JP2768209B2 - Converter steelmaking plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter steelmaking plant provided with a converter type hot metal pretreatment furnace and a converter type decarburizing furnace. More specifically, the present invention relates to a hot metal pretreatment furnace and a hot metal pretreatment furnace so that refining of steel using pretreated hot metal (hereinafter referred to as “pretreated hot metal”) can be performed with high efficiency. The present invention relates to a converter steelmaking plant in which a coal furnace is arranged.

[0002]

2. Description of the Related Art As is well known, elements such as C, Si, Mn, P, Ti and V usually contain about 5 to 8% by weight in total in hot metal discharged from a blast furnace. In addition, the composition of the hot metal greatly affects the refining efficiency and the quality of the final product steel in the subsequent steelmaking process.

[0003] Therefore, in order to streamline the steelmaking process and to facilitate the operation thereof, various pretreatment methods for hot metal have been developed according to the composition of the hot metal and the type of steel produced. Generally, the main component of the hot metal pretreatment is the phosphorus removal treatment. Preliminary treatment of hot metal in the conventional iron making and steel making processes can be classified according to the form of hot metal transport and storage.
It is classified into a mixed iron furnace storage system and (ii) a mixed iron truck transport and storage system. In recent years, (iii) a ladle direct transportation system has been introduced.

[0004] The pretreated hot metal pretreated by these hot metal pretreatment methods is sent to a converter, where oxygen and iron ore are blown into the converter to oxidize and refine impurities such as C, Si, and P. To remove it as carbon monoxide gas or slag, and the components are adjusted according to the intended use.

By the way, Japanese Patent Publication No. 54-33816 discloses that
During steelmaking using a converter, hot metal that has been dephosphorized is charged into a converter and blown, and the entire amount of converter slag generated in the converter is used as a slag-making agent in the dephosphorization process. Alternatively, by using a part of the converter slag as a dephosphorizing slag-making agent and the remainder as a blast furnace charging material, the entire amount of the converter slag can be effectively used in the iron and steel making process. There has been proposed a technology for eliminating so-called waste disposal. This technology is a technology for effectively utilizing almost all of the converter slag without waste, and is a basic technology in this type of steelmaking process.

[0006] As an improvement of the invention proposed in Japanese Patent Publication No. 54-33816, Japanese Patent Publication No. 4-37132 discloses one of two converter type furnaces having a double blow function. Is used as a hot metal pretreatment furnace (dephosphorization furnace) and the other is used as a decarburization furnace, and a refining agent mainly composed of converter slag generated in the decarburization furnace is added to the hot metal injected into the hot metal pretreatment furnace. After performing hot metal pretreatment while maintaining the hot metal temperature at 1400 ° C or less by blowing oxygen gas upward while stirring the bottom blow gas, the resulting pretreated hot metal is poured into a decarburization furnace to remove hot metal. When producing steel in the process of charcoal refining, oxygen necessary for pretreatment in the hot metal pretreatment furnace is supplied in both gaseous acid and solid acid states, and by adjusting the mixing ratio, the pretreated hot metal is A steelmaking method for adjusting the temperature and composition was proposed .

An example of the configuration of a hot metal pretreatment furnace and a decarburization furnace of a general converter steelmaking plant used when performing this method is conceptually shown in a plan view shown in FIG. In addition, in the same figure, the solid line arrow and the broken line arrow both schematically show the movement form of the hot metal, the solid line arrow shows the movement by the crane, and the broken line arrow shows the movement by the bogie.

[0008] In (a) → (b) in the figure, a hot metal pot (not shown) containing hot metal is lifted by a crane (not shown), and in (b) → (c) a hot metal pretreatment furnace The hot metal is conveyed to the hot metal pot 41 and injected into the hot metal pretreatment furnace 41.

The pre-treated hot metal pre-processed by the hot metal pre-processing furnace 41 is tapped from a tap hole 42 as shown in (d) and stored in a pouring pot (not shown) on a hot metal carriage (not shown). Then, the hot metal cart transports the hot metal to the crane position indicated by (e) via the front of the hot metal pretreatment furnace 41.

