US3356490A - Refining pig iron - Google Patents

Refining pig iron Download PDF

Info

Publication number
US3356490A
US3356490A US45038665A US3356490A US 3356490 A US3356490 A US 3356490A US 45038665 A US45038665 A US 45038665A US 3356490 A US3356490 A US 3356490A
Authority
US
United States
Prior art keywords
slag
vessel
metal
refining
iron
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
Inventor
Muller Francois
Nilles Paul
Denis Etienne
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Centre de Recherches Metallurgiques- Centrum Voor Research in the Metallurgie Asbl
Original Assignee
Centre de Recherches Metallurgiques- Centrum Voor Research in the Metallurgie Asbl
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to LU46019 priority Critical
Priority to LU46119 priority
Priority to LU46145 priority
Priority to LU46202 priority
Priority to LU46229 priority
Priority to LU46249 priority
Priority to LU46473 priority
Priority to LU47156A priority patent/LU47156A1/xx
Priority to LU47155A priority patent/LU47155A1/xx
Priority to LU47219 priority
Priority to LU47265 priority
Application filed by Centre de Recherches Metallurgiques- Centrum Voor Research in the Metallurgie Asbl filed Critical Centre de Recherches Metallurgiques- Centrum Voor Research in the Metallurgie Asbl
Application granted granted Critical
Publication of US3356490A publication Critical patent/US3356490A/en
Anticipated expiration legal-status Critical
Application status is Expired - Lifetime legal-status Critical

Links

Images

Classifications

    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28Manufacture of steel in the converter
    • C21C5/36Processes yielding slags of special composition
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00Refining of pig-iron; Cast iron
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28Manufacture of steel in the converter
    • C21C5/30Regulating or controlling the blowing
    • C21C5/32Blowing from above
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/56Manufacture of steel by other methods
    • C21C5/567Manufacture of steel by other methods operating in a continuous way
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06FLAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F37/00Details of washing machines of kinds covered by groups D06F21/00 - D06F25/00, restricted to machines of these kinds
    • D06F37/30Driving arrangements
    • D06F37/36Driving arrangements for rotating the receptacle at more than one speed
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28Manufacture of steel in the converter
    • C21C5/36Processes yielding slags of special composition
    • C21C2005/366Foam slags
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Process efficiency
    • Y02P10/21Process efficiency by recovering materials
    • Y02P10/212Recovering metals from waste

Description

Dec. 5, 1967 F. MULLER r-:TAL 3,356,490

REFINING PIG IRON Filed April 23, 1965 I 5 Sheets-Sheet 1 Dec. 5, 1967 F. MULLER ETAI.

REFINING PIG IRON 5 Sheets-Sheet 2 Filed April 25, 1965 Dec. 5, 1967 F.- MULLER ETAL REFINING PIG IRON 5 Sheets-Sheet 5 Filed April 25, 1965 Dec. 5, 1967 F. MULLER ETAL REFINING PIG IRON 5 Sheets-Sheet 4 Filed April 25, 1965 Dec. 5, 1967 F, MULLER ETAL 3,356,490

REFINING PIG IRON Filed April 25, 1965 5 Sheets-Sheet 5 c in megg Mn in metal Fe In sluq l' l' l l I (I \f Y //z J? l. Y' 4 J if me ""utes Duration of overlow ofslaq United States Patent 6 claims. (ci. *7s-6a) The present invention relates to improvements in processes for refining pig iron. Recently introduced techniques, which have now become well known, for refining pig iron comprise the top blowing of a bath of liquid pig iron with an oxidizing gas which may or may not contain slag-forming materials in suspension. Such processes have been used to make steels of a quality fully comparable with open hearth steels and electric steels while often reducing costs substantially. In the case of phosphorus-containing pig iron these known processes usually comprise two blowing periods at least, separated by a slagging operation. Such a slagging operation however has certain disadvantages such as loss of time, loss of heat, and an increase in the wear of the refractories of the vessel holding the metal since the metal remains in it longer.

On the other hand haematitic pig ironl can be refined in a single phase, that is to say without an intermediate slagging operation, though it has not been found economically advantageous to use the same slag from the beginning to the very end of the refining operation since the slag does not remain sufficiently fluid and reactive till the end of the process since it contains too many impurities.

One particular object of the present invention is the provision of a process which enables the majority of the above-mentioned disadvantages to be overcome While providing several advantages as well.

ln the process in accordance with the invention a haematitic or phosphorus-containing pig iron is blown with an oxidizing gas, such as commercially pure oxygen, and the blowing is carried out in such a manner as to produce a foaming slag, at least part of this foaming slag being evacuated from the refining vessel as it is formed. The evacuation can take place during all or during only part of the operation. The oxidizing gas can contain in suspension slag-forming materials.

