CN1052929C - Method for starting continuous casting in continuous slab casting and method for setting a dummy bar prier to the start of casting of continuous slab casting - Google Patents

Abstract

A starting method for continuous casting of slabs, comprising the following steps: placing a dummy bar at a predetermined position in the center of the mold in the up-and-down direction; keeping the short-side side plate vertical, and adjusting the gap between it and the dummy bar to 1 -3mm; Fill the sealing material; Inject molten steel to form a solidified shell; Begin to pull the dummy bar downwards, when the molten steel between the formed solidified shell and the side plate no longer flows, turn the upper end of the short side plate outwards Move, taper in downward direction for continuous casting. The method can realize the purposes of easily pulling out the dummy bar and starting the dummy bar smoothly and smoothly.

Description

Starting method of slab continuous casting

The invention relates to a continuous casting starting method for continuous casting of slabs, which includes a method for setting dummy rods before starting casting of continuous casting of slabs.

Conventionally, in the continuous casting of slabs with variable width, the dummy bar is placed in the mold at the beginning of casting, and the continuous casting of slabs is started by the conventional variable width continuous casting device, and the following description is adopted. Methods.

Fig. 3(a) is a schematic plan view of a conventional variable-width mold for continuous casting of slabs, and Fig. 3(b) is a sectional view taken along line A-A of Fig. 2(a). In the figure, 1 is the long-side side plate of the mold, and 2 is the short-side side plate. On the one hand, the short-side side plate 2 is clamped by the long-side side plate 1, and at the same time, the short-side side plate 2 is moved to the width direction of the slab through the drive devices 3a, 3b installed on the outside as a group, so that the short side plate 2 The side plate 2 moves so that it can change and adjust the width dimension of the slab.

In this case, the distance between the long-side side plates 1 is usually constant, and if the thickness of the slab needs to be changed, another method is used, such as replacing the short-side side plates 2 .

Next, referring to Fig. 3(a)-(b) and Fig. 4(a)-(b), the sequence of the casting operation in conventional slab continuous casting using the mold 10 will be described.

First, in Fig. 4(a), when inserting the dummy bar 4 from below or above the mold 10 initially, the driving devices 3a, 3b should be operated to facilitate the insertion, and the position of the upper end of the short side plate 2 Set it up according to the set width (casting slab width + compensation for heat shrinkage) plus the margin. At this time, it should be enlarged to a position larger than the set width, and then place the short side plate 2 according to the set width. . Perhaps at first the short side side plate 2 is placed by the predetermined width, and then inserts the dummy bar 4 smaller than its width 20-60mm.

The inserted dummy bar 4, as shown in Fig. 4(b), is placed at a set position in the center of the up and down direction in the mold 10, generally at a position of 1/3-1/2 from the lower end of the mold. Simultaneously, the spacing of the lower end of the short-side side plate 2 should add a taper below it on the basis of the predetermined width of the lower end.

The reason for adding a taper to the bottom of the short side plate 2 is that the solidified shell formed in the mold will shrink greatly as it cools, especially in the width direction of the slab, so that the short side plate 2 and the solidified shell There is a gap between 6a, so considering the thermal shrinkage that usually occurs in a stable casting state, a considerable amount of taper is added in the downward direction to make the width of the lower end slightly narrower.

As for the long-side side plate 1, because the thickness of the cast slab is relatively small relative to its width, which is about 1/1, and the thermal shrinkage is also small, it is usually not tapered like the short-side side plate. Also, when inserting the dummy bar 4, there is no need to particularly consider the margin of thickness. The gap between the dummy bar 4 and the long-side side plate 1 should be maintained at about 2-5mm necessary for the movement of the dummy bar.

Like this, earlier dummy bar 4 is placed in mold 10, in the gap between mold 10 and dummy bar 4, in order not to make molten steel leak, filling has elastic heat-resistant sealing material 5.

Next, as shown in Fig. 4(c), molten steel 6 is poured into the mold from the tundish. In order to be able to pull out the dummy bar 4, the poured molten steel should be kept in the mold 10 for about 40 seconds. Meanwhile, the molten steel is cooled by the mold 10 to form a solidified shell 6a.

