EP0361554B1 - Use of ferritic chromium-molybdenum steels as materials resisting concentrated sulfuric acid - Google Patents

Use of ferritic chromium-molybdenum steels as materials resisting concentrated sulfuric acid Download PDF

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Publication number
EP0361554B1
EP0361554B1 EP89202071A EP89202071A EP0361554B1 EP 0361554 B1 EP0361554 B1 EP 0361554B1 EP 89202071 A EP89202071 A EP 89202071A EP 89202071 A EP89202071 A EP 89202071A EP 0361554 B1 EP0361554 B1 EP 0361554B1
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EP
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Prior art keywords
sulfuric acid
molybdenum
chromium
carbon
concentrated sulfuric
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EP89202071A
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German (de)
French (fr)
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EP0361554A1 (en
Inventor
Karl-Heinz Dörr
Hermann Müller
Ulrich Dr. Sander
Wolfram Schalk
Ernst Dr. Wallis
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GEA Group AG
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Metallgesellschaft AG
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
    • F28F21/081—Heat exchange elements made from metals or metal alloys
    • F28F21/082—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum

Definitions

  • the invention relates to the use of a ferritic chromium-molybdenum steel with good corrosion resistance to concentrated sulfuric acid.
  • Sulfuric acid is generally produced by catalytic conversion of the SO2 content of gases to SO3 and - in the case of dry gases - subsequent absorption of the SO3 formed in concentrated sulfuric acid or - in the case of moist gases - subsequent condensation of the sulfuric acid formed.
  • DE-C-21 54 126 discloses the use of an austenitic nickel alloy containing chromium, molybdenum, cobalt, manganese, copper and silicon for acid concentrations of 65% and more. Because of its difficult deformability, this alloy is limited to use as shafts, bearings, pumps, valve components and the like elements.
  • DE-A-33 20 527 discloses the use of austenitic steels with a silicon content of 4.6-5.8%. The processability and the production of this material is difficult.
  • EP-B-0 130 967 describes four materials for use in sulfuric acid from 98 to 101% and a temperature of more than 120 ° C. The best corrosion properties are found in the ferritic alloy Alloy 26-1 (material no. 1.4131, XlCrMo261), the maximum nickel content of which is 0.5%. However, this material causes processing difficulties and its resistance to corrosion decreases sharply as the concentration of sulfuric acid decreases.
  • ferritic material 29-4-2 is mentioned as the next best material for use in sulfuric acid of 98-101%.
  • This material contains 28-30% Cr, 3.50-4.20% Mo and 2.00-2.50 Ni. This material also causes considerable difficulties in processing and its corrosion resistance decreases sharply as the concentration of sulfuric acid decreases.
  • EP-B-0 200 862 discloses the use of a molybdenum-free, chromium-containing alloy for use in sulfuric acid above 96% and temperatures up to 350 ° C., it being irrelevant whether it is ferritic or ferritic -austenitic or austenitic structure is present. This material does not have sufficient corrosion resistance, especially in the austenitic and austenitic-ferritic structure and in the case of sulfuric acids with a lower concentration.
  • the invention has for its object to provide a material which has a high corrosion resistance even in lower sulfuric acid concentrations, has good kneading properties and thus processing properties, and which can be produced inexpensively.
  • ferritic chromium-molybdenum steels 26 to 30% chrome 1.8 to 3.0% molybdenum 3.0 to 4.5% nickel carbon ⁇ 0.02% silicon ⁇ 1.00% manganese ⁇ 1.00% sulfur ⁇ 0.015% Carbon + nitrogen ⁇ 0.045% niobium ⁇ 12 x% C ⁇ 1.2% Remainder iron as well as impurities due to melting technology
  • Remainder iron As a corrosion-resistant material for the manufacture of structural parts that are resistant to sulfuric acid at a concentration equal to or greater than 94% by weight with a temperature below the boiling point.
  • Contamination-related impurities can e.g. its phosphorus, aluminum, vanadium, titanium, tantalum, calcium, magnesium, cerium, boron.
  • the material has good forming properties and is very well suited for the production of structural parts from sheet metal or strips, e.g. Heat exchangers, pipes, pump systems, sprinkler systems, absorbers, etc.
  • the material is also corrosion-resistant to cold sulfuric acid.
  • a preferred embodiment consists in the use of a ferritic chromium-molybdenum steel 27 to 29% chrome 2.0 to 3.0% molybdenum 3.0 to 4.5% nickel carbon ⁇ 0.02% Carbon + nitrogen ⁇ 0.045% (Niobium + zircon) ⁇ 10 x% (carbon + nitrogen) Remainder iron as well as impurities due to melting technology
  • This steel shows particularly good corrosion properties.
  • Table I shows the corrosion behavior of the material according to the invention at different temperatures and sulfuric acid concentrations.
  • the corrosion behavior was determined by immersion tests. The test duration was 25 days in all cases. The removal rates were determined by gravimetric differential weighing and conversion to mm / a. The test medium was renewed after each test cycle.
  • the material contained 28% Cr, 2% Mo and 4% Ni.
  • the removal rates in sulfuric acid with a concentration of 95% by weight were: at 100 ° C 0.06 mm / a at 125 ° C 0.05 mm / a at 150 ° C 0.32 mm / a
  • the advantages of the use of the material according to the invention are that the tendency to precipitate brittle, intermetallic phases is relatively low for the molybdenum.
  • the nickel content increases the elimination inertia relatively strongly and narrows the heterogeneous areas in the thermodynamic equilibrium. The combination of these two effects leads to a higher structural stability during welding and during heat treatment processes. This results in good corrosion resistance and ductility in the form of impact strength.
  • the material can be welded up to a thickness of 50 mm, while the material 29-4-2 can only be welded up to about 2 mm.
  • the material according to the invention therefore has very good processability with very good corrosion resistance.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Catalysts (AREA)
  • Heat Treatment Of Articles (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Description

