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DIN 17155 HII is a carbon-manganese steel for boiler and pressure-vessel service. The name tells you its job: the H marks it as a warmfest (“elevated-temperature”) quality steel in the DIN 17155 system, and II is the higher-strength of the two basic unalloyed grades (the other being HI). Its German material number is 1.0425. It is the workhorse plate you reach for when a boiler shell, a pressure vessel or a heat exchanger has to carry pressure at moderately elevated temperature, where the steel keeps its strength and welds cleanly.
DIN 17155 has been withdrawn and the grade carried forward into EN 10028-2 as P265GH — identical material number 1.0425, essentially the same chemistry and strength. BBN supplies the plate (normalised) and cuts and processes it for boiler and pressure-equipment fabrication; most new enquiries now reference P265GH, but both names reach the same heat. Note: HII is a pressure-vessel steel, not a gas-cylinder grade — portable gas cylinders use dedicated grades such as EN 10120 P245NB / P265NB.
410-530 MPaTensile Strengthmin-max band, not a single value
265 MPa minYield Strengthup to 16 mm; steps down with thickness
1.0425 / P265GHMaterial No. & EN GradeDIN 17155 carried into EN 10028-2
02Technical Specifications
What this page publishes, and what must be confirmed on the mill certificate when you enquire.
Item
Specification
Executive Standard
DIN 17155 (weldable steels for pressure vessels, elevated-temperature quality). The standard is withdrawn; the grade is now supplied to EN 10028-2 as P265GH. German material number 1.0425
Steel Grade
HII (DIN 17155); P265GH (EN 10028-2)
Steel Category
Non-alloy (carbon-manganese) boiler & pressure-vessel steel for elevated-temperature service
Product Form
Hot-rolled plate, supplied normalised; also available as sheet for forming into shells and drums
Thickness Range
Confirmed with the mill per rolling programme; the published mechanical values cover the standard thickness scope (up to 150 mm)
Width & Length
Per mill rolling programme; cut-to-length and cut-to-shape available
Carbon Equivalent (Ceq)
Low — it is a C-Mn steel, not an alloy grade; preheat is driven by thickness and welding process, not by high alloying. Confirm per WPS
MOQ
1 ton (mixed sizes negotiable)
Lead Time by Quantity
1 – 10 t: about 5 days; 10 – 50 t: about 10 days; > 50 t: negotiable
EN 10204 3.1 / 3.2; tensile, impact, UT, HIC / SSC on request
HII is a standard grade, but only its tested values are guaranteed. DIN 17155 (and the EN 10028-2 P265GH replacement) fix the chemistry limits and the tensile / yield / elongation floor. Actual heat analysis and mechanical results are recorded on the EN 10204 certificate of the lot you buy — confirm the exact figures against that document.
03How to Read the Grade
Every part of HII is a specification, not a marketing name.
Part
Meaning
H
Warmfest (“elevated-temperature”) quality steel in the DIN 17155 system — a steel qualified for pressure-bearing service at moderately elevated temperature, not a creep-resistant alloy steel
I / II
The two basic unalloyed grades of the system; II is the higher-strength of the two (HI is the lower). Higher-Mn and alloyed DIN 17155 grades continue as 17Mn4, 19Mn6, 15Mo3, 13CrMo44, 10CrMo910
1.0425
The German material number (Werkstoffnummer) — the unambiguous way to call up this exact steel in European procurement; identical for EN 10028-2 P265GH
04Equivalent Grades
HII is the higher-strength of the two unalloyed DIN 17155 boiler steels, now carried into EN 10028-2 as P265GH. The table maps it to its modern EN form and to the closest siblings — every linked grade opens its own page.
Pick the grade by the temperature and thickness your design demands. HII / P265GH is the general-purpose carbon-manganese boiler and pressure-vessel steel. If the duty is thicker or hotter, move up to a higher-Mn grade such as 17Mn4 / 19Mn6 or a low-alloy grade such as 16Mo3 (0.5Mo) or 13CrMo44 (1Cr-0.5Mo). Tell us the design temperature and thickness and we will point to the right grade — and remind us if you are really after a gas-cylinder grade (EN 10120 P245NB / P265NB), which HII is not.