Dovetail tenon groove is made at the head of dummy bar 4, and the molten steel that flows in this dovetail tenon groove solidifies, and the combination of dummy bar 4 and casting is tight, and just can pull out casting with dummy bar.

Next, as shown in Fig. 4(d), the dummy rod 4 is drawn downwards, while the molten steel 5 is continuously poured in, during which the solidified shell 6a also grows up at the same time, forming a continuous casting casting.

However, when the casting start is unstable like this, the width of the head portion of the dummy bar 4 filled with the sealing material 5 and the initial start shell 6a is larger than the width of the lower part of the mold 10, and the dummy bar 4 must be removed from the mold 10. When the lower part is pulled out, due to the sliding between the dummy bar 4 and the shell 6a and the mold 10, a very large pulling force is required.

At this time, if the shell 6a is not fully grown, due to the sliding between the mold 10, the shell 6a will break, the so-called steel running phenomenon will occur, and the lower end of the mold 10 will be damaged. As a result, the production efficiency will be low, and the mold Reduced life expectancy and increased maintenance costs.

In response to this problem, in order to obtain the strength of the housing 6a that can withstand a large drawing force, it can be kept in the mold 10 for a sufficient time, or as shown in Figure 4 (b), such as the dummy rod in the mold 10 The top of 4 is filled with cooling material 11 to promote the formation and solidification of shell 6a. However, all of these lead to increases in casting preparation time and operating costs, and new problems such as difficulty in automation of casting operations arise.

Also, in this case, because the short-side side plate is opened up, the gap between the upper end of the dummy bar and the mold is relatively large, and the total of the two sides is 20-45mm, which makes it difficult to fill the sealing material. . This also has problems such as increasing the casting preparation time and affecting the automation of casting operations.

The present invention was developed in view of the above problems. It is an object of the present invention to provide a starting method for continuous casting of slabs which facilitates drawing of dummy rods and enables smooth starting of continuous casting.

The object of the present invention is accomplished by a start-up method of continuous casting of slabs, in the continuous casting in which the short side plates of the mold are clamped to the long side plates and the short side plates can be adjusted along the width direction of the slab In the continuous casting of slabs by the mold, it is characterized in that the dummy bar is placed at a predetermined position in the center of the mold in the vertical direction, and then the short-side side plate is kept vertical so that the gap between the dummy bar and the dummy bar is respectively Adjust it to 1-3mm, then fill the sealing material between the long-side side plate and short-side side plate and the dummy rod, then start pouring molten steel, keep the poured molten steel while cooling to form a solidified shell, and then start pulling Pull the dummy bar, pull the dummy bar downwards, and move the upper end of the short-side side plate outward when the molten steel no longer flows into the formed solidification shell and the front plate, and add it in the downward direction. Taper for continuous casting.

As described above, according to the starting method of continuous casting of the present invention, the short side plate is kept vertical, and the gap between it and the dummy rod is adjusted to 1-3mm to start continuous casting, so the formed solidified shell and There is no abnormal sliding force between the molds, and the drawing can be done with a small pulling force, so it can prevent the accident of running steel due to the cracking of the shell at the beginning of casting, improve production efficiency and the life of the mold, and reduce the The casting preparation time of the mold can save cooling materials, casting time and operating costs, and can also promote the automation of casting operations.

According to the dummy bar placement method of the present invention, the short side side plate is kept vertical, and the gap between the dummy bar is adjusted to 1-3 mm, and then the gap is filled with sealing material, so the filling of the sealing material becomes easy, like this When the dummy bar is installed for continuous casting, the same effect as above can be obtained.

The present invention will be further described below with reference to the accompanying drawings.

