For High Service Temperatures

Therma

The Therma range contains heat- and creep-resisting stainless steels with excellent oxidation and creep resistance for use in applications with high service temperatures (≥ 550°C/1020°F).

Austenitic heat- and creep-resisting stainless steels have resistance to carburizing and nitriding/low oxygen hot gas and higher creep strength, in general.

Therma 253 MA/4835 (EN 1.4835) is an austenitic heat-resisting stainless steel with excellent oxidation and creep resistance in cyclic conditions and is best employed in high temperatures up to 1100°C/2012°F.

Therma 310S/4845 (EN 1.4951) is an austenitic heat- and creep-resisting stainless steel with excellent oxidation resistance in mildly cyclic conditions and is best employed in high temperatures up to 1050°C/1920°F.

The ferritic heat-resisting stainless steels Therma 4713 (EN 1.4713) and Therma 4724 (EN 1.4724) have good resistance to sulfur-containing hot gases and lower thermal expansion compared to nickel-alloyed grades. Therma 4713 and Therma 4724 are best employed in temperatures up to 800°C/1470°F and 850°C/1560°F, respectively

Outokumpu Therma grades

Therma 253 MA stainless steel

Therma 253 MA is an austenitic stainless steel with excellent oxidation and creep resistance in cyclic conditions that is best employed in temperatures up to 1150°C/2100°F. There is a slight susceptibility to embrittlement during continuous operation between 600–850°C/1110–1560°F.

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  • EN: 1.4835
  • ASTM type: -
  • ASTM UNS: S30815
  • Microstructure: Austenitic
Typical applications
  • Oil industry equipment
  • Conveyor belts
  • Refractory anchors
  • Expansion bellows
  • Radiant tubes
  • Rotary kilns
  • Exhaust manifolds
  • Power generation applications
  • Cyclone dip tubes
  • Impact separators
  • Bell furnaces
  • Muffle furnaces
  • Automotive exhaust components
  • Tube shields
  • Heat treatment trays
  • Dampers
  • Recuperator tubes
  • Large-scale bakery ovens
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.09
  • Cr: 21.0
  • Ni: 11.0
  • Mo: -
  • N: 0.17
  • Others: Si, Ce

Therma 310S/4845 stainless steel

Therma 310S/4845 is an austenitic product with very good oxidation resistance in general and good oxidation resistance in mildly cyclic conditions that is best employed in temperatures up to 1050°C/1920°F. There is a slight susceptibility to embrittlement during continuous operation between 600–900°C/1110–1652°F.

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  • EN: 1.4845
  • ASTM type: 310S
  • ASTM UNS: S31008
  • Microstructure : Austenitic
Typical applications
  • Furnace equipment
  • Oil industry equipment
  • Heat treatment baskets
  • Heat exchangers
  • Steam boilers
  • Thermowells
  • Automotive components
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.05
  • Cr: 25.5
  • Ni: 19.1
  • Mo: -
  • N: -
  • Others : -

Therma 4950

A austenitic creep resisting stainless steel for use in temperature up to 1000°C

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  • EN: 1.4950
  • ASTM type: 309S
  • ASTM UNS: S30908
  • Microstructure: Austenitic
Typical applications
  • Furnaces
Product forms
Chemical composition, % by mass
  • C: 0.06
  • Cr: 22.3
  • Ni: 12.3
  • Mo: -
  • N: -
  • Others: -

Therma 4951

A austenitic creep resisting stainless steel for use in temperature up to 1050°C

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  • EN: 1.4951
  • ASTM type: 310S
  • ASTM UNS: S31008
  • Microstructure: Austenitic
Typical applications
  • Furnaces
Product forms
Chemical composition
  • C: 0.05
  • Cr: 25.5
  • Ni: 19.1
  • Mo: -
  • N: -
  • Others: -

Therma 4878

A austenitic heat resisting stainless steel, stabilized 304, for use in temperatures up to 800°C

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  • EN: 1.4878
  • ASTM type: -
  • ASTM UNS: -
  • Microstructure: Austenitic
Typical applications
  • Heating elements
Product forms
Chemical composition, % by mass
  • C: 0.05
  • Cr: 17.3
  • Ni: 9.1
  • Mo: -
  • N: -
  • Others: Ti

