JP5283309B2 - Operation method of converter facilities - Google Patents

Description

  The present invention relates to a method for operating a converter facility.

Conventionally, as shown in Patent Document 1, in a converter facility, hot metal and scrap are charged into a dephosphorization furnace (converter for dephosphorization) to perform a dephosphorization process, and the hot metal after the dephosphorization process is completed. Decarburization is performed after charging the decarburization furnace (decarburization converter) together with scrap.
In the dephosphorization process, when determining the amount of scrap charged into the dephosphorization furnace (hereinafter, scrap charge amount), the hot metal temperature after the dephosphorization process and the amount of hot metal components are taken into consideration. The amount of scrap charge is determined.

In the decarburization process, when determining the scrap charge amount to be charged into the decarburization furnace, the scrap charge amount is determined in consideration of the hot metal temperature and the hot metal component amount after the decarburization process is completed. ing.
Now, in dephosphorization and decarburization operations, it was important that the molten steel temperature and each component of the molten steel reach their target values after decarburization. The hot metal temperature and the amount of each component of the hot metal after the completion are regarded as intermediate, and the fact is that they are not considered as important as the temperature of the molten steel and the amount of each component of the molten steel. That is, the hot metal temperature and the amount of hot metal components after dephosphorization, which are intermediate target values as viewed from the decarburization process, are roughly set.

Thus, in the dephosphorization process, since the intermediate target value was roughly determined, strict control in refining was not performed.
On the other hand, in the decarburization treatment, as shown in Patent Document 2, since the final molten steel temperature and the component values in the molten steel are determined, refining control is performed so that these values become target values. It was.
JP 07-41816 A JP 05-33029 A

As described above, in the dephosphorization process, since there is no strict control in refining, there are many cases where too much or too little scrap is put into the dephosphorization furnace.
If too little scrap is put into the dephosphorization furnace, the heat will increase after the dephosphorization process and the dephosphorization rate will decrease. If too much scrap is put into the dephosphorization furnace, heat will be insufficient in the entire dephosphorization process. Thus, there is a problem that scraps of scrap are generated after dephosphorization.

Further, in the decarburization process, the intermediate target value after the dephosphorization process is the initial value before the start of the decarburization, so if this initial value (intermediate target value) is roughly set, it matches the final target value. It was very difficult, and when the scrap charge was determined based on the intermediate target value, there were cases where too much or too little scrap was put into the decarburization furnace.
If the amount of scrap charged into the decarburization furnace during the decarburization process is too large, for example, heat shortage occurs in the entire decarburization process and the required temperature considering the processes after the decarburization furnace is not reached. Sometimes it is necessary to use a heating material to reach the required temperature.

If the amount of scrap charged into the decarburization furnace during the decarburization process is too small, for example, the decarburization process end temperature becomes too high, and the melting loss of the refractory in the converter increases or the decarburization end temperature In order to reduce the amount of iron oxide, it is necessary to add a large amount of iron oxide. When iron oxide is added, slopping is likely to occur and often blowing must be interrupted.
Therefore, in view of the above problems, the present invention provides a method for operating a converter facility that can normally perform dephosphorization treatment and decarburization treatment during refining that performs decarburization treatment following dephosphorization treatment. For the purpose.

In order to achieve the above object, the present invention has taken the following measures. That is, after hot metal and scrap are charged into a dephosphorization converter and dephosphorized, the dephosphorized hot metal and scrap are charged into a decarburization converter and decarburized. In the operating method of the converter equipment, the scrap charge in the dephosphorization process is determined so that the total amount of hot metal before the start of dephosphorization falls within the target range after dephosphorization, and the determined scrap charge The amount of scrap is charged during dephosphorization treatment, and the decarburization is performed so that the total amount of hot metal before decarburization started within the target range by charging the scrap becomes a target value after decarburization. The amount of scrap charged in the treatment is determined, and the scrap of the determined amount of scrap charged is charged into the decarburization process, and the target range is the liquidus line on the iron-carbon equilibrium diagram. A line shifted by 70 ° C in the direction of temperature rise and hot metal temperature It is defined in a range surrounded by a line indicated by 1330 ° C. and a line indicated by [Equation 1], and the amount of scrap charged is the amount of scrap charged in the converter for dephosphorization. There exists in the point which is set so that the charging mixing ratio Rp and the charging mixing ratio of the scrap charged into the decarburization converter may satisfy all of [Formula 2] to [Formula 4] .

The inventor verified the range for normally performing the dephosphorization process, that is, the upper and lower limits of the hot metal temperature and the upper and lower limits of the amount of the hot metal component at the end of the dephosphorization from various angles. As a result, when the range is viewed on the iron-carbon system equilibrium diagram, a line obtained by shifting the liquidus line by 70 ° C. in the temperature rising direction, a line where the hot metal temperature is 1330 ° C., and [Formula 1 ], It was found that the dephosphorization process can be performed normally and the decarburization process performed after the dephosphorization process can be performed efficiently.

Further, the inventor sets the above range as the upper and lower limits of the total calorific value (the total calorific value obtained by converting the hot metal temperature into the calorific value and the potential calorific value of each component contained in the molten iron), that is, the target range. It was decided to show the amount of scrap charging based on the total amount of heat.
By doing so, when determining the amount of scrap charge, it is easy to grasp the heat balance in each process, and the amount of scrap charge in each process is easy to determine. By determining the amount of scrap charged during the dephosphorization process based on the target range of the total heat quantity, the amount of scrap charged in the dephosphorization process can be prevented from being too much or too little. The process no longer causes heat shortage or heat increase in the entire dephosphorization process.