05Chemical Composition
Ladle (cast) analysis limits in weight percent, per DIN 17155 HII (the same grade is carried into EN 10028-2 P265GH with tighter P/S and a slightly wider Mn range). Product-analysis tolerances apply when ordered.
Element
Limit (% by mass)
C
≤ 0.20
Si
≤ 0.35
Mn
0.50 – 1.30
P
≤ 0.035
S
≤ 0.030
Al
≥ 0.02 (total, grain-refining)
Cr
≤ 0.25
Cu
≤ 0.30
Ni
≤ 0.30
Mo
≤ 0.10
Nb
≤ 0.01
Ti
≤ 0.03
V
≤ 0.03
This page publishes the standard DIN 17155 HII chemistry. The grade is a plain carbon-manganese steel — no chromium, molybdenum or nickel alloying is required (only residual limits). The EN 10028-2 P265GH replacement keeps the same C/Mn/Si picture but tightens phosphorus to ≤0.025 and sulphur to ≤0.015 and widens Mn to 0.80-1.40; the limits above are the DIN 17155 values, and your certificate shows what the heat actually made.
06Mechanical Properties
Minimum room-temperature values in the normalised condition, read against nominal thickness. Every figure is a floor the heat is tested against — not a prediction of your certificate.
Thickness (mm)
Yield ReH min (MPa)
Tensile Rm (MPa)
Elongation A min (%)
6 – 16
265
410 – 530
22
16 < t ≤ 40
255
410 – 530
22
40 < t ≤ 60
245
410 – 530
22
60 < t ≤ 100
215
410 – 530
22
100 < t ≤ 150
200
400 – 530
22
Two corrections against some supplier pages. First, the defining job of this grade is boiler and pressure-vessel service — an older listing described HII as “the most popular steel for gas cylinder manufacture”, which is wrong; HII is not a gas-cylinder grade (those are EN 10120 P245NB / P265NB, JIS G3116, GB/T 6653). Second, the standard gives the yield floor in thickness bands (265 MPa up to 16 mm, stepping down to 200 MPa at 100-150 mm), not a single value. The EN 10028-2 P265GH replacement keeps the same banding shape with slightly higher values for thicker sections; treat the table above as the DIN 17155 HII data and confirm the exact band for your thickness on the certificate.
07Heat Treatment & Delivery Condition
The condition is what makes the steel fine-grained and weldable — normalised.
Item
Requirement
Remarks
Delivery Condition
Normalised (N)
DIN 17155 HII / EN 10028-2 P265GH are supplied normalised; the normalising refines the grain so the plate welds cleanly and keeps its toughness
Steelmaking
KilledFine-grain practice
Aluminium grain-refined (Al total ≥ 0.02 %); low residual S and controlled inclusions
Hot forming
Within 850 – 1100 °C
Heavy hot forming (rolling a shell, pressing a head) can coarsen the grain; re-normalising or normalising + stress-relieving restores the condition
Welding preparation
Preheat as required
A low-carbon C-Mn steel; preheat driven by thickness and process, PWHT / stress relief as the code requires
The condition has to survive fabrication. Normalised plate keeps its properties through normal cutting and welding, but heavy hot forming or a stress-relief cycle moves those properties. Where the part will be hot formed or stress relieved, test coupons go through a simulated post-weld heat-treatment (PWHT) cycle and are tested afterwards, so the certificate reflects the condition the component will actually be in. Say at enquiry stage whether the plate will be hot formed or PWHT-treated — it changes what we have to certify.
08What This Steel Has to Prove
Six items come up again and again on a boiler / pressure-vessel enquiry. None is automatic — each has to be named on the order.
