Fotografie Haiko Hebig

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Directory of Preserved
Bessemer, Thomas, Kaldo and LD
Steelmaking Converters

Revision 2021-06-16

Thomas converter, Dortmund, Germany
Moving the DHHU Thomas converter, Dortmund, Germany

The invention of the Bessemer and basic Bessemer (Thomas) processes in 1856 and 1878 meant steel could be made in large quantities and at low cost for the first time, resulting in significant economic impact. In these processes, air is blown from the bottom or the side of cyclindric vessels –converters– through molten pig iron in order to burn excess carbon and remove impurities from the iron. They were superseded by oxygen-based processes from the mid 1950s on and phased out by the late 1970s.

Line diagram of crude steel production in West Germany by process over time Hermann Brandi, August-Thyssen-Hütte, Duisburg 1974

While many modern ironmaking plants –blast furnaces– are listed as monuments, preservation of steelmaking equipment and processes is lacking. No complete Thomas shop is preserved, no Thomas converter is remaining in its original place, and related buildings and architectural traces are getting fewer.

However, a number of converters has been preserved across the globe, covering the entire lifespan of this paramount technology from early days to obsolescence. This list is an attempt to catalog them.

Bessemer and Thomas (Basic Bessemer)
— Upright converters
— Early converters
— Swedish converters
— Small converters
— Large converters
LD (Basic Oxygen/BOF)
Recently demolished converters

Converters are listed by type and then by current location.
Russia, Ukraine, and China are not covered yet.

Bessemer and Thomas (Basic Bessemer)

31 converters known in total


Upright converters

No converter known

In its early years, the Bessemer process was performed in stationary cylindrical vessels with a ring of air nozzles in its lower part. There are two known replicas: one full size at Tekniska museet, Stockholm, Sweden, and one half size at Edsken near Hofors, Sweden, at the site of the first successful Bessemer blow in 1858.

Early converters

Three converters known

  1. UK: At Science Museum, London, from Barrow Haematite Steel Company, Barrow-in-Furness
  2. D: At Deutsches Museum, München, from Krupp, Essen
  3. AUT: At Technisches Museum, Wien, from Eisenwerk Turrach
Swedish Bessemer converters

Bottom-blown converters with narrow mouth, acidic lining, typically removable upper and lower cones and a tap weight of 3 to 4 tons as used exclusively in Sweden until 1965. A remarkable number of such converters is preserved:

Eleven converters known

  1. SWE: At Hagfors Järnverk, in its original location
  2. SWE: At Hagfors Järnverk, in its original location
  3. SWE: At Iggesunds Bruk, in its original location
  4. SWE: At Iggesunds Bruk, in its original location
  5. SWE: At Svartnäs Bruk, in its original location
  6. SWE: At Västanfors, from Västanfors bruk
  7. SWE: At Tekniska museet, Stockholm, from Västanfors bruk
  8. SWE: At Långshyttan, from Klosterverken Långshyttan
  9. SWE: At Forsbacka, from Forsbacka Bruk
  10. SWE: At Sandviken, from Sandvikens Järnverk
  11. SWE: At Högbo Bruk, from Sandvikens Järnverk
Small converters
(Baby Bessemer)

As used in foundries. Mostly side-blown converters (Tropenas) fed with hot metal from cupola furnaces.

Seven converters known

  1. D: At Henrichshütte museum, Hattingen, from Eisenwerk Rödinghausen, Menden-Lendringsen
  2. D: At DASA Working World Exhibition, Dortmund, from Stahl- und Tempergießerei Gustav Tücking, Hagen-Eckesey
  3. LUX: At Minett Park Fond-de-Gras
  4. BEL: At University of Leuven, from Usines Emile Henricot, Court-Saint-Etienne
  5. UK: At Summerlee Museum of Scottish Industrial Life, Coatbridge, Scotland, from Stewarts and Lloyds' Sun Foundry, Coatbridge
  6. NL: At TATA Ijmuiden, from DEMKA, Utrecht
  7. NOR: At Norsk Teknisk Museum, Oslo, from Strømmen Værksted, Strømmen
    Tropenas converter, first blow 29.04.1902. The foundry switched to arc furnaces in 1925, was spun off as Strømmen Stål in 1970 and shut down in 1978.
    At Norway's single integrated steel plant, Norsk Jernverk at Mo-i-Rana, three generations of converters were in use: first two 20 t DEMAG Bessemer converters from 1955 to 1961, then two 40 t DEMAG LD converters, and finally two 72 t LD converters from 1976/77 to 1989. Today, one 12 t AOD converter is in service at a Jørpeland foundry.
Large converters

