US3262772A - Process for the production of alloy steels - Google Patents

Process for the production of alloy steels Download PDF

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US3262772A
US3262772A US292127A US29212763A US3262772A US 3262772 A US3262772 A US 3262772A US 292127 A US292127 A US 292127A US 29212763 A US29212763 A US 29212763A US 3262772 A US3262772 A US 3262772A
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slag
blowing
phase
steel
alloying elements
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US292127A
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Richter Adolf
Cohnen Georg
Bauer Hansgeorg
Rinesch Rudi
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GUSSTAHLWERK WITTEN AG
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GUSSTAHLWERK WITTEN AG
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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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/005—Manufacture 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
    • C21C2007/0093—Duplex process; Two stage processes

Definitions

  • Liquid basic pig iron or iron produced in a hot blast cupola furnace is used as the star-ting material for this process.
  • iron low in manganese is used, for example iron containing 0.7% manganese, as can be pro; prised in the hot blast cupola furnace.
  • the main feature of the process according to the invention is that it is carried out in two phases.
  • first phase an intermediate product with a phosphorus content of less than 0.025% is produced under a highly basic first slag rich in iron oxide, that is to say a slag with a basicity (CaO/SiO of more than 3.
  • second phase of the process is carried out.
  • the blowing of the liquid intermediate product is carried out under a second slag (about 1 to 4% of slag-forming constituents) with a basicity of about 2.
  • second slag about 1 to 4% of slag-forming constituents
  • the process can be ended when the desired carbon content is reached.
  • blowing is conveniently carried out initially with normal blowing energy (corresponding to a lance distance of about 90 to 140 cm. and a pressure of 6 to 10 atmospheres excess pressure) and later, that is during the second half of the first phase, low blowing energy may be used (corresponding to a lance distance of 200 to 350 cm. and a pressure of 3 to 8 atmospheres excess pressure).
  • normal blowing energy corresponding to a lance distance of about 90 to 140 cm. and a pressure of 6 to 10 atmospheres excess pressure
  • low blowing energy may be used (corresponding to a lance distance of 200 to 350 cm. and a pressure of 3 to 8 atmospheres excess pressure).
  • the second phase of the process can be carried out with a normal blowing energy (corresponding to a lance distance of about 90 to 140 cm. and a pressure of 6 to 10 atmospheres excess pressure) or with increased blowing energy.
  • a normal blowing energy corresponding to a lance distance of about 90 to 140 cm. and a pressure of 6 to 10 atmospheres excess pressure
  • the alloying elements are as mentioned above added to the intermediate product before the second blowing phase, conveniently in the form of ferro-alloys or high alloy scrap, the percentage of such alloy amounting to up to 50% of the metallic charge already in the furnace.
  • Chemical heat carriers such as ferrosilicon or the like, can also be added to the bath before the second blowing phase.
  • the fluxes required for forming the highly basic first slag in the first blowing phase are quantitatively dependent on the crude iron analysis. On average they comprise 3 to lime, 1 to 3% ore or iron-rich slag, and 0.5 to 1.0% fluorspar.
  • the lance is adjusted to a normal blowing height (90 to 140 cm.) and the blowing pressure is maintained at 6 to atmospheres excess pressure.
  • the carbon ignites and there results a dazzling flame with red smoke.
  • the phosphorus content falls to below 0.025% during this phase, while the carbon content is still about 1% below the carbon content of the initial crude iron.
  • the bath temperature may be 1400 to 1500 C.
  • the first blowing phase is completed after about 10 to 12 minutes, when the supply of oxygen is shut off and the lance is withdrawn upwards.
  • the bath and the foaming slag rich in iron oxide react further with each other.
  • By slowly tilting the crucible the slag is allowed to run off.
  • the boiling of the bath and foaming of the slag gradually subside.
  • the total iron oxide content of the slag which after completion of the first blowing phase amounts to more than 30%, decreases in the tilted crucible to 10 to 15%.
  • the second blowing phase begins.
  • the melt ignites immediately upon commencement of the supply of oxygen.
  • the heat carriers added generally silicon
  • ferro-alloys are added to in troduce the alloying elements, they dissolve in the course of the first five minutes of blowing; if scrap is added the speed of dissolution is dependent upon the nature of the pieces. If the scrap is in the form of heavy pieces the dissolution time can amount to as much as 12 minutes.
  • the blowing can be ended at any desired carbon content by shutting otf the supply of oxygen.
  • the amount of slag as well as its chemical composition and the high final temperatures of blowing cause only a small loss of oxygen-sensitive alloying elements.
  • Nickel and molybdenum do not enter the slag.
  • the yield of chromium and manganese lies between and After completion of blowing reducing agents, such as aluminum granules, calcium carbide, ferrosilicon and calcium silicide powder and the like can be added to the slag, whereupon a back reduction of alloying elements from the slag into the bath occurs.
  • Deoxidation agents can likewise be added to the bath after completion of blowing. In this way the quality of the steel can be improved and precise alloying corrections can be carried out.
  • the second slag can be drawn off, powdered lime can be added and this canbe liquefied by means of fluorspar.
  • the amount of these additional slag-forming constituents amounts to about 0.5 to 1.5%.
  • This slag is heated by means of gas or oil burners and maintained in a reducing condition by the addition of reducing agents, such as calcium carbide, coke, calcium silicide and the like.
  • reducing agents such as calcium carbide, coke, calcium silicide and the like.
  • reducing agents such as calcium carbide, coke, calcium silicide and the like.
  • the bath is killed with the known deoxidising agents in the crucible. In this way it is possible to reduce the sulphur content to about 0.005%, and carry out corrective additions of alloying elements without loss and with great precision, as well as to achieve a quality of steel equivalent to the electric furnace steel.
  • the melt is tapped and poured into a mould once the necessary casting temperature is reached.
  • a process for the production of alloy steel from crude iron by the oxygen top blowing process which comprises the steps of:
  • blowing in said first phase is carried out initially using a normal blowing energy corresponding to a lance distance of from about 90 to about 140 cm. and a pressure of 6 to 10 atmospheres excess pressure and subsequently using a reduced blowing energy corresponding to a lance distance of from about 200 to about 300 cm. and a pressure of 3 to 8 atmospheres excess pressure.
  • blowing in said second phase is carried out using at least a normal blowing energy corresponding to a lance distance of from about 90 to about 140 cm. and a pressure of 6 to 10 atmospheres.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Description