Die Erfindung betrifft die Verwendung eines ferritischen Chrom-Molybdän-Stahles mit guter Korrosionsbeständigkeit gegenüber konzentrierter Schwefelsäure.The invention relates to the use of a ferritic chromium-molybdenum steel with good corrosion resistance to concentrated sulfuric acid.

Schwefelsäure wird im allgemeinen durch katalytische Umsetzung des SO₂-Gehaltes von Gasen zu SO₃ und - bei trockenen Gasen - anschließender Absorption des gebildeten SO₃ in konzentrierter Schwefelsäure oder - bei feuchten Gasen - anschließender Kondensation der gebildeten Schwefelsäure hergestellt.Sulfuric acid is generally produced by catalytic conversion of the SO₂ content of gases to SO₃ and - in the case of dry gases - subsequent absorption of the SO₃ formed in concentrated sulfuric acid or - in the case of moist gases - subsequent condensation of the sulfuric acid formed.

Dabei kommen Trockner, Absorber, Wärmeaustauscher, Pumpenvorlagen, Rohrleitungen usw. mit konzentrierter Schwefelsäure ab etwa 94 Gew.-% und erhöhter Temperatur in Berührung. Diese Schwefelsäure ist ein äußerst aggressives Medium, das auf die verwendeten Konstruktionsteile eine schnelle und starke Korrosion ausübt. Alle Konstruktionsteile, die mit dieser Schwefelsäure in Berührung kommen, müssen deshalb aus korrosionsbeständigen Materialien bestehen. Als solche Materialien werden spezielle Stahllegierungen, Gußeisen, Kunststoffe, Keramik, Glas, Graphit oder entsprechende Auskleidungen verwendet. Die nicht-metallischen Materialien haben jedoch eine geringe mechanische Festigkeit und für viele Anwendungsfälle treten Verarbeitungsprobleme auf. Die metallischen Materialien haben zwar eine gute mechanische Festigkeit, jedoch ist ihre Korrosionsbeständigkeit in manchen Fällen nicht ausreichend, das Material läßt sich schlecht verformen oder das Material ist sehr teuer.Dryers, absorbers, heat exchangers, pump systems, pipelines etc. come into contact with concentrated sulfuric acid from about 94% by weight and elevated temperature. This sulfuric acid is an extremely aggressive medium that causes rapid and severe corrosion on the construction parts used. All construction parts that come into contact with this sulfuric acid must therefore be made of corrosion-resistant materials. Special steel alloys, cast iron, plastics, ceramics, glass, graphite or corresponding linings are used as such materials. However, the non-metallic materials have a low mechanical strength and processing problems arise for many applications. Although the metallic materials have good mechanical strength, their corrosion resistance is in some cases insufficient, the material is difficult to deform or the material is very expensive.