As used in integrated steel plants for steelmaking at large scale. Bottom-blown and typically fed with hot metal from blast furnaces.

Nine converters known

  1. D: At Phoenixsee, Dortmund, from Hörder Verein (DHHU) Hermannshütte at the same siteTh
  2. LUX: At University of Luxemburg, from ARBED SchifflangeTh
  3. LUX: In Dudelange, from ARBED Dudelange, currently not on displayTh
  4. UK: At Kelham Island Museum, Sheffield, England, from Workington Iron and Steel, Moss Bay, WorkingtonBm
  5. CZ: At Mayrau colliery museum, Vinařice, previously at Vila Bachrovna, Kladno, from Vojtěšská huť (Koněv, formerly Prager Eisen-Industrie-Gesellschaft)Th
  6. USA: In Pittsburgh, PA, from A. M. Byers Company, Ambridge, PA
  7. ARG: At Altos Hornos Zapla, Palpalá, from the same site
  8. ZA: At Mittal South Africa, Pretoria, from the same siteBm
  9. J: At Kawasaki City Museum, from Kawasaki Works, Nippon Kōkan KKTh
    There are two scale models of this converter, one at Kawasaki City Museum, and one at JFE Steel Keihin Works Amenity Center.

Bm – Acid Bessemer
Th – Basic Bessemer (Thomas)

Other notable scale models and replicas of Bessemer converters on display in museums include the 1/4 sized converter at Chiba Museum of Science and Industry, Japan. It was built by English company, Garmendale, with methods, tools, and materials available in the 1850s.

At Longwy, France, a simplified scale model of a converter exists that was used in the 1979 Les Flammes de l'espoir protests against factory closures.


Bottom-blown converters using pure oxygen.

Four converters known

  1. F: At Mine musée du Val de Fer, Neuves-Maisons, from Chiers-Châtillon (USINOR) Neuves-Maisons
  2. D: At Stahlwerk Thüringen, Unterwellenborn, from the same site, Maxhütte UnterwellenbornQEK
  3. D: At Stahlwerk Thüringen, Unterwellenborn, from the same site, Maxhütte UnterwellenbornQEK
  4. D: At Henrichshütte museum, Hattingen, from Maxhütte UnterwellenbornQEK

QEK – Qualitäts- und Edelstahlkombinat Brandenburg, GDR, process


Rotating oxygen-blown converters

One converter known

  1. SWE: At Domnarvets Jernverk, Borlänge, from the same site
    There were one 30 t (1956) and two 70/80 t (1965) PINTSCH-BAMAG made industrial scale Kaldo furnaces in operation at Domnarvets Jernverk, Borlänge, Sweden, all with exchange vessel system. A 30 ton Kaldo converter was rebuilt into an OBM converter in 1974 and into a desulphurisation unit in 1978 before getting decommissioned in 1981. There were also 3 t and 30 t Dored pilot plants at Domnarvets, a direct reduction process based on Kaldo vessels. Kaldo converters were also installed at the two Swedish coastal steelworks, Luleå and Oxelösund.
Thomas converter, Dortmund, Germany
80 t Kaldo converter at Domnarvets in service and on display.
Photos: Jernkontoret, Wikipedia

Kaldo converters are also used in non-ferrous metallurgy under the generic term Top Blown Rotary Converters (TBRC).