Fig. 1 is a schematic side sectional view showing an example of the steps of the casting starting method of the present invention, figure (a) is a figure in which a dummy bar 4 is inserted in a mold 10, and figure (b) is that the short-side side plate 2 is kept perpendicular to the dummy The intervals of the ingot rods are respectively adjusted to 1-3mm. Figure (c) is a figure that begins to pour molten steel into the mold 10 so that the surface of the molten steel rises to form a solidified shell 6a. Figure (d) is a figure in which the short side plate 2 The upper end moves outwards, facing the downward direction and adding taper for continuous casting;

Fig. 2 (a) is a side sectional schematic view showing the casting state after drawing the casting from the mold of the present invention under the situation that the taper starting timing is too late after the start of drawing, and is a sectional view of B-B of Fig. 2 (b), Fig. 2 (b) is the A-A direction sectional view of Fig. 2 (a);

Fig. 3(d) is a schematic plan view of a variable-width mold for continuous casting of slabs, and Fig. 3(b) is a sectional view taken along the direction A-A of Fig. 3(d);

Fig. 4 is a schematic side sectional view showing an example of the steps of the conventional continuous casting starting method, the figure (a) is a figure in which the dummy bar 4 is inserted into the mold 10, and the figure (b) is in the downward direction of the short side plate 2 Add the figure of taper, figure (c) is to start pouring molten steel into the mold 10, make the molten steel rise to form the figure of solidification shell 6a, figure (d) is pouring molten steel on the one hand, and on the other hand pulls the casting down through the dummy bar 4 Drawing for continuous casting.

Referring to Fig. 2(a) and (b) showing the foregoing variable width mold of the present invention, and Fig. 1(a)-(d) showing an example of the starting method of the present invention, the details will be described below.

First, as shown in Fig. 1(a), the distance between the short-side side plates 2 is adjusted to be wider than the width of the dummy bar 4, and the width of one side is at least 10 mm or more.

This is the case of a die for a flat and wide slab, and it is difficult to insert a dummy bar especially if the margin in the width direction is small. The margin of the distance between the short-side side plate 2 and the dummy bar 4 in the width direction is preferably about 25-45 mm on one side.

Next, as shown in Figure 1(b), insert the dummy bar 4 from the bottom of the mold 10, and place it at a predetermined position in the center of the mold in the vertical direction, for example, at a position of 1/3-1/2 from the lower end of the mold 10. .

Then keep the short-side side plate 2 vertical, and adjust the gap with the dummy bar 4 to 1-3 mm respectively, and then fill the gap between the long-side side plate and the short-side side plate 1, 2 and the dummy bar 4 with sealing material 5 . As previously mentioned, the gap between the dummy bar 4 and the long side plate 1 should be maintained at about 2-5mm.

Between the dummy bar 4 and each plate 1, 2, considering the prevention of molten steel leakage and the convenience of filling the sealing material in the future, of course the smaller the better, but for the smooth movement of the dummy bar 4, it is necessary to have about 1-3mm .

Also, the sealing material 5 used here is made of powder of refractory materials such as SiO ₂ , Al ₂ O ₃ , and CaO as main components, and is mixed with a heat-resistant adhesive of the silicone resin series to make it have a moderate Plastic and viscous heat-resistant sealing material (such as Glitter cc100...registered trademark).

As above, the setting of the dummy bar 4 is completed, and next, as shown in FIG. 1( c ), molten steel 6 is poured into the mold 10 from the tundish. The poured molten steel should be kept in the mold for 10-30 seconds so that the dummy bar 4 can be drawn, preferably about 15-25 seconds, during which the molten steel is cooled by the mold 10 along with the rising of the molten steel surface to form a solidification shell.

In this way, in the case of the present invention, the holding time may be shorter than conventional ones. This is because the initial stage is to start without taper, and the friction between the shell and the connected short side mold is small, so the strength of the shell can be weaker than before, so reducing the pulling force can reduce the force on the shell. force.

A pit 4a is formed on the head of the dummy bar 4, and molten steel also flows into the pit to solidify, so that the combination of the dummy bar 4 and the casting is tight, and the casting is easily drawn through the dummy bar.

Next, as shown in FIG. 1( d ), molten steel 6 is continuously poured in while drawing the dummy rod 4 downward. Now, for example, start to draw the dummy bar 4, when the molten steel no longer flows between the formed solidified shell 6a and the die plate 2 (for example, the steel type, bath temperature, casting width, casting speed ( 0.4m/min) in the case of 60 seconds after the start of drawing, or before and after the dummy rod passes through the lower end of the mold, preferably after passing), the action of adding taper starts, and finally the usual stable casting mentioned above should be considered The thermal shrinkage that takes place under the condition should be equivalent to it at the upper end portion (or upper end portion and lower end portion) of the short side plate 2, by the degree of about 1% of the full width (the interval) (that is, the taper of each short side 0.5% or so) expand to the left and right, and taper in the downward direction.