Aus der DE-C-21 54 126 ist die Verwendung einer Chrom, Molybdän, Kobalt, Mangan, Kupfer und Silizium enthaltenden austenitischen Nickellegierung für Säurekonzentrationen von 65 % und mehr bekannt. Diese Legierung ist wegen ihrer schwierigen Verformbarkeit auf den Einsatz als Wellen, Lager, Pumpen, Ventilbestandteile und dergleichen Elemente beschränkt.DE-C-21 54 126 discloses the use of an austenitic nickel alloy containing chromium, molybdenum, cobalt, manganese, copper and silicon for acid concentrations of 65% and more. Because of its difficult deformability, this alloy is limited to use as shafts, bearings, pumps, valve components and the like elements.

Aus der DE-A-33 20 527 ist die Verwendung von austenitischen Stählen mit einem Siliziumgehalt von 4,6 - 5,8 % bekannt. Die Verarbeitbarkeit und die Herstellung dieses Materials ist aber erschwert.DE-A-33 20 527 discloses the use of austenitic steels with a silicon content of 4.6-5.8%. The processability and the production of this material is difficult.

In der EP-B-0 130 967 sind vier Werkstoffe für den Einsatz in Schwefelsäure von 98 bis 101 % und einer Temperatur von mehr als 120°C beschrieben. Die besten Korrosionseigenschaften hat der ferritische Werkstoff Alloy 26-1 (Werkstoff Nr. 1.4131, XlCrMo261), dessen Nickelgehalt maximal 0,5 % beträgt. Dieser Werkstoff bedingt jedoch Schwierigkeiten bei der Verarbeitung und seine Korrosionsbeständigkeit nimmt mit fallender Konzentration der Schwefelsäure stark ab.EP-B-0 130 967 describes four materials for use in sulfuric acid from 98 to 101% and a temperature of more than 120 ° C. The best corrosion properties are found in the ferritic alloy Alloy 26-1 (material no. 1.4131, XlCrMo261), the maximum nickel content of which is 0.5%. However, this material causes processing difficulties and its resistance to corrosion decreases sharply as the concentration of sulfuric acid decreases.

In der EP-A-0 181 313 wird nach dem Alloy 26-1 der ferritische Werkstoff 29-4-2 als nächstbester Werkstoff für den Einsatz in Schwefelsäure von 98-101 % genannt. Dieser Werkstoff enthält 28-30 % Cr, 3,50-4,20 % Mo und 2,00-2,50 Ni. Auch dieser Werkstoff bedingt erhebliche Schwierigkeiten bei der Verarbeitung und seine Korrosionsbeständigkeit nimmt mit fallender Konzentration der Schwefelsäure stark ab.In EP-A-0 181 313, after alloy 26-1, ferritic material 29-4-2 is mentioned as the next best material for use in sulfuric acid of 98-101%. This material contains 28-30% Cr, 3.50-4.20% Mo and 2.00-2.50 Ni. This material also causes considerable difficulties in processing and its corrosion resistance decreases sharply as the concentration of sulfuric acid decreases.