[0010] In (e) → (f), the pouring pot containing the pretreated hot metal is lifted by a crane, and
And the pretreated hot metal is injected into the decarburization furnace 43. The molten steel produced by decarburization by the decarburization furnace 43 is tapped from a tapping port 44 as shown in (g), and sent to the next continuous casting step by a crane.

[0011]

However, such a conventional converter steelmaking plant cannot operate efficiently in terms of logistics. That is, in such a conventional converter steelmaking plant, the logistics relating to the ladle around the hot metal pretreatment furnace 41 in FIG. The -tap time (the time required for one operation from the previous tapping to the next tapping) increases as the bogie withdrawal time increases, and a hot metal pot exists at the position indicated by (e) in Fig. 4. In such a case, new hot metal cannot be charged because the hot metal pots interfere with each other at the time of, for example, pouring a hot metal pot.

There is also an operation mode in which steelmaking is performed in two separate factories. FIG. 5 is an explanatory view conceptually showing such an operation mode.
, And the thus obtained pretreated hot metal is made into steel, for example, by a converter in a decarburization furnace factory 52 in a continuous casting building.

However, since the lead time from the hot metal pretreatment furnace factory 51 to the decarburization furnace factory 52 is extremely long, the amount of temperature drop of the pretreatment hot metal and the required number of ladles for transporting the pretreatment hot metal increase. There is a problem of doing it.

Japanese Patent Application Laid-Open No. 5-9550 discloses that in order to reduce the temperature drop of molten steel in a converter steelmaking plant in which various types of treatment are performed in the secondary refining process of molten steel ladle.
2. Description of the Related Art A steelmaking plant has been proposed in which various facilities such as slag removal, heating, and degassing for a ladle secondary refining are linearly arranged along the line of a carrier truck. However, this proposal relates to the layout of various equipment in the process after the converter in the converter steelmaking plant.
It does not relate to the internal layout of a converter steelmaking plant equipped with a converter type hot metal pretreatment furnace and a converter type decarburization furnace. Here, an object of the present invention is to provide a converter steelmaking plant capable of reducing the steelmaking time (tap-to-tap time) of a hot metal pretreatment furnace.

[0015]

Means for Solving the Problems The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, the hot metal pretreatment furnace and the decarburization furnace are not disposed in the same building but are separately provided. Finding that the pretreatment furnace building and the decarburization furnace building are arranged linearly in the direction of tapping and tapping makes it possible to operate efficiently in logistics and to reduce bogie withdrawal time. did.

FIG. 1 is an explanatory view conceptually showing an example of a converter steelmaking plant having such a layout. FIG. 1 (a) is a vertical sectional view and FIG. 1 (b) is a plan view. In FIG. 1 (a) and FIG. 1 (b), the pre-processed hot metal discharged from the hot metal pre-treatment furnace 10 arranged in the hot metal pre-processing
The molten iron is poured into a pouring pot 18 on the top 13, and the pouring pot 18 is lifted up by a crane as a hot metal lifting and pouring equipment 14 and injected into the decarburizing furnace 11. In addition, reference numeral 12 in FIG. 1 denotes a crane as a hot metal suspension pouring equipment, reference numeral 15 denotes a molten steel bogie, and reference numeral 17 denotes a decarburization furnace building. Also, as shown in FIG. 1 (b), in the converter steelmaking plant shown in FIG. 1, the iron receiving truck 13 and the steel receiving truck 15 run on three parallel tracks 19a, 19b and 19c. The hot metal pretreatment furnace 10, tapping from the decarburizing furnace 11, and the tapping truck 13 and the steel receiving truck 15 are appropriately used depending on the timing of tapping so that the waiting time of the receiving truck 15 is as small as possible. Can be The number of tracks is not particularly limited, and one or a plurality of tracks may be appropriately determined according to the number of converter systems.

If the layout of the hot metal pretreatment furnace 10 and the decarburization furnace 11 is set in this way, the moving distance of the pouring ladle 10 can be made extremely small as compared with the prior art, so that an extremely efficient operation from the viewpoint of logistics Can be performed. For this reason, the hot metal of the next charge can be charged immediately after tapping in the hot metal pretreatment furnace 10, and the cycle time (tap-to-tap time) of the hot metal pretreatment furnace 10 is shortened, and the production amount is increased. I do. Further, there is no interference between the pouring ladle 18 and the crane as the hot metal lifting and pouring equipment 14 between the hot metal pretreatment furnace 10 and the decarburizing furnace 11. The present inventors have further studied based on such findings, and as a result, completed the present invention.

