JP4549201B2 - Continuous casting method of different steel types - Google Patents

Description

  The present invention relates to a continuous continuous casting method for different steel types in which post-charge casting of different steel types is performed in succession to pre-charge casting.

  2. Description of the Related Art Conventionally, in a continuous casting apparatus, two charges of different steel types, that is, “continuous continuous casting of different steel types” in which continuous casting is performed without interruption are performed. In that case, if two charges of different steel types (molten steel) are injected continuously without any countermeasure, the pre-charge and post-charge with different components will be mixed in the tundish or mold, and the steel type components will be A slab having a mixed part different from the charge and the post charge is manufactured. Since such a slab mixing part cannot be a pre-charged slab or a post-charge slab, it is normally cut and not sent to the lower process. If the length of the mixed portion is long, it may reach 4 to 5 m. In this case, the continuous casting process is very poor in productivity.

In such continuous casting of different steel types, attempts have been made in the past to shorten the mixing site as much as possible. For example, there is a technique disclosed in Patent Document 1.
Patent Document 1 discloses a sequence block (joint fitting) that is used for continuous casting of different steel types and reliably connects a pre-charge and a post-charge.
This sequence block is provided with a flat plate, V-shaped, semi-cylindrical partition plate, and a pair of mounting rods erected on the partition plate. The plate is pushed into the precharged molten steel pool, after which the postcharge is injected into the mold. When the partition plate is immersed in the molten steel pool, the molten steel around it solidifies and a partition film is formed on the surface of the molten steel. This partition film prevents the mixture of the post-charge and the pre-charge to be injected later.
JP 2004-174515 A

However, the partition wall action of the technique of Patent Document 1 does not extend over the entire upper surface of the precharged molten steel pool. In other words, the melting of the sequence block submerged in the previous charge causes the solidification of the molten steel in the vicinity of the sequence block to proceed to produce a partition wall action, but the molten steel at a position away from the sequence block is still in a molten state, There is a high possibility that the post-charge and the pre-charge that will be inserted later through will be mixed.
Therefore, in view of the above problems, the present invention aims to provide a continuous casting method of different steel types that can prevent the mixing of the pre-charge and the post-charge as much as possible and produce a slab with as few mixing sites as possible. And

In order to achieve the above object, the present invention takes the following technical means.
That is, the technical means for solving the problems in the present invention is a continuous casting method of different steel types in which a post-charge casting of different steel types is performed continuously with a pre-charge casting using a continuous casting apparatus provided with a mold. The casting speed of the pre-charge is gradually reduced from 6 to 10 minutes before the supply of the pre-charge to the mold is stopped, and the exothermic powder is charged in the mold, and the pre-charged molten steel pool after the exothermic powder is charged A sequence block is inserted into the mold, and then a post-charge is injected into the mold.

By this technical means, in continuous casting of different steel types, the mixing of the pre-charge and the post-charge can be minimized, and it is possible to produce a slab with as few mixing sites as possible.
The principle will be described with reference to FIG.
As shown in FIG. 1, the slab drawn from the mold is solidified by primary cooling by the mold to form a solidified shell, but the inside remains as molten steel. The slab is transported to the downstream side while being supported by the support roll on the wide and narrow surfaces of the slab. In the meantime, the surface of the slab is cooled by a cooling means such as a cooling spray, and the thickness of the solidified shell becomes thicker and finally solidification proceeds to the inside of the slab.

If the position where solidification progresses to the inside and the entire slab is hardened is S, a pinch roll (drawing roll) is arranged from the point S and thereafter. Here, the distance from the position immediately below the mold to the point S is L1.
Here, consider a case where the casting speed of the pre-charge is slower than the casting speed in the steady state (the drawing speed at which solidification is completed at L1). Since the development speed of the solidified shell is considered to be largely related to the amount of heat removed from the slab, when the casting speed is slowed down, as shown by the broken line in FIG. It is considered that the region where the molten steel is present in the slab is reduced as a result of the completion of the solidification up to. The molten steel exists only up to the position of L2 (<L1) at a distance along the slab. Therefore, when the casting speed is slowed, the amount of molten steel mixed with the post-charge is inevitably small, and the length of the mixed portion of the pre-charge and the post-charge after casting is inevitably shortened. Therefore, even if the pre-charge and the post-charge are allowed to be mixed, the length of the mixed portion that cannot be sent to the lower process can be shortened as much as possible, and the productivity can be greatly improved. become.