It has been found that one advantage of the process in accordance with the invention is that a fresh and reactive slag is continually formed owing to the supply of slagforming materials in the gas. Owing to the continuous evacuation of foaming slag which has already reacted at least partially with the metal, the physical and chemical reactions of the refining process are accelerated and the equilibrium points are displaced so as to obtain a purer metal.

The vessel used for carrying out the invention can have a low volume, for instance between 0.3 and 0.7 cubic meter per metric ton of pig iron. The volume is therefore comparatively low since in conventional apparatus it is usually between 0.7 cubic meter and 1.4 cubic meters per metric ton of pig iron. This is evidently a substantial ad- Vantage of the invention.

The evacuation of the foaming slag can take place either by allowing it to overflow over its rim or through a lateral opening in the vessel placed ata carefully chosen height.

The choice of the height should be made to ensure that the volume of slag is small enough to enable a rapid change-over in the slag to take place without the lateral opening being so low that granules of metal are lost to any great extent with the slag being evacuated. It has been found that the height of the slag divided by the height of the bath should be between 0.5 and 1.5. In practice of course it can be adjusted by tipping the vessel.

If the degree of foaming is insufficient several methods can be used for increasing it; for instance by adding materials such as oxides of iron, chromium oxide, graphite, and magnesia to the slag, either by themselves or as constituents of powders containing slag-forming materials blown into the bath with a lance. These slag-forming materials can be added continuously throughout a refining operation or heat so as to make sure that the slag is always capable of taking up impurities from the metal being refined. It has been found that graphite and magnesia have the advantage over iron oxides of decreasing the quantity of iron lost in the slag being continually removed. Although the materials for provoking foaming can be in powder form they can also be in the particle size range 2 mm. to 100 mm. and this has been found specially so in the case of graphite.

Though it is difficult to lay down a general rule for the quantity of foam-provoking agents to be added for all steels and all grades of cast-iron, it is considered that they should make up between l and 10% of the slag in the vessel.

A second method of causing continuous foaming of the slag consists in maintaining the lower end of the lance used for refining below the lowest part of the opening for the removal of slag and controlling foaming of ythe slag using known techniques of blowing, i.e. to produce an emulsion. This technique has the advantage of facilitating deep penetration of the jet of oxidizing gas into the metal and thus accelerating reactions between the metal and the slag. The method is particularly advantageous when fresh slag-forming and foam-provoking materials are added continuously so that the level of the foaming slag is sufficiently high to cause continuous operation.

A further method of provoking foaming of the slag consists in using a lance whose bore diameter in mm. is not less than 0.02 times the diameter of the bath in meters divided by the square root of the absolute pressure-of the refining gas in atmospheres.

The yield of the process can be increased by placing the refining lance eccentrically in relation to the axis of the vessel between the axis and the lateral opening for the removal of slag, and it has been found that this arrangement substantially reduces throwing of particles or granules of metal towards the slag-removal opening. Therefore there is less risk of the particles of metal being drawn out of the vessel in the slag by the refining jet through the lateral opening. Such a loss of -metal can also be reduced by directing preferably oblique jets of gals towards the top of the vessel so as to sweep back granules of metal from the slag-removal opening and thus favour the contact of the metal and the slag.

The removal of slag at the beginning of the operation is facilitated by using a slag-removal opening which is comparatively small, and pressurizing the inside of the vessel so that gas and fumes produced during the refining are obliged to pass out through the slag-removal opening and thus help the removal of foaming slag.

The times at which slag should be removed and the rate at which it is removed should be related to the chemical composition of the slag, for instance having regard to its iron oxide and P205 contents. It is therefore advantageous to refrain :from removing slag unless the slag contains a certain maximum quantity of iron oxide (for instance 20%) and la certain minimum quantity of P205.

The composition of slag should be chosen so that there is no likelihood of two immiscible slag phases arising.

The content of iron oxide should be kept low so as to prevent such an occurrence, as can be seen from an examination of a ternary diagram of P2O5-CaO-Fe0+ MnO At this moment, the quantity of iron carried out with the slag in the course of slag removal can be considered as economically acceptable.

The continuously removed slag removed after this moment is richer in lime and P205 than the slag formed initially at the beginning of a refining operation and is therefore more suitable for agricultural uses. The content of iron oxide, low when slag is first removed, decreases to a minimum and then increases again. The continuous removal of slag should therefore be stopped so as to keep the losses of iron oxide within reasonable limits.

The ternary diagram represented in FIGURE l of the accompanying drawing, in which I and II indicate respectively the zone of immiscibility and the zone of lime saturation, indicates by way of example the manner in which this form of invention may be carried out. The variations in chemical composition during the course of an operation are shown schematically so as to indicate the limiting compositions of the slag. Thus in the curve showing the variations of composition the parts ab and cd represent the variation in composition when slag is not being continually removed, while the part bc represents the variation of the composition when the slag is continuously removed.