United States Patent 3,262,772 PROCESS FOR THE PRODUCTION OF ALLOY STEELS Adolf Richter, Munich, Georg Cohnen and Hansgeorg Bauer, Witten (Ruhr), Germany, and Rudi Rinesch, Linz (Danube), Austria, assignors to Gussstahlwerk Witten Aktieugesellschaft, Witten (Ruhr), Germany No Drawing. Filed July 1, 1963, Ser. No. 292,127 Claims priority, application Austria, July 6, 1962, A 5,474/62 8 Claims. (Cl. 75-52) The invention relates to a process for the production of alloy steels, especially of high grade steels using the oxygen top blowing process.
Liquid basic pig iron or iron produced in a hot blast cupola furnace is used as the star-ting material for this process. Preferably iron low in manganese is used, for example iron containing 0.7% manganese, as can be pro; duced in the hot blast cupola furnace.
The main feature of the process according to the invention is that it is carried out in two phases. In the first phase an intermediate product with a phosphorus content of less than 0.025% is produced under a highly basic first slag rich in iron oxide, that is to say a slag with a basicity (CaO/SiO of more than 3. After removal of the slag and addition of alloying elements the second phase of the process is carried out. In this phase the blowing of the liquid intermediate product is carried out under a second slag (about 1 to 4% of slag-forming constituents) with a basicity of about 2. The process can be ended when the desired carbon content is reached.
In the first phase blowing is conveniently carried out initially with normal blowing energy (corresponding to a lance distance of about 90 to 140 cm. and a pressure of 6 to 10 atmospheres excess pressure) and later, that is during the second half of the first phase, low blowing energy may be used (corresponding to a lance distance of 200 to 350 cm. and a pressure of 3 to 8 atmospheres excess pressure).
The second phase of the process can be carried out with a normal blowing energy (corresponding to a lance distance of about 90 to 140 cm. and a pressure of 6 to 10 atmospheres excess pressure) or with increased blowing energy.
The alloying elements are as mentioned above added to the intermediate product before the second blowing phase, conveniently in the form of ferro-alloys or high alloy scrap, the percentage of such alloy amounting to up to 50% of the metallic charge already in the furnace. Chemical heat carriers, such as ferrosilicon or the like, can also be added to the bath before the second blowing phase.
In detail, the process of invention may, for example, be carried out as follows:
The fluxes required for forming the highly basic first slag in the first blowing phase are quantitatively dependent on the crude iron analysis. On average they comprise 3 to lime, 1 to 3% ore or iron-rich slag, and 0.5 to 1.0% fluorspar. The lance is adjusted to a normal blowing height (90 to 140 cm.) and the blowing pressure is maintained at 6 to atmospheres excess pressure. In the first seconds of blowing a spot of high temperature forms on the bath surface, the carbon ignites and there results a dazzling flame with red smoke.
On the bath surface there is first produced an ironrich slag containing manganese silicate, which rapidly dissolves part of the lime. Three to six minutes after the commencement of blowing the silicon is completely taken up into the slag. The thin-flowing slag begins to foam and dissolves still further the solid lime. Approximately in the fifth to seventh minute of blowing in the first phase the lance is further withdrawn to reduce the blowing energy and thus to inhibit the combustion of carbon, for example to a distance of 200 to 350 cm., whereupon the carbon flame collapses and the decarburation speed rapidly falls. The refining process now occurs essentially only over the slag. The slag foams; the drops of iron still contained in it are oxidised by this method of blowing and the iron-oxide content of the slag is increased. The phosphorus content falls to below 0.025% during this phase, while the carbon content is still about 1% below the carbon content of the initial crude iron. The bath temperature may be 1400 to 1500 C. The first blowing phase is completed after about 10 to 12 minutes, when the supply of oxygen is shut off and the lance is withdrawn upwards. The bath and the foaming slag rich in iron oxide react further with each other. By slowly tilting the crucible the slag is allowed to run off. The boiling of the bath and foaming of the slag gradually subside. The total iron oxide content of the slag, which after completion of the first blowing phase amounts to more than 30%, decreases in the tilted crucible to 10 to 15%.
At the end of the period during which the crucible is tilted, which amounts to about 30 minutes, chemical heat carriers, such as ferrosilicon are added to-the bath. Then the alloying elements are added, alloyed with iron, in such amounts that in the finished steel the desired content of alloying elements is present. Instead of ferroalloys, high-alloy scrap can be charged for this purpose, in which case the economics of the process are improved by the utilisation of the alloying elements present in the scrap.
Before the beginning of the second blowing phase further slag-forming constitutents are added for the formation of the second slag. If, as mentioned above, heat ca rriers (FeSi) are also added, the lime charge must be balanced with the amount of silicon added; the basicity of the new slag (CaO/SiO should amount to about 2.