Two other steelmaking processes also made use of rotating vessels:

The LD-Kaldo converter could be operated by both the LD and the Kaldo method. Two built, none preserved.

The Rotor steelmaking process or Rotorstahl employed a long cylindrical converter called Graef Rotor furnace or Oberhausen Rotor furnace. Approx. nine built, none preserved.

There is a universal converter at the Luleå, Sweden, research lab that can be used to simulate, among many others, the Kaldo and the Rotovert processes. Rotovert (Sweden) and Rotored (Italy) were experimental steelmaking processes with rotary vessels that did not reach industrial scale.

LD Converters
(Basic Oxygen Furnaces/BOF)

Primarily top-blown converters using pure oxygen

Eight converters known

  1. D: At Henrichshütte museum, Hattingen, from the same site
  2. AUT: At VÖEST, Linz, from the same site
  3. AUT: At Technisches Museum, Wien, from VÖEST, Linz
  4. I: At Ilva/Italsider di Bagnoli, Naples, from the same site
  5. USA: At McLouth Steel, Trenton, MI, from the same site
  6. CAN: At Dominion Foundry and Steel Dofasco, Hamilton, ON, from the same site
  7. J: 1956 Yawata 5 ton pilot converter at Higashida Daiichi Blast Furnace No. 1 Historical Site Plaza, Kitakyushu, from the same site
  8. J: At Higashida Daiichi Blast Furnace No. 1 Historical Site Plaza, Kitakyushu

There also are cold idled converters and converters decomissioned in place.

Demolished Converters

  1. Future: 3×LD at Lackenby, England, UK
    The Lackenby Steelmaking Complex is scheduled for demolition 2022–2024 as laid out in the South Tees Regeneration Master Plan. BOS-BAP, 240 t capacity, last blow 28.09.2015. The BAP Bath Agitation Process was developed by British Steel and deployed at all its basic oxygen shops. The converters in place are from the 1990s and were last relined 2011/2012.
  2. 2021: 2×OXYVIT at Vítkovické železárny, Ostrava, CZ
    75 t bottom-blown converters with CO post combustion, built in-house 1981 (K1) and 1991 (K2), overhauled 1992 (K1). Demolition of the steel plant started 11/2020. The converters were scrapped 02/2021. They were the only OXYVIT converters made.
  3. 2019: 3×KMS at Maxhütte, Sulzbach-Rosenberg, D
    Klöckner-Maxhütte-Stahl process, 70 t capacity, converters built 1975-1977 by VÖEST, last blow 24.09.2002, scrapped 11/2019.
  4. 2019: 2×LD at National Steel, Weirton, West Virginia, USA
    320 t capacity, built 1975/77 and 1989 by VÖEST, last blow 24.09.2002, scrapped 2019.
  5. 2019: 3×K-OBM at Forges de Thy-Marcinelle et Monceau/Duferco Carsid, Charleroi, BEL
    150 t bottom-blown converters with oxygen side tuyere, converters and meltshop built by VÖEST-GHH, first blow 04/1976, last blow 11.11.2008, scrapped 2019.
    At nearby La Louvière, the Gustave Boël converter buildings were demolished in late 2020. The LD-AC converters had already been scrapped (2/3x85 t, in service 1967/71–1997). This leaves no oxygen steelmaking shops left in the Charleroi region. These were: Thomas shops at Châtelineau, Couillet, Montignies-sur-Sambre (LD-AC retrofit), Monceau-sur-Sambre (OBM retrofit), Marchienne-au-Pont (OBM retrofit), Marcinelle, Clabecq, La Louviere, LD-AC shops at Montignies-sur-Sambre, Clabecq, La Louvière, LD-Kaldo at Marchienne-au-Pont, and the Marcinelle OBM shop.
    Today, all steelmaking in the region is EAF based. A 1x180 t Siemens-VAI AOD shop with three vessels was launched at Châtelet in 2005.
  6. 2016: 2×LD at Ovako/FNsteel Koverhar, Hanko, FIN
    53 t capacity, meltshop built by Kölsch-Fölzer-Werke, converters built by VÖEST, first blow 26.11.1971, last blow 27.06.2012, scrapped 2016.
    Koverhar was one of three coke blast furnace shops and one of two basic oxygen steelmaking shops in Finland. Three new 125 t Primetals LD converters were installed at the other BOF site, Raahe, in 2015 and 2016, scheduled to be replaced by electric arc furnaces in the 2030/40s.
    There also are two large AOD converters and one mechanically similar CRC ferrochrome converter in operation at Tornio, a VODC converter at Tampere, and a small AOD converter at Karhula.
  7. 2016: 2×LD-CB/NSR at Nakayama Steel Works, Funamachi, Osaka, J
    105 t top oxygen, bottom nitrogen blown converters that were later used in a scrap melting process. Meltshop started 09/1975 with 2x70t LD converters. Replacement 2x105t converters started 07/1985, LD-CB operation –07/2002, NSR operation 09/2002–27.05.2010. In the Nipon Steel Sakai developed LD-CB process, CO2 or N2 is bubbled through a single pipe bottom plug. In the NSR Nakayama Scrap Refining Process, the same converters were operated without hot metal: 100% scrap charges were melted by adding coke through the top. Funamachi was the only shop that employed this process.