As a result of many experiments, the inventor of the present application has clarified that the casting speed of the precharge should be gradually reduced from 6 to 10 minutes before the supply stop of the precharge. Although the prior document “Japanese Patent Publication No. 1-28662” and the like have a description that the casting speed is slowed down after the injection of the pre-charge in the continuous casting of different steel types using the continuous casting apparatus, the description about the deceleration time and the effect exerted by the deceleration. There is no disclosure regarding the effect, which is different from the technique of the present invention.
On the other hand, when the casting speed of the pre-charge is slowed, it is clear that the following problems also occur.

That is, since the drawing speed is slowed down, the pre-charge stays in the mold for a longer time than usual, so that the heat removal by the mold progresses and the solidified shell develops more and the surface of the molten steel pool also solidifies. Become (skinned). If it becomes so, it will become difficult to sink the sequence block to be charged for connection with the post-charge into the molten steel pool of the pre-charge, making it difficult to properly load the sequence block.
In order to avoid this, the exothermic powder is put into a mold in which a precharge during deceleration exists. By reacting this exothermic powder, a large amount of heat is generated on the surface of the precharged molten steel, and the molten steel surface can be reliably prevented from solidifying. The inventor of the present application has made it clear that the amount of the heat generation powder charged should be 3 to 9 kg as a result of many experiments.

The continuous casting apparatus has a tundish for supplying molten steel to the mold, and the end of the precharge deceleration operation is stopped when the precharge supply from the tundish to the mold is stopped. It is very preferable to set the time.
By the way, as the most preferable technical means for solving the problems in the present invention , a slab provided with a mold for casting a slab having a thickness of 210 to 250 mm and a width of 800 to 1700 mm and a tundish for supplying molten steel to the mold. In a continuous casting method of different steel types in which a continuous charge is continuously cast after a precharge using a continuous casting apparatus, the precharge is started from 6 to 10 minutes before the supply of the precharge to the mold is stopped. The casting speed is reduced stepwise at a speed of 0.20 m / min or less per time, and a heat generating powder containing CaSi is charged into the mold with a charging amount of 3 to 9 kg, and the heat generating powder is charged. Multiple sequence blocks are placed in the molten steel pool of the previous charge, and the gap between the sequence blocks is “distance between sequence blocks / mold width ≦ Was charged to a .30 ", then, may be employed different grades of communicating people continue casting method characterized by injecting a post-charge into the mold.

  According to the present invention, in continuous casting of different steel types, mixing of the pre-charge and the post-charge is prevented as much as possible, and a slab having as few mixing parts as possible can be manufactured.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.
In the continuous casting apparatus 1, casting of the same steel type is performed continuously, as well as molten steel 2 having different steel types is continuously supplied, and slabs 3 having different components may be produced in a continuous manner. Such casting is called continuous casting of different steel types.
In the continuous casting of such different steel types, first, the molten steel 2 of the steel type A is sequentially supplied, and the slab 3 of the steel type A is continuously cast. Thereafter, the last molten steel 2 of steel type A (hereinafter referred to as precharge) is supplied to the tundish 4, and the precharge amount in the tundish 4 becomes close to zero.