  Moreover, the total amount of heat of the hot metal before the decarburization process is within the target range by scrap charging in the dephosphorization process, and the scrap charge amount is determined so that the total heat amount within the target range becomes the target value. Therefore, the amount of scrap charged into the decarburization furnace will not be too much or too little, and there will be no unmelted scrap during the decarburization process, or slopping will not occur, A decarburization process can be performed normally.

It is preferable to set the lower limit value of the total heat quantity of the hot metal converted from the target range higher than the total heat quantity of the molten steel at the end of decarburization.
In this way, the total amount of heat of the molten steel after the end of decarburization, in other words, the amount of heat output of the molten steel at the end of decarburization is greater than the total amount of heat of the hot metal before the start of decarburization, The decarburization process can be performed stably.

  According to the present invention, the dephosphorization process and the decarburization process can be normally performed when the dephosphorization process and the decarburization process are performed.

First, the converter equipment in the operating method of the converter equipment of this invention is demonstrated. However, this invention is not limited to what uses this installation.
As shown in FIGS. 1 and 2, the converter equipment 1 includes a plurality of converters 2, a ladle 3 for supplying hot metal to the converters 2, and a ladle 3 for conveying the ladle 3 to the converter 2. A plurality of transport cranes 4A and 4B are provided. Moreover, the converter equipment 1 of embodiment is equipped with the hot metal preliminary treatment equipment 5 and the scrap charging equipment 6, and after the hot metal conveyed from the blast furnace equipment is pretreated by the hot metal preliminary treatment equipment 5, the converter Hot metal and scrap are put into a converter to perform dephosphorization and decarburization.

The transport cranes 4A and 4B travel on a travel rail 7 extending linearly. In this embodiment, two transport cranes 4A and 4B travel on a single travel rail 7. . Along with the traveling rail 7, a hot metal pretreatment facility 5, a plurality of converters 2, and a scrap charging facility 6 are sequentially arranged.
The converter 2 performs hot metal dephosphorization processing and decarburization processing. In this embodiment, three converters 2 are arranged adjacent to each other in parallel. In the converter facility 1, normally, two of the three converters 2 are operating at the same time, and the other one is in reserve or being repaired. In this embodiment, one of the two operating converters 2 is used for dephosphorization, and the other one is used for decarburization.

If the converter 2 for dephosphorization is the de-P furnace 2A, the converter 2 for decarburization is the de-C furnace 2B, and the converter being repaired or spare is the spare furnace 2C, this implementation In the embodiment, the de-P furnace 2A, the de-C furnace 2B, and the preliminary furnace 2C are arranged in this order from the left side of FIG.
A track 19 composed of rails is laid on the tapping side of each converter 2A, 2B, 2C, and carts 20A, 20B travel on the track 19. Note that the track laid in the de-P furnace 2A is extended to the travel rail 7 on which the transport cranes 4A and 4B travel by passing under the de-P furnace 2A.

  The hot metal pretreatment facility 5 has two pretreatment stations 8A and 8B, and the pretreatment stations 8A and 8B are arranged in parallel with each other. Each of the pretreatment stations 8A and 8B includes a payout pit 9 for discharging hot metal to the ladle 3, a desulfurization device 10 for performing desulfurization processing on the hot metal, and a demolition device 11 (slag dragger) for removing hot metal slag. ing.

The scrap charging equipment 6 is for charging scrap into the converter 2. A scrap chute 12 for loading scrap, a scrap transport crane 13 for transporting the scrap chute 12, and a scrap chute 12 placed under the traveling rail 7. And a scrap yard 15 for receiving scrap.
Between the stage 13 and the scrap yard 15, one or a plurality (four in the present embodiment) of scrap conveyance rails 16 are laid, and the scrap chute 12 is placed on the scrap conveyance rails 16. A transfer carriage 17 that can be placed is movably arranged. Each scrap transport rail 16 is provided with a chute station 18 for stopping the transport carriage 17 on the stage 14. By stopping the transport carriage 17 on the chute station 18, the scrap chute 12 is moved to the travel rail 7. It will be located below.

The converter facility 1 has the above-described configuration. Next, the arrangement of other facilities with respect to the traveling rail 7 will be described. For convenience of explanation, the traveling rail 7 is divided into 8 sections (0 to 7 sections) having the same width and capable of accommodating one crane and a section (S section) on the stage 14 of the scrap section 4. The section to ~ S ward is omitted.
The transport crane 4A is movable on the traveling rail 7 from the 0th section to the sixth section, and the transport crane 4B is movable on the traveling rail 7 from the first section to the seventh section.

The scrap transport crane 13 is movable on the traveling rail 7 from the 4th ward to the Sth ward.
In addition, a preliminary processing station 8A is disposed in the first section, and a preliminary processing station 8B is disposed in the second section. In these preliminary processing stations 8A and 8B, a payout pit 9 is disposed under the traveling rail 7. In addition, a de-P furnace 2A, a de-C furnace 2B, and a preliminary furnace 2C are arranged at positions corresponding to the fourth, fifth, and sixth wards, respectively.

