1.4958 ForgingsX5NiCrAlTi31-20 · Alloy 800H · UNS N08810. Open-die forged rings, shafts, bars, discs, flanges and tube sheets

1.4958 designations and equivalent grades

1.4958 appears under several names depending on the standard body and the supplier. When ordering forgings, quote the EN material number 1.4958 together with the EN chemical designation X5NiCrAlTi31-20; that pair is unambiguous.

Ordering tip. EN and ASTM chemistry limits for the Alloy 800H family differ slightly in carbon and in aluminium + titanium. If your specification cites both, ask for dual certification to 1.4958 and Alloy 800H (UNS N08810); Jiangyin Jiangnan Metal Co., Ltd. supplies dual-certified 1.4958 forgings on request.

Related grades in our nickel-alloy range: Incoloy 800H, Incoloy 800HT, Incoloy 800, Inconel 617 and Inconel 625.

Chemical composition of 1.4958

Composition limits below are the EN 10095 / EN 10302 requirements for X5NiCrAlTi31-20, in mass percent. The controlled carbon window of 0.03–0.08 % and the titanium plus aluminium additions are what separate 1.4958 from plain Alloy 800.

Data correction. Silicon in 1.4958 is limited to 0.70 % max. A figure of 0.07 % circulates widely on trading sites and is a decimal-point error. Check any datasheet that shows it.

Jiangyin Jiangnan Metal Co., Ltd. melts 1.4958 in a 25 t electric arc furnace with 25 t and 50 t ladle furnaces, and sets the carbon window in 30 t and 60 t VOD converters. Vacuum oxygen decarburisation is what holds 0.03–0.08 % C repeatably without burning out the chromium. ESR (3 t and 6 t, protective atmosphere), VAR (6 t) and VIM (3 t) are available in-house where segregation, cleanliness or transverse properties are specified. Both ladle and product analyses are reported on the mill certificate.

Mechanical properties of 1.4958

Room-temperature properties apply to the solution-annealed condition. Because 1.4958 is specified for elevated-temperature service, the values that usually decide a design are creep rupture strength rather than room-temperature tensile strength.

Elevated-temperature behaviour

Creep behaviour is the reason the H grade exists. Below roughly 600 °C, 1.4958 and plain 1.4876 (Alloy 800) behave similarly; above 600 °C the controlled carbon and the coarse grain produced by the high-temperature solution anneal give 1.4958 substantially higher creep rupture strength. Design values for R_m/10 000 h and R_m/100 000 h are tabulated in EN 10095 and VdTÜV 412.

1.4958 is approved in the ASME Boiler and Pressure Vessel Code as Alloy 800H under Section I (power boilers), Section III (nuclear vessels) and Section VIII (unfired pressure vessels), with allowable stresses assigned to higher temperatures than almost any other code alloy.

Creep rupture and elevated-temperature yield tables for your specific section size are available on request. Email sales@steelforgepieces.com with the design temperature and wall thickness.

Physical properties of 1.4958

Forging and heat treatment of 1.4958

Forging

• Heating: soak uniformly; the alloy is a poor conductor of heat, so large ingots and blooms need a slow, even ramp.
• Start forging temperature: 1150–1200 °C (2100–2190 °F).
• Finish forging temperature: not below 950 °C (1740 °F). Finishing too cold causes cracking and an uncontrolled grain structure.
• Reduction: a minimum forging ratio of 3:1 is normally applied to break down the cast structure; higher ratios are used for ring blanks before rolling.
• Cooling after forging: air cool, then solution anneal.

Heat treatment

1.4958 is supplied solution annealed at 1100–1200 °C (2010–2190 °F), typically around 1150 °C, held to section thickness, then cooled rapidly in air or water. The high annealing temperature is deliberate: it produces the coarse grain (ASTM 5 or coarser) that gives the H grade its creep rupture strength. The 950 °C furnace that most forge shops run on cannot reach that temperature, so the anneal is often subcontracted and sometimes skipped. We run it on three RTX-12 bogie-hearth furnaces rated to 1200 °C, and the furnace chart goes into the certificate.

Data correction. 1.4958 is not age hardenable. Unlike Inconel 718 or Waspaloy, there is no precipitation-hardening or ageing step. The only heat treatment is solution annealing. Datasheets that describe "solution + ageing" for this grade are incorrect.

During fabrication, avoid prolonged holds in the 550–750 °C range, where chromium carbide precipitation can reduce ductility and intergranular corrosion resistance. After heavy welding or severe cold work, a re-solution anneal restores full properties.

Machining

1.4958 work hardens. Use low cutting speeds, a positive and constant feed, rigid tooling and a depth of cut that reaches below the previously work-hardened layer. Flood cooling with a water-based cutting fluid is recommended to carry heat away.