The so-called "when the molten steel no longer flows between the formed solidified shell 6a and the mold plate 2, the taper action starts and the taper is added" means that after the drawing starts, the following (1) and (2) work accidents Conditional taper is the action of giving taper when the formed solidified shell has the strength to prevent accidents (the formed solidified shell can follow the movement) when the taper is changed.

(1) After the drawing starts, if the taper is given too quickly (for example, the taper is added immediately after the drawing starts), molten steel flows into between the solidified shell 6a and the mold plate 2 at the upper end of the solidified shell 6a, and the shell may eventually be broken. Therefore, when the casting has a certain degree of drawing speed, the action of giving taper should be started to give it a taper.

(2) Secondly, when it is too slow, as shown in Figure 2 (a), (b) (Figure 2 (a) is to indicate that after the drawing starts, the taper begins to be given after the casting is started to be drawn at the mold of the present invention when it is too late. The casting state sectional sketch is the B-B sectional view of Fig. 2 (b), and Fig. 2 (b) is the A-A sectional view of Fig. 2 (a), the solidified shell 6a solidifies and shrinks, and the gap 7 between the solidified shell 6a and the mold plate 2 becomes large, resulting in poor growth of the shell (because the thickness of the solidified shell is thin), so in the air gap 7, the solidified shell 6a bulges 8 due to the pressure of molten steel, or as soon as the solidified shell 6a leaves the lower end of the mold, the solidified shell 6a due to the pressure of molten steel The protrusion 8a occurs, and therefore the solidified shell 6a is broken, and molten steel may leak therefrom.

Therefore, after the drawing starts, when the drawing speed of the casting is increased, if the taper is given smoothly, the solidified shell will be formed.

During this period, the solidified shell 6a also grows up simultaneously, and the dummy bar is pulled out by the mold 10, and the continuous casting operation is continued to form a casting.

Keep the short-side side plate vertical like this, adjust the gap between the short-side side plate 2 and the dummy bar 4 to be 1-3mm, and then arrange the dummy bar, so it becomes easy to fill the sealing material 5, which can reduce the preparation time for casting and promote The filling operation of the sealing material is automated.

Keep the gap of 1-3mm between the short side plate 2 like this. When the dummy bar 4 is placed for continuous pouring, when the dummy bar 4 is pulled out by the bottom of the mold 10, the dummy bar 4, the shell 6a and the mold 10 There is no abnormal sliding force between them, and it can be extracted with a small pulling force.

Therefore, it is possible to prevent steel running due to the rupture of the shell 6a during drawing, reduce the casting preparation time, improve production efficiency and mold life, shorten the holding time in the mold 10, save cooling materials, and save casting time and mold life. Reduce operating costs and promote the automation of casting operations.

Hereinafter, examples of the present invention will be described.

At a temperature of 1560°C, molten steel composed of C0.04wt%, Mn0.25wt%, S0.010wt%, P0.015wt%, Sol.Al0.050wt%, iron and unavoidable impurities is poured into the mold. Casting slabs (castings) with a width of 1920mm and a thickness of 250mm were manufactured with a drawing speed of 0.4m/min at the initial stage and normally 1.6m/min.

In the production of the cast slab (casting) described above, the procedure at the start of the cast slab width (cold conversion value) = 1,900 mm is described as follows.

(1) Set the width (interval) of the side plate on the short side of the mold to 1,967mm, which is 50mm larger than the width of the dummy bar (1.917mm).

(2) Insert the dummy bar into the mold, and stop at a predetermined position (the position where the mold is 900 mm long and 500 mm from the upper end of the mold).

(3) Keep the short-side side plate vertical, so that the gap between the dummy bar and the short-side side plate is 1.5mm, and the distance is moved to 1920mm.

(4) Fill the sealing material between the dummy rod and the mold.

(5) Set the cooling material, for example, combine steel sheets, iron plates or iron rods by welding.

(6) Start pouring molten steel from the tundish to the mold.

(7) After the molten steel is poured, in order to ensure the minimum holding time necessary to form a solid solidified shell, the level of the molten steel rises, and when the level reaches a predetermined position 100-150 mm from the upper end of the mold, the dummy bar is drawn.