As mentioned above, according to the converter equipment 1 mentioned above, a dephosphorization process and a decarburization process are performed as follows.
First, when the kneading wheel 22 coming from the blast furnace arrives at the converter 1 and the hot metal is discharged from the kneading wheel 22 to the ladle 3 in the pit 9, the hot metal is desulfurized by the desulfurization device 10 and then removed. The hot metal slag is removed by the dredging device 11.
When the molten iron slag is removed, the ladle 3 is lifted by the transport cranes 4A and 4B and transported toward the de-P furnace 2A where dephosphorization is performed. At this time, the scrap transport crane 13 lifts the scrap chute 12 and goes to the de-P furnace 2A, and the scrap is charged into the de-P furnace 2A before the hot metal. After the scrap is charged into the de-P furnace 2A, the hot metal is charged into the de-P furnace 2A through the ladle 3 lifted by the transport crane 4B, and dephosphorization processing is performed in the de-P furnace 2A.

When the dephosphorization process is completed, the hot metal is discharged from the de-P furnace 2A to the ladle 3, and the ladle 3 is transported under the traveling rail 5 by the carriage 20A and then lifted by the transport crane 4B for decarburization. It is conveyed to the de-C furnace 2B. At this time, the scrap transport crane 13 lifts the scrap chute 12 and goes to the de-C furnace 2B, and the scrap is charged into the de-C furnace 2B before the hot metal. After scrap is charged into the de-C furnace 2B, the hot metal after dephosphorization is charged into the de-C furnace 2B through the ladle 3 lifted by the transport crane 4B, and decarburized in the de-C furnace 2B. Is done.

When the decarburization process is completed in the de-C furnace 2B, the molten steel is discharged to the ladle 3 of the carriage 20B and transferred to the secondary refining equipment or the continuous casting equipment.
The operation method of the converter equipment of the present invention, that is, the dephosphorization process and the decarburization process will be described in detail with reference to FIGS. FIGS. 3 and 4 show general iron-carbon system equilibrium state diagrams showing changes in the amount of carbon in molten iron (molten steel) and changes in molten iron temperature during dephosphorization and decarburization in this embodiment. It is a plot.

As shown in FIGS. 3 and 4, in the dephosphorization process, the hot metal A at the start of dephosphorization changes as indicated by an arrow a, and after dephosphorization, the process is performed so as to fall within a preset range B before the start of dephosphorization. Is going. Further, in the dephosphorization process, the hot metal in the range B is changed as indicated by an arrow b so that the molten steel C is determined as one point after the decarburization process.
In the dephosphorization treatment of the present invention, when the amount of carbon and hot metal temperature in the hot metal A before the start of dephosphorization is replaced with total heat, and the amount of carbon and hot metal temperature in the range B are replaced with total heat, After the dephosphorization process, the hot metal dephosphorization process is performed so that the total heat quantity within the range B falls within the total heat range within the range B (hereinafter, the range where the range B is indicated by the total heat quantity is set as the target range E). Specifically, before charging the scrap into the de-P furnace 2A, the scrap charging amount is determined so that the total heat amount of the hot metal A at the start of dephosphorization falls within the target range E after the completion of dephosphorization, When performing the dephosphorization process, the determined amount of scrap charged is charged into the de-P furnace 2A.

  Further, in the decarburization treatment of the present invention, the total amount of heat of the hot metal before the start of decarburization is made to fall within the target range E, and after this total amount of heat has been decarburized, the total amount of heat of the molten steel C (etc. The decarburization process is performed so as to match the value of the heat ray k6. Specifically, before charging the scrap into the de-C furnace 2B, the scrap charging amount is determined so that the total amount of hot metal in the target range E becomes the value of the isotherm k6 after dephosphorization is completed. When the decarburization process is performed, scrap with a scrap charge amount is charged into the de-C furnace 2B.

The above-described definition of total heat, isotherm, and target range E (range B) will be described.
Here, the vertical axis | shaft of FIG.3, 4 has shown temperature, and this temperature can be converted into a calorie | heat amount naturally. Moreover, the horizontal axis of FIGS. 3 and 4 indicates the amount of carbon. Since carbon generates heat with oxidation, the amount of carbon can be converted into the amount of heat. Assuming that the amount of carbon converted to heat is the equivalent amount of heat, and the sum of the amount of equivalent heat and the amount of heat is the total amount of heat, FIGS. , Isotherm). In FIG. 3, the isotherm of hot metal A at the start of dephosphorization can be represented by a one-dot chain line k1.

When the upper limit value of the range B is represented by an isotherm, it can be represented by a one-dot chain isotherm k2, and when the lower limit value of the range B is represented by an isotherm, it can be represented by a one-dot chain line isotherm k3. When the range B is expressed as the upper and lower limit values of the isotherm, that is, the upper and lower limit values of the total heat amount, the target range E is obtained.
Note that the amount of heat increases as the amount of carbon increases, and the amount of heat increases as the hot metal temperature increases. Therefore, in FIG. 3, the value of the isotherm increases toward the right on the horizontal and vertical axes. Specifically, the value of the isotherm increases as it goes to the upper right in FIG. 3, and the value of the isotherm decreases as it goes to the lower left, so the value of the isotherm k1 is the highest in FIG. The value of the isotherm k2 is higher than the value of the isotherm k3.

