US3754894A - Nitrogen control in argon oxygen refining of molten metal - Google Patents

Nitrogen control in argon oxygen refining of molten metal Download PDF

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US3754894A
US3754894A US00245733A US3754894DA US3754894A US 3754894 A US3754894 A US 3754894A US 00245733 A US00245733 A US 00245733A US 3754894D A US3754894D A US 3754894DA US 3754894 A US3754894 A US 3754894A
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nitrogen
melt
decarburization
percent
injected
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J Saccomano
F Death
J Ellis
R Choulet
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Union Carbide Industrial Gases Technology Corp
Joslyn Manufacturing and Supply Co
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Joslyn Manufacturing and Supply Co
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • C21C7/0685—Decarburising of stainless steel
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/05—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]

Definitions

  • the nitrogen content of molten metal may be controlled during refining by the selective subsurface injection of nitrogen during argon-oxygen decarburization. Nitrogen may be used to replace the argon entirely during the early stages of decarburization, and partially in the latter stages. in addition, nitrogen injection may be used after decarburization has been completed to achieve a final upward adjustment in the nitrogen conent of the metal.
  • This invention relates, in general, to methods for controlling the nitrogen content of molten metal by the selective injection of nitrogen gas during at least a portion of the time the metal is being refined by subsurface injection of oxygen and/or an inert gas. More specifically, the present invention relates to an improvement in the argon-oxygen decarburization of steels.
  • argon-oxygen refining or argonoxygen decarburization refer to a process for refining molten metal by the subsurface injection of oxygen and argon or an equivalent inert gas, primarily for the purpose of lowering the carbon content of the melt.
  • the basic AOD process is disclosed in Krivsky, U.S. Pat. No. 3,252,790 and an improvement thereon relating to programmed blowing is disclosed in Nelson et al., U.S. Pat. No. 3,046,107.
  • the AOD process is a duplex process,v particularly useful for refining of stainless steels without substantial loss of chromium, by using a furnace, commonly an arc-furnace, for melting scrap and alloy.
  • a furnace commonly an arc-furnace
  • a suitable refining vessel which can be rotated to the horizontal position for charging, holding, sampling and tapping, is disclosed by Saccomano and Ellis in French Patent No. 2,056,845, which corresponds to U.S. Pat. No. 3,703,279.
  • the vessel is rotated to the vertical position and varying ratios of argon and oxygen mixtures are injected through tuyeres mounted in the bottom or sides of the vessel.
  • This quantity is commonly referred to as the equilibrium nitrogen level, and may be calculated from theoretical thermodynamic considerations by techniques known to those skilled in the art; see: for example, Chipman and Corrigan Prediction of the Solubility of Nitrogen in Molten Steel, Trans. AIME. Vol. 233, July I965.
  • the present invention comprises: in a process for refining molten metal comprising the step of decarburizing a mass of molten metal by injecting into said mass from beneath the surface thereof, oxygen and at least one inert gas selected from the group consisting of helium, neon, argon, zenon and nitrogen, the improvement comprising: producing a refined molten metal mass having a predetermined nitrogen content within the range of from about I0 ppm to about percent of the equilibrium level, by (a) injecting a gas mixture consisting essentially of oxygen and nitrogen throughout a first period of the decarburization step, wherein the percentage of nitrogen in said gas mixture is maintained such that the partial pressure of the nitrogen in the ambient atmosphere in contact with the melt is greater than the partial pressure of nitrogen in equilibrium with the predetermined nitrogen content sought for the refined melt, thereby causing the nitro gen content of the melt at the end of said first period of said
  • the decarburization step is generally followed by a reduction step. Thereafter, the melt may be finished by one or more of pan the optional steps of deslagging, desulfurizing, deoxidizing, adjusting the temperature and adjustment of the composition of the melt by the addition of alloying materials.
  • a three component gas mixture containing oxygen, nitrogen and another of said inert gases may be injected during at least a portion of the decarburization step. That is, the three component gas mixture may be used during only the first period of the decarburization step, during only the second or subsequent periods of the decarburization step, or during the entire decarburization step.