In order to provide for easy control of the quantity of slag removed and to estimate its iron content at any given instant, the slag is preferably weighed continuously and the rate of slag formation is modified as desired, for instance by tilting the vessel so that the ratio between the depths of the slag and of the metal is changed.

It is known that at a certain point, the iron oxide content of the slag begins to increase in such a fashion that the slag has a composition at the end of the ope-ration which enables a low phosphorus content to be attained in the metallic bath. At this moment it is necessary to slow down or even stop the flow of the slag from the vessel for the purpose of avoiding a reduction in the yield of refined metal.

By means of analysing the composition of the slag it is possible to determine the moment at which it is convenient to reduce or stop the removal of the slag; however continuous Weighing is quicker and simpler. Another advantage of continuous Weighing (preferably carried out with electronic weighing equipment), results from the fact that if the content of metallic iron in the slag increases suddenly, the sudden increase in the weight of the slag is quickly detected so that the operator can react rapidly to take effective steps to limit losses in iron, something that would not be possible with other methods. Such other methods being based on computations of the total quantities of lime and oxygen injected bear less relation to the composition of the slag.

It has been found that the quantity of citric acid soluble P205, which is important from the agricultural point of view, is more particularly related to the percentage of silica divided by the percentage of P205 in the slag and, to achieve solubility, this ratio should always be above 0.3.

In accordance with the invention it has been found comparatively easy to produce a slag having a P205 content sufficient to give a high citric acid solubility. Thus, to achieve this, during the whole of the refining operation blowing is carried out in such a manner with the addition of slag-forming materials, for instance limestone, that the liquid slag emerging from the vessel or converter always contains at least 14%, and preferably 18% of P205 and as the refining operation proceeds silicaor siliconcon taining materials yare added so that the silica-P205 ratio always exceeds 0.3.

These additions can, in accordance with this embodiment of the invention, be carried out preferably outside the refining vessel.

lDifferent processes can be used for slowing down or stopping the production or the removal of slag. One can for example change the height of the blowing lance and/ or the rate of feed of lime or of oxygen. These methods though efficient are slow, and it has been found surer and more effective to raise the height of the slag-removal opening by tilting the vessel. The slag-removal opening can be provided with an elongated lip. The slag level can be raised by using a block of refractory material, wood, or a plastic substance fitting in the opening so as to dam it.

The present invention has a further embodiment providing for the recovery of metal entrained with the slag as it is evacuated and for this the slag is collected in a receptacle distinct from the refining vessel. The slag can be separated from the metal in it by decantation or centrifuging and the metal thus recovered can either be treated as being fully refined or can be replaced in the vessel in the following heat.

In the case of decantation, the slag flowing from the vessel when overfiowing begins is preferably collected in an empty ladle which is in the turned up position. Droplets of steel and metal are then separated by decantation. The slag retained in the ladle during the decantation may frequently have a relatively high silica content, since it will contain a proportion of the slag that first overows from the refining vessel and therefore the slag collected in the ladle, after steps have been taken to see that it is homogeneous, is particularly suitable for use as an agricultural fertiliser. In the course of another phase of overflow, the ladle can be inclined in such a fashion that only particles of metal are retained in it and the slag fiows continuously so that the ladle only represents a temporary receptacle for the slag overflowing from the refining vessel (for instance a converter) into a further slag container. Towards the end of a heat, the ladle can be tilted into its upright position again so as to retain the iron-rich slag which then starts to flow, until the slag outlet opening is blocked or until the vessel is turned up. Proceeding thus, a mixing of the lastnamed, iron-rich slag, with the slag in the further slag containing vessel used, is avoided, something that would be unavoidable if the ladle were not used during the blocking of the opening inthe converter.

It has been found that the particles of metal entrained with the slag are nearly or practically completely refined, and a further embodiment of the invention is based on an intentional encouragement of such entrainment, the entrained metal being separated from the entraining slag by decantation or centrifuging, while to make up for the loss of metal from the vessel, metal is continually added to it.

The partially or totally refined liquid metal can be forced out of the refining vessel by adding pig iron to the vessel either continuously or interruptedly. The pig iron can be added from the side or from above, above or below the level of the bath through it is preferable to place it in the bottom of the bath as directly as possible in order to avoid disturbing the refining operation being carried out. Another reason for adding the pig iron to the bottom of the bath is that as the pig iron rises to the surface its temperature gradient increases and decarburisation progresses.

The quantity of pig iron to be added is substantially equal to the amount of metal evacuated from the vessel. The rate at which pig iron is evacuated from the vessel can be controlled in various manners, for instance by varying the distance between the lance and the bath or varying the kinetic energy of the gas striking the bath. The gas can be projected obliquely down on to the bath so as to vary its impact pressure and the quantity of slag-forming material suspended in the gas can be varied. Also it is possible to vary the pressure of the gas, the height of the foaming slag and the pressure in the vessel.

