EN 10088-2 X7CrNiAl17-7 1.4568 Stainless Steel Plate

EN 10088-2 X7CrNiAl17-7 1.4568 stainless steel is a precipitation hardening flat product supplied to EN 10088-2, the European standard for stainless steel sheet, plate and strip for general purposes. X7CrNiAl17-7 contains up to 0.09 % carbon, 16.0 – 18.0 % chromium, 6.5 – 7.8 % nickel and 0.70 – 1.50 % aluminium. It is the composition known as Type 631 (UNS S17700). After solution annealing it can be formed in a soft condition, then transformed and aged to very high strength. EN 10088-2 places 1.4568 among its special grades, defined as grades for special use and/or with limited availability, and Table 11 lists it only as cold rolled strip (C) up to 8 mm, in the solution annealed condition +AT and the hardened condition +P1450. Hot rolled plate of the same composition is ordered to GB/T 4237 or ASTM A693, or by special agreement.

SHH STEEL works as a steel sourcing partner with long-term relationships with Chinese stainless mills that roll precipitation hardening cold rolled strip and hot rolled plate. 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 1.4568 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 X7CrNiAl17-7 sheet and plate from China, and how SHH STEEL deals with each of them.

In American practice, precipitation hardening plate, sheet and strip are covered by ASTM A693; 1.4568 corresponds to A693 Type 631, UNS S17700. In China, 07Cr17Ni7Al (S51770) is listed in GB/T 4237 for hot rolled plate; see GB/T 4237 07Cr17Ni7Al S51770 plate. The composition is widely sold as 17-7 PH, a registered trademark of Cleveland-Cliffs Inc. (AK Steel). SHH STEEL orders and certifies by EN steel number and UNS number; a specific producer’s branded product has to be named and agreed in the order.

EN 10088-2 is tighter on silicon and sulphur, while ASTM A693 and GB/T 4237 cap nickel at 7.75 % and require at least 0.75 % aluminium. A heat with nickel of 6.5 – 7.75 % and aluminium of 0.75 – 1.50 % can therefore be certified to all three. Footnote d to Table 4 lets the nickel maximum rise to 8.3 % for better cold deformability; such a heat no longer meets S17700. SHH STEEL checks these limits when a buyer needs dual certification.

1.4568 is not listed in EN 10028-7. Footnote i to Table 11 refers to EN 10151, Stainless steel strip for springs, for the spring-hard rolled condition.

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 1.4568 chemical composition below is the cast (heat) analysis from EN 10088-2:2014 Table 4. Values are percentages by mass; a single figure is a maximum.

The 1.4568 chemical composition balances chromium and nickel so that the steel stays largely austenitic after solution annealing but can be transformed to martensite, while 0.70 – 1.50 % aluminium provides the hardening precipitates. Footnote d to Table 4 allows the nickel maximum to be raised to 8.3 % for better cold deformability. SHH STEEL checks chromium, nickel and aluminium on every certificate.

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 1.4568 mechanical properties below are the room-temperature values from EN 10088-2:2014 Table 11 for precipitation hardening steels. Unlike the austenitic and duplex grades, the values depend on the heat treatment condition as much as on the product form, so the condition must be named in the order.

Footnotes to Table 11: +AT = solution annealed, +P = precipitation hardened, +SR = strength relieved. A80 values apply to test pieces of 80 mm gauge length and 20 mm width (50 mm × 12.5 mm may also be used); A values apply to a proportional gauge length of 5.65√S0. For bigger sizes the mechanical values shall be agreed at the time of enquiry and order. Under section 7.4.2, the 1 % proof strength is determined for austenitic steels only, so Table 11 gives none.

For cold rolled strip, Table 11 gives a single elongation value for both gauge lengths. +AT is the delivery condition, and footnote i refers to EN 10151 for the spring-hard rolled condition. +P1450 is a condition of application, and other precipitation hardening temperatures may be agreed.

Table 11 gives no impact values for 1.4568, and EN 10088-2 rates no resistance to intergranular corrosion for precipitation hardening steels. Brown Metals’ Type 17-7PH data sheet gives typical (not minimum) values of about 310 MPa yield strength, 900 MPa tensile strength and 30 % elongation annealed, and about 1 380 MPa and 1 520 MPa after RH 950, for its product.