Aus der EP-B-0 200 862 ist die Verwendung einer Molybdän-freien, Chrom-haltigen Legierung für den Einsatz in Schwefelsäure oberhalb 96 % und Temperaturen bis 350°C bekannt, wobei es nicht von Bedeutung ist, ob sie in ferritischer, ferritisch-austenitischer oder austenitischer Gefügeform vorliegt. Dieser Werkstoff hat, insbesondere in austenitischer und austenitisch-ferritischer Gefügeform und bei Schwefelsäuren mit geringerer Konzentration keine ausreichende Korrosionsbeständigkeit.EP-B-0 200 862 discloses the use of a molybdenum-free, chromium-containing alloy for use in sulfuric acid above 96% and temperatures up to 350 ° C., it being irrelevant whether it is ferritic or ferritic -austenitic or austenitic structure is present. This material does not have sufficient corrosion resistance, especially in the austenitic and austenitic-ferritic structure and in the case of sulfuric acids with a lower concentration.

Der Erfindung liegt die Aufgabe zugrunde, einen Werkstoff zur Verfügung zu stellen, der auch in niedrigeren Schwefelsäurekonzentrationen eine hohe Korrosionsbeständigkeit aufweist, gute Kneteigenschaften und damit Verarbeitungseigenschaften hat, und der kostengünstig hergestellt werden kann.The invention has for its object to provide a material which has a high corrosion resistance even in lower sulfuric acid concentrations, has good kneading properties and thus processing properties, and which can be produced inexpensively.

Die Lösung dieser Aufgabe erfolgt erfindungsgemäß durch die Verwendung ferritischer Chrom-Molybdän-Stähle mit 26 bis 30 % Chrom 1,8 bis 3,0 % Molybdän 3,0 bis 4,5 % Nickel Kohlenstoff ≦ 0,02 % Silizium ≦ 1,00 % Mangan ≦ 1,00 % Schwefel ≦ 0,015 % Kohlenstoff + Stickstoff ≦ 0,045 % Niob ≧ 12 x % C ≦ 1,2 % Rest Eisen sowie schmelztechnisch bedingte Verunreinigungen als korrosionsfester Werkstoff zur Herstellung von Konstruktionsteilen, die gegenüber Schwefelsäure einer Konzentration gleich/größer 94 Gew.-% mit einer Temperatur bis unterhalb des Siedepunktes beständig sind.This object is achieved according to the invention by using ferritic chromium-molybdenum steels 26 to 30% chrome 1.8 to 3.0% molybdenum 3.0 to 4.5% nickel carbon ≦ 0.02% silicon ≦ 1.00% manganese ≦ 1.00% sulfur ≦ 0.015% Carbon + nitrogen ≦ 0.045% niobium ≧ 12 x% C ≦ 1.2% Remainder iron as well as impurities due to melting technology As a corrosion-resistant material for the manufacture of structural parts that are resistant to sulfuric acid at a concentration equal to or greater than 94% by weight with a temperature below the boiling point.

Schmelztechnisch bedingte Verunreinigungen können z.B. sein Phosphor, Aluminium, Vanadium, Titan, Tantal, Calzium, Magnesium, Cer, Bor.Contamination-related impurities can e.g. its phosphorus, aluminum, vanadium, titanium, tantalum, calcium, magnesium, cerium, boron.

Diese Verunreinigungen sollen zusammen nicht mehr als 1 % betragen. Der Werkstoff hat gute Umformungseigenschaften und eignet sich sehr gut zur Herstellung von Konstruktinsteilen aus Blechen oder Bändern, wie z.B. Wärmeaustauscher, Rohrleitungen, Pumpenvorlagen, Berieselungssysteme, Absorber usw. Der Werkstoff ist auch gegen kalte Schwefelsäure korrsionsfest.Together, these impurities should not amount to more than 1%. The material has good forming properties and is very well suited for the production of structural parts from sheet metal or strips, e.g. Heat exchangers, pipes, pump systems, sprinkler systems, absorbers, etc. The material is also corrosion-resistant to cold sulfuric acid.