As shown in FIG. 5, the range B includes a line U1 obtained by shifting the liquidus line U4 by 70 ° C. in the temperature rising direction, a line U2 where the hot metal temperature is 1330 ° C., and a line U3 represented by [Formula 1]. The range is surrounded by This range B is obtained by a plurality of past operation data, experiments, physical calculations, and the like. By making the molten iron after removal within the range B, the dephosphorization process can be performed efficiently. I know.

  The line U1 is a line obtained by shifting the liquidus line U4 in the iron-carbon system equilibrium diagram by 70 ° C. parallel to the temperature rising direction, and the hot metal temperature after dephosphorization is made larger than the value of the line U1. Thus, it has been found through experiments and the like that even if hot metal after dephosphorization is placed in a ladle, it becomes difficult for the metal to adhere to the ladle. That is, if the temperature difference between the hot metal temperature after dephosphorization and the liquidus U4 is ΔT, ΔT ≧ 70 ° C. is preferable.

  FIG. 6 shows the results of measuring the hot metal temperature after dephosphorization treatment to determine the temperature difference (ΔT) and examining the relationship between this temperature difference and the metal adhesion rate adhering to the ladle. As can be seen from these, when ΔT becomes 100 ° C. or less, the metal adhesion speed at which the metal sticks to the ladle gradually increases, and when ΔT = 70 ° C. or less, the metal adhesion speed rapidly increases. If ΔT = 70 ° C or less, the metal adhesion rate increases rapidly, so the ladle's internal volume decreases sharply from the stage where the number of charges is low, and the necessary hot metal cannot be transported, or the ladle becomes heavy immediately and transports. Can not be. Moreover, it takes time to remove the bullion attached to the ladle. Therefore, by setting the temperature difference to 70 ° C. or more, the metal adhesion speed can be suppressed to 0.5 t / ch or less, and the metal adhesion to the ladle is delayed.

  The line U2 is a line drawn to the hot metal temperature of 1330 ° C. in the iron-carbon system equilibrium diagram, and the dephosphorization rate is improved by setting the hot metal temperature after dephosphorization to 1330 ° C. or lower. FIG. 7 summarizes the hot metal temperature and dephosphorization rate after dephosphorization. By setting the hot metal temperature after dephosphorization to 1330 ° C. or less, a dephosphorization rate of 30% or more is secured. The dephosphorization reaction does not proceed at a high temperature, and when the temperature exceeds 1330 ° C., the dephosphorization rate is significantly reduced, and the necessary dephosphorization rate cannot be obtained. It is preferable to do.

In the dephosphorization process, oxygen is blown into the molten iron to perform the dephosphorization process. At this time, the blown oxygen reacts with the carbon in the molten iron to perform decarburization. If the decarburization is inadvertently promoted during the dephosphorization process, the solidification temperature of the hot metal rises, and the hot metal may be easily solidified during the dephosphorization process.
Therefore, it is preferable to suppress the decarburization action as much as possible during the dephosphorization process, and during the dephosphorization process, the carbon amount and the temperature of the hot metal should be operated in a state close to the line shown by [Formula 1]. Good things are known from past operations and experiments. The coefficient a (change in hot metal temperature / carbon amount) in [Equation 1] is set to 400 or less from FIG. 8 showing the relationship between the coefficient a and the dephosphorization rate. The relationship between the coefficient a and the dephosphorization rate shown in FIG. 8 is a summary of experiments and past data. In this embodiment, the coefficient a is 400.

Now, as shown in FIGS. 3 and 4, consider the case where scrap is charged at the start of dephosphorization. When scrap is inserted into the hot metal A at the start of dephosphorization, the scrap takes the heat of the hot metal A and lowers the hot metal temperature of the hot metal A. Therefore, the value of the isotherm for the hot metal A after dephosphorization is It becomes lower than the value of the isotherm k1 at the start of dephosphorization.
Considering the amount of change between the value of hot metal isotherm at the start of dephosphorization and the value of hot metal isotherm at the end of dephosphorization (the amount of decrease in total heat), the more scrap is added at the start of dephosphorization, The amount of decrease in the value of the isotherm becomes large. In other words, if the scrap charging ratio with respect to the hot metal is high, the value of the isotherm of the hot metal after the dephosphorization process becomes low.

Here, considering the isothermal line of the scrap itself charged into the hot metal, the temperature of the charged scrap itself is low at around 25 ° C. Therefore, if the isothermal line of the scrap itself is drawn in FIG. It can be represented by k4.
Assuming that a large amount of scrap is charged during the dephosphorization process and the value of the isotherm of hot metal after the dephosphorization process is the same value as the isothermal line k4, the value of the isotherm of hot metal after the dephosphorization process is scrap. Since it is the same as the value of its own isotherm k4, it can be seen that the scrap charging ratio is 100%, that is, all are scrap amounts.

As shown in FIG. 3, a predetermined amount of scrap was charged into hot metal A at the start of dephosphorization and dephosphorization was performed. What was hot metal A at the start of dephosphorization changed to arbitrary hot metal A ′ after dephosphorization. And the isotherm of the optional hot metal A ′ is the isotherm k5. Consider that the scrap charging ratio Rp for hot metal A at the start of dephosphorization when hot metal A becomes arbitrary hot metal A ′ is considered.
The value obtained by subtracting the value of the isotherm k4 of the scrap itself from the value of the isotherm k1 of the hot metal A at the start of dephosphorization is set as a value G (the line segment G is shown in FIG. 3). When the value obtained by subtracting the isotherm k5 of the hot metal A ′ after dephosphorization from the value of the isotherm k1 of A is the X value (shown in FIG. 3 is the line segment X), this X value is the amount of decrease. Therefore, the ratio of the X value to the G value becomes the scrap charging ratio Rp, and can be expressed by Rp = X / G.