Here, the gist of the present invention is, for example, as shown in FIGS. 1A and 1B, a converter type hot metal pretreatment furnace 10 and a converter type decarburizing furnace 11. A converter steelmaking plant equipped with a hot metal pretreatment furnace 10 and a hot metal pre-treatment furnace 10
Iron receiving equipment 13, 18 and hot metal lifting and pouring equipment 14 arranged on the tapping side of the steelmaking machine, and steel receiving equipment arranged on the tapping side of the decarburization furnace 11
This is a converter steelmaking plant characterized by a combination of No.15 and No.15. In the present invention, the hot metal pretreatment refers to desiliconization, dephosphorization, desulfurization, and the like for hot metal. Further, the converter type furnace refers to a converter of a type such as top blowing, top and bottom blowing, bottom blowing, and side blowing.

[0019]

Hereinafter, the present invention will be described in detail together with the functions and effects. The converter steelmaking plant according to the present invention provides an efficient layout when a converter type hot metal dephosphorization treatment is adopted in a steelmaking plant to be installed in the future.

In the present invention, as described with reference to FIGS. 1 (a) and 1 (b), the tapping side of the hot metal pretreatment furnace 10 and the pouring side of the decarburization furnace 11 are adjacent to each other, And hot metal pretreatment furnace 10
By setting the hot metal pretreatment furnace 10 and the decarburization furnace 11 continuously in this order so that the tapping direction of the iron and the pouring direction of the decarburization furnace 11 are in the same direction, Reduce the flow around these furnaces efficiently.

Thus, in the present invention, the hot metal pretreatment furnace
10 and the decarburization furnace 11 are not arranged in the same building, and in the horizontal plane, the molten metal pretreatment furnace building 16 and the decarburization furnace building 17 are tilted in the converter in a tapping direction and a tapping direction (see FIG. 1). (In the direction of the arrow), and the hot metal pretreatment furnace 10 and the decarburization furnace 11 are arranged in a straight line in the tapping and tapping direction so as to correspond one-to-one.

Therefore, in the converter steelmaking plant according to the present invention, compared with the conventional converter steelmaking plant, the movement of the ladle around the hot metal pretreatment furnace 10 can be prevented from becoming complicated, so that the bogie withdrawal time is reduced. The hot metal pretreatment furnace 10
The p-to-tap time can be reduced. Therefore, hot metal can be newly charged at the converter position of the hot metal pretreatment furnace 10 even at the time of pouring a pouring ladle, and as a result, extremely highly efficient physical distribution can be performed.

The present invention generally relates to an efficient arrangement of a hot metal pretreatment furnace and a decarburization furnace in a converter steelmaking plant having a hot metal pretreatment furnace and a decarburization furnace. Therefore, the hot metal suspension pouring equipment, the hot metal receiving equipment, the steel receiving equipment, and the like defined in the present invention may be any known equipment, and are not limited to specific equipment or equipment. For example, an existing crane can be used as the hot metal lifting and pouring equipment, a receiving pan and a receiving truck can be used as the receiving device, and a receiving pot and a receiving truck can be used as the receiving device.

Further, the installation height of the hot metal pretreatment furnace and the decarburization furnace are not particularly limited. In the examples shown in FIGS. 2 and 3 to be described later, since the installation height of the hot metal pretreatment furnace and the decarburization furnace each affect the flow of the hot metal, it is necessary to limit the installation positions of the two. Such a limitation is not required because of the placement of the lifting pouring equipment.

Further, an improved example of the converter steelmaking plant according to the present invention will be described with reference to FIGS. FIG.
FIGS. 2A and 2B are explanatory views showing an improved example of a converter steelmaking plant according to the present invention. FIG. 2A is a vertical sectional view, FIG. 2B is a plan view, and FIG. It is explanatory drawing which expands and shows the vicinity of.