Eine vorzugsweise Ausgestaltung besteht in der Verwendung eines ferritischen Chrom-Molybdän-Stahles mit 27 bis 29 % Chrom 2,0 bis 3,0 % Molybdän 3,0 bis 4,5 % Nickel Kohlenstoff ≦ 0,02 % Kohlenstoff + Stickstoff ≦ 0,045 % (Niob + Zirkon) ≧ 10 x % (Kohlenstoff + Stickstoff) Rest Eisen sowie schmelztechnisch bedingte Verunreinigungen A preferred embodiment consists in the use of a ferritic chromium-molybdenum steel 27 to 29% chrome 2.0 to 3.0% molybdenum 3.0 to 4.5% nickel carbon ≦ 0.02% Carbon + nitrogen ≦ 0.045% (Niobium + zircon) ≧ 10 x% (carbon + nitrogen) Remainder iron as well as impurities due to melting technology

Dieser Stahl zeigt besonders gut Korrosionseigenschaften.This steel shows particularly good corrosion properties.

In der Tabelle I wird das Korrosionsverhalten des erfindungsgemäßen Werkstoffes bei verschiedenen Temperaturen und Schwefelsäurekonzentrationen gezeigt.Table I shows the corrosion behavior of the material according to the invention at different temperatures and sulfuric acid concentrations.

Das Korrosionsverhalten wurde durch Tauchversuche ermittelt. Die Versuchsdauer betrug in allen Fällen 25 Tage. Die Abtragungsraten wurden durch gravimetrische Differenzwägung und Umrechnung auf mm/a bestimmt. Das Prüfmedium wurde nach jedem Prüfzyklus erneuert.The corrosion behavior was determined by immersion tests. The test duration was 25 days in all cases. The removal rates were determined by gravimetric differential weighing and conversion to mm / a. The test medium was renewed after each test cycle.

Der Werkstoff enthielt 28 % Cr, 2 % Mo und 4 % Ni.

Figure imgb0001
Figure imgb0002
 The material contained 28% Cr, 2% Mo and 4% Ni.
Figure imgb0001
Figure imgb0002

In Schwefelsäure mit einer Konzentration von 95 Gew.-% betrugen die Abtragungsraten: bei 100°C 0,06 mm/a bei 125°C 0,05 mm/a bei 150°C 0,32 mm/a The removal rates in sulfuric acid with a concentration of 95% by weight were: at 100 ° C 0.06 mm / a at 125 ° C 0.05 mm / a at 150 ° C 0.32 mm / a

Die Vorteile der erfindungsgemäßen Verwendung des Werkstoffes bestehen darin, daß im angegebenen Bereich für das Molybdän die Ausscheidungsneigung von spröden, intermetallischen Phasen relativ gering ist. Der Nickelgehalt erhöht die Ausscheidungsträgheit relativ stark und engt im thermodynamischen Gleichgewicht die heterogenen Gebiete ein. Die Kombination dieser beiden Wirkungen führt zu einer höheren Gefügestabilität beim Schweißen und bei Wärmebehandlungsvorgängen. Diese ergibt eine gute Korrosionsbeständigkeit und Duktilität in Form von Kerbschlagfestigkeit. Der Werkstoff ist bis zu einer Dicke von 50 mm schweißbar, während der Werkstoff 29-4-2 nur bis zu etwa 2 mm schweißbar ist.The advantages of the use of the material according to the invention are that the tendency to precipitate brittle, intermetallic phases is relatively low for the molybdenum. The nickel content increases the elimination inertia relatively strongly and narrows the heterogeneous areas in the thermodynamic equilibrium. The combination of these two effects leads to a higher structural stability during welding and during heat treatment processes. This results in good corrosion resistance and ductility in the form of impact strength. The material can be welded up to a thickness of 50 mm, while the material 29-4-2 can only be welded up to about 2 mm.

Der erfindungsgemäße Werkstoff weist also bei sehr guter Korrosionsfestigkeit eine sehr gute Verarbeitbarkeit auf.The material according to the invention therefore has very good processability with very good corrosion resistance.