Therma 316H

A high carbon 316 version for use at elevated temperatures

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  • EN: -
  • ASTM type: 316H
  • ASTM UNS: S31609
  • Microstructure: Austenitic
Product forms
Chemical composition, % by mass
  • C: 0.04
  • Cr: 17.1
  • Ni: 10.1
  • Mo: 2.1
  • N: -
  • Others: -

Therma Alloy 800/800H/800T

Outokumpu Therma Alloy 800/800H/800T is a series of high-temperature alloys design for high creep strength, resistance to carburization, oxidation, and other types of high-temperature corrosion. Therma Alloy 800 series (EN 1.4876/1.4958/1.4959 UNS, N08800/N08810/N08811) are stabilized austenitic alloys with high Nickel and Chromium content as well as controlled additions of Carbon, Titanium and Aluminum. Additionally, grain size is controlled for improved creep strength properties.

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  • EN: 1.4876 1.4958 1.4959
  • :
  • ASTM UNS: N08800 N08810 N08811
  • Microstructure: Austenitic
Typical applications
  • General high-temperature service
  • Steam/hydrocarbon reformers
  • Ethylene pyrolysis
  • Acetic anhydride cracking furnaces
  • Heat exchangers
  • Heating element sheaths
  • High temperature process equipment
Product forms
Typical chemical composition, % by mass
  • C: <0.10
  • Cr: 21
  • Ni: 31
  • Mo: -
  • N: -
  • Others: Ti, Al

Therma 4713 stainless steel

Therma 4713 is a ferritic low-alloyed stainless steel best employed at 550–800 °C/1020– 1470 °F when you need higher mechanical loading compared to other ferritic grades. Offers good resistance against sulfur attack compared to nickel-alloyed grades.

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  • EN: 1.4713
  • ASTM type: -
  • ASTM UNS: -
  • Microstructure : Ferritic
Typical applications
  • Furnace equipment
  • Air heaters
  • Annealing boxes
  • Conveyor belts
  • Thermowells
Product forms
Typical chemical composition, % by mass
  • C: 0.06
  • Cr: 6.5
  • Ni: -
  • Mo: -
  • N: -
  • Others: Al, Si 

Therma 4724 stainless steel

Therma 4724 is a ferritic low-alloyed product with improved oxidation resistance in temperatures up to 850°C/1560°F.

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  • EN: 1.4724
  • ASTM type: -
  • ASTM UNS: -
  • Microstructure: Ferritic
Typical applications
  • Furnace equipment
  • Thermal boiler components
  • Grids
  • Burner nozzles
  • Conveyor belts
  • Thermowells
Product forms
Typical chemical composition, % by mass
  • C: 0.07
  • Cr: 12.5
  • Ni: -
  • Mo: -
  • N: -
  • Others: Al, Si

Therma 304H/4948 stainless steel

Therma 304H/4948 is an austenitic Core 304/4301 variant with improved high-temperature creep strength that is best employed in temperatures up to 750°C/1380°F. It offers good formability and weldability.

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  • EN: 1.4948
  • ASTM type: 304H
  • ASTM UNS: S30409
  • Microstructure: Austenitic
Typical applications
  • Tubes
  • Pressure vessels
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.05
  • Cr: 18.1
  • Ni: 8.3
  • Mo: -
  • N: -
  • Others : -

Therma 321H/4878 stainless steel

Therma 321H/4878 is an austenitic heat resisting stainless steel with comparable wet corrosion resistance to Core 321/4541 that is best employed in temperatures up to 850 °C/1560 °F.

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  • EN: 1.4878
  • ASTM type: 321H
  • ASTM UNS: -
  • Microstructure: Austenitic
Typical applications
  • Furnace equipment
  • Case hardening boxes
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.05
  • Cr: 17.3
  • Ni: 9.1
  • Mo: -
  • N: -
  • Others: Ti 

Therma 347H stainless steel

Therma 347H is an austenitic heat resisting stainless steel with excellent long-term creep resistance at at 550–600°C/1020–1110°F and comparable wet corrosion resistance to Core 347/4550.

