Basic oxygen steelmaking

The Linz- Donawitz process ( " LD process "; english basic oxygen process, BOP ) is a basic oxygen refining, so the production of steel by conversion of high-carbon pig iron in low-carbon steel.

With the LD- about two-thirds of the world production of crude steel are produced. Steel Works by this method can be used royalty- free in that all important patents have expired. It is named after the two Austrian steelworks in Linz (Upper Austria ) and Donawitz (Styria ), where it was used on an industrial scale, first in the 1950s.

Description

The LD process is a base- lined converter, the so-called LD converter, supplied with liquid pig iron, a cooling means ( scrap or sponge iron ) and limestone or dolomite as a slag. Then is blown through a water-cooled lance extendable pure oxygen to the molten iron.

The fierce onset of combustion ( oxidation) of iron companion provides for agitation of the melt. For better mixing, argon is injected through nozzles in the bottom. The argon bubbles absorb the dissolved hydrogen in the melt ( backpack method ), which is designed to prevent the formation of so-called hydrogen traps in the later work. During the refining process, the contents of carbon, silicon, manganese, sulfur and phosphorus decrease steadily.

The blowing time is between 10 and 20 minutes and is selected so that the desired combustion or oxidation and decarburization of the undesired impurities is obtained. The burnt iron companion escape as gases or be bound by the added quicklime in the liquid slag.

Depending on the nature of the to be produced alloy and steel materials can be added at the end of the refining. Only the steel bath is at a temperature of more than 1600 ° C (up to 1750 ° C. Today, the possible ) tapped through the tap hole into a ladle, and then the slag is poured via the converter rim. The steel bath can be supplied to a secondary metallurgical treatment.

The maximum size is 380 t converter ( ThyssenKrupp Steel, Duisburg-Bruckhausen/Germany ).

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

Formation

Predevelopment

In 1928 was the Swiss Robert Durrer professor of metallurgical engineering at the Technische Hochschule in Berlin- Charlottenburg, where he began his pioneering research and experiments on the replacement of air by pure oxygen.

Between 1936 and 1940, the Estonian native, now has become a U.S. citizen Lellep Otto ( 1884-1975 ) had to make in the Gutehoffnungshütte the opportunity attempts in the hearth furnace and the converter using concentrated oxygen. This prefused Kalkferrite were to bring forward the dephosphorisation and tested from below applied oxygen nozzles. Both caused problems and had no reliable reproducibility. Since the Ministry of Economic Affairs of the Third Reich after Lelleps, landscaped abroad for old age sought, Lellep moved back to the U.S. and the experiments were discontinued.

Durrer returned to Switzerland in 1943, where his overall management of the metallurgical enterprises of all works of Roll'schen iron Werke AG and the management of Gerlafingen work was transferred and he occupied a newly created Department of Ferrous Metallurgy at the ETH Zurich. At his instance 1948, the factory Gerlafingen performed experiments, which was first inflated in a basic 2-t- Klein converter pure oxygen through a water- cooled nozzle on pig iron of different composition. H. Hellbrügge reported on the trials and Durrer suggested that further work in Linz.

LD process

The LD method was developed in Austria from June 1949 at the VÖEST in Linz, to operational readiness. The experiments in a 2.5 - ton converter lasted from 3 to 25 June, until finally hired a success with the participation of Theodor Eduard Suess and Rudolf Rinesch. There a large series of experiments with a 5- ton converter in Donawitz and a 15 -tonne vessel in Linz was then performed. The invention Rineschs led among other things to his dissertation The LD method, which was held for the know-how contained therein for a long time under lock and key. Herbert Trenkler worked as Director hut the primary authors of the new development.

Due to the much lower production costs, the VÖEST oriented on December 9, 1949 by the LD process, which had convinced through testing and cost calculations:

" Dr. Richter- Brohm, who alone responsible stewards of VÖEST, decided due to these facts to make the steel production in Linz on an entirely new basis, and to build an oxygen converter steel plant. [ ... ] In October 1950 the contract for the first LD- steel plant and on 27 November 1952, the production was taken. "

On December 15, 1950, the patent was filed. The LD replaced the previously common method of open-hearth method (SM ) method and Thomas procedures.

Designation

The origin of the abbreviation LD is unclear. Today it is mostly derived from the production sites in Linz and Donawitz, where the process was brought to production. An old, rarely used term is also Linzer steel nozzles, since the oxygen through special heat resistant nozzle is blown.

Another possible origin represents Linz -Durrer, Durrer since carried out important groundwork. He was, however, been of the opinion, the oxygen jet had "deep, like a solid body ," are blown, but in the end was unsuccessful because not form a reactive slag. In addition, upon the " no depth " Show or inflating the oxygen is quickly becoming a very hot reaction zone and the liquid slag, which ultimately helped the LD process for metallurgical breakthrough.

The terms " not deep " and " blow deep " are patent unclear due to lack of degree or area information. This was the reason why a U.S. court, between the patentee and the U.S. applicant ultimately ruled in favor of the applicant and the U.S. patent declared invalid because it does not contain any clear technical teaching.

A further development of the LD method is the LD -AC method (A stands for the ARBED in Luxembourg, C for the Centre National de Metallurgique in Liège ). In this case lime is blown together with the oxygen through the lance to the molten metal.

Award

1959 were honored as the inventor of the LD method with the Karl Renner Prize Ortwin Cuscoleca, Felix Grohs, Hubert Hauttmann, Fritz Klepp, Wolfgang Kühnelt, Rudolf Rinesch, Kurt Rosner and Herbert Trenkler.