(8) After starting to draw the dummy rod, the short-side side plate is moved by the width-variable device, so that the upper end is enlarged to the left and right, according to the predetermined taper ratio of the short-side side plate in the downward direction (that is, the casting width )set up.

In addition, as shown in Figure 1 (d), the length of the mold is: Ldo, the distance between the lower ends of the short side plates is Ld1, and when the distance between the upper ends of the short side plates is Ld2, the taper ratio T _A (%/ m) is defined by the following formula (1). $T_A(\%/m)=\frac{L_{d2}\left(\mathrm{mm}\right)-L_{d1}\left(\mathrm{mm}\right)}{L_{d1}\left(\mathrm{mm}\right)\×L_{d0}\left(m\right)}\×100----\left(1\right)$

In the formula:

T _A : Taper ratio (%/m)

Ld0: Die length (m) of the side plate on the short side.

Ld1: Die lower end width (interval) (mm) of the short-side side plate

Ld2: Die upper end width (interval) (mm) of the short-side side plate

In the above-mentioned process (8), a solid solidified shell is formed, and when the molten steel no longer flows into between the solidified shell 6a and the short side plate 2 (for example, after 60 seconds from the beginning of drawing or after the dummy bar passes through the lower end of the mold), for example The mold length Ld0 of the short-side side plate is 0.9m, and the width Ld1 of the lower end of the mold of the short-side side plate is kept at 1920mm. The mold upper end width Ld2 of the side plate was set to 1937 mm (taper ratio T _A =0.98%/m).

According to the results of the above (1)-(8) steps, as shown in Table 1, the preparation time is shortened, the life of the mold is prolonged, and accidents at the beginning of casting are reduced. Compared with the previous method, the superiority can be confirmed. of.

In the present invention, for example, the range of the ideal taper ratio (%/m) is expressed by the following formula (2) under the steel types and casting speeds described in the examples.

0.5%/m≤T _A ≤2%/m...(2)

The effects of the present invention are summarized in Table (2).

Table 1 distinguish Casting according to the example of the present invention begins The conventional casting starts project When the dummy bar is inserted (A) When drawing starts (B) After drawing starts (C) When the dummy bar is inserted When drawing starts After drawing starts Width at the upper end of the mold Taper ratio of the width at the lower end of the mold (%/m) Width of the dummy bar 1.9671.96701.917 1.9201.92001.917 1.9371.9200.981.917 1.9371.9200.981.900 1.9371.9200.981.900 1.9371.9200.981.900 evaluate Preparation time 2 minutes 10 points Die life 500 refills 200 refills accident at the beginning 0 times/year 10 times/year

Preparation time = inserting the dummy rod into the mold. Finished at the desired location. The sealing operation is completed (including the placement of cooling materials)

Table 2 project Example of the invention History Effect 1 Reduced holding time at the start of casting (steel pouring starts, dummy rod drawing starts) 15 seconds 30-90 seconds (1) Improve production capacity 2 Shortened preparation time (sealing work time) [construction by operator] 3 points 10 points (1) Improve production capacity (2) Reduce workload Shortened preparation time (sealing work time) [construction by robots] 2 minutes 10 points (1) Increase production capacity (2) Reduce investment 3 Reduce sealing material and cooling material 2,000 yen/time 4,800 yen/time (1) Reduce costs 4 Prolong life of short-side electrodes (nickel-plated specification) 500 loading 200 loading (1) Reduce costs 5 Reduce sound output at the start of casting (per 1 slab caster) 0 times/year 10 times/year (1) Increase production capacity (5) Reduce maintenance costs

In the above table (2), the effect of the starting method of the present invention is the shortening of the holding time during starting, the shortening of the preparation time, the reduction of sealing materials and cooling materials, the prolongation of the life of the short side plate, and the The effect is remarkable, such as the reduction of accidents at the start of casting.

In addition, in the above table (2), the effect obtained by the dummy bar installation method of the present invention is the shortening of the preparation time, the reduction of sealing materials and cooling materials, the reduction of accidents at the beginning of casting, etc., the effect significantly.