At that time, when the subsequent molten steel 2 of steel type B (hereinafter referred to as post-charge) is continuously injected without any countermeasure, the pre-charge and post-charge with different components are mixed in the tundish 4 or the mold 5, The slab 3 having the mixed portion formed by the solidification of the mixed charge is cast.
As one of the measures to suppress the mixing of the pre-charge and the post-charge, the sequence block 7 is inserted into the mold 5 after the slide valve 6 of the tundish 4 is once closed to stop the molten steel 2 to the mold 5. ing. The sequence block 7 is inserted in order to connect the pre-charge and the post-charge without any interruption, and in addition, a solidified film is formed on the surface of the molten steel pool of the pre-charge, It has the purpose of preventing mixing with post-charge as much as possible.

In parallel with the loading of the sequence block 7, a post charge is injected into the tundish 4, and when the post charge in the tundish 4 reaches a specified amount, the slide valve 6 is opened, After the injection into the mold 5, the drawing of the charge is resumed.
The present invention, in the continuous casting of the above different steel types,
(i) From 6 to 10 minutes before the supply stop of the precharge, the casting speed of the precharge is gradually reduced and the heat generating powder 11 is inserted into the mold 5;
(ii) After that, the sequence block 7 is charged into the pre-charged molten steel pool after the heating powder 11 is charged.
(iii) After that, it has three steps of injecting a post-charge into the mold 5 and restarting casting.

FIG. 1 shows a schematic diagram of a continuous casting apparatus 1 of the present embodiment. The continuous casting apparatus 1 is a vertical bending slab continuous casting apparatus. A cast piece 3 (hereinafter referred to as a slab 3) drawn from the lower end of a mold 5 is initially drawn in a vertical direction. It is gently bent while being supported and pulled out in the horizontal direction.
Specifically, the continuous casting apparatus 1 includes a tundish 4 that temporarily stores molten steel 2 and injects the molten steel 2 into a mold 5, a plurality of support rolls 8 (wide surfaces) that transport the mold 5 while supporting the slab 3 that has come out of the mold 5. Support roll and narrow surface support roll).

The molten steel 2 carried by the ladle 9 is poured into the tundish 4 and injected into the mold 5 through the immersion nozzle 10 at the bottom of the tundish 4. Whether the molten steel 2 is injected or not is adjusted by a slide valve 6 provided at the upper end of the immersion nozzle 10. In the mold 5, the injected molten steel 2 is cooled (primary cooling), and only the surface portion thereof becomes a solidified slab 3 which is pulled out from the lower part of the mold 5.
As shown in FIG. 1, in the continuous casting apparatus 1, the slab 3 drawn in the vertical direction is gradually curved in the horizontal direction while being held by the support rolls 8, and the horizontal slab 3 is provided on the downstream side. The gas cutting machine is divided into slabs 3. The cross section of the slab 3 is substantially rectangular as shown in FIG. Between each support roll 8, a plurality of cooling sprays for injecting a coolant to perform secondary cooling of the slab 3 are disposed.

In the description, the side on which the slab 3 is transferred is referred to as the downstream side. The slab 3 to be cast has a thickness of 210 to 250 mm and a width of 800 to 1700 mm.
In the present embodiment, continuous casting of different steel types is performed in the above-described continuous casting apparatus 1 according to the procedure described below.
FIG. 2 and FIG. 3 show the casting procedure as a transition diagram and a flowchart.
First, it is assumed that the slab 3 is continuously cast with a pre-charge (molten steel 2 of steel type A). FIG. 2A shows a situation in which the amount of precharge in the tundish 4 is reduced after the last precharge from the ladle 9 is charged into the tundish 4.

Under such circumstances, the casting speed of the pre-charge is decelerated from the casting speed in the steady state (the drawing speed at which solidification is completed at L1). Specifically, the slide valve 6 of the tundish 4 is closed in the next step, but the speed is decelerated from 6 minutes to 10 minutes before that point. Regarding the deceleration speed of the pre-charge, the deceleration adjustment of the continuous casting apparatus 1 is performed in stages, so that it is 0.20 m / min or less per time. (S31)
In combination with the above deceleration operation, 3 to 9 kg of exothermic powder 11 per mold is put into the mold 5 so that heat is generated on the molten metal surface. By doing so, it is possible to prevent the precharged molten steel pool in the mold 5 from solidifying (S32). The exothermic powder is an additive that causes a chemical reaction by the heat of molten steel and generates a large amount of heat. FIG. 13 shows the composition of slag generated by the exothermic powder 11. The composition of the exothermic powder 11 is not limited to the one that generates the slag, and any composition that contains CaSi as a composition and generates heat due to oxidation of the CaSi may be used.