Therefore, at the time of dephosphorization treatment, the scrap charging ratio Rp such that the total amount of heat of the hot metal A falls within the target range E (range B) can be obtained as follows.
The difference from the value of the isotherm k1 to the value of the isotherm k2 is set as a value H (the line segment H is shown in FIG. 3), and the difference from the value of the isotherm k1 to the isotherm k3 is set as a value I (see FIG. 3, the line segment I), the scrap charging ratio Rp during the dephosphorization process is H / G ≦ Rp ≦ I / G.

  Here, as shown in FIG. 3, not only carbon but also other components contained in the molten iron are taken into consideration, and the conversion factors are used to give the above-mentioned G to I as follows. G = Σ (Apmi / Bpmi) / Ypp-Σ (Apsi / Bpsi) / Ypp, H = Σ (Apmi / Bpmi) / Ypp- (1736 + Dp), I = Σ (Apmi / Bpmi) / Ypp- (1612 + Dp) Become. Σ (Apmi · Bpmi) / Ypp in the above equation corresponds to the value of the isotherm k1, the equation (1736 + Dp) corresponds to the value of the isotherm k2, and (1612 + Dp) in the equation corresponds to the value of the isotherm k3. .

  When these formulas are summarized, the scrap charging ratio Rp can be expressed as in the following [Formula 2]. In the present embodiment, the scrap charging ratio Rp is obtained using the [Formula 2]. .

In the present embodiment, the conversion factor can calculate the amount of temperature rise when carbon in a scrap or hot metal is oxidized and changed to heat, and the conversion factor is called a temperature conversion factor. I will do it. The amount of heat calculated by the temperature conversion coefficient can be expressed in the form of temperature.
Therefore, [Equation 2] is a relational expression that is converted into temperature instead of calorie, and when the value of the isotherm k2, that is, the upper limit value at the time of dephosphorization is obtained, it becomes “1736”, and the isotherm The value of k3, that is, the lower limit at the time of dephosphorization was “1612”. In calculating [Equation 2], the heat output constant taking into account the heat of the exhaust gas after dephosphorization and the heat taken as an auxiliary material used during dephosphorization was set to “130”. This heat output constant is calculated empirically through experiments and actual operations. In addition, as described above, the yield Ypp in dephosphorization was taken into account when calculating the amount of heat.

  In the decarburization process, in order to reach a necessary temperature considering the processes after the decarburization furnace and an appropriate component value according to the steel type, for example, hot metal in the range B is used. What is necessary is just to make it become the said molten steel C after completion | finish of decarburization. That is, the scrap charging ratio Rc is as follows so that the total amount of heat of the hot metal in the range B before the decarburization treatment becomes the value of the isothermal line k6 of the molten steel C after decarburization (in other words, the target value). Can be requested.

In addition, the value of the total calorie | heat amount of the molten steel C, ie, the said target value, is set higher than the lower limit of the target range E, in order to perform a decarburization process stably. In other words, as shown in FIG. 5, the lower limit value of the target range E is set higher than the total amount of heat of the molten steel after the decarburization treatment.
That is, as shown in FIG. 5, the range B is indicated by a line U5 (isothermal line k6) in which the target value of the molten steel C is indicated by an isotherm in the iron-carbon equilibrium diagram, and the hot metal temperature is 1330 ° C. You may change into the range B1 enclosed by the line U2 and the line U3 shown by [Formula 1].

As shown in FIG. 4, the isotherm k6 of the molten steel C is drawn, and a value obtained by subtracting the upper limit value (the value of the isotherm k2) of the target range E from the isotherm k6 is defined as a line segment N, from the value of the isotherm k2 If the value obtained by subtracting the value of the isotherm k4 of scrap is L (the line segment L is shown in FIG. 3), the scrap mixing ratio Rc after decarburization can be expressed as Rc ≦ N / L.
Further, the value M (the line segment M in FIG. 3) is obtained by subtracting the lower limit value (the value of the isotherm k3) of the target range E from the isotherm k6, and the scrap or the like from the value of the isotherm k3. When the value obtained by subtracting the value of the heat ray k4 is taken as a value J (shown in FIG. 3 is a line segment J), the scrap mixing ratio Rc after decarburization is Rc ≧ M / J.

In consideration of not only carbon but also other components contained in the molten iron as shown in FIG. 4, J to N are as follows when conversion factors are used. J = (1612−Σ (Acsi · Bcsi)) / Ycp, M = 1621 / Ycp−Σ ((Acci · Bcci) + Dc)], N = [1736 / Ycp−Σ ((Acci · Bcci) + Dc)] Become. In the above equation, Σ (Acci · Bcci) / Ycp corresponds to the value of the isotherm k6.
These formulas are summarized as shown in the following [Formula 3]. In this embodiment, the scrap charge ratio Rc is obtained using the [Formula 3].

