Linz-Donawitz procedure

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One of the first two productive LD crucibles from 1952 from the VÖEST plant in Linz, weighing 120 tons, is now in the Vienna Technical Museum .

The Linz-Donawitz process ( LD process ; English basic oxygen process , BOP ) is an oxygen blowing process for refining , i.e. for steel production by converting high-carbon pig iron into low-carbon steel .

72% of the world's crude steel production is currently produced using the LD process (as of 2013). Steel works using this process can be operated license-free, as all important patents have expired. It is named after the two Austrian steelworks Linz (Upper Austria) and Donawitz (Styria), whose engineers developed the process.

description

The LD process is a further development of the Thomas process. Instead of blowing in atmospheric air from below, oxygen is blown from above.

Principle of the LD converter

In the LD process, a basic-lined converter, the so-called LD converter, is charged with liquid pig iron, a coolant ( scrap or sponge iron , approx. 20% in total) and lime or dolomite as a slag-forming agent. Then pure oxygen is blown onto the molten iron from above through an extendable, water-cooled lance . Therefore, the LD process is also known as the oxygen inflation process.

Filling a converter

The violent combustion ( oxidation ) of the iron companions causes a swirling of the melt and a strong increase in temperature. For better mixing and lowering of the hydrogen partial pressure, argon is blown through nozzles in the floor. The solubility of hydrogen (a steel pest) in the melt is reduced. This gasses out what is to prevent the formation of so-called hydrogen traps in the later workpiece. During the fresh process, the contents of carbon , silicon , manganese , sulfur and phosphorus steadily decrease, as these are slagged with the added rock flour.

The blowing time is between 10 and 20 minutes and is selected in such a way that the desired decarburization and the combustion or oxidation of the undesired impurities is achieved. The burnt iron components escape as gases or are bound by added burnt lime in the liquid slag .

During the converter process, carbon monoxide (CO) is created through the oxidation of the carbon , which rises in the form of bubbles in the melt. Since the carbon content of the melt is still highest at the beginning of the converter process, the decarburization reaction is strongest at this point in time. The CO bubbles rise and cause the slag to foam .

During the steel production process in the converter, the distance between the water-cooled oxygen lance and the steel bath and slag surface can be varied. The lance position influences u. a. the strength of the convection in the steel bath, the foaming of the slag and also has an influence on the wear and tear of the refractory lining of the converter. The amount of oxygen that is blown onto the bath per unit of time (oxygen flow rate) can also be set.

The carbon monoxide produced during the decarburization phase can be used to generate energy later. In order to prevent the gas from escaping and the carbon monoxide from reacting to form carbon dioxide , the converter is sealed off as well as possible from the ambient atmosphere.

The steel bath is tapped through the tap hole into a pan at a temperature of more than 1600 ° C (up to 1750 ° C possible today). During tapping, deoxidizing agents and alloys can be added. The slag is then poured over the converter edge. The crude steel can then be sent to a secondary metallurgical treatment.

After a converter process, a slag residue is often left in the converter. This can be used as the basis for the slagging reactions of the next converter batch. Another possibility is to use the residual slag remaining in the converter for so-called slag splashing. The slag is distributed in the converter interior by blowing nitrogen through the lance. The aim is to form a protective layer on the converter lining and thereby achieve a longer service life .

The converter size achieved so far is 380 t ( ThyssenKrupp Stahl, Duisburg-Bruckhausen).

A major technical problem at the beginning was the removal of the brown smoke (iron (Fe), which evaporates at the high reaction temperature and escapes from the converter as FeO), which was visible from afar and would have been an obstacle to the worldwide spread of the LD process; however, the problem was technically solved.

Emergence

Advance developments

In 1928, the Swiss Robert Durrer became professor of iron and steel engineering at the Technical University in Berlin-Charlottenburg , where he began his fundamental research and experiments on the replacement of air with pure oxygen.

Between 1936 and 1940, Otto Lellep (1884–1975) , who came from Estonia and has since become a US citizen, had the opportunity to make experiments in the hearth furnace and converter using concentrated oxygen in the Gutehoffnungshütte . Pre-melted lime ferrites to advance the dephosphorization and oxygen nozzles applied from below were tested. Both caused problems and did not allow reliable reproducibility. Since the Reich Economics Ministry of the Third Reich was looking for Lellep's old-age insurance abroad, Lellep moved back to the USA and the experiments were not continued.

Durrer returned to Switzerland in 1943, where he was entrusted with the overall management of the metallurgical operations of all the von Roll'schen Eisenwerke AG plants and the management of the Gerlafingen plant , and he filled a newly created chair for metallurgy at the ETH Zurich . At his instigation, tests were carried out in the Gerlafingen plant in 1948, whereby for the first time pure oxygen was blown onto different types of pig iron in a basic 2 t small converter through a water-cooled nozzle. H. Hellbrügge reported on the experiments and Durrer suggested that the work be continued in Linz.