  • the percentage of nitrogen in the three component gas mixture is maintained such that the partial pressure of the nitrogen in the gaseous atmosphere in contact with the melt is equal to the calculated partial pressure of nitrogen divided by X, where X 0.7 to 1.0, in equilibrium with the predetermined 'nitrogen level sought in the refined metal melt.
  • nitrogen gas or a mixture of nitrogen and argon may be injected into the melt for a sufficient time to increase the nitrogen content of the molten metal mass to any desired level of nitrogen up to within about 90 percent of its equilibrium level.
  • this alloying nitrogen injection may follow the finishing steps rather than the de carburization step.
  • molten metal as used throughout the present specification and claims is intended to include low carbon iron, carbon steels, stainless steels, ferrous alloys and nickel based alloys. These may contain chromium, tungsten, vanadium, zirconium, copper, aluminum, silicon, sulfur, titanium, manganese, molybdenum and other commonly used alloying ingredients.
  • stainless steel is intended to include ferrous alloys containing about 13-40 percent chromium.
  • decarburization is used to mean lowering of the carbon content of the molten metal from any given level to any desired lower level by the injection of oxygen into the melt.
  • mass is intended to mean a batch or heat of molten metal, as well as a changing mass as in a continuous process.
  • reduction is used to mean the recovery from the slag of metallic materials, such as, for example, chromium or manganese which were oxidized during the decarburization step, by adding a less valuable material such as silicon or aluminum which has a greater affinity for oxygen than the desired materials, thereby causing the reduced chromium or manganese metal to go backinto the melt.
  • metallic materials such as, for example, chromium or manganese which were oxidized during the decarburization step
  • a less valuable material such as silicon or aluminum which has a greater affinity for oxygen than the desired materials, thereby causing the reduced chromium or manganese metal to go backinto the melt.
  • the reduction is 'not limited to being carried out with solid materials.
  • desulfurizationT is used to mean the lowering of the sulfur content of the melt by providing the proper thermodynamic and kinetic conditions to move the sulfur from the molten metal phase to the slag phase.
  • finishing is used to mean any or all of the conventional steps after reduction which prepare the molten metal for tapping and casting, e.g., deslagging, desulfurization, final composition adjustment, temperature adjustment and deoxidation.
  • FIG. 1 is a graphic representation'of the change in the nitrogen content of a melt during refining in accordance with the present invention, in which an oxygennitrogen mixture is injected during a first period of the decarburization step, followed by a second period in which argon is either substituted for the nitrogen in the mixture (curve X) or added to the mixture (curve Y), and then finished with argon alone.
  • FIG. 2 is a graphic representation of the change in the nitrogen content of a molten metal heat refined in accordance with the present invention, in which a three component gas mixture (curve A) of oxygen, nitrogen and argon is used throughout the decarburization step, compared to two curves illustrating the use of oxygen in combination with either argon (curve B) or nitrogen (curve C) in accordance with the prior art.
  • curve A three component gas mixture
  • curve B argon
  • curve C nitrogen
  • FIG. 3 is a graphic representation illustrating the change in the nitrogen content of a melt during decarburization with a mixture of argon and oxygen and reduction and finishing with argon alone in accordance with the prior art, followed by nitrogen injection for alloying.
  • FIG. 1 shows that during the first period of the decarburization step, using a mixture of oxygen and nitrogen, the level of nitrogen in the melt will be raised close to its equilibrium level N, at the particularly conditions of melt temperature and composition, and ambient gas pressure in the refining vessel.
  • the substitution of argon for the nitrogen (curve X) will cause a rapid decrease in the nitrogen level of the melt. This second period is continued until the desired carbon level and a specified nitrogen level N,, depending upon the final nitrogen level desired on tapping N, is reached.
  • Curve Y discloses the path that the nitrogen level in the melt will take if a higher nitrogen level N is sought in the tapped heat and in which a three component argon-oxygen-nitrogen gas mixture is used during the second period of the decarburization step.
  • Curve Z shows the path which would be taken by the nitrogen level in the melt if the same final nitrogen level N: were sought using a three component nitrogeb-oxygen-ar'gon mixture during the second period of the decarburization step. In this ca se the first period would stop sooner at time T rather than at time T as in the previous example, since the rate at which the nitrogen level in the melt drops is slower with nitrogen in the blowing mixture than without any nitrogen as 'in curve X.