If the metal evacuated from the vessel during the operation is not sufficiently refined, the treatment of the metal can be carried out in a secondary refining vessel in which the metal is subjected in a continuous or discontinuous fashion to a reheating operation and then to a subsidiary refining operation in accordance with its condition possibly followed by the addition of alloying elements and to deoxidation.

A particularly advantageous form of process described in the last preceding paragraph consists in allowing the mixture of foaming slag and metal falling from the primary vessel to drop into a secondary vessel (for example a ladle) provided with a means for separating the slag and the metal, for example a tipping device for the carefully controlled pouring off of the supernatant slag, either continuously or discontinuously, from the secondary vessel while the metal remains behind in it.

The primary and secondary vessels or receptacles can be arranged in such a manner that `while metal and foaming slag passes from the first vessel into the second vessel, the metal is continually decanted from the second vessel.

On the other hand if a batch rather than a continuons method is used, the secondary vessel is allowed to fill with metal and a further secondary vessel is then filled from the primary vessel while the metal from the rst secondary vessel is given further treatment. This further treatment can be of a conventional nature though a preferred form of it comprises injecting an oxidizing gas, preferably commercially pure oxygen, down intoA the metal and nely divided slag-forming materials may be added in the gas. The metal after this treatment can be separated finally from its slag in a continuous or discontinuous manner, or, if it is needed, la further purifying treatment can be carried out. It is therefore possible to carry out a three-stage cascade continuous process of steel making in which the metal to be treated flows continuously from the primary vessel, then to the secondary vessel, and then to the tertiary vessel, pneumatic refining producing a foamingslag. being carried out in each vessel.

If such a continuous cascade process is used using two vessels instead of threerthe operation can be carried `out in such a manner that a low-iron slag is used in the first vessel, for instance with an iron content between 5% and 30% and preferably between 10% and 20%, while the P205 content is at least This slag removed from the primary vessel is therefore of high value as a fertilizer for agriculture.

In the secondary vessel oxidation of the metal is encouraged so a-s to obtain an iron-rich slag which does not contain much phosphorus and can be added to the primary vessel together with the necessary pig iron and scrap.

Scrap may be added to the secondary vessel. In order' t ously cast.

A further aspect of the invention is the pneumatic granulation of the slag produced since as the slag is produced continuously the granulating apparatus can be considerably simpler than known apparatus in which the slag has to be stored while molten, since it is produced in batches, until it can be dealt with by the granulating device. 4

In accordance with the present invention the slag which is allowed to run continuously from the vessel in which steel is being produced is granulated by means of one or more jets of gas or liquid blown obliquely or perpendicularly towards the flow of liquid slag.

A further advantage of the present invention from the point of View of granulating slag pneumatically or by means of a liquid is that the slags produced are liquid and of fairly even consistency, as opposed to the slags produced in conventional batch processes for making steel. The granulation can be carried out on slag leaving any one of three stages of a cascade process in accordance with the invention or on slag leaving all of them.

As for apparatus used for carrying out the invention,

the top blowing of a melt of pig iron so as to produce a foaming slag which is allowed to overfiow continuously can be carried out in an approximately cylindrical vessel having a lateral opening and la solid fiat bottom. The top part of the vessel can converge conically.

The vessel can be provided with a cover to enable a gauge pressure to be obtained inside it so as to encourage fumes to emerge through the lateral opening together with some of the supernatant slag. The metal can be teemed through a tapping hole in the side of the vessel preferably opposite the lateral opening for the removal of slag. The tapping hole is higher than the slag-removal opening, the vertical component of the distance between both openings being preferably between one and two times the thickness of the slag, this being sufficient to prevent the slag emerging as it foams, without requiring an exceptionally tall vessel. As already mentioned the vessel can be provided with an elongated lip or trough for guiding liquid slag leaving through the lateral opening. In order to discourage metal from fiowing out along such a trough, the bottom of the trough can be made so that the first part of it nearest the vessel slopes upwards or the trough can-be provided with a separate interior duct which rotates.

Various embodiments of the invention and apparatus for carrying it out are now described with reference to the attached drawings.

FIGURE 1 (whic-h has already been described above) is a ternary diagram of the system P2O5-CaO-Fe0+ MnO FIGURES 2 and 3 show vessels in the form of converters for carrying out the process in accordance with the invention.

FIGURE 4 is a section of a further converter.

FIGURE 5 shows yet another converter.

FIGURES 6 and 7 show methods of operating converters when carrying out the process in accordance with the invention.

FIGURES 8 and 9 show an apparatus for carrying out the invention in different positions.

FIGURE 10 shows a further apparatus for carrying out the invention.

FIGURES l1 and 12 show somewhat similar apparatus.

FIGURE 13 illustrates a cascade steel-making process in acco-rdance with the invention.

FIGURE 14 is a graph showing the course of a steelmaking operation in accordance with invention.

