US3885958A - Method of producing chromium containing alloys - Google Patents

Method of producing chromium containing alloys Download PDF

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Publication number
US3885958A
US3885958A US427094A US42709473A US3885958A US 3885958 A US3885958 A US 3885958A US 427094 A US427094 A US 427094A US 42709473 A US42709473 A US 42709473A US 3885958 A US3885958 A US 3885958A
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nitrogen
carbon
melt
aluminum
content
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Expired - Lifetime
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US427094A
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English (en)
Inventor
Gunnar Grunbaum
John Erik Wallen
John Kjell Gustafsson
Gustaf Widmark
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Santrade Ltd
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Sandvik AB
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Assigned to SANTRADE LTD., A CORP. OF SWITZERLAND reassignment SANTRADE LTD., A CORP. OF SWITZERLAND ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SANDVIK AKTIEBOLAG, A CORP. OF SWEDEN
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting

Definitions

  • ABSTRACT A chromium-containing alloy, having very low contents of nitrogen and carbon, is produced by refining with a small but effective addition of aluminum, or an aluminum alloy, preferably an aluminum-lithium alloy.
  • the present invention relates to a method of producing chromium-containing alloys with low contents of nitrogen and carbon.
  • ferritic chromium steels normal contents of carbon or nitrogen cause material problems such as lowered impact strength, a high (ductile-to-brittle) transition temperature, and disposition towards intergranular corrosion. These phenomena are ascribed to chromium-containing nitrideand carbide precipitations which take place as a result of the too low solubility of carbon and nitrogen in ferrite.
  • Remelting of chro mium and iron with low contents of carbon and nitrogen in an inert atmosphere in, for example, a HF-(high frequency induction) furnace is impeded because available chromium raw materials such as ferrochromium have too high contents of nitrogen and carbon.
  • Chromium pig iron produced in a cupola furnace is decarburized in an LD- converter to about 0.3 C, after which the melt is vacuum-oxidized to the above-mentioned low content of carbon.
  • a low nitrogen content of less than 100 ppm is reached thereby that the carbonand silicon-rich chromium pig iron having a relatively low nitrogen content is refined from nitrogen by the very vigorous evolution of gas in the LD-converter during a decrease of the carbon content from 5 to 0.3 percent.
  • the method pre-supposes, however, the opportunity of using special equipment.
  • the low contents of carbon and nitrogen have been obtained at a Cr content of about 18 percent, thus a rather low content of chromium.
  • a low nitrogen content is obtained by using strong nitrideformers to separate the nitrogen from a melt. This nitrogen-impoverished melt is then refined with respect to carbon and finished to steel in, for example. an AOD-converter.
  • FIG. 1 is a diagram showing equilibria of Al and N in aluminum nitride formation
  • FIG. 2 is a diagram showing influence of lithium in cooperation with aluminum in achieving a low content of nitrogen.
  • FIG. 1 A 0 I535 B 0 25 I500 C 2 25 I300 D 2 25 I500
  • the diagram in FIG. 1 is thus specifically constructed for the purpose of explaining the invented method, and it shows that a low content of nitrogen in the presence of a high content of chromium ought to be obtained by an addition aluminum to a melt containing carbon at a low temperature, i.e., a temperature near the melting temperature.
  • a low content of nitrogen in the presence of a high content of chromium ought to be obtained by an addition aluminum to a melt containing carbon at a low temperature, i.e., a temperature near the melting temperature.
  • the equilibrium 5 A] at 1,300 C. corresponds to 2 ppm nitrogen in a steel melt with 2 C and Cr.
  • the importance of chromium is shown in the curves A and B. It may be mentioned that in case of titanium, the dissolved N- content first decreases with increasing Ti-content, but already at a Ti-level of about 1 with the equilibrium content of N in the
  • Al-metal corresponding to 5.0 percent was added at 1.350" C. After mixing. a sample taken from the furnace showed 57 ppm nitrogen.
  • Al-metal corresponding to 9 percent was added at 1.350 C.
  • the nitrogen content was 40 ppm in samples taken from the furnace. From the examples [-3 it is obvious that the nitrogen is reduced with increased additions of Al. See also the diagram in FIG. 2.
  • EXAMPLE 5 The influence of the chromium content was examined. A charge was produced in a 50 kilogram open HF furnace. Starting analysis:
  • EXAMPLE 7 Pure lithium was added in two charges to control the effect in the foregoing example. The amounts were 0.05 and 0.20 Li, respectively. The content of nitrogen before the addition was 285 ppm. After addition of Li the content was 250 ppm nitrogen. No important effect was thus obtained by an addition of Li as such.
  • EXAMPLE 8 The influence of changing from an iron-base to a nickel-base alloy was examined. A charge was produced in a 50 kg HF furnace. Starting analysis:
  • Example 8 shows the result when using a nickel base alloy.
  • the example 9 relates to a Cr-Ni steel.
  • the example l0 shows the final removal of C and Al which should be done in a larger charge and not in a small 50 kg furnace. (Examples 2, 3 and 4 have iron as remainder.)
  • the given examples all relates to chromium steel.
  • nickel has an increasing effect upon the activity of the nitrogen, it is self-evident that the invention is applicable also to chromium steels.
  • other Al-alloys than pure Al and LiA] can be used, for example CaAl and MgA].
  • the raw materials may for example be melted in a normal arc furnace so that a carbon content of 1-2 percent is obtained.
  • a charge may be based upon cheap raw materials and also contain a high content of circulating internal scrap. The latter material has great economical importance.
  • the melt is then taken for example to an ADD-converter, vacuum furnace or the like, in which aluminum or aluminum-lithium is added to the melt. After that, the normal process of removing carbon is carried out.
  • An intermediate slag separation preferably is made, because aluminum gives rise to great amounts to slag during the oxidation.
  • A] is oxidized by oxygen gas, a great amount of heat is evolved.
  • the metal bath may then be cooled by substituting chromium ore for the oxygen gas or by adding suitable scrap.
  • the nitrogen refining addition of Al or LiAl may also be performed in a ladle.
  • the metal must, however, be protected from nitrogen pick up from the air when the content of the ladle is taken to the unit for oxidation of carbon. If the ladle has a high freeboard, meaning that the level of the melt is far below the upper edge of the ladle, vacuum oxidation can be done directly in the la die.
  • the carbon content should be relatively high in the melt bath when the addition of Al is effected. Carbon has a favorable inlluence, as it in itself decreases the solubility of nitrogen as well as lowering the melting point of the melt bath. A suitable content of carbon has shown to be at least 1 at C.
  • the invented method is particularly applicable to melts containing between and 7: Cr. At actual contents of Cr and C the melt should have a temperature between l 300-l ,500 C.
  • Method of producing a chromium-containing alloy having very low contents of nitrogen and carbon not amounting, in toto, to more than 0.01 percent by 8 weight. which comprises melting a charge containing at least 1 percent by weight of carbon and consisting essentially of a chromium-containing initial material together with a base metal and desired alloying elements;
  • a nitridable member of the group consisting of aluminum and aluminum alloys. in an amount corresponding to at least 3 percent by weight of said melt. thereby converting nitrogen to aluminum nitride in the form of a constitutent of the resulting slag;