  Next, when the amount of remaining steel in the tundish 4 reaches a predetermined value (for example, 3 tons), as shown in FIG. 2 (b), the slide valve 6 is closed and the casting to the mold 5 is temporarily suspended. The tundish 4 is raised (S33, S34). At this time, if the withdrawal of the previous charge is stopped completely, the subsequent slab withdrawal may not be successful. Therefore, after the tundish 4 is raised, the withdrawal of the previous charge is continued at a slow speed. ing. For example, after raising the tundish 4, the casting is continued at a drawing speed of 0.1 m / min for 3 minutes and 30 seconds. By doing so, the effect of securing the immersion nozzle space in the mold 5 is also produced, which is advantageous in operation.

And the slag bear adhering between the side surface in the mold 5 and the mold 5 to the slab 3 is removed, and as shown in FIG. 2 (b), the sequence block 7 (joint metal) is inserted into the molten steel pool of the previous charge. Then, the lower part is immersed in the molten steel 2 to be melted. (S35)
Specifically, after the immersion nozzle 10 is removed from the tundish 4, the person in charge of the work loads the sequence block 7 into the mold 5 using a dedicated lifting tool or the like. At the time of charging, the lower part of the sequence block 7 is submerged in the molten steel pool, and is moved so that the front and rear and left and right positions become predetermined in the mold 5. When the sequence block 7 is moved to a predetermined position, the state is maintained for a certain time (for example, 5 seconds).

The position where the sequence block 7 is arranged is a certain distance in the horizontal direction from the inner wall of the mold 5 so that there is no gap between the end of the molten steel shell developing in the slab 3 and the end of the sequence block 7. (For example, 100 mm).
Further, when a plurality of sequence blocks 7 are inserted into the mold 5, the gap between the sequence blocks 7 and 7 may be set to “distance between sequence blocks / template width ≦ 0.30”. By doing so, the partition action by the sequence block 7 is effectively worked, and the molten steel flow of the post-charge injected from the immersion nozzle 10 later is mixed with the pre-charge, and the mixed portion of the slab is prevented from extending. Is possible.

After inserting the sequence block 7, the immersion nozzle 10 is attached to the tundish 4 and the tundish 4 is lowered. Then, the charging of the post-charge from the ladle 9 to the tundish 4 is started. When the post-charge in the tundish 4 reaches 50 tons, the slide valve 6 is opened and the casting into the mold 5 is resumed. (S36)
Further, the post-charge is pooled up to a preset meniscus level in the mold 5, and then casting drawing is resumed (S37). At this time, until the portion where the sequence block 7 is inserted, that is, the connecting portion between the pre-charge and the post-charge passes through the vertical bending portion of the continuous casting apparatus 1, Is a slow speed of 0.8 m / min.

4 and 5 show changes in casting speed and tundish weight in three cases in which different steel types are continuously cast in the above-described procedure. FIG. 5 shows numerical data on which the graph of FIG. 4 is based.
In case 1, the casting speed of the pre-charge is reduced from 9 minutes before closing the slide valve 6, and in case 2 the speed is reduced from 10 minutes before and in case 3 slightly longer 11 minutes. In each case, the front charge is supplied in a reduced amount from the tundish 4 in conjunction with the deceleration, and the tundish weight is reduced accordingly. In any of the cases 1 to 3, the inventor of the present application has confirmed that continuous casting of the pre-charge and the post-charge is performed well and the mixing portion is short.