As shown in the drawings, and with more particular reference to FIGURES 2 and 3, it can be seen that the process of the invention in which pig iron is continuously top blown so as to produce a foaming slag on it which is allowed to overflow, can conveniently be carried out in an approximately cylindrical converter vessel 1 provided with a lateral opening 2 for the continuous overflow of the slag, and a tapping opening 3 for teeming the metal. The converter is provided with a cover 4 and a lance 5 for the top blowing with an oxidizing gas such as commercially pure oxygen containing slag-forming materials in suspension. The cover 4 seals the top of the converter and causes the fumes generated in it to be blown out through the lateral slag-removal opening 2 entraining with them the foaming slag. For teeming the metal the vessel is turned down in a clockwise direction. FIGURE '3 shown asimilar apparatus for carrying out the present invention.

centric position in relation to the center axis of the converter. It tends to blow the foaming slag away from the slag outlet opening 2. It will be noted that the duct 2 leading from the slag outlet openings slopes upwards to discourage the loss of metal from the vessel with the overflowing slag.

In the converter shown in FIGURE 5 the process is v'carried out in such a manner that the foaming slag overcylindrical so as to increase the slag capacity, to facilitate decantation of the steel, and reduce the quantity of metal entraiued with the slag leaving along the spout 8. Preferably the volume available for slag before it overflows and that available for the metal should be in a ratio of between 0.25 and 3 or preferably between 0.75 and 2.

The ratio in the actual embodiment shown is 1.96. In the converter shown in FIGURES 6 and 7 the overfiow `of slag can be reduced or shut off completely by tilting lin an anti-clockwise direction as shown in FIGURE 7. 'The cover 4 of the converter is provided with a slot 4 which enables the converter to be tilted without moving the lance 5. The metal is represented by M. During refining slag is allowed to overflow continuously through 'the lateral opening 2. It will be noted that this lateral -opening is provided with a spout having a Weir 9 to hold .back the metal.

The apparatus shown in FIGURE 8 comprises a converter vessel 1 similar to the converter vessel shown in FIGURE 5. Slag flows continuously from it to a decanting `vessel 10 and thence into a slag container 11. The decanting vessel 10 can be in a horizontal position so as to retain `the metal and (temporarily) the slag or it can be inclined las shown in FIGURE 9 so that it only serves for decanting vthe metallic particles. The apparatus shown in FIGURE 9 is similar to that shown in FIGURE 8 apart from the provision of a wall of the converter above the spout.

FIGURES 10, 11 and 12 all show apparatus for the continuous refining of pig iron, that is to say apparatus in which the pig iron is caused to flow continually through :the apparatus instead of being treated in batches.

In the apparatus shown in FIGURE 10 we utilise a Iconverter 1 fed continuously at its bottom with liquid pig iron through a duct 12. The cover 4 is provided with an opening 4l whose size is chosen to achieve the desired pressure inside the vessel 1. Slag and metal fiow continu- Iously through the lateral opening 2 into a decanting vessel 13 provides with decanting openings 14 and 15 for the removal of metal and slag respectively. 16 indicates a device for the addition of ferro-manganese.

In the apparatus shown in FIGURE 11 scrap is added through a lateral opening 17 down a chute 18 and is preheated by fumes generated during the refining process.

yThe bore at the bottom of the lance 5 is inclined obliquely towards the lateral opening 2 for the removal of slag and metal. The decanting vessel 13 is similar to that shown in FIGURE 10 but cannot be tilted and has a cover.

In the apparatus shown in FIGURE 12 the lance 5 is inclined and enters the vessel through a side wall. An oxygen-hydrocarbon fuel burner 19 serves for heating up the scrap as it enters the vessel.

As shown in FIGURE 13, apparatus for a cascade process for the continuous manufacture of steel from pig iron in accordance with the invention comprises two vessels 1 in which the metal is refined by means of top blowing with an oxidizing gas, for instance commercially pure oxygen, containing powdered lime in suspension. Metal and foaming slag continuously tiow from the primary vessel 1 into the decanting vessel 20 which is provided with an overfiow 21 for the slag, which is low in iron and rich in phosphorus, and an outlet pipe 22 with an inverted U bend or syphon for the removal of metal which flows into a second refining vessel also denoted by the reference numeral 1 in which it is top blown again by commercially pure oxygen containing lime in suspension. The emulsion of slag and metal is allowed to overiiow into a further decanting vessel 20 Where the slag which is rich in iron is removed and returned to the first vessel 1. The steel passes from the vessel 20 to a receptacle 23 in which alloying elements and deoxidizing agents are added. After leaving this receptacle the steel passes to a continuous casting plant schematically indicated at 24.

For granulating the slag produced it is possible to provide jets of liquid or gas acting on the slag as it ows continuously from the spout of a ladle of slag, provision being made for tilting the ladles so that the rate of flow of slag can be maintained at an even rate.

The following is an example of a process embodying the invention.

