EN 10028-7 X5NiCrAlTi31-20 1.4958 Pressure Vessel Stainless Plate

EN 10028-7 X5NiCrAlTi31-20 (1.4958) is a creep-resisting austenitic steel for high-temperature pressure parts, listed in EN 10028-7:2016 for flat products used in pressure equipment. It is delivered solution annealed (+AT) as hot-rolled plate (P) up to 75 mm, and plate in that condition has a minimum 0.2% proof strength of 170 MPa with a tensile strength of 500 – 750 MPa (Table 9). Its nearest ASTM counterpart is 800H, but the two specifications are not identical.

X5NiCrAlTi31-20 1.4958 is described by two designations: the steel name X5NiCrAlTi31-20, which is built from the carbon content (in hundredths of a percent) and the main alloying elements with their approximate percentages, and the steel number 1.4958, which is the five-digit material number used throughout European standards. EN 10028-7 is Part 7 of the EN 10028 series, the harmonized European standard for flat steel products for pressure purposes, and the part that covers stainless steels. Plate certified to it can be used under the Pressure Equipment Directive 2014/68/EU and design codes such as EN 13445, which is why every X5NiCrAlTi31-20 pressure vessel plate we ship is tested to the 2016 edition.

X5NiCrAlTi31-20 is a 31Ni-20Cr alloy with aluminium and titanium, the European counterpart of Alloy 800H. EN 10028-7 lists it in two conditions: solution annealed (+AT) for creep service and recrystallizing annealed (+RA) with higher proof strength for lower temperatures.

SHH STEEL is a stainless steel producer and exporter based in Shanghai. We act as sales agent for well-known mills, run our own processing warehouse for cutting, bevelling and polishing, and ship every EN 10028-7 stainless plate with EN 10204 3.1 or 3.2 certificates. Buyers who already know the ASTM grade can compare this page with our ASTM A240 Type 800H page, and related grades sit in our pressure vessel steel plates.

Why designers specify 1.4958

Material selection for a pressure vessel starts from the design conditions: medium, design temperature, pressure and the minimum design metal temperature. Creep-resisting grades are chosen when the design temperature is high enough that time-dependent strength (creep), not short-term proof strength, governs the wall thickness. Because X5NiCrAlTi31-20 is a harmonized EN 10028-7 grade, its proof strength values can be used directly for the nominal design stress in EN 13445-3, without a particular material appraisal, which shortens approvals on CE-marked equipment.

In short, EN 10028-7 1.4958 is the pressure-equipment certification of X5NiCrAlTi31-20; outside pressure equipment the same steel is sold to EN 10088-2. The specification of 1.4958 is the set of requirements in EN 10028-7:2016 that a plate must meet before it can be certified for pressure equipment. The summary below gives the clauses and tables that apply to this grade.

EN 10028-7 does not repeat the general delivery rules: it refers to EN 10028-1 for general requirements, to EN 10088-1 for physical properties, and to the EN ISO tolerance standards listed above. The maximum thicknesses in the table are those for which Table 9 gives mechanical property values; thicker material can be produced by some mills, but it falls outside the standard and the properties must be agreed separately.

Scope in plain terms

The standard covers flat products in the form of plate, sheet and strip. Product form C is cold-rolled strip and the sheet cut from it, form H is hot-rolled strip and the sheet or plate cut from it, and form P is hot-rolled plate rolled individually on a plate mill. This grade is listed only in form P, so very thin gauges are not available as an EN 10028-7 product. The process route (1D, 2B and so on) must be named on the order, because the standard leaves the surface condition open.

The 1.4958 chemical composition is the cast (heat) analysis reported by the steelmaker for each heat, and it must fall within EN 10028-7:2016 Table 3. Values are in percent by mass; a single value is a maximum unless marked otherwise.