As shown in FIGS. 2 (a) to 2 (c), this embodiment comprises a converter type hot metal pretreatment furnace 20 and a hot metal pretreatment furnace 20.
A converter steelmaking plant equipped with a converter type decarburization furnace 21 disposed in a position lower than 20 in this order,
A hot metal hoisting and pouring equipment 22 disposed on the pouring side of 20; a pouring pot 23a disposed on the pouring side of the hot metal pretreatment furnace 20 and the pouring side of the decarburizing furnace 21; An iron receiving trolley 23 having a receiving iron pot lifting and reversing arm 23c arranged at a height at which molten iron can be directly injected into the decarburization furnace 21 by rotating the iron 23a.
This is a converter steelmaking plant equipped with a combination of a hot metal charger consisting of b and steel receiving equipment arranged on the tapping side of the decarburization furnace 21. Reference numeral 25 denotes a steel receiving cart, reference numeral 26 denotes a hot metal pretreatment furnace building, reference numeral 27 denotes a decarburizing furnace building, and reference numeral 28 denotes a steel receiving pan. As in the converter steelmaking plant of FIG.
In the converter steelmaking plant shown in Fig. 1, the iron receiving truck 23b and the steel receiving truck 25 are both installed so as to travel on two parallel tracks 29a and 29b. Iron receiving truck 23b according to the timing of tapping and tapping from 21
The standby time of the steel receiving cart 25 is appropriately selected so as to be as short as possible. The number of tracks is not particularly limited, and one or a plurality of tracks may be appropriately determined according to the number of converter systems.

In the converter steelmaking plant according to the present invention shown in FIGS. 2 (a) and 2 (b), the hot metal pretreatment furnace 20 and the decarburization furnace 21 are not arranged in the same building, The furnace building 26 and the decarburizing furnace building 27 are arranged continuously in the tapping and tapping direction. Also,
The hot metal pretreatment furnace 20 is placed one floor above the decarburization furnace 21 (for example, about 10,400 mm in vertical direction distance), and in a horizontal plane, the hot metal pretreatment furnace 20 and the decarburization furnace 21 have a one-to-one correspondence. Correspondingly, they are arranged in a straight line in the tapping-tapping direction.

Further, as shown in FIG.
The hot metal charger having a hot iron cart 23b that supports the hot pot raising and reversing arm 23c that holds and rotates the hot metal a is located below the tapping side of the hot metal pretreatment furnace 20 and the It is located above the pig side. The hot metal charger receives the pre-processed hot metal from the hot metal pre-treatment furnace 20 at the tapping side of the hot metal pre-treatment furnace 20, then moves to the pouring side of the decarburization furnace 21 and injects it into the decarburization furnace 21. .

In this manner, the pretreated hot metal that has been tapped from the hot metal pretreatment furnace 20 is supplied to the receiving pan 23 on the hot metal charger.
a It can be directly charged into the decarburization furnace 21 without going through the hot metal lifting and pouring equipment (for example, a crane).

Further, in the converter steelmaking plant shown in FIG. 2, since the suspension is not changed by the hot metal hoisting and pouring equipment (reference numeral 14 in FIG. 1), the preprocessed hot metal after tapping from the hot metal pretreatment furnace 20 is immediately discharged. Since the decarburizing furnace 21 can be charged, the temperature of the pretreatment hot metal charged into the decarburizing furnace 21 can be increased. In addition, between the hot metal pretreatment furnace 20 and the decarburizing furnace 21 and between the decarburizing furnaces, the interference of the hot metal lifting and pouring equipment does not occur at all, so that the degree of freedom of operation is improved.

As described above, in the hot metal pretreatment furnace 20, the hot metal of the next charge can be immediately charged by using the hot metal lifting and pouring equipment 22 after tapping by its own rotation. Tap-to-tap time is reduced.

It should be noted that, similarly to the converter steelmaking plant in FIG. 1, the hot metal suspension pouring equipment, hot metal receiving equipment and steel receiving equipment in FIG. Can be applied.