An experimental converter was used having an internal diameter of cm. The converter was provided with a lateral opening with a diameter of 30 cm., its bottom being 60 cm. above the level of the bath. The depth of the bath (composed of Thomas pig iron and cooling scrap) was 60 cm. The bath contained two metric tons of metal with the following analysis:

Percent C 3.75 P 1.80 Si 0.3 Mn 0.2

Commercially pure oxygen was blown down on to the bath using a lance whose -bore diameter was 21 mm. The rate of injection was 7.5 Nm.3 of oxygen per minute. One minute after the beginning of the operation the injection of lime powder was begun at the rate of 16 kg. per minute and this was kept up for twelve minutes. Overflowing of the slag began at the eighth minute and lasted for tive minutes. kg. of slag were collected for each metric ton of metal.

The slag which overflowed had the following analysis:

Percent CaO 52 P205 21 Fe 15 SiO2 4 As the slag overfiowed the lance was gradually lowered towards the bath. At the thirteenth minute the slag overflow opening was blocked up with a refractory. The rate of feed of lime was then altered to 40 kg. per minute during a period of 11/2 minutes while the feed of oxygen was reduced to 6 Nm.3 per minute until the end of the operation after nineteen minutes.

The graph of FIGURE 14 shows the changes in the composition of the metal as regards carbon, phosphorus, silicon and manganese and also as regards changes in the iron content of the slag. The final content of the steel, as shown, was C, 0.04%, P, 0.015%, and S, 0.015%. The final slag composition was CaO, 50%, P205, 8%, SiO2, 3%, Fe, 25%.

The first slag was therefore quite suitable for use as a fertilizer while the second slag could be returned to the converter for use at the beginning of a refining operation.

In a further embodiment of the invention the same converter was charged with 3 metric tons of pig iron and scrap and a decantation receptacle was placed to receive material emerging from the lateral opening o-f the converter. The slag was allowed to overflow out of this vessel into a slag container while metal was removed from a tapping hole in it and transferred to a ladle in which final additions were made to achieve the desired composition. A tilting ladle was placed somewhat above and to the side of the converter so as to allow pig iron to flow continuously into the converter. During the first part of the operation before overflowing of metal began, the metal was top blown as described in the first example.

75 The slag that overflowed had the same composition as in the first example while the metal which was entrained with the slag into the decantation receptacle had a carbon content of 0.05% and a phosphorus content of 0.015%.

While I have described specific embodiments of my invention so as to enable those skilled in the art to take full advantage of it, it is to be understood that the monopoly I seek in the United States is not to be limited to these particular embodiments but is to be defined by the gist and spirit of the following patent claims.

We claim:

1. In a process of refining pig iron which comprises top blowing pig iron in a refining vessel with an oxidizing gas, the improvement comprising producing a foaming slag on the molten metal, and removing at least part of said foaming slag by continuously overflowing from the refining vessel during at least part of the operation.

2. A process for refining pig iron according to claim 1, wherein the refining vessel is a converter and the height of said foaming slag divided by the height of the molten metal in the converter is between 0.5 and 1.5.

3, A process for refining pig iron according to claim 1, wherein the foaming slag formed contains fine particles of iron and the slag is caused to overflow from the refining vessel when it contains 20% or less of iron.

4. A process for refining pig iron according to claim 1, wherein the foaming slag overfiowing from the vessel contains particles of iron and continuously weighing the slag to determine the percentage of iron therein.

5. A process for refining pig iron according to claim 1, wherein the foaming slag contains line particles of iron and collecting said overflowing foaming slag in a receptacle distinct from the refining vessel, and separating the slag from the iron entrained with it in said receptacle.

6. A process for refining pig iron according to claim 1, wherein the foaming slag formed contains fine particles of iron in suspension, removing said foaming slag containing fine particles of iron in suspension by continuously overflowing from the refining vessel into a receptacle distinct from said refining Vessel, continuously adding iron into the refining vessel to make up for the loss of iron from said refining vessel, and separating the entrained iron from the entraining slag, said metal then passing continuously into a secondary refining vessel in which it is refined again by top blowing while the slag is collected in a slag ladle.

References Cited UNITED STATES PATENTS 3,145,255 8/1964 Chedaille 75-60 3,215,424 11/1965 Kanamori 75-60 3,275,432 9/ 1966 Alexandovsky 75-60 724,770 4/1903 Young 75-51 1,032,653 7/1912 Brassert 75-52 1,032,655 7/1912 Brassert 75-51 2,800,631 7/1957 Suess et al. 75-60 2,962,277 11/ 1960 Morrill 7560 FOREIGN PATENTS 361,887 11/1906 France.

BENJAMIN HENKIN, Primary Examiner. DAVID L. RECK, Examiner.

Disclaimer 3,356,490.-Francoz's Muller, Griiith, Ind., and Paf/ul Nlles, Embour and Etze'rme Denis, Grivegnee, Belgium. REFININ G PIG IRON. abent dated Dec. 5, 1967. Disclaimer filed June 30, 1969, by the assignee, I nstz'tut de Recherches de la Sidemrgz'e Fmvwazse. Hereby enters this disclaimer to claims 1, 5 and 6 of said patent.