[Experiment 1 for obtaining casting conditions]
As described above, the time for decelerating the withdrawal of the precharge is set to 6 to 10 minutes before the slide valve of the tundish 4 is closed, but the present inventor has clarified this condition through the following experiment. .
That is,
(i) The slab 3 was cast by continuously casting different steel types with various deceleration start times of the pre-charge.
(ii) Collect a plurality of cross-sectional samples in the longitudinal direction of the slab from the vicinity of the connecting part (stepped crop) before and after the slab 3 (see FIG. 6),
(iii) Analyzing the steel type composition of each cross-section sample to determine the length of the mixing site (see Fig. 7),
(v) Summarize the data from the viewpoint of what conditions the deceleration start time of the pre-charge satisfies, so that the length of the mixed part can be shortened (see FIG. 8).
I conducted an experiment.

  FIG. 6A shows the slab 3 from which the cross-sectional sample 12 is collected as viewed from the narrow surface side. The left side is the slab that is made up of the pre-charge, and the right side is the slab that is made up of the back charge. The slab 3 was cut at a position indicated by a broken line starting from the connecting portion, and a plurality of cross-sectional samples 12 were collected. Specific cutting positions are 5 points from the connection part on the front charge side: 0.7 m, 1.0 m, 1.5 m, 2.0 m, and 3.0 m, and 0.5 m from the connection part on the rear charge side. There were 7 points of 0 m, 1.5 m, 2.0 m, 2.5 m, 3.0 m, and 4.0 m, and a total of 12 cross-sectional samples 12 were collected.

FIG. 6 (b) shows a cross-sectional sample 12, and chips samples were collected from six locations of the cross-sectional sample 12. By analyzing the components of the chip sample, the steel type component of the cross-section sample can be clarified. 6 points | pieces which extract | collect a chip | tip are P1-P6 of FIG.6 (b), and are a place of 10, 40, and 80 mm from the surface of the slab 3 of a narrow surface center part wide surface center part.
FIG. 7 is a graph in which the relationship between the component change rate obtained from the above-described chip sample and the distance from the connection portion is plotted for each slab 3.

The component change rate means that the component value in the ladle 9 of the previous charge (below pan determined component value) is 0%, the component value in the ladle 9 of the post charge (below pan determined component value) is 100%, the precharge This value indicates how the component changes from the side to the post-charge side. In the case of this embodiment, the carbon equivalent CE calculated by Formula (1) is used as a component of the steel type.

CE = C + Si / 5 + Mn / 5 + P + 1.2V + 2.5Nb (1)

As can be seen from FIG. 7, the component change rate of the portion corresponding to the previous charge (left side from the point d) is close to 0%, and the component change rate of the portion corresponding to the rear charge (left side from the point c) is 100%. Close to. In the vicinity of the connection portion, the component change rate changes linearly. Therefore, if the component change rate is equal to or less than the value indicated by the broken line b, that is, the component allowable standard, it is considered as the slab 3 by the pre-charge, and if the component change rate is equal to or greater than the value indicated by the broken line a, that is, the component allowable standard. Think of it as slab 3 by post-charge. Based on this consideration, the length between the broken line c and the broken line d is defined as the component influence length. In other words, the component influence length is a length in which the component change rate calculated from the component values of the pre-charge and the post-charge deviates from a preset reference value (component allowable reference). The part of the slab 3 corresponding to is a mixed part different from the pre-charge component and the post-charge component, and cannot be sent to a lower process such as rolling.

FIG. 8 summarizes the relationship between the “component influence length” and the “pre-charge deceleration time” when casting the slab after obtaining the component influence length of each slab 3.
As can be seen from this figure, when the deceleration time is 6 minutes or less, there are cases where the component influence length is 1 m or less, but there are cases where it exceeds 1 m and becomes 1.3 m or 1.4 m. become. Thus, when the component influence length becomes long, the part must be discarded as a crop part (cut-off part), resulting in casting with a low yield. Further, the value of the component influence length varies for each casting, and the casting lacks reliability.