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  • EN: -
  • ASTM type: 347H
  • ASTM UNS: S34709
  • Microstructure: Austenitic
Typical applications
  • Oil refineries
  • Fired heater tubes
  • Boiler casings
  • Pressure vessels
  • Reactor vessels
  • Welded tubes
  • Fittings
  • Stack liners
  • Tanks for storing organic chemicals
  • Furnace heating elements
  • Tanks for thermal storage
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.05
  • Cr: 17.5
  • Ni: 9.5
  • Mo: -
  • N: -
  • Others: Nb

Therma 4828 stainless steel

Therma 4828 is an austenitic heat resisting stainless steel with improved oxidation resistance in temperatures up to 1000°C/1830°F. There is a slight susceptibility to embrittlement during continuous operation atbetween 600–850°C/1110– 1560 °F.

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  • EN: 1.4828
  • ASTM type: -
  • ASTM UNS: -
  • Microstructure: Austenitic
Typical applcations
  • Furnace equipment (especially supporting parts)
  • Annealing and hardening boxes
  • Air heaters
  • Exhaust systems
  • Automotive components such as turbochargers
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.05
  • Cr: 19.3
  • Ni: 11.2
  • Mo: -
  • N: -
  • Others: Si

Therma 309S/4833 stainless steel

Therma 309S/4833 is an austenitic stainless steel with improved oxidation resistance in temperatures up to 1000°C/1830°F. There is a slight susceptibility to embrittlement during continuous operation at 600–900°C/1110–1652°F.

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  • EN: 1.4833
  • ASTM type: 309S
  • ASTM UNS: S30908
  • Microstructure: Austenitic
Typical applications
  • Furnace equipment
  • Annealing boxes
  • Thermowells
  • Baffle plates
  • Pots for quenching salt
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.06
  • Cr: 22.3
  • Ni: 12.3
  • Mo: -
  • N: -
  • Others: -

Therma 314/4841 stainless steel

Therma 314/4841 is an austenitic heat resisting stainless steel with excellent oxidation resistance in temperatures up to 1150°C/2100°F. There is a high susceptibility to embrittlement during continuous operation at 600–900°C/1110–1652°F

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  • EN: 1.4841
  • ASTM type: 314
  • ASTM UNS: S31400
  • Microstructure: Austenitic
Typical applications
  • Furnace equipment
  • Superheater suspensions
  • Enameling grates and hardening boxes
  • Valves and flanges
Product forms
Typical chemical composition, % by mass
  • C: 0.06
  • Cr: 24.3
  • Ni: 19.2
  • Mo: -
  • N: -
  • Others: Si

Standards and approvals

EN 10028-7 Flat products for pressure purposes – Stainless steels
EN 10088-1 Stainless steels – Part 1: List of stainless steels
EN 10088-2 Stainless steels – Corrosion resisting sheet/plate/strip for general and construction purposes
EN 10088-3 Stainless steels – Corrosion resisting semi-finished products/bars/rods/wire/sections for general and construction purposes
EN 10088-4 Stainless steel flat products, technical delivery conditions, steels for constructions
EN 10217-7 Welded steel tubes for pressure purposes – Stainless steel tubes
EN 10296-2 Welded circular steel tubes for mechanical and general engineering purposes - Stainless Steel tubes
ASTM A182 / ASME SA-182   Forged or rolled alloy-steel pipe flanges, forged fittings etc. for high temperature service
ASTM A240 / ASME SA-240 Heat-resisting Cr and Cr-Ni stainless steel plate/sheet/strip for pressure purposes
ASTM A276 Stainless and heat-resisting steel bars/shapes
ASTM A479 / ASME SA-479 Stainless steel bars for boilers and other pressure vessels
Eurocode 3 / EN 1993-1-4 Design of steel structures – Part 1-4: General rules – Supplementary rules for stainless steels
ISO 15510 Stainless steels – chemical composition

 

The most commonly used international product standards are given in the table. For a list of standards by product, visit Steel Finder.

Therma range use cases and articles

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Outokumpu Therma range downloads

Outokumpu Therma range datasheet
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Outokumpu Product Ranges chart
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Machining guidelines for heat resistant aistenitic stainless steel 153 MA™ and 253 MA®
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Machining guidelines for heat resistant austenitic stainless steel 4845
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Machining guidelines for standard austenitic stainless steel grades
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