[Ocal Gazette November .4, 1.969.]

Claims (1)

1. IN A PROCESS OF REFINING PIG IRON WHICH COMPRISES TOP BLOWING PIG IRON IN A REFINING VESSEL WITH AN OXIDIZING GAS, THE IMPROVEMENT COMPRISING PRODUCING A FOAMING SLAG ON THE MOLTEN METAL, AND REMOVING AT LEAST PART OF SAID FOAMING SLAG BY CONTINUOUSLY OVERFLOWING FROM THE REFINING VESSEL DURING AT LEAST PART OF THE OPERATION.
US45038665 1964-05-04 1965-04-23 Refining pig iron Expired - Lifetime US3356490A (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
LU46019 1964-05-04
LU46119 1964-05-21
LU46145 1964-05-23
LU46202 1964-05-30
LU46229 1964-06-02
LU46249 1964-06-04
LU46473 1964-07-07
LU47156A LU47156A1 (en) 1964-10-17 1964-10-17
LU47155A LU47155A1 (en) 1964-10-17 1964-10-17
LU47219 1964-10-27
LU47265 1964-10-31

Publications (1)

Publication Number Publication Date
US3356490A true US3356490A (en) 1967-12-05

Family

ID=27582350

Family Applications (1)

Application Number Title Priority Date Filing Date
US45038665 Expired - Lifetime US3356490A (en) 1964-05-04 1965-04-23 Refining pig iron

Country Status (7)

Country Link
US (1) US3356490A (en)
JP (1) JPS537370B1 (en)
BE (1) BE662026A (en)
DE (1) DE1458830A1 (en)
GB (1) GB1097811A (en)
LU (9) LU46019A1 (en)
NL (1) NL6505692A (en)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3486882A (en) * 1964-12-24 1969-12-30 Siderurgie Fse Inst Rech Continuous steel making process
US3527598A (en) * 1966-09-28 1970-09-08 Siderurgie Fse Inst Rech Process of making steel from prereduced products
US3528799A (en) * 1967-03-18 1970-09-15 Centro Speriment Metallurg Process for continuously refining cast iron into steel
US3617257A (en) * 1967-03-13 1971-11-02 Inst Derecherches De Lasiderur Process for continuously refining metal
US3802682A (en) * 1969-08-19 1974-04-09 Voest Ag Method for continuously refining pig iron and plant for carrying out such method
US3971549A (en) * 1975-03-05 1976-07-27 Habig Alan L Process and apparatus for treating and transferring metal in the liquid state
US4052043A (en) * 1968-05-18 1977-10-04 Stahlwerke Peine-Salzgitter Ag Apparatus for continuously refining molten metals
EP0723023A1 (en) * 1995-01-19 1996-07-24 LTV STEEL COMPANY, Inc. Controlled foamy slag process
EP0735147A1 (en) * 1995-03-30 1996-10-02 VOEST-ALPINE STAHL Donawitz GmbH (HRB Nr. 502) Process and installation for limiting the volume of foam slag in a metallurgical vessel
US5885323A (en) * 1997-04-25 1999-03-23 Ltv Steel Company, Inc. Foamy slag process using multi-circuit lance
CN103333981A (en) * 2013-06-09 2013-10-02 武汉钢铁(集团)公司 Method for smelting high-silicon molten iron by using limestone as slagging material

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5647935B2 (en) * 1978-06-30 1981-11-12
US4457777A (en) * 1981-09-07 1984-07-03 British Steel Corporation Steelmaking

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US724770A (en) * 1902-05-31 1903-04-07 Frank E Young Art of making steel.
FR361887A (en) * 1905-11-04 1906-12-10 Antoine Henri Imbert A method of nickel metallurgy
US1032655A (en) * 1904-11-28 1912-07-16 Herman A Brassert Method of manufacturing steel.
US1032653A (en) * 1904-11-11 1912-07-16 Herman A Brassert Method of manufacturing steel.
US2800631A (en) * 1955-11-16 1957-07-23 Voest Ag Method of carrying out melting processes
US2962277A (en) * 1958-05-15 1960-11-29 Gen Electric Apparatus for continuous process of steel making
US3145255A (en) * 1962-04-26 1964-08-18 Bausch & Lomb Projection objective for photo mechanisms
US3215424A (en) * 1960-12-07 1965-11-02 Kanamori Kuro Apparatus for refining iron
US3275432A (en) * 1965-02-23 1966-09-27 Alexandrovsky George Oxygen steel making