LD process

The LD process was developed in Austria from June 1949 at VÖEST in Linz until it was ready for operation. The tests in a 2.5 t converter lasted from June 3rd to June 25th until they were finally successful with the participation of Theodor Eduard Suess and Rudolf Rinesch. A large series of tests was then carried out with a 5-ton converter in Donawitz and a 15-ton container in Linz. The invention of Rinesch led u. a. on his dissertation on the LD process , which was kept under lock and key for a long time because of the know-how it contained . Herbert Trenkler played a key role in the new development as the smelter's director.

Due to the much lower production costs, VÖEST reoriented itself to the LD process on December 9, 1949, which had convinced through tests and cost calculations:

" Dr. Richter-Brohm , the sole administrator of VÖEST, decided on the basis of these facts to put steel production in Linz on a completely new basis and to build an oxygen-blown converter steelworks. […] In October 1950 the order was placed for the first LD steelworks and production started on November 27, 1952. "

The invention was registered on August 31, 1949 and the Austrian patent AT168589 was granted on December 15, 1950. The LD process replaced the previously common Siemens-Martin process (SM process) and the older Thomas process .

designation

The origin of the abbreviation LD is unclear. Today it is mostly derived from the Linz and Donawitz production sites , where the process was brought to production maturity. An old, seldom used name is Linzer Düsenstahl, as the oxygen is blown in via special, heat-insensitive nozzles.

Another possible origin is Linz-Durrer , as Durrer had done decisive preparatory work. He was of the opinion, however, that the oxygen jet had to be blown in “deeply, like a solid body”, but this was unsuccessful in the end because no reactive slag was formed. In contrast, the “not deep” blowing in or puffing up the oxygen quickly led to a very hot reaction zone and liquid slag, which ultimately helped the LD process to break through.

The terms “not deep” and “blow in deeply” are unclear under patent law due to missing dimensions or areas. This was the reason why a US court between the patent proprietor and the US plaintiff ultimately ruled in favor of the plaintiff and declared the US patent to be invalid because it did not contain any clear teaching on technical action.

A further development of the LD process is the LD-AC process ( A stands for ARBED in Luxembourg , C for the Center National de Metallurgique in Liège ). Lime dust is blown together with the oxygen through the lance onto the metal bath.

Award

In 1959 Otwin Cuscoleca, Felix Grohs, Hubert Hauttmann, Fritz Klepp, Wolfgang Kühnelt, Rudolf Rinesch, Kurt Rösner and Herbert Trenkler were awarded the Karl Renner Prize as inventors of the LD process .

See also

Web links

Commons : Linz-Donawitz-Procedure  - collection of pictures, videos and audio files

Preface

Individual evidence

  1. ↑ stahl-online.de
  2. ↑ bdsv.org ( Memento of the original from April 2, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF) @1@ 2Template: Webachiv / IABot / www.bdsv.org
  3. ^ Helmut Burghardt, Gerd Neuhof: steel production . Ed .: Hans-Joachim Eckstein. 1st edition. VEB German publishing house for basic industry, Leipzig 1982, p. 68-75 .
  4. ↑ Michael Degner u. a.,: steel brooch . Ed .: Steel Institute VDEh. Verlag Stahleisen GmbH, Düsseldorf 2007, ISBN 978-3-514-00741-3 , p. 53-59 .
  5. ↑ a b Schweizerische Bauzeitung: Wochenschrift für Architektur, Ingenieurwesen, Maschinentechnik , Volume 83, 1965, p. 858
  6. ↑ Günter Bauhoff:  Lellep, Otto. In: New German Biography (NDB). Volume 14, Duncker & Humblot, Berlin 1985, ISBN 3-428-00195-8 , p. 179 ( digitized version ).
  7. ↑ a b c Steel and Iron , Volume 73, Association of German Ironworking People, A. Bagel, 1953, p. 7
  8. ↑ Helmut Heiber (ed.): Files of the party chancellery of the NSDAP: register , volume. 1, Oldenbourg Verlag, 1983, ISBN 978-3-486-49641-3 , p. 472 (act 14120, limited preview in the Google book search)
  9. ^ A b c Metallurgy and Foundry Technology, Volumes 1–2, Verlag Technik, 1951, p. 173
  10. ^ Steel and iron. Journal for the German Ironworks , Volume 72, 1952, p. 993
  11. ↑ Herbert Hiebler, Wilfried Krieger: Prof. Dr. mont. Herbert Trenkler on his 100th birthday . In: Berg- und Hüttenmännische monthly books (BHM), Vol. 152, 2007, Issue 11, pp. 378-380, here p. 378 ( doi: 10.1007 / s00501-007-0332-7 ).
  12. ^ Austrian construction journal: Organ of the specialist groups for construction of the Austrian engineering and architecture associations and the municipal testing and research institute for construction Vienna , volumes 11-12, Springer-Verlag in Vienna, 1956, p. 25
  13. ^ Activity report of the Austrian Federation of Trade Unions , ÖGB, 1956, p. U-46
  14. ↑ Vienna City Hall Correspondence, December 12, 1959, sheet 2461
  15. ^ Wiener Rathauskorrespondenz, January 23, 1960, sheet 114