# 1.4912 / X7CrNiNb18-10 (347H) Open-Die Forgings > Niobium-stabilised austenitic creep-resisting stainless steel, forged to drawing in Jiangyin, > Jiangsu, China. | | | | --- | --- | | **Source** | https://www.steelforgepieces.com/Stainless-Steel/1.4912.html | | **Manufacturer** | Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory | | **Address** | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China | | **Tel** | +86 189 2135 9659 | | **Email** | sales@steelforgepieces.com | | **Reviewed** | 2026-09-27 | Jiangyin Jiangnan Metal forges 1.4912 on its own open-die press: rolled rings, flanges, shafts, discs, round bars, sleeves, bushings, tube sheets and forged pipe. Prices are quoted per drawing, because forged weight, tolerance class and test scope all move the number. --- ## What is material 1.4912? EN 1.4912 is the material number for **X7CrNiNb18-10**, a niobium-stabilised austenitic creep-resisting stainless steel. It is the high-carbon member of the 18/10 niobium-stabilised family. Closest international equivalents are **AISI 347H**, **UNS S34709** and **JIS SUS347H**. The grade appears in EN 10222-5 (steel forgings for pressure purposes), EN 10216-5 (seamless tubes for pressure purposes) and EN 10088-1 (list of stainless steels). Carbon is held at 0.04 to 0.10 percent so creep strength can be calculated for design, and niobium at 0.40 to 1.20 percent ties that carbon up as niobium carbide instead of chromium carbide. ### Key data | Item | Value | | --- | --- | | EN material number | 1.4912 | | EN name | X7CrNiNb18-10 | | Type | Austenitic creep-resisting stainless steel | | Density | 7.9 g/cm3 | | Delivery condition | +AT, solution annealed | | Standards | EN 10222-5:2017, EN 10216-5:2014, EN 10088-1 | | Forged forms | Rings, flanges, shafts, discs, bars, sleeves, bushings, tube sheets, pipe, valve parts | --- ## Chemical composition EN 10216-5:2014, percent by mass, iron balance. | Limit | C | Si | Mn | P | S | Cr | Ni | N | Nb | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | **Min** | 0.04 | - | - | - | - | 17.0 | 9.0 | - | 0.40 | | **Max** | 0.10 | 1.00 | 2.00 | 0.040 | 0.015 | 19.0 | 12.0 | 0.10 | 1.20 | Stabilisation rule: **10 x C < Nb < 1.2 percent**. The American grades treated as equivalent run slightly wider bands. Where a drawing quotes both an EN number and an ASTM grade, state which governs and we melt to the tighter window. --- ## Mechanical properties, solution annealed (+AT) Room temperature minimums per EN 10216-5:2014. | Property | Longitudinal | Transverse | | --- | --- | --- | | Tensile strength Rm | 510 to 710 MPa | 510 to 710 MPa | | Proof strength Rp0.2 | 205 MPa min | 205 MPa min | | Elongation A | 40 percent min | 30 percent min | | Impact energy KV at +20 C | 100 J min | 60 J min | | Impact energy KV at -196 C | - | 40 J min | Published values for guidance, **not acceptance criteria**: hardness about 180 HB, Young's modulus 200 GPa, shear modulus 77 GPa, Poisson's ratio 0.28, thermal conductivity 16 W/m.K, thermal expansion 16 micrometre/m.K, specific heat 480 J/kg.K, melting range 1390 to 1430 C, PREN about 18. One published source gives a maximum mechanical service temperature near 940 C and a maximum corrosion service temperature near 520 C. Allowable stress comes from the governing design code. --- ## Equivalent grades | System | Designation | | --- | --- | | EN | X7CrNiNb18-10, 1.4912 | | AISI / ASTM | 347H | | UNS | S34709 | | JIS | SUS347H | Cross-references are a starting point for enquiry, not a substitute for the purchase order standard. > **1.4912 is not 1.4550.** 1.4550 (X6CrNiNb18-10, AISI 347) is the lower carbon general purpose > grade. 