​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Outokumpu Therma range

High service temperatures​​

  • Stainless steels for high service temperatures(> 550 °C/1020 °F)
  • Ferritics are resistant to sulfur-containing hot gases and have lower thermal expansion than austenitics
  • Austenitics are resistant to carburizing and nitriding/low-oxygen hot gases. They also have higher creep strength than ferritics
  • Due to their higher creep strength and oxidation resistance, Therma MA (micro alloyed) stainless steels give you a longer product lifecycle compared to products like Therma 309S/4833 and Therma 310S/4845

Therma 253 MA Therma 321H/4878
Therma 310S/4845 Therma 347H
Therma 4713 Therma 4828
Therma 4724 Therma 309S/4833
Therma 4742 Therma 153 MA
Therma 304H/4948 Therma 314/4841
Typical applications
Chemical industry (drums)
Power industry (coal burners)
Metalworking industry (heat treatment boxes)
Furnace technology (walls, doors)
Iron, steel, and non-ferrous industries
Energy conversion plants
Automotive exhaust applications
Heat treatment industry

​Compare ​product performance​​

​Pr​oduct properties​​

 Corrosion resistance

The resistance of a material to high-temperature corrosion is in many cases dependent on its ability to form a protective oxide layer. In a reducing environment, when such a layer cannot be created (or maintained), the corrosion resistance of the material will be determined by the alloy content of the material.

For more information

Check Stainless Steel Finder to find corrosion information by products in the Outokumpu Therma range​

Check the online corrosion table and search by chemical name, formula corrosion rates or alphabetically for stainless steel pr​oducts.

Find an Outokumpu sales office near you to get the printed version of the Outokumpu Corrosion Handbook​​​​​​​​​​


​​Ferritic products

Generally, ferrites are difficult to form in the cold condition. They are formable at room temperature when sheets are no thicker than 3 mm/0.11 in (6 mm/0.23 in for Therma 4713). Machining is considered to be less problematic due to their low strain hardening rates. When welding, the same precautions as for carbon steels are normally required.

Austenitic products

Like other austenitic stainless steels, heat-resisting steels can be formed in the hot or cold condition. As a result of their relatively high nitrogen content, the mechanical strength of certain products is higher and consequently greater deformation forces will be required. The relatively high hardness of austenitic stainless steels and their ability to strain harden must be taken into consideration in connection with machining

Outokumpu high temperature steels have good or very good weldability and can be welded using SMA, gas-shielded welding and submerged arc welding.

More information is available in the Outokumpu Welding Handbook, available from our Outokumpu sales offices ​​

 Forms & dimensions

The available forms for Outokumpu Therma​​ range products can include:
To see the forms available for a specific product or to get information about dimensions, check Stainless steel finder​​​​​​​​​​

 Standards and approvals


  • ​​EN 10028-7 Flat products for pressure purposes – Stainless steels
  • EN 10095 Heat resisting steels and nickel alloys
  • EN 10302 Creep resisting steels and nickel alloys
  • ASTM A167 Stainless and heat-resisting Cr-Ni steel plate/sheet/strip
  • ASTM A240 / ASME SA-240 Heat-resisting Cr and Cr-Ni stainless steel plate/sheet/strip for pressure purpose
  • ASTM A276 Stainless and heat-resisting steel bars/shapes
  • ASTM A312 / ASME SA-312 Seamless and welded austenitic stainless steel pipe
  • ASTM A314 Standard specification for stainless steel billets and bars for forging
  • ASTM A358 / ASME SA-358 Electric fusion-welded austenitic Cr-Ni alloy steel pipe for high temperature
  • ASTM A409 / ASME SA-409 Welded large diameter austenitic pipe for corrosive or high-temperature service
  • ASTM A473 Stainless steel forgings for general use
  • ASTM A479 / ASME SA-479 Stainless and heat-resisting steel bars and shapes for use in boilers and other pressure vessels

Certificates and approvals

  • ​​AD 2000 Merkblatt
  • Approval of Material Manufacturers
  • Factory Production Control Certificate
  • ISO 9001
  • ISO 14001
  • ISO 50001
  • ISO/TS 16949
  • OHSAS 18001
  • Pressure Equipment Directive (PED)




Stainless steel finder

Stainless Steel Finder is a tool for easily comparing and finding details of all Outokumpu stainless steel grades​​​​

Go to Steel Finder