Welding

GTAW, GMAW, SMAW and SAW are all used. For service above 600 °C, nickel-based filler metals such as ERNiCr-3 (AWS A5.14) or electrodes of the ENiCrFe-2 / ENiCrFe-3 type are normally specified. Preheat is not required; keep interpass temperature low and heat input moderate. Post-weld heat treatment is not normally necessary.

1.4876 vs 1.4958 vs 1.4959 (Alloy 800, 800H and 800HT)

These three grades are the same base Ni–Fe–Cr alloy. What separates them is the carbon level, the aluminium + titanium level and the annealing treatment, which together decide creep strength and the sensible service temperature.

If your drawing calls for Alloy 800H but the design temperature sits below 600 °C, plain 1.4876 is usually the cheaper and equally suitable choice. If the component must hold a design life of 100 000 h above 800 °C, 1.4959 / 800HT is normally specified instead. We forge all three. Ask if you are unsure which fits your service condition.

1.4958 forged product forms we manufacture

Every item below is open-die forged from 1.4958 to the customer's drawing: no die cost, no minimum quantity, and a free choice of dimensions between the standard sizes.

Delivery condition options: as-forged, solution annealed, rough machined with machining allowance, or finish machined to drawing tolerance.

Manufacturing capability for 1.4958 forgings

Jiangyin Jiangnan Metal Co., Ltd. runs the whole route in-house: melting, secondary refining, remelting, open-die forging, high-temperature solution annealing, machining and testing. On this grade that matters more than usual. The 0.03–0.08 % carbon window and the 1100–1200 °C anneal are the two steps most often missed when melting or heat treatment goes out to a subcontractor.

Melting and refining

The controlled carbon window that defines the H grade is set in the VOD converters. Vacuum oxygen decarburisation takes carbon below 0.08 % without burning out the 19–22 % chromium, which is why this grade is not made on a plain EAF route. Where a specification calls for reduced segregation, cleaner inclusion ratings or better transverse properties, the heat is remelted by ESR or VAR, or melted from VIM stock.

Open-die forging

Three hydraulic open-die presses and five hammers cover everything from a 20 kg valve seat ring to a heavy shaft or tube sheet. Rings are upset, punched and expanded over a mandrel on the presses, so they come out seamless with grain flow following the circumference. Because there is no closed die, there is no tooling cost and a single piece can be quoted.

Heat treatment

Heat treatment decides whether a 1.4958 forging meets the H grade at all. The solution anneal has to run at 1100–1200 °C to produce the coarse ASTM 5 grain that carries the creep strength, and a standard 950 °C annealing furnace cannot reach it. Three RTX-12 high-temperature bogie-hearth furnaces rated to 1200 °C cover that window in-house, so the anneal is not subcontracted and the furnace chart goes into the certificate. The 950 °C furnaces handle stress relieving, ageing of other grades and the large sections.

Rated temperatures follow the furnace model designation (RTX-12 = 1200 °C class, RTX-9 / RJ-9 = 950 °C class). Every furnace is temperature-surveyed and produces a chart record that is issued with the certificate.

Machining

Forgings can be shipped as-forged, rough machined with an agreed allowance, or finish machined to drawing tolerance. The Ø5000 mm vertical lathe takes large ring and tube-sheet work; the deep-hole drilling machine bores hollow bars and sleeves up to 10 m long.

Commercial data

Testing, inspection and certification of 1.4958 forgings

Chemistry, mechanical testing, metallography and non-destructive testing are all carried out in the works laboratory, so results are traceable to the heat number without waiting on an outside lab.

Laboratory and NDT equipment

Third-party 3.2 certificates can be countersigned by TÜV, SGS, BV, DNV or Lloyd's Register. Positive material identification on the handheld analyser at loading, marking and painting to your specification, and full heat-number traceability are available at no extra charge.

Applications of 1.4958 forgings by industry

1.4958 is chosen where a part must carry load at temperature in an aggressive atmosphere for years. Oxidation resistance, carburisation resistance and creep rupture strength together justify its cost over stainless steel.

How to order 1.4958 forgings

1. Send the drawing or dimensions. Email a 2D drawing, a 3D model, or simply the rough sizes to sales@steelforgepieces.com. For rings give OD × ID × height; for bars and shafts give diameter × length; for discs give diameter × thickness.
2. Confirm grade and standard. State 1.4958 / X5NiCrAlTi31-20 and the governing standard (EN 10095 or EN 10302). Say if you also need dual certification to 1.4876 H or Alloy 800H / UNS N08810.
3. State delivery condition and testing. As-forged, solution annealed, rough machined or finish machined; UT to EN 10228-3, SEP 1921 or ASTM A388; certificate to EN 10204 3.1 or 3.2.
4. Receive the quotation within 24 hours, with unit price, forging weight, lead time and Incoterms.