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
US427094A 1972-12-29 1973-12-21 Method of producing chromium containing alloys Expired - Lifetime US3885958A (en)

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SE17146/72A SE368420B (pt) 1972-12-29 1972-12-29

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US3885958A true US3885958A (en) 1975-05-27

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US (1) US3885958A (pt)
JP (1) JPS5222889B2 (pt)
DE (1) DE2365054C3 (pt)
FR (1) FR2212437B1 (pt)
GB (1) GB1395873A (pt)
IT (1) IT1002432B (pt)
SE (1) SE368420B (pt)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3985550A (en) * 1975-01-23 1976-10-12 United States Steel Corporation Method of producing low sulfur steel
US4589916A (en) * 1984-02-23 1986-05-20 Daido Tokushuko Kabushiki Kaisha Ultra clean stainless steel for extremely fine wire
US5578265A (en) * 1992-09-08 1996-11-26 Sandvik Ab Ferritic stainless steel alloy for use as catalytic converter material

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS53143992U (pt) * 1977-04-19 1978-11-13
JPS6023182B2 (ja) * 1979-12-01 1985-06-06 新日本製鐵株式会社 中炭素高クロム溶湯の溶製方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3314782A (en) * 1963-12-12 1967-04-18 Fur Tech Entwicklung Und Verwe Refining agent for steel-works
US3333954A (en) * 1963-08-10 1967-08-01 British Cast Iron Res Ass Manufacture of inoculants for cast iron
US3467167A (en) * 1966-09-19 1969-09-16 Kaiser Ind Corp Process for continuously casting oxidizable metals

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3333954A (en) * 1963-08-10 1967-08-01 British Cast Iron Res Ass Manufacture of inoculants for cast iron
US3314782A (en) * 1963-12-12 1967-04-18 Fur Tech Entwicklung Und Verwe Refining agent for steel-works
US3467167A (en) * 1966-09-19 1969-09-16 Kaiser Ind Corp Process for continuously casting oxidizable metals

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3985550A (en) * 1975-01-23 1976-10-12 United States Steel Corporation Method of producing low sulfur steel
US4589916A (en) * 1984-02-23 1986-05-20 Daido Tokushuko Kabushiki Kaisha Ultra clean stainless steel for extremely fine wire
US5578265A (en) * 1992-09-08 1996-11-26 Sandvik Ab Ferritic stainless steel alloy for use as catalytic converter material

Also Published As

Publication number Publication date
IT1002432B (it) 1976-05-20
SE368420B (pt) 1974-07-01
DE2365054A1 (de) 1974-07-11
JPS4998318A (pt) 1974-09-18
FR2212437A1 (pt) 1974-07-26
DE2365054B2 (de) 1979-07-05
JPS5222889B2 (pt) 1977-06-21
DE2365054C3 (de) 1980-03-06
GB1395873A (en) 1975-05-29
FR2212437B1 (pt) 1976-10-08

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Owner name: SANTRADE LTD., ALPENQUAI 12, CH-6002, LUCERNE, SWI

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SANDVIK AKTIEBOLAG, A CORP. OF SWEDEN;REEL/FRAME:004085/0132

Effective date: 19820908