  • curve C shows the increase in the nitrogen content of the melt using the prior art technique of oxygen-nitrogen decarburization, followed by nitrogen injection during the reduction and finishing steps. It will be noted that the nitrogen level continues to rise throughout, and that the level of nitrogen in the tapped heat will be close to its equilibrium level.
  • Curve B discloses conventional argon-oxygen practice in which argon and oxygen are used throughout the decarburization step followed by argon injection during the reduction and finishing steps. It will be seen that the nitrogen level of the melt in curve B continues to decrease throughout the refining steps, with the result that an extremely low level of nitrogen N, is obtained in the tapped heat.
  • Curve A which represents an example of the present invention, discloses a three component gas mixture of argon, nitrogen and oxygen which is injected throughout the decarburization step, followed by a two component argon-nitrogen mixture during reduction and finishing, in which the nitrogen level of the melt is gradually increased throughout the refining process. It will be evident that by proper ratioing of the quantity of the gases in the three component mixture, curve A may be caused to follow a path lying anywhere in the area on the graph between curve C and curve B. This is necessarily so, because in the limiting case, where the amount of argon in the gas mixture is zero, curve A is obtained; whereas in the limiting case where the amount of nitrogen in the gas mixture is zero, curve B is obtained. For example, the cruves X and Z from FIG.
  • FIG. 1 may be superimposed onto FIG. 2 where they are shown as broken lines X and Z.
  • the slope of the curve will be determined principally by the relative amount of nitrogen in the blowing mixture.
  • an appropriate three component gas mixture (the proportions of which will vary during the decarburization step) to arrive at a nitrogen level in the melt lying anywhere between the nitrogen values represented by points N and N of the graph. Thereafter, the nitrogen level may be increased to level N, by blowing with nitrogen, decreased to level N, by blowing with argon, or kept essentially the same at N by use of an appropriate argon-nitrogen mixture.
  • FIG. 3 shows graphically the change in nitrogen level which may be achieved by nitrogen alloying, i.e. rapidly increasing the nitrogen level of the melt by the injection of nitrogen gas following decarburization with a mixture of argon and oxygen, and argon blowing during the reduction and finishing steps.
  • nitrogen alloying i.e. rapidly increasing the nitrogen level of the melt by the injection of nitrogen gas following decarburization with a mixture of argon and oxygen, and argon blowing during the reduction and finishing steps.
  • the use of a pure nitrogen blow at the end of these steps may be used to quickly and conveniently raise the nigrogen level of the heat to any level up to close to within about percent of the equilibrium value of nitrogen at the conditions of the melt.
  • Example 1 shows the results obtained on a 16 1% ton test heat in which a three component mixture of argon, oxygen and nitrogen was used throughout the decarburization step, followed by a reduction step using a mixture of argon and nitrogen.
  • the type 304 stainless steel melt composition at the beginning of the decarburization step contained 0.17% C, 0.96% Mn, 0.27% Si, 19.38% Cr and 8.54% Ni. A maximum residual nitrogen level of 0.08 percent was sought in this heat.
  • Table 1 shows the temperature, flow rates of the gas and nitrogen content of the melt at the end of each noted period of the decarburization step and at the end of the reduction step. It should be noted that the decarburization was carried out in three steps, i.e., with three dilferent gas mixtures and oxygen to inert gas ratios. N.A. indicates the figure is not available.
  • the equilibrium partial pressure of nitrogen in a steel melt of the composition of Example 1 containing 0.08 percent nitrogen is calculated in accordance with the techniques disclosed by Chipman and Corrigan, in the article referred to previously, to be approximately 0.1 atmospheres. Therefore, sufficient nitrogen was injected, along with the argon and oxygen, to provide .a nitrogen partial pressure in the atmosphere in contact with the surface of the melt of 0.1 atmospheres.
  • considerable amount of CO care evolved which dilute the N partial pressure.
  • larger ratios of nitrogen to argon can be used during the early portions of the decarburization, than during the latter portions and during reduction and finishing.
  • the nitrogen to argon ratio must be lowered and controlled to give a nitrogen partial pressure of no more than 0.1 atmospheres.
