EN 10088-2 X6CrNiNb18-10 1.4550 Stainless Steel Plate

EN 10088-2 X6CrNiNb18-10 1.4550 stainless steel plate is an austenitic flat product supplied to EN 10088-2, the European standard for stainless steel sheet, plate and strip for general purposes. X6CrNiNb18-10 contains up to 0.08 % carbon, 17.0 – 19.0 % chromium, 9.0 – 12.0 % nickel and niobium from 10 × C up to 1.00 %. The niobium binds carbon as niobium carbide, which stabilises the steel against chromium carbide precipitation during welding or service heating. EN 10088-2 lists it among the special grades rather than the standard grades, and Table 7 rates it resistant to intergranular corrosion both as delivered and when sensitized. Product forms are cold rolled strip up to 8 mm, continuously hot rolled strip up to 13.5 mm and hot rolled plate up to 75 mm.

SHH STEEL works as a steel sourcing partner with long-term relationships with Chinese stainless mills that roll austenitic CrNi hot rolled plate, coil and cold rolled sheet. For large tonnages, the buyer can contract directly with a suitable mill, with SHH STEEL assisting for a modest service fee and handling follow-up and documents. For small orders we consolidate demand, so that 1 – 5 t lots are placed against genuine mill production instead of stock of unknown origin. Each shipment can be released after third-party inspection by TUV, ABS, BV, DNV, CCS or an agency the buyer nominates, and payment by TT or LC is accepted. The rest of this page covers the technical side of EN 10088-2 1.4550 and the steps we take so that the sheet that arrives is the sheet that was ordered.

The table below lists the concerns buyers raise most often when sourcing EN 10088-2 X6CrNiNb18-10 sheet and plate from China, and how SHH STEEL deals with each of them.

1.4550 is the EN counterpart of UNS S34700, Type 347, in ASTM A240 (see ASTM A240 Type 347 sheet and plate). For pressure equipment it is ordered to EN 10028-7; see EN 10028-7 1.4550 pressure vessel plate.

The niobium rule is the same in EN 10088-2 and ASTM A240-22. The differences are silicon, where ASTM allows only 0.75 %, and nickel, where ASTM and JIS allow up to 13.0 %. A heat with silicon at most 0.75 % and nickel at most 12.0 % can meet both. SHH STEEL checks this when a buyer needs dual certification.

1.4550 is also listed in EN 10028-7:2016 for pressure purposes. That standard may set its own test and property requirements, which we have not reproduced here.

Edition note: the values on this page are taken from EN 10088-2:2014. A revised edition (EN 10088-2:2024) has since been published. If your contract names the newer edition, SHH STEEL checks the order against that text before production, and any difference is raised at the quotation stage rather than after rolling.

The 1.4550 chemical composition below is the cast (heat) analysis from EN 10088-2:2014 Table 1. Values are percentages by mass; a single figure is a maximum.

The 1.4550 niobium content of at least ten times the carbon is what stabilises the steel; no nitrogen limit is set. SHH STEEL checks carbon and niobium on every certificate as part of the 1.4550 chemical composition review.

Product analysis tolerances (EN 10088-2 Table 5)

A product analysis is a check made on the delivered sheet. It is not mandatory under EN 10088-2; it is carried out when agreed at the time of enquiry and order, and SHH STEEL can arrange it through a partner laboratory. The permissible tolerances on the cast limits are:

Where several product analyses are made on one cast, individual results may exceed the maximum or fall below the minimum, but not both for the same element. If a product analysis is required, it should be stated in the order together with the Table 5 tolerances.

The 1.4550 mechanical properties below are the room-temperature values from EN 10088-2:2014 Table 7 for austenitic steels in the solution annealed condition. Test pieces are transverse; the A80 elongation applies below 3 mm and the proportional elongation A from 3 mm.

Rp1.0 values are for guidance only. For continuously hot rolled products, 20 MPa higher minimum Rp0.2 and 10 MPa higher Rp1.0 may be agreed. For strip in rolling widths below 300 mm tested longitudinally, the minimum proof strength is reduced by 15 MPa and elongation by 5 % (constant gauge) or 2 % (proportional gauge). For bigger sizes than those listed, mechanical values are to be agreed.

Table 7 rates 1.4550 resistance to intergranular corrosion (EN ISO 3651-2) as “yes” in both the delivery and the sensitized condition.

Cold worked condition (process route 2H)

EN 10088-2 Table 17 defines the tensile strength levels for the cold worked condition (process route 2H): +C700 = 700 – 850 MPa, +C850 = 850 – 1 000 MPa, +C1000 = 1 000 – 1 150 MPa, +C1150 = 1 150 – 1 300 MPa and +C1300 = 1 300 – 1 500 MPa. Table 18 defines 0.2 % proof strength levels: +CP350 = 350 – 500 MPa, +CP500 = 500 – 700 MPa, +CP700 = 700 – 900 MPa, +CP900 = 900 – 1 100 MPa and +CP1100 = 1 100 – 1 300 MPa. Intermediate values may be agreed. The steel may be specified by tensile strength, by proof strength or by hardness, but only one parameter in the order. The maximum thickness for each level decreases as the strength rises, and remaining elongation depends on the work-hardening behaviour, so more exact information should be requested from the mill.