UTinternal soundness
Ultrasonic examination
Pressure-bearing plate is examined ultrasonically to EN 10160 (or EN 10228 / customer spec) so the full section is sound. It is the line most often left off an enquiry and the one that matters most once the part is welded into a seam that cannot be repaired from inside.
HTat temperature
Elevated-temperature property
HII is a warmfest (elevated-temperature) grade; for elevated-temperature design the property at temperature is what the vessel is built on. State the design temperature so the right band and any temperature-dependent acceptance are applied.
HIC/SSCsour service
Hydrogen-induced / sulphide-stress cracking
Although HII is a C-Mn grade (not low-alloy), it is regularly specified for wet-H2S / sour refinery and petrochemical service, where HIC and SSC testing to NACE MR0175 / ISO 15156 or NACE MR0103 is added on top of controlled cleanliness. This has to be raised at enquiry: it changes the steel route as well as the testing.
PWHTafter heat treatment
Simulated post-weld heat treatment
Pressure parts are almost always welded and then stress relieved, and the properties have to survive that. Coupons are put through a simulated PWHT cycle and tested afterwards, so the certificate shows the condition the part will actually see rather than the as-delivered one.
CVNtoughness
Charpy V-notch impact
HII / P265GH is a strength grade; impact testing is not a default requirement and must be specified by the order (temperature and acceptance value). It is commonly added for low-temperature start-up or storage and for sour-service qualifications.
3.2documentation
Traceability and EN 10204 certification
Standard supply is a mill test certificate to EN 10204 type 3.1 giving heat number, chemical analysis and mechanical results for the actual heat delivered, with the plate marked so it can be traced through fabrication. Where the project asks for independent verification, type 3.2 with third-party witness — SGS, BV, Lloyd’s, DNV or your own inspector — is arranged with the order.
None of this turns the page into a code book. Which of these tests applies, at what acceptance level and at what sampling frequency, is set by your purchase specification and the code you build to — not by us, and not by the tables above.
09Typical Applications
Where a carbon-manganese boiler and pressure-vessel steel carries the load.
Boiler Shells & Drums
Shell courses, drums and headers for utility and industrial boilers operating at elevated temperature — the original DIN 17155 application for this grade.
Pressure Vessels
Reactors, separators and process columns in high-pressure, elevated-temperature or sour service, built to a pressure-equipment code.
Heat Exchangers
Shells and channels for elevated-temperature heat transfer, where the C-Mn chemistry keeps its strength and weldability.
Storage Tanks
Pressure storage for gases and liquids where a fine-grain normalised C-Mn plate gives clean welding and reliable service.
Petrochemical Plant
Process equipment, separators and piping in oil, gas, chemical and power generation where moderate temperature and sour-service options matter.
Selection advice: choose HII / P265GH when the design is a general-purpose boiler or pressure vessel at moderately elevated temperature and a carbon-manganese steel is enough. If the duty is thicker or hotter, step up to 17Mn4 / 19Mn6 or a low-alloy grade such as 16Mo3 or 13CrMo44; if you actually need a portable gas cylinder, that is a different family (EN 10120 P245NB / P265NB) — tell us the application and we will steer you to the right grade.
10Processing, Testing & Supply
From plate to a cut, certified, ready-to-fit pressure part.
1
Cutting & Edge Prep
Flame, plasma or laser cutting to drawing or a nesting layout, with weld-edge bevels prepared to the joint detail you are fabricating.
2
Forming
Rolling to shell-course or drum radius and press forming of head blanks, cold where the thickness allows; heavy hot forming followed by re-normalising or normalising + stress-relieving to restore the condition.
3
Heat-Treatment Verification
Simulated PWHT and (where ordered) impact coupons tested, so the certificate reflects the post-fabrication condition, not just the as-delivered one.
4
Inspection & Certified Delivery
UT, impact where required, HIC / SSC testing for sour service, and surface inspection; EN 10204 3.1 with heat-number traceability, 3.2 or third-party witness arranged on request.