Cold worked condition (process route 2H)

EN 10088-2 Tables 19 and 20 list no cold worked (2H) strength levels for 1.4568. Footnote i to Table 11 refers to EN 10151 for spring-hard rolled strip.

Elevated-temperature properties

EN 10088-2 Table 16 gives elevated-temperature proof strengths only for 1.4542, so there are no EN 10088-2 design values for 1.4568 at elevated temperature; they have to be agreed if needed. Under section 7.4.3, only the 0.2 % proof strength is determined at elevated temperature for precipitation hardening steels. ASTM A693 gives 600 °F (315 °C) as the upper end of the temperature range for these steels.

EN 10088-2 Table A.5 gives the following guideline temperatures for 1.4568:

Hot forming: 1 150 – 900 °C, cooling in air (shared with 1.4542 in Table A.5). The footnotes to Table A.5 state that solution annealing temperatures shall be agreed for simulated heat-treated test pieces, and that with a continuous furnace the upper part of the range is usually preferred or even exceeded.

The 1.4568 heat treatment for +P1450 includes a sub-zero sequence from footnote d to Table A.5; the Euro Inox tables give the same temperatures. The sequence transforms the austenite to martensite before ageing.

Brown Metals’ Type 17-7PH data sheet describes a similar American route, RH 950: conditioning at 955 °C, transformation at −73 °C and ageing at 510 °C. It also describes TH 1050, with conditioning at 760 °C and ageing at 565 °C; this route is not listed in EN 10088-2 and would have to be agreed. SHH STEEL states the solution annealing record on each certificate, and the hardening record where the mill hardens.

The values below are approximate reference figures for X7CrNiAl17-7 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 worldstainless table gives 1.4568 a density of 7.8 g/cm³, a modulus of 200 GPa, a thermal conductivity of 16 W/(m·K), a specific heat of 500 J/(kg·K) and an electrical resistivity of 0.80 Ω·mm²/m, and lists it under the ferromagnetic grades. Its expansion values of 11.0 and 11.6 × 10⁻⁶ /K are footnoted to the AISI manual as 0 – 100 °C and 0 – 315 °C means. Brown Metals’ Type 17-7PH data sheet shows that expansion depends on the condition: about 15.3 × 10⁻⁶ /K annealed, against about 10.1 – 10.3 × 10⁻⁶ /K after hardening (21 – 93 °C). It describes the grade as weakly ferromagnetic when annealed and strongly ferromagnetic when hardened.

Brown Metals’ Type 17-7PH data sheet describes corrosion resistance comparable to Type 304 in most media and generally superior to the hardenable 400-series grades. The Euro Inox fabrication tables list 1.4568 for hinges, hose clips, springs, valve parts and pressure vessels. EN 10088-2 does not rate resistance to intergranular corrosion for this grade: under section 6.4, NOTE 1, EN ISO 3651-2 is not applicable to precipitation hardening steels.

For corrosion comparisons the usual reference is EN 10088-2 1.4301 plate; for high-strength spring strip without an ageing step, it is EN 10088-2 1.4310 strip.

As NOTE 2 to section 6.4 of EN 10088-2 points out, corrosion resistance depends strongly on the environment and cannot always be clearly ascertained through laboratory tests, so experience with the grade in similar service should be used.

1.4568 is not a grade chosen for welded construction. The Euro Inox fabrication tables rate its weldability as “u”, which they define as poor, with specialised processes only.

• The Euro Inox tables list 1.4316 as the filler material for 1.4568, and give no process ratings for TIG, MMA or resistance welding.
• Because strength comes from transformation and ageing, any weld has to be made before the final hardening treatment.
• Where joining is unavoidable, the fabricator should qualify the procedure on strip from the same heat and condition.
• EN 10088-2 does not specify welding procedures; these are published guidelines and general practice.

These points reflect industry practice for precipitation hardening stainless steels rather than requirements of EN 10088-2, which does not specify welding procedures. In the SHH STEEL workshop, strip and blanks are slit or cut with clean, burr-free edges for forming, spot welding or brazing by the customer.

In the +AT condition, Table 11 allows a tensile strength of up to 1 030 MPa with 19 % elongation, so 1.4568 strip can be formed before hardening; footnote d allows a higher nickel content for better cold deformability. Once hardened to +P1450, elongation falls to 2 %, so forming must be finished first.