FIG. 3 is an explanatory view showing another example of an improved converter steelmaking plant according to the present invention. FIG. 3 (a) is a vertical sectional view,
FIG. 3B is a plan view. As shown in FIGS. 3 (a) and 3 (b), a converter steelmaking plant equipped with a converter type hot metal pretreatment furnace 30 and a converter type decarburizing furnace 31 in this order, Hot metal hoisting and pouring equipment located on the pouring side of pretreatment furnace 30
32, and a combination of a steel receiving cart 35 and a steel receiving pan 38 arranged on the tapping side of the decarburizing furnace 31. Preferably, furthermore, pouring is performed between the hot metal pretreatment furnace 30 and the decarburizing furnace 31. A converter steelmaking plant with gutter 33 is provided. Reference numeral 36 denotes a hot metal pretreatment furnace building, and reference numeral 37 denotes a decarburization furnace building. FIG.
In the converter steelmaking plant shown in FIG. 3, the steel receiving trolley 35 is installed so as to run on two parallel tracks 39a and 39b. 30, depending on the timing of tapping and tapping from the decarburizing furnace 31, the standby time of the steel receiving cart 35 is appropriately selected so as to be as short as possible. Also in this case, the number of tracks is not limited to two, and may be appropriately determined according to the number of converters for decarburization.

In the converter steelmaking plant according to the present invention shown in FIG. 3, the hot metal pretreatment furnace 30 and the decarburization furnace 31 are not arranged in the same building, but the hot metal pretreatment furnace building 36 and the decarburization furnace building 37 are connected to each other. Are arranged linearly in the tapping and tapping direction (inverter tilt direction). Further, the hot metal pretreatment furnace 30 is placed one floor above the decarburization furnace 31 (for example, 10, 40).
0 mm above), and the hot metal pretreatment furnace 30
And the decarburizing furnace 31 are arranged on a straight line in the tilting direction one by one.

The hot metal pretreated by the hot metal pretreatment furnace 30 and tapped is directly or through a pouring gutter 33.
The pig iron is poured directly into the decarburization furnace 31, not in the ladle. For this reason, in the hot metal pretreatment furnace 30, the hot metal of the next charge can be charged immediately after tapping, and the cycle time (tap-to-tap time) of the hot metal pretreatment furnace 30 can be reduced. Become.

As described above, according to the converter steelmaking plant shown in FIG. 3, since the pretreated hot metal can be directly charged into the decarburization furnace 31 without receiving the hot metal in the receiving pan, The charging temperature of the pretreated hot metal into the furnace 31 can be increased.
Needless to say, there is no interference between the hot metal lifting and pouring equipment between the hot metal pretreatment furnace 30 and the decarburizing furnace 31 and between the decarburizing furnaces.

The specific structure of the pouring gutter 33 does not need to be limited at all, and is provided with a structure capable of sending the pretreated hot metal discharged from the hot metal preprocessing furnace 30 to the decarburization furnace 31. Just do it. Specifically, a pre-treated hot metal flow path made of heat-resistant stainless steel subjected to refractory running can be exemplified.

It should be noted that, similarly to the converter steelmaking plant shown in FIG. 2, the hot metal suspension pouring equipment, the hot metal receiving equipment, the steel receiving equipment, etc. in FIG. Can be applied. Further, the present invention will be described in detail with reference to examples, but this is an exemplification of the present invention, and the present invention is not limited thereto.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of the present invention, a converter steelmaking factory having the layouts shown in FIGS.
Hot metal pretreatment and decarburization treatment of 100 (300 in total) charge were performed respectively. In addition, as a comparative example, using a conventional converter steelmaking plant described with reference to FIGS. 4 and 5, pretreatment and decarburization treatment of 100 (200 in total) charged hot metal were similarly performed.

In these hot metal pretreatments and decarburization treatments, the on-orbit pretreatment hot metal transport distance (km) and the tap-
To-tap time (min), pre-treatment furnace tap-to-tap time (min)
, Time required for tapping from pretreatment furnace to charging of decarburization furnace (min),
The pre-treatment pig charging temperature to the decarburization furnace (° C), the productivity of the 300-ton converter (T / hr), the cost of the pre-treatment pig refractory (index), and the total cost of steelmaking work (index) were investigated. The overall evaluation results were investigated. The results are summarized in Table 1.

[0041]

[Table 1]

As can be seen from Table 1, the converter steelmaking plant according to the present invention is extremely excellent in both productivity and production cost.
It can be seen that the layout has a very efficient layout.