  • the final nitrogen level obtained was 0.061 percent as against a calculated equilibrium level of 0.08 percent, showing that the nitrogen level attained by the melt during the refining process was greater than 75 percent of the calculated equilibrium level.
  • Example 1 It has been found that the results demonstrated by Example 1 above are highly reproducible, not only in the same vessel, but from one vessel to another, and that the nitrogen level reached after refining is consistently greater than 70 pereentofthe calculated equilibrium level; usually between 75-90 percent of the equilibrium level.
  • the closeness with which the equilibrium level is approached depends upon the specific design of the vessel, the size and composition of the heat, the depth of the melt, the number and arrangementofinjection tuyeres, gas flow rates and other system variables. However, after one or two trials the appropriate equilibrium factor, which will lie between 0.7 and 1.0 for any particular vessel system, can be easily determined.
  • Example 1 above represents one embodiment of the present invention
  • nitrogen for argon as the inert gas component during at least the early phases of the decarburization period, even though a considerable amount of nitrogen is absorbed by the melt.
  • the amount of nitrogen which can be substituted for argon is related to the ultimate level desired in the melt at tapping. For example, with type 304 stainless steel, if the aimed for residual level of nitrogen is less than 0.05 percent, nitrogen can be used during the decarburization step until approximately percent of the oxygen calculated as necessary for decarburization has been injected. in general, the point at which nitrogen is replaced by argon takes place when between 50-70 percent of the oxygen calculated as necessary for the decarburization step has been injected.
  • This quantity of oxygen is calculated by conventional stoichiometric means, taking intoaccount the oxygen necessary to oxidize not only the carbon to be removed as CO, but also to oxidize the silicon and other metallic elements in the melt which conventionally enter the slag as oxides.
  • argon is used to replace the nitrogen for purposes of further decarburization, as well as for lowering the dissolved nitrogen content of the melt to the desired level.
  • Curves X and Z in FIG. 1 illustrate schematically the change in the nitrogen content of a melt during the decarburization step.
  • the point in time, T or T at which it is necessary to either switch from nitrogen to argon (curve X) or to reduce nitrogen and add argon (curve 2) is also a function of the overall blowing program, the melt composition and the refining temperature. Hence, it is necessary with each vessel system to run several trial heats from which, however, it is easy to establi h the switch point at which the changeover from nitrogen to argon should be made.
  • EXAMPLE 2 The following example illustrates the embodiment of the present invention in which nitrogen is used as the sole inert gas during the first period of the decarburization step, followed by the second period in which argon is used to replace the nitrogen.
  • the type 303 stainless steel melt prior to decarburization contained: 0.78% C, 0.51% Mn, 0.41% Si 18.25% Cr and 8.05% Ni. The heat size was 17 tons.
  • Table 2 below shows the changes in temperature, carbon content, gas flows and nitrogen level at the start, during the first and second periods of the decarburization step, and after the reduction step.
  • Example 3 illustrates the use of nitrogen throughout the entire decarburization step, wherein; however, the ratio of :N was changed from 2:1 in the first period, to 1:2 during the second period, and demonstrates the high residual level of nitrogen in the melt at the end of the oxygen blowing step.
  • Table 3 below shows the two stage decarburization step followed by reduction, desulfurization and finishing, as well as the duration of each of these steps. The change in the carbon level during the process, as well as the nitrogen level, together with the oxygen, argon and nitrogen gas flow rates are also shown.
  • Example 4 illustrates the embodiment of the present invention in which nitrogen is used as the inert gas during the first period of the decarburization step, followed by the second step in which argon is used to replace the nitrogen.
  • the type 430 stainless steel melt prior to decarburization contained: 0.35% C, 0.34% Mn, 0.36% Si, 16.22% Cr and 0.14%Ni. The heat size was 17 tons.
  • Table 4 below shows the changes in temperature, carbon content, gas flows and nitrogen level at the start, and after the first and second steps and the decarburization as well as after the reduction steps.