On the other hand, by setting the deceleration time to 6 minutes or more, the area where the molten steel 2 exists in the slab 3 of the pre-charge is reduced, and the amount of the molten steel 2 mixed with the post-charge is inevitably reduced. The component influence length is always 0.7 m or 0.8 m, and the length is short and the variation is small, which is a very preferable situation.
However, it is disadvantageous from the viewpoint of productivity to slow down the pre-charge for a long time. Therefore, the inventor of the present application also studied from that viewpoint, and clarified that the deceleration start time should be about 20 to 10 minutes before the slide valve 6 is closed. It is very preferable to decelerate from 10 minutes in particular.

[Experiment 2 for obtaining casting conditions]
In turn, in this embodiment, 3 to 9 kg of exothermic powder 11 is introduced into one mold 5 and heat is generated on the surface of the molten metal. The amount of exothermic powder 11 introduced is obtained through the following experiment. It is what was done.
That is,
(i) Continuously casting different steel types by varying the amount of exothermic powder 11 to be charged, casting a plurality of slabs 3;
(ii) In the slab 3, a plurality of cross-sectional samples 13 are collected in order from the surface side of the slab narrow surface so as to include the front and rear charge connection portions (see FIG. 9).
(iii) Check how much noro (slag other than iron or exothermic powder 11 that did not melt) remains in the vicinity of the connection part included in each cross-section sample 13 (see FIG. 10).
(v) Summarize the relationship between the amount of exothermic powder input and the thickness of the generated slot (horizontal length) (see FIGS. 11 and 12).
I conducted an experiment.

In addition, since the mixing part including the connection part is a part (crop part) that is finally cut and discarded, it seems that noro may remain, but the part with noro has a pre-charge and a post-charge. It is a portion that is not securely connected, and the greater the thickness, the worse the connectivity, and in the worst case, it may lead to a leak of hot water. Therefore, such noro does not exist at all, or even if it exists, its thickness is desirably equal to or less than a predetermined value.
FIG. 9 shows how to cut the cross-section sample 13 for measuring the thickness. As shown in the figure, five cross-sectional samples 13 having a thickness of 50 mm and a slab drawing direction of 500 mm are cut out from the narrow surface side of the slab 3 toward the inner side so as to include the connecting portion. The lower part 400 mm of the cut sample corresponds to the pre-charge, and the upper part 100 mm corresponds to the post-charge.

FIG. 10 schematically shows a state of noro appearing in the cross-sectional sample 13. FIGS. 10 (a) and 10 (b) show a state in which skinning occurs at the connecting portion, and noro enters and remains on the lower surface side (front charge side). FIG.10 (c) has shown the situation where there is no hot_water | molten_metal skinning in a connection part and there is no slot. Although it is preferable that the state of (c) is satisfied on all the connection surfaces, even in the cases (a) and (b), the thickness of the groove may be equal to or less than a predetermined value.
Here, the thickness of the slot means the length of the slot shown in A, B, C and A ′, B ′ in FIGS. 10A and 10B in the horizontal direction (perpendicular to the longitudinal direction of the slab). is there.

FIGS. 11A and 11B summarize the relationship between the thickness obtained from the plurality of cross-sectional samples 13 and the amount of the heat generation powder 11 to be put into the mold 5. The horizontal axis indicates the distance from the surface of the slab narrow surface, and the first sample (section A) corresponds to 50 mm, and the fifth sample (section E) corresponds to 250 mm. The vertical axis represents the thickness of the slot, and is the total thickness of the slots in one cross-sectional sample.
FIG. 11A shows the result of the preliminary experiment, in which the sequence block 7 is not inserted into the connection portion between the precharge and the postcharge. When the exothermic powder 11 is not charged (● in the figure), the molten steel meniscus is covered with skin, and the situation where slag other than iron remains as noro clearly appears. The thickness of the groove is as large as about 150 mm in the first cross section sample 13 (cross section A) and about 60 mm in the fifth cross section sample 13 from the narrow surface of the slab. However, since 3 kg or more of the exothermic powder 11 is added, the molten steel temperature rises and the skinning can be suppressed, so that the thickness of the slot is slightly reduced. In particular, when 6 kg (▲ data) or 9 kg (× data) of the exothermic powder 11 is charged, it has been clarified that the thickness of the paste is substantially zero, that is, no paste is generated.