Product analysis tolerances (Table 5)

The product analysis is the composition measured on the finished plate. EN 10028-7 Table 5 sets how far it may deviate from the cast limits; the deviations below are applied to the X5NiCrAlTi31-20 limits of Table 3.

The footnote to Table 5 matters for acceptance: if several product analyses are made on one cast, an element may lie above the maximum or below the minimum of the range, but not both. Calculated from the minimum chemistry, PREN = Cr + 3.3Mo + 16N gives about 19.0 for 1.4958, a ranking value used for pitting resistance.

Product analysis is a check analysis made on a sample taken from the delivered plate, and under EN 10028-7 it is carried out only when the purchaser requests it at the time of ordering (Table 16). The cast analysis is always reported.

When a product analysis is agreed, the order should state the number of samples and the elements to be determined. Samples are taken through the thickness or from millings so the result represents the whole cross-section, and the analysis method follows the reference methods cited by EN 10028-1. Results are judged against the cast limits widened by the Table 5 deviations shown above; a result outside those limits normally leads to retests on further samples before a plate or a test unit is rejected.

PMI and laboratory checks at SHH STEEL

Every plate that leaves our Shanghai warehouse is checked by positive material identification (PMI) with a handheld XRF analyser, which confirms chromium, nickel, copper and the other heavier elements. XRF cannot measure carbon, nitrogen or boron, so when those elements decide the grade, we arrange spark-OES or combustion analysis through our steel testing service. Product analysis results are added to the 3.1 certificate, or reported by the inspector on a 3.2 certificate.

Why the check matters

Mixed-up plates are a real risk in stock-holding: an 18-8 grade and a molybdenum or stabilized grade look identical, and grades in the same family differ only by a few tenths of a percent. A product analysis or PMI record ties the physical plate to the certificate and protects the fabricator at the notified-body inspection.

The 1.4958 mechanical properties are the room-temperature minimum values in EN 10028-7:2016 Table 9 for material in the solution annealed (+AT) condition. Unlike ASTM A240, EN 10028-7 gives a separate row for each product form, so the rolling route matters as much as the thickness.

Impact energy and intergranular corrosion

Table 9 also sets Charpy V-notch impact energy and states whether the grade resists intergranular corrosion when tested to EN ISO 3651-2.

For comparison, the American plate specification ASME SA240 800H uses a single set of minimums for all thicknesses, so a plate that meets one standard does not automatically meet the other. Dual certification is common, but each value must be tested and reported against each standard.

How designers use these values

Under EN 13445-3 the nominal design stress of an austenitic steel with A ≥ 35% is based on the 1% proof strength: the greater of Rp1.0/1.5 and the lower of Rp1.0/1.2 and Rm/3 at the calculation temperature; for the other stainless classes it follows from Rp0.2 and Rm with the safety factors of the code. The room-temperature values above are therefore only the starting point; for operation above 50 °C the elevated-temperature values in the next section are used.

1.4958 solution annealing is the delivery heat treatment of X5NiCrAlTi31-20: Annex A of EN 10028-7 recommends 1 100 – 1 200 (+AT); 920 – 1 000 (+RA) °C followed by cooling in water or air, cooling fast enough to avoid precipitation. Hot forming is carried out in the range of about 1 150 – 850 °C. The treatment dissolves carbides and intermetallic phases, restores full corrosion resistance and gives the soft, ductile austenite that the tensile values assume. Annex A values are guidelines; the actual temperature and cooling method are recorded on the mill certificate.

The grade can also be delivered recrystallizing annealed (+RA) at 920 – 1 000 °C, which gives a finer grain and higher proof strength (210 MPa for plate) for service below the creep range; the solution annealed (+AT) condition is used where creep strength governs.

Heat treatment after fabrication

Annex B of EN 10028-7 covers post-weld and post-forming heat treatment. For austenitic grades it is generally not required; where hot forming or heavy cold forming makes it necessary, a full solution anneal is preferred to stress relieving, because holding in the range of about 500 – 900 °C can cause carbide or sigma precipitation. Cold-formed heads and shells are checked against the forming-strain limits of the design code (for example EN 13445-4), which decide whether a heat treatment is needed.

