from 0.020 % to 0.015 %. It raises the molybdenum allowance from 0.08 % to 0.25 % and nickel from 0.30 % to 0.50 %, and classifies P355QH1 as an alloy special steel. A sulphur maximum of up to 0.015 % may still be agreed at order.
Who manufactures P355QH1 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. manufactures P355QH1 (1.0571) forgings to EN 10222-4 at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The company was founded in 1997, melts its own steel, forges, heat treats, machines and tests on one site, and holds CCS, BV, DNV, LR and NK approvals. Contact sales@steelforgepieces.com or +86 189 2135 9659.
What certificate comes with P355QH1 forgings?
We supply an EN 10204 3.1 inspection certificate as standard, traceable to the melt number, with heat-treatment charts and NDT reports as supporting records. An EN 10204 3.2 certificate witnessed by BV, DNV, LR, SGS, TÜV or the customer's inspector is available on request.
What sizes, minimum order and lead time apply to P355QH1 forgings?
We forge single pieces up to 30 t, roll rings up to 6,000 mm outside diameter and machine discs and tube sheets up to 5,000 mm in diameter. Minimum order is 10 kg, with no minimum number of pieces. Lead time is 20 to 60 days, usually at the lower end for P355QH1. As a guide, a 2,000 mm diameter tube sheet blank 200 mm thick weighs about 4.9 t.
Glossary
- Weldable fine-grain steel
- Steel refined with aluminium and elements such as niobium and vanadium to give a fine grain. The fine grain provides strength and toughness at a low carbon content, so the steel stays weldable.
- Quenched and tempered (+QT)
- Hardened by rapid cooling from the austenitizing temperature, then reheated below the transformation range to restore toughness and set the final strength.
- Ruling section (equivalent thickness, teq)
- The section thickness that governs the cooling rate in heat treatment, derived from the forging's shape according to EN 10222-1. It decides which property band applies.
- ReH, Rm and Rp0.2
- Upper yield strength, tensile strength and 0.2 % proof strength. For P355QH1, Rp0.2 is specified at temperatures from 50 °C to 400 °C.
- KV2
- Energy in joules absorbed when a Charpy V-notch test piece is broken with a 2 mm striker, as defined in EN ISO 148-1.
- Cast analysis
- The chemical composition of the liquid steel, taken from a sample during casting. EN 10222-4 limits apply to it, with product-analysis tolerances in Table 3 of the standard.
- EN 10204 3.1 and 3.2
- A 3.1 inspection certificate is issued by the manufacturer's inspection department, independent of production. A 3.2 certificate is also validated by the purchaser's inspector or an inspection body named in the order.
- Hydrogen-induced cracking (HIC)
- Internal cracking of steel exposed to wet hydrogen sulphide, known as sour service. A test to EN 10229 may be agreed for P355QH1 forgings in that service.