Claims (19)

1. the starting method of a slab direct casting, be held in the long side plate at short brink plate holder with mould, and use the minor face side plate in the slab direct casting that the continuous casting mold that the fabric width direction of slab can be adjusted carries out, it is characterized in that: the institute's allocation that dummy bar is placed in the above-below direction central portion in the mould; Then the minor face side plate is kept vertical, make the gap between itself and the dummy bar be adjusted into 1-3mm respectively; Underfill sealants between long side plate and minor face side plate and dummy bar then; Begin to inject molten steel thereupon, the molten steel that the one side maintenance pours into, the one side cooling forms solidified shell; Then begin the drawing dummy bar, with the drawing downwards of dummy bar one side, one side moves the upper end outward direction of minor face side plate when molten steel no longer flows between formation solidified shell and the preceding note plate, adds that in downward direction tapering carries out direct casting.

2. according to the method described in the claim 1, it is characterized in that: the upper end and the bottom outward direction of short slab side plate are moved, give tapering in downward direction.

3. according to the method described in claim 1 or 2, it is characterized in that: when the minor face side plate being kept vertically make gap between itself and the dummy bar to be adjusted into 1-3mm respectively, the gap between dummy bar and the long side plate is adjusted into 2-5mm.

4. method according to claim 1 is characterized in that: from beginning to pour into the retention time of molten steel when the casting of beginning drawing dummy bar begins is 10-30 second.

5. according to the method described in the claim 4, it is characterized in that: from beginning to pour into the retention time of molten steel when the casting of beginning drawing dummy bar begins is about 15 seconds.

6. according to the method described in the claim 1, it is characterized in that: beginning drawing dummy bar, when advanced downwards in about 1/5 position from the lower end of mould in the upper end of dummy bar, the upper end of minor face side plate begins downward direction moved, and gives tapering in downward direction and carries out direct casting.

7. according to the method described in the claim 6, it is characterized in that: the upper end of minor face side plate and bottom begin outward direction moves, and gives tapering in downward direction.

8. according to the method described in the claim 6, it is characterized in that: beginning drawing dummy bar, the upper end of dummy bar is by behind the lower end of mould, and the upper end of minor face side plate begins outward direction moves, and gives tapering in downward direction and carries out direct casting.

9. according to the method described in the claim 1, it is characterized in that: beginning drawing dummy bar made the upper end outward direction of minor face side plate move beginning after 30 seconds, gave tapering in downward direction and carried out direct casting.

10. according to the method described in the claim 9, it is characterized in that, make the upper end of minor face side plate and bottom outward direction begin to move, give tapering in downward direction.

11. the method according to described in the claim 9 is characterized in that: after the drawing dummy bar begins 60 seconds, the upper end outward direction of minor face side plate is moved, give tapering in downward direction and carry out direct casting.

12. according to the method described in the claim 1, it is characterized in that: consider that foundry goods is stablizing the thermal contraction that takes place under the casting state usually, in the upper end of minor face side plate, with a great deal of of foundry goods thermal contraction, by about about 1%/m of its overall with, give tapering in downward direction.

13. the method according to described in the claim 1 is characterized in that:

After dummy bar begins drawing, at the tapering ratio T of following formula (1) expression _ACan satisfy under the influence of following formula (2), on downward direction, give tapering with the upper end of the minor face side plate of mould and carry out direct casting: $T_A(\%/m)=\frac{L_{d2}\left(\mathrm{mm}\right)-L_{d1}\left(\mathrm{mm}\right)}{L_{d1}\left(\mathrm{mm}\right)\×L_{d0}\left(m\right)}\×100----\left(1\right)$

In the formula:

T _A: tapering ratio (%/m)

Ld0: the die length of minor face side plate (m)

Ld1: the mould bottom width (at interval) of minor face side plate (mm)

Ld2: the mould upper end width (at interval) of minor face side plate (mm)

0.5％/m≤T _A≤2.0％/m…(2)

14. the method according to described in the claim 1 is characterized in that:

It is position from the lower end 1/3-1/2 of mould that dummy bar is placed in above-below direction central portion institute allocation in the mould.