  • a refined molten metal mass having a predetermined nitrogen content within the range of from about 10 ppm to about percent of the equilibrium level by (a) injecting a gas mixture consisting essentially of oxygen and nitrogen throughout a first period of the decarburization step, wherein the percentage of nitrogen in said gas mixture is maintained such that the partial pressure of the nitrogen in the ambient atmosphere in contact with the melt is greater than the partial pressure of nitrogen in equilibrium with the predetermined nitrogen content sought for the refined melt, thereby causing the nitrogen content of the melt at the end of said first period of the decarburization step to be greater than the predetermined nitrogen content sought for the refined melt, and thereafter (b) substituting an inert gas other than nitrogen in place of said nitrogen in said gas mixture during the remainder of said decarburization step, and continuing the injection of said other inert gas until the nitrogen content of the melt is reduced to said predetermined value.
  • molten metal is selected from the group consisting of carbon steel, stainless steel, ferrous alloys and nickel based alloys.
  • a process for refining molten metal comprising the step of decarburizing a mass of molten metal by injecting into said mass from underneath the surface thereof, oxygen and at least one inert gas selected from the group consisting of helium, neon, argon xenon and nitrogen, the improvement comprising:
  • a refined molten metal mass having a predetermined nitrogen content within the range of from about ppm to about 90 percent of the 'equilibrium level by (a) injecting a gas mixture consisting essentially of oxygen and nitrogen throughout a first period of the decarburization step, wherein the percentage of nitrogen in said gas mixture is maintained such that the partial pressure of the nitrogen in the ambient atmosphere in contact with the melt is greater than the partial pressure of ni trogen in equilibrium with the predetermined nitrogen content sought for the refined melt, thereby causing the nitrogen content of the melt at the end of said first period of the decarburization step to be greater than the predetermined nitrogen content sought for the refined melt, and thereafter (b) adding an inert gas other than nitrogen to said oxygennitrogen gas mixture during the remainder of said decarburization step and continuing the injection of said other inert gas until the nitrogen content of the melt is reduced to said predetermined value.
  • molten metal is selected from the group consisting of carbon steel, stainless steel, ferrous alloys and nickel based alloys.
  • a process for refining molten metal comprising the step of decarburizing said molten metal by injecting into said molten metal from underneath the surface thereof, oxygen and at least one inert gas selected from the group consisting of helium, neon, argon, xenon and nitrogen, the improvement comprising:
  • a refined molten metal charge having a predetermined nitrogen content within the range of from about 10 ppm to about percent of the equilibrium level, by injecting a three component gas mixture of oxygen, nitrogen and another of said inert gases, throughout at least a first period of the decarburization step, and wherein the percentage of nitrogen in the said mixture is maintained such that the partial pressure of the nitrogen in the gaseous atmosphere in contact with the melt is equal to the partial pressure of nitrogen in equilibrium with the predetermined nitrogen content sought in the refined melt divided by X where X; 0.7 to 1.0.
  • molten metal is selected from the group consisting of carbon steel, stainless steel, ferrous alloys and nickel based alloys.
  • molten metal is selected from the group consisting of carbon steel, stainless steel, ferrous alloys and nickel based alloys.