Similarly to [Formula 2], [Formula 3] is a relational expression in terms of temperature, not calorific value. In the calculation of [Formula 3], the heat output constant considering the heat of the exhaust gas after decarburization and the heat taken for the auxiliary material used at the time of decarburization was set to “30”. This heat output constant is calculated empirically through experiments and actual operations. In addition, as described above, the yield Ycp in decarburization was taken into account when calculating the amount of heat. The temperature conversion coefficient shown in [Expression 3] is obtained by various experiments in the same manner as in [Expression 2], and is the same numerical value as in [Expression 2].

For example, the hot metal temperature at the start of dephosphorization is set to 1380 ° C., the amount of each component of the hot metal is set to Si = 0.34%, C = 4.5%, and the upper and lower limits of the scrap charging ratio Rp in [Formula 2] When the value was calculated | required, the scrap charging compounding rate became 4.1% or more and 10.5% or less.
For example, assuming that the molten steel temperature after decarburization is 1640 ° C., the amount of each component of the hot metal is Si = 0% and C = 0.05%, the upper and lower limit values of the scrap charging ratio Rc are obtained by [Equation 3]. As a result, the scrap charging ratio Rc was 1.4% or more and 8.5% or less.

The above [Formula 2] and [Formula 3] are used to obtain the scrap charging ratio Rp and the scrap charging ratio Rc, and according to the scrap charging ratios Rp and Rc, the scrap is dephosphorized and decarburized. When charged in the converter corresponding to the treatment, the refining temperature was kept within the set range, and the dephosphorization treatment and decarburization treatment could be performed normally.
Now, considering the total heat input (total heat at the start) and heat output (total heat at the end) during the dephosphorization and decarburization processes, if the heat input is smaller than the output heat, dephosphorization In addition, heat is deprived by the decarburization treatment, the hot metal treatment temperature is lowered, and the dephosphorization treatment and the decarburization treatment may not be performed normally, and the heat input is preferably larger than the heat output.

Here, as shown in FIG. 10, the amount of tapping at the end of decarburization (the amount of molten steel) is “1”, and the amount of charging (the amount of hot metal and scrap) at the time of dephosphorization treatment based on this tapping amount. ), The amount of tapping water, and the amount of charging and tapping during decarburization treatment are considered from the relationship of the correction factor (yield).
Since the yield during decarburization is Ycp, the total charge at the start of decarburization is 1 / Ycp (a combination of hot metal and scrap). Here, Rc is the scrap compounding rate, so Rc × 1 / Ycp
(Rc / Ycp) is the amount of scrap charged at the start of decarburization, and (1-Rc) × 1 / Ycp is the amount of hot metal charged at the start of decarburization.

Since the amount of hot metal charged at the start of decarburization is the same as the amount of hot water at the end of dephosphorization, the amount of hot metal discharged at the end of dephosphorization can be expressed as (1-Rc) / Ycp.
Since the amount of hot metal discharged at the end of dephosphorization is (1-Rc) / Ycp, the total charge at the start of dephosphorization (1- Rc) / Ycp / Ypp can be obtained.

Therefore, the scrap charge at the start of dephosphorization is Rp (1-Rc) / Ycp / Ypp], and the hot metal charge at the start of dephosphorization is (1-Rp) (1-Rc) / Ycp / Ypp. Become.
Here, the amount of heat input during the dephosphorization process is obtained from the relationship between the amounts of charge summarized in FIG. 10. The amount of heat input during the dephosphorization process is (1-Rp) (1-Rc) / Ycp / Ypp · Σ (Apmi · Bpmi), and the heat input of scrap is Rp (1-Rp) (1-Rc) / Ycp / Ypp · Σ (Apsi · Bpsi). Further, when the heat input during the decarburization process is obtained, Rc / Ycp · Σ (Acsi · Bcsi) is obtained.

As described above, when the dephosphorization process and the decarburization process are performed, it is better that the amount of heat input is larger than the amount of heat output, and this is expressed by the following [Expression 4].
That is, in the embodiment, when decarburization is performed after dephosphorization as described above, in addition to satisfying [Equation 2] and [Equation 3], scrap is also satisfied so as to satisfy [Equation 4]. The charging ratio Rp and the charging ratio Rc of scrap are set.

  [Equation 4] is the sum of the heat input calculated by combining the total heat input at the start of dephosphorization calculated by combining the scrap and hot metal during the dephosphorization process and the heat input of the scrap during the decarburization process ( The sum total heat quantity) is larger than the sum of the total heat output Σ (Acci · Bcci) + Dc + Dp] of the dephosphorization process and the decarburization process. In other words, it is preferable that the lower limit value of the target range E in the total amount of heat of the hot metal after dephosphorization is set higher than the total amount of heat of the molten steel after decarburization.

  The scrap charging ratio Rp shown above is a ratio of the scrap amount to the total charging amount of the molten iron put into the de-P furnace 2A and the scrap charging amount, and can be expressed by the following [Equation 5]. .

  Further, the scrap charging ratio Rc shown above is the ratio of the amount of clap to the total charging amount of the molten iron put into the de-C furnace 2B and the scrap charging amount, and is expressed by the following [Equation 6]. Can do.

  The scrap charging ratio Rp during the dephosphorization process and the scrap charging ratio Rc during the decarburization process are summarized as shown in FIG. As can be seen from FIG. 9, the scrap charging ratio Rp was 4.1% to 10.5%, and the scrap charging ratio Rc was 1.4% to 8.5%. Further, in the dephosphorization process and the decarburization process, the range satisfying all of [Formula 2] to [Formula 4] is the range M1.