Quote checklist — faster if you send: the standard and edition (DIN 17155 HII or EN 10028-2 P265GH), the material number (1.0425), thickness, width and length, quantity, the design temperature, any sour-service / HIC requirement, the certification type, and the destination port.
11Frequently Asked Questions
Q1What does DIN 17155 HII actually mean?
HII is a carbon-manganese steel for boiler and pressure-vessel service. The H marks it as a warmfest (elevated-temperature) quality in the DIN 17155 system, and II is the higher-strength of the two basic unalloyed grades (the other being HI). Its German material number is 1.0425, and the same grade is carried forward into EN 10028-2 as P265GH.
Q2Is HII the same as P265GH?
Effectively yes for procurement. HII is the old DIN 17155 designation and P265GH is the current EN 10028-2 designation for the identical steel, both carrying material number 1.0425 and essentially the same chemistry and strength floor (P265GH tightens P/S and widens Mn slightly). DIN 17155 has been withdrawn, so most new enquiries reference P265GH; both names reach the same heat.
Q3What is HII equivalent to in JIS / ASTM?
The Japanese equivalent is JIS G3103 SB410. In the US system the nearest grades are ASTM A516 Grade 60 and ASTM A285 Grade C (approximate — equivalence is for procurement mapping only; confirm the actual strength and toughness values against your code). Other historical cross-references include NFA 36-205 A 42 CP, BS 1501 161/164/224 Gr. 400 and UNI 5869 Fe 410-1KW.
Q4Can HII be welded?
Yes — it is a readily weldable carbon-manganese steel. Because it is low-carbon and fine-grain (aluminium-refined), normal preheat for the thickness and a qualified WPS with low-hydrogen consumables are usually enough; post-weld heat treatment (PWHT) / stress relief is applied as the fabrication code requires. Agree the preheat and PWHT with whoever is responsible for the component.
Q5What thickness, how fast, what paperwork?
From 1 ton, with typical lead times of about 5 days for 1–10 t, about 10 days for 10–50 t and negotiable above 50 t. Each heat ships with an EN 10204 3.1 mill test certificate carrying ladle analysis and mechanical results; 3.2 or third-party inspection can be arranged on request.
Q6Your old page called this a gas-cylinder steel — is that right?
No. The figures and wording on this page are corrected against DIN 17155 and the EN 10028-2 P265GH replacement. An older listing described HII as “the most popular steel for gas cylinder manufacture” — but HII is a boiler and pressure-vessel carbon-manganese steel, not a gas-cylinder grade (those are EN 10120 P245NB / P265NB, JIS G3116, GB/T 6653). We also publish the material number 1.0425 and the fact that DIN 17155 has been withdrawn and replaced by EN 10028-2, neither of which the old page stated. The corrected chemistry, mechanical values and cross-references are published above with note boxes flagging each change.
Sources and limits: the figures on this page are reference information drawn from DIN 17155 (HII, material no. 1.0425) and the EN 10028-2 replacement P265GH, and published steel data sheets. HII / P265GH is a carbon-manganese boiler and pressure-vessel steel; the chemistry limits and the tensile/yield/elongation floor are the standard requirements, while actual heat values are recorded on the EN 10204 certificate of the lot supplied. Older listings of this grade mislabelled it as a gas-cylinder steel and omitted the material number and the DIN 17155 → EN 10028-2 replacement — we have corrected those against the standard. BBN supplies, cuts and processes the plate.
Get Your DIN 17155 HII / P265GH Quotation Now
Send us your standard and edition (DIN 17155 HII or EN 10028-2 P265GH), material number (1.0425), thickness, width and length, quantity, design temperature and any sour-service / HIC requirement. We will reply with what the mill can roll and certify at that thickness, plate or cut-length options, mill price and production lead time — and tell you plainly if a higher grade (17Mn4, 16Mo3, 13CrMo44) would better suit a hotter or thicker duty, or if you actually need a gas-cylinder grade (EN 10120 P245NB / P265NB).
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