1.4912 carries a guaranteed carbon minimum, and that is what makes creep design possible. --- ## Heat treatment 1.4912 is austenitic. It cannot be quenched and tempered and cannot be age hardened. Normal delivery condition is +AT, solution annealed and cooled fast enough to keep carbon in solution. EN 10222-5 also recognises a stabilising anneal below the usual solution temperature for niobium and titanium bearing grades. Every forging is re-annealed after forging, with soak time and quench set from the governing section thickness. Furnace charts are recorded and can be issued with the certificate on request. > A supplier offering solution treatment plus ageing on this grade has confused it with a > precipitation hardening steel such as A286. --- ## Corrosion behaviour Niobium holds carbon more strongly than chromium, so carbon precipitates as niobium carbide rather than chromium carbide at grain boundaries. Even so, the European data record for 1.4912 under EN 10216-5 does not list resistance to intergranular corrosion as a guaranteed property of the grade. Where the service needs proven IGC resistance, name the test on the purchase order, for example ASTM A262 Practice E or EN ISO 3651-2, and it will be run and reported on the certificate. --- ## Machining and welding 1.4912 work hardens quickly. Use rigid setups, positive rake tooling, a real depth of cut, reduced surface speed and continuous flood coolant. Dwelling glazes the surface and destroys tool life. For welding, a niobium-stabilised filler matching the base metal is normal practice. --- ## Forged products Seamless rolled rings, forged flanges, shafts and spindles, discs, round bars, sleeves and bushings, tube sheets, forged tube and pipe, valve bodies, valve seat rings, valve stems, blocks, nozzles, gears, forging rolls, crankshafts and eccentric shafts, manifolds, forged wheels. All to drawing or specification. **Typical service:** pressure vessels, shell and tube heat exchangers, columns and towers, preheaters, superheater and reheater components, refinery units including fluid catalytic cracking, chemical and pharmaceutical process plant, waste heat recovery and recuperators, turbine and power transmission parts, gas compressors, offshore and subsea production equipment. --- ## Melting, testing, certification | Item | Options | | --- | --- | | Melting route | EAF + VOD, with ESR remelting where cleanliness or segregation control justifies it | | Ultrasonic examination | EN 10228-3, SEP 1921 or ASTM A388, as nominated | | Certification | EN 10204 type 3.1, or type 3.2 with third party endorsement | To quote we need the drawing or rough dimensions with tolerance, the governing standard and its edition, the quantity, and the delivery condition. --- ## Questions **Is 1.4912 the same as 347H?** Treated as equivalent in practice. 1.4912 / X7CrNiNb18-10 is the European designation, 347H / UNS S34709 the American one. Composition windows are close but not identical, so state which standard governs. **What is the difference between 1.4912 and 1.4550?** Carbon. 1.4550 is the lower carbon standard grade; 1.4912 holds 0.04 to 0.10 percent carbon, which supports creep design. **Can 1.4912 be hardened by heat treatment?** No. It is austenitic and supplied solution annealed. Strength rises only by cold work, which does not apply to heavy forgings. **What is the chemical composition of 1.4912?** Per EN 10216-5:2014: C 0.04 to 0.10, Si max 1.00, Mn max 2.00, P max 0.040, S max 0.015, Cr 17.0 to 19.0, Ni 9.0 to 12.0, N max 0.10, Nb 0.40 to 1.20 percent, iron balance. **What sizes can you forge?** Open-die work, so the limit is the drawing rather than a stock list. Send dimensions for feasibility and forged weight the same working day. **Who supplies 1.4912 forgings from China?** Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Tel +86 189 2135 9659, email sales@steelforgepieces.com. --- ## Related grades | Grade | Note | Page | | --- | --- | --- | | AISI 321H | Titanium-stabilised creep-resisting austenitic | https://www.steelforgepieces.com/Stainless-Steel/AISI-321H.html | | 904L | High alloy austenitic for acid service | https://www.steelforgepieces.com/Stainless-Steel/904L.html | | A182 F44 | Six percent molybdenum super austenitic | https://www.steelforgepieces.com/Stainless-Steel/A182-F44.html | | A182 F51 | Duplex | https://www.steelforgepieces.com/Stainless-Steel/A182-F51.html | | A182 F53 | Super duplex | https://www.steelforgepieces.com/Stainless-Steel/A182-F53.html | | A286 | Precipitation hardening iron base alloy | https://www.steelforgepieces.com/Stainless-Steel/A286.html | --- Values are from the EN 10216-5, EN 10222-5 and EN 10088-1 records for 1.4912 and are given for guidance. The standard named on the purchase order governs.