Next, in the dephosphorization process and the decarburization process, the procedure for determining the scrap charge amount and performing the operation will be described based on the flowcharts of FIGS.
First, in the case of dephosphorization, in step 1, before the start of dephosphorization, the hot metal before the dephosphorization, that is, the hot metal temperature Bpmi (i = 1) of the hot metal from which the slag has been removed by the demetalizer 11, the carbon component The amount Bpmi (i = 2) and the silicon component amount Bpmi (i = 3) are measured, and these values and the temperature conversion coefficient Apmi (i = 1 to 3) known in advance and the correction coefficient Ypp in dephosphorization The total amount of heat in the hot metal is obtained from (yield) (value of the isotherm k1 in FIG. 3).

In step 2, before the start of dephosphorization, the charging temperature Bpsi (i = 1), the carbon component amount Bpsi (i = 2), and the silicon component amount Bpsi (i = 3) of the scrap charged into the de-P furnace 2A And the total amount of heat in the scrap is obtained from these values and the previously known temperature conversion coefficient Bpsi (i = 1 to 3) and correction coefficient Ypp (yield) in dephosphorization (isothermal line k4 in FIG. 3). The value of the).
In step 3, before starting the dephosphorization, the heat output constant Dp at the time of dephosphorization is determined from the operating conditions, etc., and this value, the total amount of heat in the hot metal and the total amount of heat in the scrap are substituted into [Equation 2] The charging compounding ratio Rp is determined.

In step 4, before the start of dephosphorization, the scrap charging amount is calculated using [Formula 5] from the scrap charging ratio Rp and the hot metal charging amount to be put into the de-P furnace. The amount of hot metal charged into the de-P furnace 2A is the amount of hot metal contained in the ladle 3 moving toward the de-P furnace 2A.
In step 5, the amount of scrap determined in step 3 is loaded on the scrap chute 12, and the scrap is loaded into the de-P furnace 2 </ b> A with the scrap chute 12.

In the case of decarburization processing, it is as follows.
In step 10, before starting decarburization, the molten steel temperature Bcci (i = 1), carbon component amount Bcci (i = 2), and silicon component amount Bcci (i = 3) after decarburization are determined. And the temperature conversion coefficient Acci (i = 1 to 3) known in advance and the correction coefficient Ycp (yield) in decarburization, the total amount of heat in the molten steel is obtained (the value of the isotherm k6 in FIG. 4).

In step 11, before starting decarburization, the charging temperature Bcsi (i = 1), the carbon component amount Bcsi (i = 2), and the silicon component amount Bcsi (i = 3) of the scrap charged into the de-C furnace 2B And the total heat quantity in the scrap is obtained from these values and the temperature conversion coefficient Apsi (i = 1 to 3) known in advance and the correction coefficient Ycp (yield) in decarburization (isothermal line k4 in FIG. 4). The value of the).
In step 12, before the start of decarburization, the heat output constant Dc at the time of decarburization is determined from the operating conditions, and this value, the total amount of heat in the molten steel, and the total amount of heat in the scrap are substituted into [Equation 3]. The charging compounding ratio Rc is determined.

In step 13, before starting decarburization, the scrap charging amount is calculated using [Formula 6] from the scrap charging ratio Rc and the hot metal charging amount put into the de-C furnace 2B. The amount of hot metal charged into the de-C furnace 2B is the amount of hot metal discharged from the de-P furnace 2A and put into the ladle 3.
In step 14, the amount of the scrap determined in step 3 is loaded on the scrap chute 12, and the scrap is loaded into the de-C furnace 2 </ b> B with the scrap chute 12.

In the above description, the actual measured values at the hot metal temperature, the carbon component amount, and the silicon component amount are used. However, predicted values predicted before the start of dephosphorization may be used. The calculation in each of the above steps is performed by a control device (for example, a process computer) that controls converter facilities and the like.
In the dephosphorization process and the decarburization process, the [Formula 2] and [Formula 3] are used to obtain the scrap charging ratio Rp and the scrap charging ratio Rc. When used, it is as follows.

  That is, before starting dephosphorization, the total amount of heat of the molten steel after decarburization, the total amount of heat in the hot metal before the start of dephosphorization, the total amount of heat of scrap charged during dephosphorization, and the total amount of scrap charged during decarburization. By determining the amount of heat and substituting these into [Formula 4], the scrap charge ratio Rp and scrap charge ratio Rc satisfying all [Formula 2] to [Formula 4] are determined. The scrap charging ratio Rp and the scrap charging ratio Rc thus obtained are substituted into the above [Formula 5] and [Formula 6] to determine the scrap charge amount during the dephosphorization process or the decarburization process.

9 and 13 summarize the results of actual operation. Reference examples 1 and 5 in FIG. 13 were operated by setting the scrap charging ratio Rp so as to satisfy only [Formula 2], and Reference Examples 2 and 4 were scraps so as to satisfy only [Formula 3]. In this example, the charging ratio Rp of scrap and the charging ratio of scrap were set so as to satisfy [Formula 2], [Formula 3] and [Formula 4]. The compounding ratio Rc was set and operated. In FIG. 9, the points of the scrap charging ratio in the examples and reference examples are plotted.