15. the method according to described in the claim 1 is characterized in that: the interval of minor face side plate is adjusted into than after more than the one-sided wide at least 10mm of the fabric width of dummy bar, dummy bar is placed in institute's allocation of the above-below direction central portion in the mould.

16. the method according to described in the claim 15 is characterized in that: the interval of minor face side plate is adjusted into than behind the one-sided wide 25-45mm of the fabric width of dummy bar, with dummy bar be placed in above-below direction central portion in the mould fixed position.

17. the starting method of a slab direct casting, be held in the long side plate at short brink plate holder with mould, and use the minor face side plate in the slab direct casting that the continuous casting mold that the fabric width direction of slab can be adjusted carries out, it is characterized in that: the interval with the minor face side plate is adjusted into than more than the one-sided wide at least 10mm of the fabric width of dummy bar earlier, then insert dummy bar from the below or the top of mould, be placed in above-below direction central portion in the mould fixed position; Secondly vertically, the gap with dummy bar is adjusted into 1-3mm respectively with the maintenance of minor face side plate; Simultaneously, the gap with dummy bar and long side plate is adjusted into 2-5mm respectively; Underfill sealants in the gap of long side plate and minor face side plate and dummy bar then; Begin to pour into molten steel then, the molten steel that one side keeps 10-30 to pour into second, the one side cooling forms solidified shell; Then begin the drawing dummy bar, when advance downwards in about 1/5 position from the lower end of mould in the upper end of dummy bar, the upper end of minor face side plate begins outward direction and moves, with the drawing downwards of dummy bar one side, one side moves the upper end outward direction of minor face side plate, at the tapering ratio T of following formula (1) expression _ASatisfy under the form of following formula (2), the upper end of the minor face side plate of mould is given tapering in downward direction and is carried out direct casting: $T_A(\%/m)=\frac{L_{d2}\left(\mathrm{mm}\right)-L_{d1}\left(\mathrm{mm}\right)}{L_{d1}\left(\mathrm{mm}\right)\×L_{d0}\left(m\right)}\×100----\left(1\right)$ In the formula:

T _A: tapering ratio (%/m)

Ld0: the die length of minor face side plate (m)

Ld1: the mould bottom width (at interval) of minor face side plate (mm)

Ld2: the mould upper end width (at interval) of minor face side plate (mm)

0.5％/m≤T _A≤2.0％/m…(2)

18. the starting method of a slab direct casting, be held in the long side plate at short brink plate holder with mould, and use the minor face side plate in the slab direct casting that the continuous casting mold that the fabric width direction of slab can be adjusted carries out, it is characterized in that: the interval with the minor face side plate is adjusted into than more than the one-sided wide at least 10mm of the fabric width of dummy bar earlier, then insert dummy bar from the below or the top of mould, be placed in the desired location of the above-below direction central portion in the mould, secondly the minor face side plate is kept vertical, be adjusted into 1-3mm respectively with the gap of dummy bar, simultaneously, the gap of the long side plate of dummy bar aligned respectively be 2-5mm, underfill sealants in the gap of long side plate and minor face side plate and dummy bar then, begin to inject molten steel then, the molten steel that one side keeps 10-30 to pour into second, the one side cooling forms solidified shell, then begin the drawing dummy bar, after 60 seconds, the upper end of minor face side plate begins outward direction and moves, one side is the drawing dummy bar downwards, the outward direction in the upper end of minor face side plate moves, at the tapering ratio T of following formula (1) expression _ASatisfy under the form of following formula (2), the upper end of the minor face side plate of mould is given tapering in downward direction and is carried out direct casting: $T_A(\%/m)=\frac{L_{d2}\left(\mathrm{mm}\right)-L_{d1}\left(\mathrm{mm}\right)}{L_{d1}\left(\mathrm{mm}\right)\×L_{d0}\left(m\right)}\×100----\left(1\right)$

In the formula:

T _A: tapering ratio (%/m)

Ld0: the die length of minor face side plate (m)

Ld1: the mould bottom width (at interval) of minor face side plate (mm)

Ld2: the mould upper end width (at interval) of minor face side plate (mm)

0.5％/m≤T _A≤2.0％/m…(2)

19. the method according to described in the claim 18 is characterized in that, the upper end of minor face side plate and bottom begin downward direction moves, and gives tapering in downward direction.

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