JP2950127B2 - Method of drawing slab in early stage of continuous casting and dummy bar head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a casting method in a continuous casting process, in which the drawing speed reaches a steady casting speed from the initial drawing after the start of molten metal injection, and further, the dummy bar is separated from the slab at the initial casting. The present invention relates to a one-side drawing method and a dummy bar head used in the method.

[0002]

2. Description of the Related Art In continuous casting of molten metal, for example, steel, molten steel conveyed by a ladle or the like is temporarily stored in a tundish, then cast into a mold through an immersion nozzle, and is primarily cooled by the mold and subsequently supported by a roll. The molten steel is solidified by secondary cooling in the guide device (roller apron), and the flow rate of molten steel is controlled by a flow control device such as a sliding nozzle provided on the tundish so that the crater end (unsolidified tip) maintains a predetermined position. The slab is drawn out at a steady speed while performing.

[0003] At the start of the continuous casting, a dummy bar head is inserted into the lower portion of the bottomless mold to form a temporary bottom, and molten steel is cast into such a mold from an immersion nozzle, and a molten metal surface in the mold is formed. Reaches a preset control level, when a solidified shell of a predetermined thickness is formed in the cast molten steel and there is no fear of breakout, the dummy bar starts to be pulled out, and thereafter, the drawing speed (casting speed) is reduced. To a steady casting state.

As a method of controlling the slab drawing speed at the start of casting, a conventional method has been disclosed in, for example, Japanese Patent Publication No. 60-39.
There is a control method described in Japanese Patent Publication No. 00. In this control method, as shown in FIG. 13 (a), when a certain time has elapsed from the start of the molten metal injection and the slab drawing start time at which the molten metal level in the mold reaches the control level, the slab drawing speed is increased stepwise. As a result, a steady casting speed is reached (conventional method I).

Further, as shown in FIG. 13 (b), the first acceleration α ₁ (the minimum speed at which the initial nozzle clogging does not occur when a predetermined time elapses from the start of casting of the slab after the start of molten metal injection) at the start of molten metal injection. Acceleration) from the initial speed zero,
Then the second acceleration when cast strip withdrawing speed reaches V ₁ alpha
₂ (minimum mold residence time at the time of securing the accelerations reach steady cast strip withdrawing speed) speed-up to the dummy bar of the vertices are tighten lead to steady casting speed V _c to reach the mold bottom ( Conventional method II).

The dummy bar used in the initial stage of the casting employs a top loading method in which charging is performed from above the mold or a bottom charging method in which charging is performed from a subsequent stage of the pinch roll. Conventionally, the dummy bar head inserted into the mold has a hook-shaped concave groove into which molten steel enters, and is integrated with the solidified cast piece so that the dummy bar and the cast piece do not come off on the way, and at a predetermined position, It is common to make it easy to remove.

[0007]

However, in the control method according to the conventional method I as described above, the level of the molten steel in the mold fluctuates up and down due to the stepwise change in the drawing speed.
The coating powder on the hot water surface is involved. The surface properties of the slab top deteriorate. Since the throughput of molten steel at the immersion nozzle is small in a low drawing speed range, the flow of molten steel is suppressed, the temperature of molten steel in the mold is low, and the floating of inclusions is hindered. There are problems such as.

On the other hand, in the control method according to the conventional method II, although the vertical fluctuation of the molten metal level in the mold can be suppressed, the steady pouring speed is reached when the dummy bar head, that is, the lower end (top) of the slab passes the lower end of the mold. For,
Seal leakage between the dummy bar head and the inner wall surface of the mold and breakout occur. There are problems such as.