FIG. 11B shows a case where the sequence block 7 is inserted after the heat generation powder 11 is inserted in order to improve the connectivity between the pre-charge and the post-charge. In this case, when the heating powder 11 is 9 kg (x data), it has been clarified that a slight amount of noro occurs. However, since the molten steel temperature increases and the skinning can be suppressed by inserting the exothermic powder 11, it has been confirmed that there is no change in the situation where the thickness of the slot is reduced.
FIG. 12 shows the relationship between the average thickness and the input amount of the heat generation powder 11. The average furnace thickness is calculated based on the data shown in FIGS. 11A and 11B, and the average noro thickness = the sum of the average noro thicknesses of the cross-sectional samples / the number of cross-sectional samples (5).

As can be seen from FIG. 12, when 6 kg of exothermic powder 11 is charged into the mold 5, it is understood that no skinning occurs and no residue remains. This indicates that the connectivity between the pre-charge and the post-charge is very good. When the heating powder 11 is 3 kg, the average thickness is about 100 mm. On the other hand, when the heating powder 11 is 9 kg, the average thickness is about 60 mm. It is confirmed that the connectivity is better than the case.
Based on the results of this experiment, the connection rate defined as “Noro thickness / mold thickness × 100%” is calculated. The connection rate is 45.7% when 3 kg of exothermic powder is introduced, and the connection is established when 6 kg of exothermic powder is introduced. When the rate is 0.0% and the heat generating powder is 9 kg, the connection rate is 20.8%.

The present invention is not limited to the above embodiment .

It is a schematic diagram of a continuous casting apparatus. It is a figure which shows the procedure of the continuous casting method of different steel types. It is a flowchart which shows the procedure of the continuous casting method of different steel types. It is the figure which showed the change of the casting speed in the best embodiment, and the change of the tundish weight. It is the numerical data of FIG. It is a figure which shows the collection position of the cross-sectional sample for calculating | requiring deceleration time. It is the figure which showed the relationship between slab length and a component change rate. It is the figure which showed the relationship between deceleration time and component influence length. It is a figure which shows the collection position of the cross-sectional sample for grasping | ascertaining a roll-in state. It is a figure which shows Noro entrainment situation. It is a figure which shows the relationship between the distance from a slab narrow surface, and Noro thickness. It is a figure which shows the relationship between exothermic powder and average thickness. It is a figure which shows the composition of the slag produced by the exothermic powder.

Explanation of symbols

1 Continuous casting equipment 3 Slab (slab)
4 Tundish 5 Mold 6 Slide valve 7 Sequence block 8 Support roll 10 Immersion nozzle

Claims (2)

After different types of steel continuously using a slab continuous casting apparatus equipped with a mold for casting a slab having a thickness of 210 to 250 mm and a width of 800 to 1700 mm and a tundish for supplying molten steel to the mold. In the continuous casting method of different steel types that perform charge casting,
From 6 to 10 minutes before the supply of the precharge to the mold is stopped, the casting speed of the precharge is gradually reduced at a deceleration speed of 0.20 m / min or less per time, and the exothermic powder containing CaSi in the mold 3-9 kg is charged, and a plurality of sequence blocks are placed in the precharged molten steel pool after the exothermic powder is charged. The gap between the sequence blocks is “distance between sequence blocks / mold width ≦ 0. .30 ", and then, after-charge is injected into the mold, a continuous casting method of different steel types.   2. The continuous casting method of different steel types according to claim 1, wherein the end of the precharge deceleration operation is a time point when the precharge supply from the tundish to the mold is stopped.

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