EN 10088-2 lists 1.4550 2H material at the +C700 and +C850 tensile levels and the +CP350 and +CP500 proof strength levels (X = available).

Minimum proof strength at elevated temperature (EN 10088-2 Table 12, +AT)

EN 10088-2 Table 12 gives values from 100 °C to 550 °C for this grade, for the solution annealed condition (+AT). They are minimum values for design and are not tested unless agreed.

EN 10088-2 Table A.1 gives the following guideline temperatures for 1.4550:

The footnotes to Table A.1 state that with a continuous furnace the upper part of the range is usually preferred or even exceeded, and that the lower end of the range should be aimed at when the heat treatment is part of further processing, because otherwise the mechanical properties may be affected. Solution annealing may be omitted if hot working and cooling achieve the required mechanical properties and resistance to intergranular corrosion.

The Euro Inox tables give the same 1 020 – 1 120 °C range with cooling in air or water. The range is slightly higher than for 1.4541 (1 000 – 1 100 °C). Plate is delivered solution annealed (+AT); we check the condition on each certificate.

The values below are approximate reference figures for X6CrNiNb18-10 at room temperature, from the worldstainless “Tables of Technical Properties”, which follow EN 10088-1. They are suitable for design estimates and weight calculation; where a figure is critical, use EN 10088-1 itself.

The physical properties are essentially those of the other 18-10 austenitic grades. Thermal expansion is higher and conductivity lower than for ferritic grades, which matters for welding distortion and for mixed-material assemblies in heated plant.

1.4550 has the general corrosion resistance of the 18-10 austenitic steels. The Euro Inox fabrication tables describe it as resistant to intergranular corrosion in continuous service at up to 400 °C and list it for the power and chemical industries. EN 10088-2 Table 7 rates its resistance to intergranular corrosion, tested to EN ISO 3651-2, as “yes” both in the delivery condition and in the sensitized condition.

The titanium-stabilised alternative is EN 10088-2 1.4541 plate, which is listed among the standard grades.

As EN 10088-2 notes, corrosion resistance depends strongly on the environment and cannot always be judged from laboratory tests, so experience with the grade in similar service should be used.

1.4550 is readily weldable by the common arc and resistance processes, and niobium stabilisation keeps the heat-affected zone resistant to intergranular corrosion.

• The Euro Inox fabrication tables rate TIG/MIG, manual metal arc and resistance welding as suitable for 1.4550, and autogenous welding as suitable with restrictions.
• Filler materials listed are 1.4316, 1.4551 and 1.4576; 1.4551 is the matching niobium-stabilised filler.
• No preheat is listed in those tables.
• EN 10088-2 does not specify welding procedures; these are published guidelines and general practice.

These points reflect industry practice for austenitic CrNi stainless steels rather than requirements of EN 10088-2, which does not specify welding procedures. In the SHH STEEL workshop, blanks and slit strips are cut with clean, burr-free edges so that seam, spot and tube welding run without edge preparation problems.

Annealed 1.4550 forms well with standard austenitic practice and work-hardens during forming, so springback should be allowed for. 2H material needs larger bend radii.

Thick plate is cut by plasma or waterjet, and sheet by laser or shearing. Machining needs sharp tools and positive feeds to avoid work hardening at the cut.

We run our own workshop next to the warehouse, so 1.4550 hot rolled plate and X6CrNiNb18-10 plate blanks can be delivered cut to size, laser-cut or bent. Details are on our steel cutting services and bending and forming services pages.

1.4550 is listed in EN 10088-2 as cold rolled strip, continuously hot rolled strip and hot rolled plate.

EN 10088-2 Table 7 gives mechanical values for hot rolled plate up to 75 mm; for bigger sizes the mechanical values shall be agreed at the time of enquiry and order. Under section 6.9 of the standard, EN ISO 18286 normally applies only to individually rolled quarto plate, while continuously rolled material follows EN ISO 9444-2.

SHH STEEL can supply 1.4550 hot rolled plate and 1.4550 cold rolled sheet, in standard sizes or cut to your drawing, subject to mill campaigns for this special grade.

Surface finish is ordered by the process route symbols of EN 10088-2 Table 6; trade names from ASTM and JIS are shown for reference. Not every route is available for every grade, and the mill confirms which ones it can supply.