This Resource

This directory of preserved steelmaking converters is meant as a research aid. It is compiled by Haiko Hebig.

First published: 2020-05-20
Revision: 2021-06-16

Please send additions and corrections to my email address:

With special thanks to Lauri Holappa and Tomáš Voldráb.


Revision 2021-06-16
- Added: Scale models of NKK Kawasaki converter

Revision 2021-06-02
- Added: Scrapped LD-CB/NSR converters at Osaka

Revision 2021-05-20
- Added: Yawata pilot LD converter at Kitakyushu

Revision 2021-04-08
- Added: Scheduled demolition at Lackenby
- Updated: Scrapped OXYVIT converters at Vítkovice
- Updated: Type of converter at Pretoria

Revision 2020-12-02
- Expanded: Scrapped K-OBM converters Marcinelle
- Updated: Scrapped LD converters at Koverhar, thanks to Lauri Holappa

Revision 2020-11-27
- Updated: Tropenas converter at Norsk Teknisk Museum

Revision 2020-11-22
- Added: Converter model used in Longwy protests in 1979
- Updated: Name of ferrochrome converter at Tornio

Revision 2020-11-16
- Added: Origin of converter at Neuves Maisons
- Updated: Type of converter at Neuves Maisons

Revision 2020-11-15
- Added: Scrapped OXYVIT shop at Vítkovice
- Expanded: Section on upright converters

Revision 2020-11-13
- Added: Section on Swedish Bessemer converters

Revision 2020-11-07
- Expanded: Tropenas converter at Norsk Teknisk Museum

Revision 2020-11-06
- Expanded: Kaldo converter at Domnarvet

Revision 2020-11-03
- Added: Tropenas converter at Norsk Teknisk Museum
- Added: Scrapped LD converters at Weirton
- Added: Scrapped LD converters at Koverhar
- Expanded: Scrapped KMS converters at Maxhütte
- Expanded: Scrapped K-OBM converters at Carsid

Revision 2020-06-26
- Added: LD converter at VÖEST, Linz

Revision 2020-06-20
- Added: Rotovert, Rotored

Revision 2020-06-08
- Added: Thomas converter at Mayrau mining museum

Revision 2020-05-28
- Added: Note on LD-Kaldo and Rotor converters
- Added: Section on recently demolished converters

Revision 2020-05-26
- Added: Origin of converter at Summerlee Museum
- Added: LD converter at Dofasco

Revision 2020-05-25
- Added: LD converter at Higashida Park
- Added: Thomas converter at Kawasaki City Museum
- Added: Scale model at Chiba museum

Revision 2020-05-23
- Added: Origin of converter at DASA Dortmund

Revision 2020-05-20
- Original publication