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Cited By (18)

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US3998666A (en) * 1975-07-30 1976-12-21 United States Steel Corporation Subscale reaction strengthening of low carbon ferrous metal stock
US4081270A (en) * 1977-04-11 1978-03-28 Union Carbide Corporation Renitrogenation of basic-oxygen steels during decarburization
EP0030818A2 (en) * 1979-12-12 1981-06-24 Allegheny Ludlum Steel Corporation Improved method of decarburizing molten metal
JPS57155314A (en) * 1981-02-25 1982-09-25 Sumitomo Metal Ind Ltd Refining of high-cr steel
US4436553A (en) 1982-01-22 1984-03-13 Union Carbide Corporation Process to produce low hydrogen steel
EP0140001A1 (de) * 1983-09-02 1985-05-08 MAN Gutehoffnungshütte Aktiengesellschaft Verfahren zur Herstellung von Stählen mit hohem Reinheitsgrad und geringen Gasgehalten in Stahlwerken und Stahlgiessereien
EP0240998A1 (en) * 1986-04-08 1987-10-14 Union Carbide Corporation Melting furnace and method for melting metal
US5327357A (en) * 1991-12-03 1994-07-05 Praxair Technology, Inc. Method of decarburizing molten metal in the refining of steel using neural networks
EP1230012A2 (en) * 1999-10-13 2002-08-14 Atomic Ordered Materials, L.L.C. Tailoring compositions of matter
US20040113130A1 (en) * 1999-10-13 2004-06-17 Nagel Christopher J. Composition of matter tailoring: system I
US6790254B1 (en) * 2000-03-16 2004-09-14 Vsg Energie - Und Schmiedetechnik Gmbh Method for controlling and adjusting the concentration of a gas component in a melt and a device for carrying out the same
US20060186800A1 (en) * 2005-02-23 2006-08-24 Electromagnetics Corporation Compositions of matter: system II
US20110041653A1 (en) * 2007-12-12 2011-02-24 Joo Hyun Park Method of manufacturing ultra low carbon ferritic stainless steel
CN102021272B (zh) * 2009-09-17 2012-07-18 宝山钢铁股份有限公司 不锈钢冶炼的氮含量控制方法
CN106950932A (zh) * 2017-04-14 2017-07-14 长江大学 运用灰色系统gm（1，n）模型的天然气脱碳装置效果分析方法
US9790574B2 (en) 2010-11-22 2017-10-17 Electromagnetics Corporation Devices for tailoring materials
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CN115125366A (zh) * 2021-03-25 2022-09-30 上海梅山钢铁股份有限公司 一种吹氩站智能生产控制方法

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JPS5955972U (ja) * 1982-10-05 1984-04-12 三洋電機株式会社 電気かみそり用収納ケ−ス
JPH08928B2 (ja) * 1988-09-29 1996-01-10 川崎製鉄株式会社 高ｎステンレス鋼の精錬方法

Cited By (38)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3998666A (en) * 1975-07-30 1976-12-21 United States Steel Corporation Subscale reaction strengthening of low carbon ferrous metal stock
US4081270A (en) * 1977-04-11 1978-03-28 Union Carbide Corporation Renitrogenation of basic-oxygen steels during decarburization
EP0030818A2 (en) * 1979-12-12 1981-06-24 Allegheny Ludlum Steel Corporation Improved method of decarburizing molten metal
EP0030818A3 (en) * 1979-12-12 1981-12-30 Allegheny Ludlum Steel Corporation Improved method of decarburizing molten metal
JPS57155314A (en) * 1981-02-25 1982-09-25 Sumitomo Metal Ind Ltd Refining of high-cr steel
JPS6159366B2 (pt) * 1981-02-25 1986-12-16 Sumitomo Metal Ind
US4436553A (en) 1982-01-22 1984-03-13 Union Carbide Corporation Process to produce low hydrogen steel
EP0140001A1 (de) * 1983-09-02 1985-05-08 MAN Gutehoffnungshütte Aktiengesellschaft Verfahren zur Herstellung von Stählen mit hohem Reinheitsgrad und geringen Gasgehalten in Stahlwerken und Stahlgiessereien
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JPS4921317A (pt) 1974-02-25
AT340453B (de) 1977-12-12
NO134527C (pt) 1976-10-27
FR2180999B1 (pt) 1976-05-28
IL42068A0 (en) 1973-06-29
ATA351373A (de) 1977-04-15
BE798482A (fr) 1973-10-19
ES413940A1 (es) 1976-02-01
FR2180999A1 (pt) 1973-11-30
AU5430573A (en) 1974-10-10
IL42068A (en) 1975-11-25
DD103264A5 (pt) 1974-01-12
CS283873A2 (en) 1987-09-17
IT980292B (it) 1974-09-30
DE2320165B2 (de) 1976-02-26
BR7302813D0 (pt) 1974-06-27
HU166874B (pt) 1975-06-28
PL85660B1 (pt) 1976-04-30
FI73740C (fi) 1988-11-22
CA980127A (en) 1975-12-23
NO134527B (pt) 1976-07-19
FI73740B (fi) 1987-07-31
DE2320165A1 (de) 1973-10-31
AU472272B2 (en) 1976-05-20
GB1420179A (en) 1976-01-07
JPS5213493B2 (pt) 1977-04-14
SE426175B (sv) 1982-12-13
CS256352B2 (en) 1988-04-15

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