The No.1, No.4 and BA cross-references follow worldstainless and IMOA comparison tables; EN 10088-2 itself defines only the EN symbols, and not every route is available for every grade. Special finishes such as 1J and 2J apply to one surface unless otherwise agreed. The Euro Inox tables rate the polishability of 1.4550 as suitable with restrictions.

The usual 1.4550 equivalent, and the answer to most 347 equivalent enquiries, is UNS S34700.

For ASME pressure work the grade is ordered as ASME SA-240 347 plate, and for Chinese pressure vessels as GB/T 713.7 S34778 pressure vessel plate.

1.4550 vs 1.4541 and 1.4307

Compared with 1.4541, 1.4550 is stabilised with niobium instead of titanium; Table 7 gives the same room-temperature properties, and Table 12 values are almost identical. The Euro Inox tables rate 1.4550 polishability better (with restrictions, against poor for 1.4541). Compared with EN 10088-2 1.4307 plate, it keeps higher elevated-temperature proof strength (136 against 100 MPa Rp0.2 at 300 °C).

Typical applications of 1.4550 plate, based on the Euro Inox fabrication tables and its stabilised chemistry, include:

• Power plant components
• Chemical industry equipment
• Welded parts in continuous service up to 400 °C
• Heat exchanger fabrication
• Vessels and piping fabricated from plate
• Pressure parts (to EN 10028-7)

For pressure equipment, 1.4550 plate is ordered to EN 10028-7; for other uses, EN 10088-2 applies.

Because 1.4550 is a special grade, buyers often check whether 1.4541 would serve. SHH STEEL can compare both for a given duty.

For 1.4550 the main risks are low niobium, substitution with titanium-stabilised steel and limited mill availability.

None of these steps is complicated, but they need to be agreed at the start. When you send an enquiry, tell us which of these points matters most to you, and the order will be built around it.

Every 1.4550 order is supported by documents and checks that make the material traceable to the heat:

• Cast analysis with carbon, chromium, nickel and niobium checked
• Tensile test (transverse) to Table 7, or to the ordered 2H level
• Impact test for plate over 10 mm when agreed
• Intergranular corrosion test to EN ISO 3651-2 when agreed
• Thickness, flatness and surface inspection
• Additional checks through our third-party testing service: PMI, dimensional, flatness and surface inspection

If the order does not name an inspection document, EN 10088-2 requires only a test report 2.2. Because this is rarely enough for power and chemical plant or export work, SHH STEEL supplies an EN 10204 3.1 inspection certificate as standard and a 3.2 certificate when an independent inspector (TUV, ABS, BV, DNV, CCS or an agency you nominate) witnesses testing and countersigns the document.

Ordering example and lead time

Following the pattern of the example in EN 10088-2, a typical order line would read: 6 plates, 16 mm × 2 000 mm × 6 000 mm, EN ISO 18286, EN 10088-2, steel X6CrNiNb18-10 (1.4550), process route 1D, inspection certificate 3.1 to EN 10204. Mill production lead time is generally 30 – 40 days from order confirmation, depending on the rolling schedule, the size and the tests requested; because 1.4550 is a special grade, the campaign date should be confirmed at enquiry. Consolidated small lots follow the same mill schedule, and we send progress updates at rolling, testing and packing.

• Mill relationships: long-term cooperation with Chinese stainless mills helps us secure competitive pricing and steadier delivery for 1.4550 and related austenitic grades.
• Direct mill contracts: for larger tonnages you can contract directly with a suitable mill, for a modest service fee, while we handle follow-up and documents.
• Order consolidation: 1 – 5 t lots are combined so they can be placed against genuine mill production.
• Own workshop: slitting, cut-to-length, laser cutting, bending and protective film before shipment.
• Inspection and certificates: third-party inspection by TUV, ABS, BV, DNV, CCS or your nominated agency, with EN 10204 3.1 or 3.2 certificates.
• Flexible payment: TT, LC or a combination of both.
• Port logistics: coil and sheet are packed seaworthy with heat-number labels and shipped through our worldwide shipping service, together with other grades if needed.

As a 1.4550 plate supplier SHH STEEL also stocks and sources the wider range of stainless steel sheets and plates, so mixed orders of different stainless grades can travel in one container with one set of paperwork.

EN 10088-2 X6CrNiNb18-10 1.4550 is the niobium-stabilised 347-type austenitic steel, a special grade supplied as hot rolled plate up to 75 mm and cold rolled sheet for welded power and chemical plant. Choosing it is the easy part. Getting genuine material that matches the certificate, in the gauge and finish your parts need and on a predictable schedule, is where a sourcing partner earns its place, and that is the work SHH STEEL does every day through long-term mill cooperation, consolidation and its own workshop.

The next step is simple. Send SHH STEEL your drawing, or an enquiry with the quantity, thickness, width, finish and delivery destination, and we will judge whether a direct mill contract or consolidation with processing fits your order better, and quote accordingly. Send your sizes and quantities for a quotation.