After addition of the alloying elements and the slagforming ingredients the second blowing phase begins. The melt ignites immediately upon commencement of the supply of oxygen. The heat carriers added (generally silicon) burn away first on account of their afiinity for oxygen and in this way promptly raise the temperature of the liquid bath. If ferro-alloys are added to in troduce the alloying elements, they dissolve in the course of the first five minutes of blowing; if scrap is added the speed of dissolution is dependent upon the nature of the pieces. If the scrap is in the form of heavy pieces the dissolution time can amount to as much as 12 minutes.
Since the phosphorus has already been removed during the first blowing phase and the necessary final temperature can be controlled by the addition of heat carriers, the blowing can be ended at any desired carbon content by shutting otf the supply of oxygen. The amount of slag as well as its chemical composition and the high final temperatures of blowing (over l'680 C.) cause only a small loss of oxygen-sensitive alloying elements. Nickel and molybdenum do not enter the slag. The yield of chromium and manganese lies between and After completion of blowing reducing agents, such as aluminum granules, calcium carbide, ferrosilicon and calcium silicide powder and the like can be added to the slag, whereupon a back reduction of alloying elements from the slag into the bath occurs.
Deoxidation agents can likewise be added to the bath after completion of blowing. In this way the quality of the steel can be improved and precise alloying corrections can be carried out.
If the best quality steel is required with the lowest possible sulphur content, a portion of the second slag can be drawn off, powdered lime can be added and this canbe liquefied by means of fluorspar. The amount of these additional slag-forming constituents amounts to about 0.5 to 1.5%. This slag is heated by means of gas or oil burners and maintained in a reducing condition by the addition of reducing agents, such as calcium carbide, coke, calcium silicide and the like. In general a slag is thus obtained which, like the electric arc furnace refining slag, possesses a strongly desulphurising and deoxidising action. Simultaneously the bath is killed with the known deoxidising agents in the crucible. In this way it is possible to reduce the sulphur content to about 0.005%, and carry out corrective additions of alloying elements without loss and with great precision, as well as to achieve a quality of steel equivalent to the electric furnace steel.
After the slag reduction operations, bath deoxidation and corrective addition of alloying elements, the melt is tapped and poured into a mould once the necessary casting temperature is reached.
We claim:
1. A process for the production of alloy steel from crude iron by the oxygen top blowing process which comprises the steps of:
(1) blowing in a. first phase to form an intermediate product with a phosphorus content of less than 0.025% under a highly basic first slag which is rich in iron oxide and has a basicity of more than 3,
(2) removing the slag,
(3) adding alloying elements,
(4) blowing in a second phase under a second slag in which the slag-forming constituents comprise from about 1 to about 4% and which has a basicity of about 2, and,
(5) after completion of said second blowing phase, partially removing the resultant slag and adding fresh slag-forming constituents, liquefying the slag by external heating and maintaining it in a reducing condition by the addition of reducing agents, so that a reducing slag similar to that in an electric are refining slag results, whereby the quality of the steel is improved and the sulphur content of the steel is reduced to 0.005%.
2. A process according to claim 1 in which blowing in said first phase is carried out initially using a normal blowing energy corresponding to a lance distance of from about 90 to about 140 cm. and a pressure of 6 to 10 atmospheres excess pressure and subsequently using a reduced blowing energy corresponding to a lance distance of from about 200 to about 300 cm. and a pressure of 3 to 8 atmospheres excess pressure.
3. A process according to claim 1.in which blowing in said second phase is carried out using at least a normal blowing energy corresponding to a lance distance of from about 90 to about 140 cm. and a pressure of 6 to 10 atmospheres.
4. A process according to claim 1 in which said alloying elements are introduced in the form of ferro-alloys or high-alloy steel scrap, the percentage of alloy added amounting to up to of the metallic charge.
5. A process according to claim 1 in which chemical heat carriers are added to said intermediate product before said second blowing phase.
6. A process according to claim 1 in which after completion of said second blowing phase reducing agents are added to the slag to cause a back reduction of alloying elements from the slag into said resultant steel.
7. A process according to claim 1 in which deoxidising agents are added to said resultant steel after completion of said second'blowing phase.
8. A process according to claim 1, including terminating the blowing in the second phase as soon as the desired carbon content is attained in the resultant steel.
References Cited by the Examiner UNITED STATES PATENTS 2,303,064 11/1942 Perrin 46 2,557,458 6/1951 Ogan 75 51 2,815,275 12/1957 Richter 7552 2,853,377 9/1958 Kalling et al 7560 2,893,861 7/1959 Rinesch 7552 3,004,847 10/1961 Lambert et a1. 7560 FOREIGN PATENTS 858,377 l/1961 Great Britain.
BENJAMIN HENKIN, Primary Examiner.