ASTM A693 notes that precipitation hardening steels are suitable for machining in the solution-annealed condition and can then be hardened without danger of cracking or distortion. Strip is slit, sheared or laser cut in the +AT condition.

We run our own workshop next to the warehouse, so 1.4568 cold rolled strip and X7CrNiAl17-7 plate blanks to GB/T 4237 can be delivered slit, cut to size or blanked. Details are on our steel cutting services and bending and forming services pages.

EN 10088-2 Table 11 lists 1.4568 only as cold rolled strip (C) up to 8 mm.

For bigger sizes the mechanical values shall be agreed at the time of enquiry and order. Strip in the spring-hard rolled condition is ordered to EN 10151 (footnote i to Table 11).

SHH STEEL supplies 1.4568 cold rolled strip as coil, slit strip or sheets. Buyers who need 1.4568 stainless steel plate thicker than 8 mm can order the same composition as GB/T 4237 07Cr17Ni7Al or ASTM A693 Type 631 plate, after confirming availability with the mill.

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.

EN 10088-2 lists 1.4568 as cold rolled strip only, so hot rolled routes 1D and 1E are not part of the standard offer. The Euro Inox tables rate its polishability as good (“l”). The trade-name cross-references follow worldstainless and IMOA comparison tables.

The usual 1.4568 equivalent is ASTM A693 Type 631 (UNS S17700), so the 1.4568 Type 631 pairing is the one used for dual certification. GB/T 20878 gives SUS631 as the Japanese counterpart of the Chinese grade 07Cr17Ni7Al (S51770).

Equivalent grades are close in chemistry but not identical, and the hardening routes are named differently: EN 10088-2 uses +P1450, while American practice uses conditions such as RH 950 and TH 1050. The order must therefore state the standard, the condition and the test values.

1.4568 vs 1.4542

On 1.4568 vs 1.4542: EN 10088-2 1.4542 plate (Type 630) is martensitic after solution annealing and is hardened by copper precipitates in a single ageing step, while 1.4568 is largely austenitic after solution annealing, so it can be formed first and then needs conditioning, sub-zero cooling and ageing. EN 10088-2 lists 1.4542 as strip and plate up to 50 mm, but 1.4568 only as cold rolled strip up to 8 mm. In strip, 1.4568 +P1450 needs 1 310 MPa proof strength against 1 150 MPa for 1.4542 +P1300. Compared with the nitrogen-alloyed EN 10088-2 1.4318 plate, 1.4568 reaches far higher strength but only after hardening.

Typical applications of 1.4568 strip listed in the Euro Inox fabrication tables include:

• Springs
• Hinges
• Hose clips
• Valve parts
• Pressure vessels

Brown Metals’ Type 17-7PH data sheet adds aerospace components and springs, noting that the grade is formed in a soft austenitic condition and hardened at low temperature with far less distortion than quench-and-temper hardening. As 1.4568 spring steel strip, it is often compared with 1.4310.

ASTM A693 notes that precipitation hardening steels are used for parts needing corrosion resistance and high strength at room temperature or at temperatures up to 600 °F (315 °C).

For 1.4568 the main risks are ordering plate under EN 10088-2 where only strip is listed, an unclear hardening condition, nickel above 7.75 % on a dual-certified order, and welding or forming after hardening.

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 1.4568 order is supported by documents and checks that make the material traceable to the heat:

• Cast analysis with chromium, nickel and aluminium checked
• Tensile test to Table 11 in the ordered condition (+AT, or +P1450 on hardened samples)
• Hardness test when agreed
• Heat treatment record for the solution annealing and any hardening
• 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 spring, valve and aerospace 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: 2 t cold rolled strip, 1.5 mm × 300 mm, EN ISO 9445-1, EN 10088-2, steel X7CrNiAl17-7 (1.4568), condition +AT, process route 2B, 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 1.4568 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 1.4568 and related precipitation hardening and spring 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 1.4568 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 X7CrNiAl17-7 1.4568 is the Type 631 precipitation hardening special grade, listed as cold rolled strip up to 8 mm in +AT and +P1450, with plate of the same composition available to GB/T 4237 or ASTM A693, for springs, hinges, valve parts and aerospace components. 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.