In the examples and reference examples , the presence or absence of scraps remaining in the dephosphorization and decarburization processes and the occurrence of slopping were also examined.
In the case where there is unmelted scrap, it is preferable that there is no unmelted scrap because the specified molten steel cannot be secured. In addition, when there is occurrence of slopping, it is preferable that there is no occurrence of slopping, because the blowing time may be extended or the blowing may have to be temporarily interrupted, which reduces productivity. Has been.

In Reference Examples 1 and 5, there is no unmelted scrap in the de-P furnace, no slopping occurs in the de-P furnace, no heating material is required (no heating material), and the dephosphorization process is good. there were.
In Reference Examples 2 and 4, there is no unmelted scrap in the de-C furnace, there is no slopping in the de-C furnace, no heating material is required (zero heating material), and the decarburization process is It was good.
In Example 3, there was no unmelted scrap in the de-P furnace and de-C furnace, no slopping occurred in the de-P furnace and de-C furnace, and the dephosphorization and decarburization processes were very good. It was.

As described above, when the operation results are summarized, as can be seen from FIGS. 9 and 13, as shown in Reference Examples 1 and 5, the scrap charging ratio Rp at the time of dephosphorization treatment is set within the range of [Formula 2], thereby removing P Scrap remaining in the furnace and slopping in the de-P furnace could be suppressed.
Also, as in Reference Examples 2 and 4, the scrap charging ratio Rc at the time of decarburization treatment is set within the range of [Equation 3], so that scraps remaining in the de-C furnace and slopping in the de-C furnace are reduced. Occurrence could be suppressed.

Further, in both the dephosphorization process and the decarburization process as in Example 3, the scrap charging ratios Rp and Rc are set within the ranges of [Expression 2] and [Expression 3], and [Expression 4]. ] (Within the range of M1 in FIG. 9), it was possible to suppress the unmelted scrap of both the de-P furnace and the de-C furnace and the occurrence of slopping in the de-C furnace.
FIG. 14 summarizes the operation results when the hot metal after the dephosphorization process is operated so as to fall within the range B. In Example 6, the operation was performed so that the hot metal after the dephosphorization treatment was in the range B. Comparative Example 1 was operated so that the temperature difference between the hot metal temperature after dephosphorization and the liquidus became 70 ° C. or less at 35 ° C., and Comparative Example 2 had a hot metal temperature after dephosphorization of 1330 ° C. The operation was performed as described above, and Comparative Example 3 was operated so as not to satisfy [Equation 1]. In Example 6, there was little bullion to the ladle and the dephosphorization rate was 90%, and after dephosphorization, the target dephosphorization component could be obtained, that is, there was no derailment of the P component.

  In Comparative Example 1 in which the temperature difference (ΔT) is less than 70 ° C., there are many metal bars, and in Comparative Example 2 in which the hot metal temperature after dephosphorization is 1330 ° C. or higher, the dephosphorization rate is less than 30% and very low. became. In Comparative Example 1, the P component of the hot metal after dephosphorization deviated from the target value, and the dephosphorization rate was as low as 20%.

It is a schematic plan view of converter equipment. It is a schematic side view of converter equipment. It is the figure which showed the relationship between the carbon content and hot metal temperature in a dephosphorization process. It is the figure which showed the relationship between the carbon content and hot metal temperature in a decarburization process. It is a detailed view of a target range. It is a figure which shows the relationship between temperature difference (DELTA) T and a base metal adhesion rate. It is a figure which shows the relationship between hot metal temperature and a dephosphorization rate. It is a figure which shows the relationship between the value which divided the hot metal temperature change by the carbon content change, and the dephosphorization rate. It is the figure which showed the scrap charging compounding rate. It is the figure which showed the relationship between the charging amount in the dephosphorization process and a decarburization process, and the amount of tapping. It is a flowchart figure which shows the procedure which determines the amount of scrap charges and performs operation in the case of a dephosphorization process. It is a flowchart figure which shows the procedure which determines the amount of scrap charge and performs operation in the case of a decarburization process. It is a figure which shows an Example and a reference example . It is a figure which shows an Example and a comparative example.

1 Converter 2 Converter 2A Dephosphorizer 2B Decarburizer 6 Scrap charging equipment

Claims (2)

After hot metal and scrap are charged into a dephosphorization converter and dephosphorized, the dephosphorized hot metal and scrap are charged into a decarburization converter and decarburized. In the operation method of the converter equipment,
The scrap charge in the dephosphorization process is determined so that the total amount of hot metal before the start of dephosphorization falls within the target range after dephosphorization, and the scrap with the determined scrap charge amount is subjected to the dephosphorization process. Charging,
The scrap charging amount in the decarburization process is determined so that the total amount of hot metal before decarburization starts within the target range by charging the scrap becomes a target value after decarburization. The amount of scrap is charged into the decarburization process,
On the iron-carbon system equilibrium diagram, the target range is a line obtained by shifting the liquidus line by 70 ° C. in the temperature rising direction, a line where the hot metal temperature is 1330 ° C., and a line represented by [Formula 1]. Stipulated in the range surrounded by
Further, the scrap charging amount is determined by the following formula: [Formula 2] The scrap charging ratio Rp charged into the dephosphorizing converter and the scrap charging ratio charged into the decarburizing converter ] It sets so that all of [Formula 4] may be satisfy | filled, The operating method of the converter equipment characterized by the above-mentioned.

  The operating method of the converter equipment according to claim 1, wherein the lower limit value of the total amount of heat of the hot metal converted from the target range is set higher than the total amount of heat of the molten steel at the end of decarburization.

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