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF ALLOY STEEL FROM CRUDE IRON BY THE OXYGEN TOP BLOWING PROCESS WHICH COMPRISES THE STEPS OF: (1) BLOWING IN A FIRST PHASE TO FORM AN INTERMEDIATE PRODUCT WITH PHOSPHORUS CONTENT OF LESS THAN 0.025% UNDER A HIGHLY BASIC FIRST SLAG WHICH IS RICH IN IRON OXIDE AND HAS A BASICITY OF MORE THAN 3, (2) REMOVING THE SLAG, (3) ADDING ALLOYING ELEMENTS, (4) BLOWING IN A SECOND PHASE UNDER A SECOND SLAGA IN WHICH THE SLAG-FORMING CONSTITUENTS COMPRISES FROM ABOUT 1 TO ABOUT 4% AND WHICH HAS A BASICITY OF ABOUT 2, AND (5) AFTER COMPLETION OF SAID SECOND BLOWING PHASE, PARTIALLY REMOVING THE RESULTANT SLAG AND ADDING FRESH SLAG FORMING CONSTITUENTS, LIQUIDFYING THE SLAG BY EXTERNAL HEATING AND MAINTAINING IT IN A REDUCING CONDITION BY THE ADDITION OF REDUCING AGENTS, SO THAT A REDUCING SLAG SIMILAR TO THAT IN AN ELECTRIC ARC REFINING SLAG RESULTS, WHEREBY THE QUALITY OF THE STEEL IS IMPROVED AND THE SULPHUR CONTENT OF THE STEEL IS REDUCED TO 0.0005%.
US292127A 1962-07-06 1963-07-01 Process for the production of alloy steels Expired - Lifetime US3262772A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524742A (en) * 1967-07-05 1970-08-18 Jackson L Williams Process for refining steel
US3847592A (en) * 1971-02-25 1974-11-12 Koninklijke Hoogovens En Staal Method for adding a granular or powdered reaction component to a molten metal, as well as an improved granular or powdered reaction component for carrying out a corrective reaction on a molten metal

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3601337A1 (en) * 1986-01-16 1987-07-23 Mannesmann Ag METHOD FOR PRODUCING HIGH ALLOY STEELS IN THE OXYGEN BLOW CONVERTER

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2303064A (en) * 1939-06-23 1942-11-24 Electro Chimie Metal Process for simultaneously dephosphorizing and deoxidizing steel
US2557458A (en) * 1950-03-31 1951-06-19 United States Steel Corp Method of fusing alloy additions to a steel bath
US2815275A (en) * 1954-11-02 1957-12-03 Brassert Oxygen Technik A G Method for refining pig iron
US2853377A (en) * 1954-11-25 1958-09-23 Stora Kopparbergs Bergslags Ab Two step refining process in a tiltable rotary furnace
US2893861A (en) * 1957-05-10 1959-07-07 Bot Brassert Oxygen Technik A Method of refining crude iron
GB858377A (en) * 1958-02-12 1961-01-11 Arbed Improvements relating to the manufacture of steel
US3004847A (en) * 1957-12-23 1961-10-17 Bot Brassert Oxygen Technik Ag Refining of crude iron

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2303064A (en) * 1939-06-23 1942-11-24 Electro Chimie Metal Process for simultaneously dephosphorizing and deoxidizing steel
US2557458A (en) * 1950-03-31 1951-06-19 United States Steel Corp Method of fusing alloy additions to a steel bath
US2815275A (en) * 1954-11-02 1957-12-03 Brassert Oxygen Technik A G Method for refining pig iron
US2853377A (en) * 1954-11-25 1958-09-23 Stora Kopparbergs Bergslags Ab Two step refining process in a tiltable rotary furnace
US2893861A (en) * 1957-05-10 1959-07-07 Bot Brassert Oxygen Technik A Method of refining crude iron
US3004847A (en) * 1957-12-23 1961-10-17 Bot Brassert Oxygen Technik Ag Refining of crude iron
GB858377A (en) * 1958-02-12 1961-01-11 Arbed Improvements relating to the manufacture of steel

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524742A (en) * 1967-07-05 1970-08-18 Jackson L Williams Process for refining steel
US3847592A (en) * 1971-02-25 1974-11-12 Koninklijke Hoogovens En Staal Method for adding a granular or powdered reaction component to a molten metal, as well as an improved granular or powdered reaction component for carrying out a corrective reaction on a molten metal

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AT249714B (en) 1966-10-10
DE1433534A1 (en) 1968-11-21
LU43915A1 (en) 1963-08-17

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