What can go wrong

An incorrectly heat-treated plate shows up as high hardness, low elongation or poor impact energy, and in corrosion tests as intergranular attack. Slow cooling through about 850 – 450 °C allows chromium carbides to form at grain boundaries in non-stabilized grades. When plate arrives in our warehouse we check the heat-treatment record on the certificate against Annex A and the tensile results before releasing it.

The 1.4958 elevated temperature properties below are an essential input for hot equipment. Elevated-temperature properties are the minimum proof strengths that EN 10028-7 gives at temperatures above room temperature, and they are the values a designer uses to calculate the wall thickness of 1.4958 equipment operating hot.

For the recrystallizing annealed (+RA) condition the 0.2% / 1% proof strengths are:

Proof-strength values follow Table 13 and tensile values Table 15 of EN 10028-7; the 50 °C values are marked in the standard as determined by linear interpolation, and a dash means no value is given. We cross-checked the 2016 values against the 2007 tables, and they agree over the lower temperature range; above that range we quote the table values as published and recommend confirming critical design values against the edition named in the contract.

Creep data

Annex D of EN 10028-7 gives informative creep data (1% creep strain and creep rupture strength for 10 000 and 100 000 hours) for the creep-resisting grades, including 1.4958. Those values, not the short-term proof strengths, govern the design above the creep threshold, typically above about 550 – 600 °C for these steels. Because Annex D is informative, the design code and the project specification decide which values are used. This is the main reason buyers order 1.4958 creep resistant plate rather than a standard corrosion-resisting grade.

A X5NiCrAlTi31-20 equivalent is a grade in another standard with similar chemistry and properties; it is a comparison, not an interchangeable certificate.

On 1.4958 vs 800H: the chemistry ranges overlap, but EN 10028-7 sets its own limits, its own strength values per product form and its own impact requirements. On steelspecs.com you can compare the related pages ASTM A240 Type 800 and ASME SA240 800. For background reading, see our plate processing techniques guide.

Substitution rules

Replacing 1.4958 with a foreign grade in PED equipment needs the agreement of the designer and, where applicable, the notified body, usually through a particular material appraisal. The reverse also applies: an ASME vessel cannot simply use EN 10028-7 plate without the code’s material rules. Where both certificates are needed, we can often arrange dual certification at the mill, provided both sets of chemistry and property limits are met in one heat.

Welding of X5NiCrAlTi31-20 is done by GTAW, SMAW, GMAW, FCAW or SAW with nickel-base ERNiCr-3 or matching filler. No preheat is needed; interpass temperature is kept below about 150 °C and heat input moderate to limit distortion and hot cracking. Pickling and passivation after welding restore the passive film in corrosive service.

Weld procedures for PED equipment are qualified to EN ISO 15614-1, and welders to EN ISO 9606-1. Where a fabricator lacks capacity, our welding team and partner workshops can prepare bevels and sub-assemblies. Our power and energy sector page shows the type of projects we supply.

Practical welding notes

• Clean the joint with stainless-only brushes and solvent; iron contamination leaves rust spots.
• Back purge root passes with argon to avoid heavy oxidation.
• Keep a small ferrite content in Cr-Ni weld metal to avoid hot cracking, unless fully austenitic weld metal is required for corrosion or cryogenic toughness.

Forming and cutting

Austenitic plate work-hardens quickly during cold forming, so press capacity must allow for it; plasma, laser and waterjet cutting are all suitable, and heat-tinted edges should be ground before welding.

Corrosion resistance is the ability of the plate to stay passive in the process medium, and 1.4958 is chosen for strength at temperature; its wet corrosion resistance is comparable to the corresponding corrosion-resisting grade, while high chromium gives good oxidation resistance. Its minimum PREN is about 19.0.

The intergranular corrosion entries of Table 9 (yes in the delivery condition, no in the sensitized or welded condition) tell the designer whether welds can be left without heat treatment. Austenitic steels of this alloy level can suffer chloride stress-corrosion cracking above about 50 – 60 °C; where that risk exists, duplex or higher-nickel grades are often preferred. For comparison of pitting resistance across standards, see our ASTM A240 Type 310H page.

Media guide

The table is general guidance. Final material selection should be based on the actual medium, temperature and concentration, and where possible on plant experience or corrosion testing.

Applications of X5NiCrAlTi31-20 follow from its creep strength at high temperature. As a austenitic stainless steel plate certified to EN 10028-7, it is used for:

• Steam reformer and cracking equipment
• Heat exchangers and headers above 600 °C
• Heat-treatment and furnace equipment
• Petrochemical high-temperature vessels

Selection guidance by application

For storage tanks and low-pressure vessels the choice is usually driven by corrosion resistance and price, and plate thickness is moderate. For high-pressure or large-diameter vessels strength becomes important, and nitrogen-alloyed or duplex grades can reduce the wall thickness. For heat exchangers, the shells, channels and tube sheets often use different grades, and we can supply all of them in one order with consistent certification.

Every 1.4958 stainless steel plate supplied for these duties is traceable to its heat, which is essential for CE marking under the PED.

Comparing 1.4958 with its neighbours in EN 10028-7 shows where it fits: the differences come down to carbon, nitrogen, molybdenum and the stabilizing elements.

How to choose

Start from the corrosion requirement and the design temperature, then compare strength, availability and cost. Among the creep-resisting grades, 1.4948 is the basic 18-10 choice, 1.4941 and 1.4961 are stabilized, 1.4910 adds molybdenum, nitrogen and boron, 1.4950 and 1.4951 give higher oxidation resistance, and 1.4958 and 1.4959 cover the highest temperatures. Our engineers can review your design conditions and suggest the most economical grade. A related grade page on our site is AISI 310S.

The dimensions of 1.4958 plate are limited by the product forms that EN 10028-7 lists for the grade and by the rolling capacity of the mill.

Weight per square metre is the thickness in millimetres multiplied by the density in g/cm³: with a density of about 7.9 – 8.0 g/cm³, a 10 mm plate weighs roughly 79 – 81 kg/m². Lengths are cut to order or supplied as mill lengths; for heads and dished ends we can supply circular blanks cut to the developed diameter.

Tolerance and flatness notes

For plate (form P), EN ISO 18286 gives thickness tolerance classes A to D and flatness classes; class B is a common choice for pressure vessels because it limits the negative tolerance. For strip and sheet cut from coil, EN ISO 9445-2 and EN ISO 9444-2 apply, and normal or special tolerances can be ordered. State the class on the order, since it decides the acceptance criteria.

Surface finish is the process route defined by the EN 10088-2 codes that EN 10028-7 Table 6 uses, and it must be named on the order for 1.4958.

We offer steel cutting services and surface finishing in our Shanghai warehouse, along with plate bending and forming service and protective PE film.

Choosing a finish

1D is the standard finish for hot-rolled pressure vessel plate and suits shells, heads and parts that will be pickled after fabrication. Cold-rolled 2B is used for thin vessels, liners and parts where a smoother surface helps cleaning. Polished finishes are specified for hygienic vessels in food and pharmaceutical plants, where surface roughness limits are part of the design.

Testing and certification of 1.4958 follow EN 10028-7 Table 16 and EN 10028-1: each test unit is plate from the same cast, the same thickness range and the same heat-treatment batch.

• Cast analysis on every heat; product analysis when ordered (Table 16)
• Tensile test at room temperature per test unit, to EN ISO 6892-1, against Table 9
• Charpy V-notch impact test where the order or the design requires it; Table 16 makes it mandatory for austenitic products over 20 mm intended for cryogenic service
• Tensile test at elevated temperature by agreement (verification of Rp0.2 or Rp1.0)
• Intergranular corrosion test to EN ISO 3651-2 by agreement
• Visual and dimensional inspection; ultrasonic testing by agreement
• 100% PMI and dimensional check by SHH STEEL
• EN 10204 3.1 inspection certificate; 3.2 with a third-party or purchaser’s inspector

Third-party inspection

For export and PED projects a 3.2 certificate is often required. An independent inspector then witnesses sampling and testing at the mill and countersigns the certificate. We coordinate SGS, BV, TUV, Lloyd’s or a client-named inspector and schedule witness points so inspection does not delay rolling. In our warehouse we check dimensions, flatness, surface and marking, and repeat PMI on each plate before packing.

For PED equipment in categories II to IV, EN 10028-7 plate is normally supplied with a 3.1 certificate issued by a manufacturer with a quality system assessed by a competent body; check the requirement with your notified body.

An order for X5NiCrAlTi31-20 should identify the product, the standard and every option the standard leaves to agreement. The ordering example in EN 10028-7 follows a pattern like this:

10 plates, 8 × 2000 × 5000 mm, EN ISO 18286 tolerance class B, steel EN 10028-7 – X5NiCrAlTi31-20 (1.4958)+AT, process route 1D, inspection certificate EN 10204 – 3.1.

• Standard and edition: EN 10028-7:2016
• Steel name or number: X5NiCrAlTi31-20 / 1.4958 and heat-treatment condition
• Product form (P), thickness, width, length and quantity
• Tolerance standard and class
• Process route / surface finish (Table 6)
• Optional tests: product analysis, impact at a stated temperature, IGC, elevated-temperature tensile, UT
• Inspection document: EN 10204 3.1 or 3.2, and the inspector for 3.2

Common ordering mistakes

• Ordering to EN 10088-2 instead of EN 10028-7 for pressure parts; EN 10088-2 plate is not certified for pressure purposes.
• Leaving out the process route, which the standard requires on the order.
• Not stating optional tests, which are only carried out if written into the contract.
• Specifying a thickness beyond the limit of the product form.

A short technical review before order placement avoids these problems, and our sales engineers do this as part of the quotation.

Mill sourcing for 1.4958 is handled through the mills we represent that are approved for this grade; we place a mill order and confirm the minimum quantity per thickness. Lead time for mill production is generally 30 – 40 days, and the rolling slot can be scheduled to suit your fabrication plan.

Every plate is traceable to its heat number, and copies of the mill certificates stay on file for repeat orders and audits. Mixed-grade and mixed-standard orders can be consolidated, so 1.4958 plate can ship with flanges, pipe or other grades in one container through our export logistics team.

Packing and export documents

Plates are packed on fumigated wooden or steel pallets with waterproof wrapping, edge protectors and steel straps, and each bundle is labelled with grade, standard, heat number, size and weight. Documents include the commercial invoice, packing list, mill certificates and certificate of origin. Browse our GB/T 713.7 pressure vessel stainless plates and our stainless sheet and plate range for other plate standards we supply.

EN 10028-7 X5NiCrAlTi31-20 (1.4958) is a creep-resisting austenitic steel for high-temperature pressure parts, defined by Table 3 chemistry and Table 9 properties, with plate in the solution annealed (+AT) condition reaching Rp0.2 ≥ 170 MPa and Rm 500 – 750 MPa. Typical uses include steam reformer and cracking equipment and heat exchangers and headers above 600 °C.

Before ordering, state the standard edition, the steel name and number, the product form, the process route and any optional tests, so that the certificate matches your design documents. SHH STEEL supplies 1.4958 from mill production in generally 30 – 40 days, with cutting and finishing in our own warehouse and EN 10204 3.1 or 3.2 certificates. Send your sizes and quantities for a quotation.