[0043]

As described above in detail, according to the present invention, a converter steelmaking plant capable of reducing the steelmaking time (tap-to-tap time) of the hot metal pretreatment furnace can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view conceptually showing an example of a converter steelmaking plant according to the present invention. FIG. 1 (a) is a vertical sectional view, and FIG. 1 (b) is a plan view.

2 is an explanatory view showing an improved example of a converter steelmaking plant according to the present invention. FIG. 2 (a) is a vertical sectional view, FIG. 2 (b) is a plan view, and FIG. FIG. 4 is an explanatory diagram showing an enlarged view of the vicinity of a pot 23a.

FIGS. 3A and 3B are explanatory views showing another example of an improved converter steelmaking plant according to the present invention. FIG. 3A is a vertical sectional view, and FIG. 3B is a plan view.

FIG. 4 is a plan view conceptually showing an example of a configuration of a conventional hot metal pretreatment furnace and a decarburization furnace of a converter steelmaking plant.

FIG. 5 is an explanatory view conceptually showing another example of a configuration of a hot metal pretreatment furnace and a decarburization furnace of a conventional converter steelmaking plant.

[Explanation of symbols]

10: Hot metal pretreatment furnace 11: Decarburization furnace 12: Hot metal hoisting and pouring equipment 13: Hot metal trolley 14: Hot metal hoisting and pouring equipment 15: Hot metal trolley 16: Hot metal pretreatment building 17: Decarburizing furnace ridge 18: Receiving Pig pans 19a to 19c: Track 20: Hot metal pretreatment furnace 21: Decarburizing furnace 22: Hot metal hoisting and pouring equipment 23a: Receiving pan 23b: Receiving truck 23c: Lifting arm for reversing the receiving pan 25: Receiving truck 26 : Hot metal pre-processing building 27: Decarburization furnace building 28: Receiving pan 29a, 29b: Track 30: Hot metal pre-processing furnace 31: Decarburizing furnace 32: Hot metal lifting equipment 33: Pouring gutter 35: Hot steel truck 36: Hot metal pretreatment furnace building 37: Decarburization furnace building 38: Receiving pan 39a, 39b: Track 41: Hot metal pretreatment furnace 42: Taphole 43: Decarburization furnace 44: Steelmaking port 51: Hot metal pretreatment furnace plant 52 ： Decarburization furnace factory

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C21C 5/28 C21C 1/00

Claims (4)

(57) [Claims] 1. A converter steelmaking plant provided with a converter type hot metal pretreatment furnace and a converter type decarburization furnace in this order from upstream to downstream , wherein A hot metal hoisting and pouring equipment disposed on the pig iron side, an iron receiving apparatus disposed on the tapping side of the hot metal pretreatment furnace, and the hot metal
A converter steelmaking plant comprising a combination of a hot metal lifting and pouring facility disposed on a tapping side of a treatment furnace and a steel receiving facility disposed on a tapping side of the decarburization furnace. 2. A converter steelmaking plant comprising, in this order, a converter type hot metal pretreatment furnace and a converter type decarburization furnace disposed at a lower position than the hot metal pretreatment furnace. A hot metal hoisting and pouring equipment disposed on the pouring side of the hot metal pretreatment furnace; a tapping pot disposed on the tapping side of the hot metal pretreatment furnace and on the pouring side of the decarburizing furnace; A hot metal charger having an arm for raising and reversing a hot pot, which is arranged at a height at which hot metal can be injected directly into the decarburizing furnace by rotating the hot pan, and disposed on the tapping side of the decarburizing furnace. A converter steelmaking plant, characterized in that it is provided in combination with selected steel receiving equipment. 3. A converter type hot metal pretreatment furnace, and a converter disposed at a position lower than the hot metal pretreatment furnace and at a position where molten iron pretreated from the hot metal pretreatment furnace is directly injected. A converter steelmaking plant equipped with a decarburizing furnace of the type in this order, a hot metal lifting and pouring equipment disposed on the pouring side of the hot metal pretreatment furnace, and disposed on the tapping side of the decarburizing furnace. A converter steelmaking plant comprising a combination of steel receiving equipment. 4. A pouring gutter disposed between the hot metal pretreatment furnace and the decarburization furnace, the pouring gutter for guiding pretreated hot metal injected from the hot metal pretreatment furnace to the decarburization furnace. The converter steelmaking plant according to claim 3, characterized in that: