KR20160029204A - Method for converter oxygen clowing - Google Patents

Abstract

According to an embodiment of the present invention, a method to refine steel comprises: a process of starting blowing by supplying oxygen to a container wherein metal is contained to remove impurities in the metal melt; a first half input process of keeping the oxygen supply, and inputting a sub-material and quicklime to the container with the start of blowing; an input stop process of keeping the oxygen supply, and stopping the input of the sub-material and quicklime at a preset first input time point; a second half input process of keeping the oxygen supply, and inputting the quicklime until blowing is completed from a preset second input time point; and a process of stopping the oxygen supply and the quicklime input, and completing blowing.

Description

{Method for converter oxygen clowing}

TECHNICAL FIELD The present invention relates to a refining method for steel, and more particularly, to a refining method for removing carbon, phosphorus, and the like in a molten iron in a converter.

The conversion process for oxidizing and refining impurities contained in molten iron is the most important process among various steelmaking processes, and many refining techniques and equipment have been continuously developed. The converter is divided into two phases: a phase-shifting furnace that utilizes a lance lance to supply oxygen, a low-power furnace that utilizes a low-temperature lance to supply oxygen, and a combined furnace furnace that compensates for both advantages and disadvantages. Currently, the most common type of converter used in the world is an inert gas-filled combined-blower that has a simple facility, good refining ability, and low risk of equipment accidents.

Meanwhile, due to the oversupply of steel in recent years, each of the leading steel mills is making efforts to reduce steel manufacturing cost. In particular, iron ore and anthracite, which are inexpensive and inferior in quality, are being used to reduce the cost of producing iron ore, which is the main raw material of steelworks. In such a case, the contents of the main impurity elements (Si, P) and the like in the charcoal are increased, thereby increasing the refining burden of the steelmaking. In particular, silicon (Si) and phosphorus (P) are impurities which are typically oxidized and removed in a converter, and when the content of the molten iron increases, the conversion work becomes very difficult. For this reason, in many steel mills, pre-treatment of molten iron (Si) and phosphorus (P) is carried out in advance.

However, pretreatment of the charcoal is accompanied by side effects such as an increase in the process load and an increase in the cost. Therefore, most of the charcoals containing silicon (Si) and phosphorus (P) are processed in the converter as much as possible. Currently, double slag (double slag) method is applied to treat the high Si and P containing charcoal. The double slag method is a primary smelting step in which silicon (Si) etc. having a high affinity with oxygen during the converter winding operation is preliminarily removed, and thereafter a step of removing carbon (C) and phosphorus (P) It is divided into a tea-blasting stage. The primary blower supplies oxygen to the level of about 15% to 30% of the total amount of oxygen normally supplied. After a certain amount of oxygen is supplied, the blower is stopped and the blower is tilted to reject the slag. Conduct. Depending on the contents of silicon (Si) and phosphorus (P) in the charcoal, triple slag (double slag) is also carried out by repeating this operation twice or more.

However, in the case of performing the shunting in this manner, there is a problem that the time for shunting is increased compared with the single slag method, and a decrease in the water content rate and heat loss are inevitably caused due to leaking of the molten iron during the discharge of the slag.

Korean Patent Publication No. 10-2005-0005622

The technical problem of the present invention is to provide a single method of blowing for charcoal. Further, the technical problem of the present invention is to manufacture molten steel of high quality at the same time while shortening the time of hunting of molten iron.

An embodiment of the present invention provides a method of manufacturing a metal melt, comprising the steps of: initiating a blowing operation of supplying oxygen to a container containing a metal melt to remove impurities in the metal melt; A first half feeding step of maintaining the oxygen supply and simultaneously feeding the raw material and quicklime into the vessel at the start of the blowing; An input stopping step of stopping the supply of the sub-raw material and quicklime at a preset first input time point while maintaining the oxygen supply; A second half injection process of maintaining the oxygen supply and inputting the quicklime from the preset second input time to the completion of the blowing; And stopping the supply of oxygen and burnt lime and terminating the blowing.

The container may be a converter, and may be a low-charge furnace that blows oxygen at the lower side of the converter.

Oxygen flow rate to be supplied in the container may have a ^{1.0Nm 3 / min ~ 6.0Nm 3 /} min range.

An oxygen flow rate supplied from the first input point to the second input point is referred to as an intermediate oxygen flow rate and an oxygen flow rate supplied from the second input point to the end of the refueling The initial oxygen flow rate, the terminal oxygen flow rate, and the intermediate oxygen flow rate may be different from each other.

The initial oxygen flow rate, the late oxygen flow rate and the intermediate oxygen flow rate may have a relationship of an initial oxygen flow rate < an end-of-oxygen flow rate &gt;

The sub ingredient may include at least one of dolomite and ladle slag agent (LSA).

If the total time of the tune operation from the start of the tune to the end of the tune is T, the first input time may be any one point within the range of 0.1T to 0.3T.

If the total time of the tinning operation from the start of the tune to the end of the tune is T, the input second time may be any point within the range of 0.7T to 0.9T.

The amount of burnt lime injected in the first half portion charging process may be larger than the amount of burnt lime charged in the second half charging process.

When the amount of quicklime introduced in the first half portion is X and the amount of quicklime charged in the second half portion is Y, X: Y may have a range of 6: 4 to 9: 1.

According to the embodiment of the present invention, high-quality molten steel can be produced only by the first-stage refining process by changing the oxygen flow rate, the subsidiary material, and the input pattern of the quicklime for each section. Therefore, since the secondary winding process is not required, the winding time can be shortened. In addition, since the process of dispensing slag, which is a precondition of the secondary tinning work, is not necessary, the rate of real water loss and heat loss are not generated due to leaking of molten iron.

Fig. 1 is a view simply showing the structure of a low-power-transmission path according to an embodiment of the present invention.
2 is a flow chart showing a process of winding a low-electric-charge path according to an embodiment of the present invention.
FIG. 3 is a graph showing an input pattern of an oxygen flow rate, an additive, and quicklime according to an embodiment of the present invention.
Fig. 4 is a graph showing changes in the phosphorus content during the curing process in the low electric furnace.
5 (a) is a graph showing the content of phosphorus (P) and the content of carbon (C) measured after 100% fresh lime was charged in the early stage and the low-temperature liquor was carried out.
5 (b) is a graph showing the phosphorus (P) content and carbon (C) content when the amount of fresh lime is further increased in section A at a ratio of section A: section C = 8: 2 according to an embodiment of the present invention It is a graph.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Wherein like reference numerals refer to like elements throughout.

In the following, the converter in which the metal melt is contained will be described as an example of a converter, but various containers containing metal melts other than converters may be applicable.

Fig. 1 is a view simply showing the structure of a low-power-transmission path according to an embodiment of the present invention.

In order to oxidize and remove the excess carbon remaining in the molten metal which is a metal melt, it is necessary to mix and refine scrap iron, iron oxide, etc., and blow the oxygen to oxidize and remove the carbon. The steel making furnace used for blowing is generally a converter, and electric furnaces, crucibles, etc. may also be used. There are two types of converters used for blowing: an upper blowing furnace, a lower blowing furnace, and a combined blowing furnace (upper and lower furnace furnace).

The embodiment of the present invention will be described by taking as an example a low-emission path that blows oxygen at the lower side of the converter.

A low noise nozzle unit 130 for injecting low-oxygen gas (oxygen, inert gas) and burnt lime to the charcoal of the converter unit 110; And an upturned lance 120 into which molten material is supplied to the molten iron 150.

The converter unit 110 is a member in which a molten iron 150, which is a metal melt, is accommodated. An opening 111 is formed at one side of the converter unit 110 to receive the chartered wire, thereby providing a space for decarbonizing and detaching the chartered wire 150. [ Accordingly, the converter unit 110 can be realized in the form of a container provided with a space portion therein. A support base (not shown) is provided on the outer side of the converter unit 110 to support the converter unit 110 when the converter unit 110 flows. In addition, the molten steel in which the decarburization and demolding processes have been performed can be discharged through the opening 112 formed in the side surface of the converter unit 110.

The dressing lance 120 is located on one side of the opened portion of the converter unit 110 and supplies the additive material to the charcoal line in the converter unit 110. A part of the dressing lance 120 may be inserted into the converter unit 110 through the opening 111 of the converter unit 110 so as to inject the additive material into the charcoal 150 in the converter unit 110. [ Also, the dressing lance 120 can be realized to be manually or manually moved by using a motor or the like. Therefore, the position where the subsidiary material of the dressing lance 120 is inserted can be easily adjusted. The additive to be input into the charcoal 150 through the dressing lance 120 may include at least one of dolomite and LSA. For reference, dolomite is a carbonate mineral with chemical composition of CaMg (CO ₃ ) _2. LSA (Ladle Slag Agent) is manufactured by recycling slag generated during steelmaking process. Collecting the hot slag, cooling it, and crushing it to a certain size. In the embodiment of the present invention, the supplementary material introduced through the dressing lance 120 is put into the initial stage of the entire process of the swirling process. So as to prevent slopping or the like by controlling the rate at which SiO ₂ is produced at the beginning of the blowing. It is preferable that the amount of the subsidiary raw material and quicklime introduced at the beginning of the blowing is 300 kg to 800 kg (300 kg / min to 800 kg / min) per minute.

The low-noise nozzle unit 130 has a plurality of nozzles for injecting a low-temperature gas to the molten iron in the converter unit 110. The plurality of nozzles of the low-noise nozzle unit 130 may be formed to pass through the bottom surface 113 of the converter unit 110, and accordingly, the low-temperature gas may be injected through the low-noise nozzle unit 130. The low-noise nozzle unit 130 is supplied with the oxygen (O ₂ ), inert gas (N ₂ , Ar), quicklime, and the like from the nozzle pipe 140 according to the input pattern and can be injected to the bottom of the converter unit 110 .

In order to supply oxygen, inert gas, and quicklime to the low-noise nozzle unit 130, the nozzle pipe 140 connected to the low-noise nozzle unit 130 may be realized as a double pipe. Oxygen (O ₂ ) is injected into the converter unit 110 through the main lance pipe, and the main lance pipe is connected to the main lance pipe at the center of the nozzle pipe 140 having a double pipe structure. An inert gas (N ₂ , Ar, etc.) may be injected.

When oxygen is injected through the low-concentration nozzle unit 130, oxygen bubble columns are generated in the molten iron in the converter unit 110 and can be raised to the upper surface of the charcoal. Further, the carbon (C) contained in the charcoal can be oxidized and removed. For example, carbon (C) contained in the charcoal may be converted into carbon monoxide (CO) or carbon dioxide (CO ₂ ) by reaction with oxygen gas injected through the inert gas nozzle unit 130. Therefore, the decarburization of the molten iron and the molten steel can be performed efficiently in the same manner as described above.

Jeochwi flow rate of the oxygen that is injected through the nozzle jeochwi unit 130 is preferably has a ^{1.0Nm 3 / min ~ 6.0Nm 3 /} min range. In the case of the low flow rate injected from the hypothetical furnace, it is possible to have a uniform mixing time within 20 seconds when the measurement result is 1.0 Nm ³ / min or more. However, when the flow rate per nozzle is more than 6.0 Nm ³ / min, erosion of the refractories around the nozzles is accelerated, so that the range of the lower flow rate can be increased to the range of As well.

On the other hand, when oxygen is not injected, an inert gas (N ₂ , Ar, etc.) is supplied to prevent the molten iron 150 in the converter unit 110 from flowing back to the nozzle pipe 140 through the low- It can be sprayed. In addition, heat may be generated when oxygen is supplied through the nozzle piping 140, so that LNG or the like is supplied to the outside of the nozzle piping 140 to cool the nozzle piping 140.

In addition, fresh lime may be supplied to the nozzle piping 140 and may be introduced into the converter unit 110 together with oxygen. By adding quicklime, the rapid formation of calcium-ferrite can accelerate the talline reaction. In the present invention, the timing of inputting the production meeting is made in the first half and the second half of the entire process of blowing. In other words, quicklime is input until 10% ~ 30% of the entire working time, and quicklime input is made from 70% to 90% of the entire working time until the end of the operation. Preferably, the quicklime is introduced until the point of 25% of the entire process, and the quicklime is introduced from the point of time 75% of the entire operation time to the end of the operation.

As described above, the present invention is characterized by an oxygen flow rate, an additive material (dolomite, LSA), and an input pattern of burnt lime at the time of charging a charcoal using a low-charge furnace. Therefore, the converter control unit (not shown) performs control to control the input of oxygen, additives, and quicklime in accordance with the oxygen flow rate, the additive material (dolomite, LSA) and the input pattern of quicklime during the curing process. This will be described in detail below.

FIG. 2 is a flow chart showing a refining process using a low-temperature furnace according to an embodiment of the present invention, and FIG. 3 is a graph showing an input pattern of an oxygen flow rate, an additive material, and quicklime according to an embodiment of the present invention.

First, there is a process of starting the blowing to remove impurities in the molten iron by supplying oxygen to the low-emission furnace containing the molten iron (S21). The low-burning furnace contains charcoal produced in a furnace, which is a kind of iron produced directly from iron ore and contains high carbon content in iron. Oxygen is supplied in a manner that oxygen is blown into the interior of the converter at a low-odor nozzle portion on the lower side of the converter. Oxygen is supplied all the way from the low temperature of the converter, so it is possible to obtain very good agitating force. The occurrence of slopping can be remarkably reduced because the low-temperature tractive force is strong. Generally, in the case of high-Si content in the high-Si converter, the SiO ₂ production rate is faster than that of the burnt lime, so that a high-viscosity slag having a high SiO ₂ content is formed in the slag, And the slogging phenomenon frequently occurs, which increases the apparent bulk of the slag and overflows out of the furnace. However, in the case of the low-velocity furnace, the gas force of the gas supplied from the low-temperature furnace is very strong, so that the gas generated from the molten bath is smoothly discharged to the slag surface, and slopping hardly occurs.

Jeochwi flow rate of the oxygen supplied through the nozzles is preferably jeochwi having ^{1.0Nm 3 / min ~ 6.0Nm 3 /} min range. In the case of the low flow rate injected from the hypothetical furnace, it is possible to have a uniform mixing time within 20 seconds when the measurement result is 1.0 Nm ³ / min or more. Also, since jeochwi flow is strong stirring force steel more excellent when the flow rate is increased but the polishing characteristics, the supply nozzles per 6.0Nm ³ / min or more a problem of accelerating the erosion of the refractory material surrounding the nozzle generating a jeochwi flow becomes 1.0Nm ³ / min to 6.0 Nm ³ / min. For reference, unit [Nm ³ / min] is a unit for expressing the volume under actual temperature and pressure conditions, and 'N' means 'Normal Condition' and indicates a condition of 1 atm (atmospheric pressure) at 0 ° C.

Oxygen supplied through the low-noise nozzle portion is continuously performed from the start of the blowing to the end of blowing. And to oxidize and remove impurities such as carbon (C) in the charcoal. However, the same amount of oxygen is not supplied from the start of the blowing to the end of blowing, and the flow rate of oxygen supplied to each section during the blowing process is controlled to be different. The oxygen flow rate supplied from the start point of the low-temperature fusing to the first input point is referred to as the initial oxygen flow rate, the oxygen flow rate supplied from the first zone to the second zone is referred to as the intermediate oxygen flow rate, End oxygen flow rate < intermediate oxygen flow rate &quot; when the oxygen flow rate supplied from the section C to the end of the cigarette is the terminal oxygen flow rate. That is, the terminal oxygen flow rate is larger than the initial oxygen flow rate, and the intermediate oxygen flow rate is larger than the terminal oxygen flow rate. In this way, the flow rate of oxygen is maintained at a low rate in the section from the 10% to 30% point of the total operating time of the blowing to the first input, which is controlled by slopping by adjusting the rate of generation of SiO _{2 at} the initial stage of blowing, And the like. From the first input, the oxygen supply rate is controlled to the maximum for decarburization, and the residual carbon (C) content is measured from the second input point of 70% to 90% point, and depending on the carbon content To regulate the oxygen flow rate and actively induce the talline reaction.

Meanwhile, as shown in FIG. 4, the winding process of the low-electric-charge path can be divided into the period I and the period II. Referring to FIG. 4, in section I, the slag FeO is rapidly reduced by the carbon (C) in the charcoal due to the strong agitation of the low-emission in the hypersonic incinerator, and the talline is small. And thereafter the FeO is increased in the slag, so that the talline proceeds rapidly. Therefore, the subordinate material input pattern is set in consideration of the characteristic of the low power induction furnace. Most of the sub-raw materials (Dolomite, LSA, etc.) at the initial stage of the blowing process are put into the low-burning furnace, and quick lime is also put into the furnace. Preferably, the quicklime is introduced after one minute of blowing. After the point of 70% ~ 90% of the entire working time of the blowing, adjust the time of injection and add additional quicklime. This is to accelerate the talline reaction by the rapid formation of calcium ferrite by injecting quicklime at the time when the carbon content in the melt is lowered, that is, at the time when FeO is produced.

Hereinafter, the application pattern of the sub-raw material and quicklime will be described.

When the low-oxygen supplying the oxygen to the converter is started (S22), the supply of oxygen to the low-charge furnace is maintained while the sub-raw material and quicklime are charged into the low-charge furnace. The first half where the additive material and quicklime are input corresponds to the section A, which is the section from the start of the blowing to the first injection. The oxidation of slag is very low due to the excellent agitating force in the low-charge furnace. Unlike the conventional composite drilling method using the lance lance, since the firing point is formed at the nozzle part, the slag temperature is low, which is disadvantageous to the products such as burnt lime. If the quality of the slag is not smooth, the refining ability may be lowered and the operating efficiency may be deteriorated. For this reason, in order to secure the talline capability in the low-emission furnace and ensure the operability, quicklime is supplied together with oxygen through the low-noise nozzle unit 130.

The sub ingredient may include at least one of dolomite, LSA. For reference, dolomite is a carbonate mineral with chemical composition of CaMg (CO ₃ ) ₂ , and LSA (Ladle Slag Agent) is manufactured by recycling slag generated during steelmaking process. The amount of the subsidiary raw material and quicklime introduced at the initial stage of the blowing may be determined according to the amount of the molten iron in the converter. For example, it is preferable that the amount is 300 kg to 800 kg per minute (300 kg / min to 800 kg / min).

When the section A, which is the first half of the period during which the subsidiary raw material and quicklime are introduced (from the start of the blowing to the first injection), is terminated, the flow rate of oxygen is continuously increased for decarburization. In the section B, there is a process of stopping the input of the additive and quicklime (S23). And to perform decarburization by increasing the flow rate of oxygen beyond the section A.

Thereafter, in the section C from the preset second feeding time point to the end of the blowing, while the oxygen supply is maintained (S24). In the section C, which is the section from the second input point to the end of the blowing, the quicklime is introduced again to promote the talline reaction. At this time, the flow rate of the oxygen supplied to the low-temperature supply is less than the low flow rate of the region B, so that the talline reaction is promoted.

After the above-mentioned second-half charging process, the oxygen supply and the burnt lime are stopped and the brewing is terminated (S25).

On the other hand, assuming that the total first operation time from the start of the blowing to the end of blowing is T, the first input time point is a time point within a range of 0.1T to 0.3T to be. Preferably 0.25T. That is, the first input time point is set to the time point of 10% to 30% of the total time of the operation, preferably set to the time point of 25%. This is a section where the reduction of the slag by the carbon (C) in the solubility of FeO rapidly proceeds and the talline is insignificant until 10 to 30% of the initial stage of the low temperature is strong.

Further, when the total time of the tinning operation from the start of the tune to the end of the tune is T, the second input time is within a range of 0.7T to 0.9T. It is preferably 0.75T. That is, the input second time point is set to a time point of 70% to 90% of the entire working time of the entire operation, preferably set to a time point of 75%. As shown in FIG. 4, since talline is actively performed from 70% to 90%, it is time to promote talline.

As described above, the quicklime is divided into the first section A (the section from the start of blowing to the first intake point) and the C section (the second section from the second intake point to the final blowing end) Can be maximized. FIG. 5 is a graph showing such an experimental example. FIG. 5 (a) is a graph showing the content of phosphorus (P) and the content of carbon (C) after 100% , And FIG. 5 (b) is a graph showing phosphorus (P) content and carbon (C) content when the amount of fresh lime is further increased in section A at a ratio of section A: section C = 8: 2.

(100%), 0.129% in the period A (the period from the start of the blowing to the first starting point), 0.08% in the period B (the period from the first input to the second input) And the phosphorus content is 0.038% in the section from the second feeding point to the finishing point).

On the other hand, when the amount of burnt lime is divided by the ratio of A: C section = 8: 2, it is found that phosphorus content is 0.131% in section A, 0.026% in section B and 0.025% in section C. Therefore, it can be seen that 0.13% talline (130ppm content reduction) was achieved in the C section, which is the final section of the curing process, when the cement paste was added in the early stage without the addition of the quick lime.

Meanwhile, it is effective to divide and input the quicklime in this manner. The amount of quicklime introduced into the section A (the section from the start of blowing to the first point of input) in the first half is the C section in the latter half Is set to be larger than the amount of burnt lime to be charged in the period from the beginning to the beginning of the period. This is to prevent slopping or the like by controlling the production rate of SiO _{2 by} injecting more additives at the beginning of the curing process. Therefore, let X be the amount of quicklime introduced in the first section A, and let Y be the amount of the quicklime introduced in the section C, which is the second part of the input process. The ratio X: Y ranges from 6: 4 to 9: 1 .

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

S21: Starting process of blowing S22:
S23: Disconnection of additives and quicklime S24: Post-insertion process
S25: End of the process

Claims (10)

Initiating a blowing operation of supplying oxygen to a container containing the metal melt to remove impurities in the metal melt;
A first half feeding step of maintaining the oxygen supply and simultaneously supplying the raw material and quicklime to the vessel at the start of the blowing;
An input stopping step of stopping the supply of the sub-raw material and quicklime at a preset first input time point while maintaining the oxygen supply;
A second half injection process of maintaining the oxygen supply and inputting the quicklime from the preset second input time to the completion of the blowing; And
Stopping the supply of oxygen and burnt lime and terminating the blowing;
Wherein the steel refining method comprises:
The method according to claim 1, wherein the vessel is a converter, and oxygen is blown on the lower side of the converter.
The method according to claim 1, the oxygen flow rate to be supplied in the container is polished with a STEEL ^{1.0Nm 3 / min ~ 6.0Nm 3 /} min range.
2. The method according to claim 1, wherein an oxygen flow rate supplied to the first input time is defined as an initial oxygen flow rate, an oxygen flow rate supplied from the first input time point to the second input time point as an intermediate oxygen flow rate, Wherein the initial oxygen flow rate, the terminal oxygen flow rate and the intermediate oxygen flow rate are respectively different when the supplied oxygen flow rate is the terminal oxygen flow rate.
5. The method of claim 4, wherein the initial oxygen flow rate, the late oxygen flow rate,
A method of refining steel having a relationship of an initial oxygen flow rate < an end-of-oxygen flow rate &gt;
The method according to claim 1, wherein the sub ingredient includes at least one of dolomite and ladle slag agent (LSA).
The method according to claim 1, wherein the total first operation time from the start of the tune to the end of the tune is T, and the first input time is within a range of 0.1T to 0.3T.
The method for refining steel according to claim 1, wherein the total second operation time from the start of the tune to the end of the tune is defined as T, and the second input time is within a range of 0.7T to 0.9T.
The method according to claim 1, wherein the amount of quicklime introduced in the first half portion is larger than the amount of quicklime charged in the second half portion.
The method according to claim 9, wherein when the amount of quicklime introduced in the first half portion is X and the amount of quicklime charged in the second half portion is Y, X: Y ranges from 6: 4 to 9: 1 .

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