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US724770A (en) * 1902-05-31 1903-04-07 Frank E Young Art of making steel.
US1032653A (en) * 1904-11-11 1912-07-16 Herman A Brassert Method of manufacturing steel.
US1032655A (en) * 1904-11-28 1912-07-16 Herman A Brassert Method of manufacturing steel.
FR361887A (en) * 1905-11-04 1906-12-10 Antoine Henri Imbert A method of nickel metallurgy
US2800631A (en) * 1955-11-16 1957-07-23 Voest Ag Method of carrying out melting processes
US2962277A (en) * 1958-05-15 1960-11-29 Gen Electric Apparatus for continuous process of steel making
US3215424A (en) * 1960-12-07 1965-11-02 Kanamori Kuro Apparatus for refining iron
US3145255A (en) * 1962-04-26 1964-08-18 Bausch & Lomb Projection objective for photo mechanisms
US3275432A (en) * 1965-02-23 1966-09-27 Alexandrovsky George Oxygen steel making

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3486882A (en) * 1964-12-24 1969-12-30 Siderurgie Fse Inst Rech Continuous steel making process
US3527598A (en) * 1966-09-28 1970-09-08 Siderurgie Fse Inst Rech Process of making steel from prereduced products
US3617257A (en) * 1967-03-13 1971-11-02 Inst Derecherches De Lasiderur Process for continuously refining metal
US3528799A (en) * 1967-03-18 1970-09-15 Centro Speriment Metallurg Process for continuously refining cast iron into steel
US4052043A (en) * 1968-05-18 1977-10-04 Stahlwerke Peine-Salzgitter Ag Apparatus for continuously refining molten metals
US3802682A (en) * 1969-08-19 1974-04-09 Voest Ag Method for continuously refining pig iron and plant for carrying out such method
US3971549A (en) * 1975-03-05 1976-07-27 Habig Alan L Process and apparatus for treating and transferring metal in the liquid state
EP0723023A1 (en) * 1995-01-19 1996-07-24 LTV STEEL COMPANY, Inc. Controlled foamy slag process
US5584909A (en) * 1995-01-19 1996-12-17 Ltv Steel Company, Inc. Controlled foamy slag process
EP0735147A1 (en) * 1995-03-30 1996-10-02 VOEST-ALPINE STAHL Donawitz GmbH (HRB Nr. 502) Process and installation for limiting the volume of foam slag in a metallurgical vessel
US5885323A (en) * 1997-04-25 1999-03-23 Ltv Steel Company, Inc. Foamy slag process using multi-circuit lance
CN103333981A (en) * 2013-06-09 2013-10-02 武汉钢铁(集团)公司 Method for smelting high-silicon molten iron by using limestone as slagging material
CN103333981B (en) 2013-06-09 2014-09-17 武汉钢铁(集团)公司 Method for smelting high-silicon molten iron by using limestone as slagging material

Also Published As

Publication number Publication date
GB1097811A (en) 1968-01-03
NL6505692A (en) 1965-11-05
LU46119A1 (en) 1965-11-21
BE662026A (en) 1965-10-04
LU46019A1 (en) 1965-11-04
LU46229A1 (en) 1965-12-02
JPS537370B1 (en) 1978-03-17
DE1458830A1 (en) 1969-03-27
LU46202A1 (en) 1965-12-01
LU46473A1 (en) 1972-01-01
LU46249A1 (en) 1964-12-03
LU47219A1 (en) 1966-04-27
LU47265A1 (en) 1966-05-03
LU46145A1 (en) 1965-11-23

Similar Documents

Publication Publication Date Title
US3771998A (en) Method and converter for refining pig iron
KR100396071B1 (en) Method and apparatus for manufacturing metal and metal alloy
US3724829A (en) Apparatus for the introduction of volatile additives into a melt
CN1308464C (en) Refining agent and refining method
US3955965A (en) Refining metals
US2991173A (en) Metal refining method and apparatus
US3230074A (en) Process of making iron-aluminum alloys and components thereof
US3554521A (en) The treating or refining of metal
US4457777A (en) Steelmaking
US2817584A (en) Method for refining pig iron
EP0030220B1 (en) Method for adding solids to molten metal
KR20060009941A (en) Method for utilizing slag
CS244826B2 (en) Method and apparatus for production of liquid pig iron or steel pre-products
US3819365A (en) Process for the treatment of molten metals
US3241825A (en) Blowing device
US3322530A (en) Method for adding additives to molten steel
EP1511871B1 (en) Refining ferroalloys
US3664652A (en) Method and apparatus for the treatment of molten metal
US4298192A (en) Method of introducing powdered reagents into molten metals and apparatus for effecting same
US4518422A (en) Process and apparatus for refining steel in a metallurgical vessel
CZ20002097A3 (en) Direct smelting vessel
CS196250B2 (en) Device for treatment of molten metal
JP4195106B2 (en) Alloy steel manufacturing method and alloy steel manufacturing plant
US3634065A (en) Method for refining metals
US2862810A (en) Process and apparatus for reducing the silicon content and increasing the temperature of molten pig iron