Claims (2)

  1. The use of ferritic chromium-molybdenum steels containing 26 to 30 % chromium 1.8 to 3.0 % molybdenum 3.0 to 4.5 % nickel
    carbon ≦ 0.02% silicon ≦ 1.00% manganese ≦ 1.00% sulphur ≦ 0.015% carbon + nitrogen ≦ 0.045% niobium ≧ 12 x % C ≦ 1.2% remainder iron and impurities due to melting
    as a corrosion-resistant material for the production of structural elements which are resistant to sulphuric acid of a concentration of 94% by weight or more at a temperature to below the boiling point of the sulphuric acid.
  2. The use of ferritic chromium-molybdenum steels according to Claim 1, containing 27 to 29 % chromium 2.0 to 3.0 % molybdenum 3.0 to 4.5 % nickel
    carbon ≦ 0.02% carbon + nitrogen ≦ 0.045% (niobium + zirconium) ≧ 10 x % (carbon + nitrogen) remainder iron and impurities due to melting
    as a corrosion-resistant material for the production of structural elements which are resistant to sulphuric acid of a concentration of 94% by weight upwards at a temperature to below the boiling point of the sulphuric acid.
EP89202071A 1988-09-07 1989-08-10 Use of ferritic chromium-molybdenum steels as materials resisting concentrated sulfuric acid Revoked EP0361554B1 (en)

Applications Claiming Priority (2)

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DE3830365A DE3830365C2 (en) 1988-09-07 1988-09-07 Use of ferritic chromium - molybdenum steels as a material resistant to concentrated sulfuric acid
DE3830365 1988-09-07

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EP0361554B1 true EP0361554B1 (en) 1993-06-09

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JP (1) JP3137968B2 (en)
AU (1) AU615105B2 (en)
DE (2) DE3830365C2 (en)
ES (1) ES2040981T3 (en)
ZA (1) ZA896817B (en)

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US5207980A (en) * 1991-10-27 1993-05-04 Westinghouse Electric Corp. Top nozzle-mounted replacement guide pin assemblies
ZA938889B (en) * 1992-12-07 1994-08-01 Mintek Stainless steel composition
DE4342188C2 (en) * 1993-12-10 1998-06-04 Bayer Ag Austenitic alloys and their uses
DE102005008109A1 (en) 2005-02-21 2006-08-24 Outokumpu Technology Oy Process and plant for the production of sulfuric acid
ES2351281B1 (en) * 2009-02-03 2011-09-28 Valeo Termico, S.A. HEAT EXCHANGER FOR GASES, ESPECIALLY OF EXHAUST GASES OF AN ENGINE.

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EP0018131A1 (en) * 1979-04-06 1980-10-29 Kureha Kagaku Kogyo Kabushiki Kaisha Crosslinked, carboxyalkylated and deacetylated derivative of chitin, process for preparation thereof, and use thereof as an adsorbent material

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JPS524418A (en) * 1975-06-24 1977-01-13 Sandvik Ab Stainless steel
GB1565419A (en) * 1976-04-27 1980-04-23 Crucible Inc Stainless steel welded articles
CA1181569A (en) * 1982-06-11 1985-01-29 Frank Smith Apparatus and process
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Publication number Priority date Publication date Assignee Title
EP0018131A1 (en) * 1979-04-06 1980-10-29 Kureha Kagaku Kogyo Kabushiki Kaisha Crosslinked, carboxyalkylated and deacetylated derivative of chitin, process for preparation thereof, and use thereof as an adsorbent material

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Title
STAHL UND EISEN, 1990; Seite 73# *
STAHLSCHLÜSSEL, 1985; Seite 344, Nr. 41# *
STAHLSCHLÜSSEL, 1992; Seite 292, Nr. 1.4575# *

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AU4107389A (en) 1990-03-15
AU615105B2 (en) 1991-09-19
US5030415A (en) 1991-07-09
ES2040981T3 (en) 1993-11-01
DE3830365C2 (en) 1996-06-27
JP3137968B2 (en) 2001-02-26
DE58904618D1 (en) 1993-07-15
JPH02107745A (en) 1990-04-19
ZA896817B (en) 1991-05-29
DE3830365A1 (en) 1990-03-15

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