Further, in the structure of the conventional dummy bar head, if the pulling speed is increased at a relatively high acceleration in the initial stage of the pulling, the dummy bar head and the slab separate from each other in the roller apron, which causes operational troubles. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to improve the surface quality and internal quality of a slab in the early stage of casting while maintaining the quality of a dummy bar head and an inner wall surface of a mold. A method of drawing a slab at the beginning of casting, which can prevent seal leakage and breakout between the slab and the separation of the dummy bar and the slab at the start of slab drawing and can be easily separated and taken out at a predetermined position. And its dummy bar head.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems (1) to (4), the present invention provides a method in which the drawing speed reaches a steady casting speed from the start of molten metal injection, and further, the dummy bar head is cut from the slab. In the early stage of casting until release, control and operation are performed by combining the following means.

(A) The slab drawing speed is increased linearly so that the level of the molten metal in the mold does not fluctuate up and down.

(B) The slab withdrawing speed is maintained at a constant speed from the start of injecting the molten metal into the mold to the start of slab drawing, and from the start of slab drawing until the slab top passes through the lower end of the mold.

(C) In order to increase the temperature of the molten steel in the mold, the acceleration for increasing the drawing speed to the steady pouring speed is increased to a certain value or more.

(D) In order to raise the temperature of the molten steel in the mold, a heat-generating powder is used as a powder for covering the molten metal surface used in the start of drawing.

(E) When the slab withdrawal speed is increased at a constant value or more after the tip of the slab passes through the lower end of the mold, the slab does not separate from the dummy bar head due to the pull-out resistance generated in the roller apron and the slab. Thus, when the dummy bar reaches a predetermined position, the dummy bar head can be easily separated from the slab.

In the first method of drawing a slab at the start of casting according to the present invention, the slab is drawn from the start of pouring into the mold at the start of casting in continuous casting until the casting speed reaches a steady casting speed, as shown in FIG. as such, the molten metal injection start after a certain period of time to the cast strip withdrawing start time T ₀ which mold molten steel surface has reached the control level, the first casting speed V of the cast strip withdrawing speed from the initial speed zero
Speed up to ₁ . Then, after holding the first casting speed V ₁ given time, linearly temperature in the vicinity of the time T ₁ in which the dummy bar head is passed through the mold bottom in 0.6 m / min ² or more <br/> constant acceleration a Hayashi, occupies lead to steady-state casting speed V _c.

Here, the acceleration a is (V _c -V ₁ ) / (T
₂₋ T ₁ ) (T ₂ : time point at which the steady-state speed _Vc is reached), and is increased to a certain value or more. These accelerations and the like differ depending on the type of steel, the casting speed, and the like. For example, when the steady casting speed is 0.8 m / min, the first casting speed V ₁ ≦ 0.25
m / min and acceleration a ≧ 0.6 m / min ² .

In the second method of drawing a slab at the start of casting according to the present invention, as shown in FIG. 5, the slab is drawn from the start of pouring into the mold at the start of casting in continuous casting until the casting speed reaches a steady casting speed. as such, the molten metal injection start after a certain period of time to the cast strip withdrawing start time T ₀ which mold molten steel surface has reached the control level, the first casting speed V of the cast strip withdrawing speed from the initial speed zero
Speed up to ₁ . Then, after holding the first casting speed V ₁ given time, linearly temperature in the vicinity of the time T ₁ in which the dummy bar head is passed through the mold bottom in 0.6 m / min ² or more <br/> constant acceleration a Hayashi, occupies lead to steady-state casting speed V _c. Further, the exothermic powder is used as the powder for covering the molten metal surface in the mold from the start of the molten metal injection until the steady pouring speed is reached. After reaching the steady pouring speed, it is preferable to use a normal powder used in a steady state.

After reaching the steady pouring speed, it is preferable to use the usual powder used in the steady state.

In the third method of drawing a slab at the start of casting according to the present invention, as shown in FIG. 11, the slab is drawn from the start of pouring into the mold at the start of casting in continuous casting until the dummy bar is separated from the slab. using the dummy bar head having an arc hook-shaped groove cutting into the curve direction of the casting line to a cast slab connecting portion, the cast strip withdrawing start time T ₀ has elapsed molten metal injection start to a predetermined time as shown in FIG. 1 , the temperature of the cast strip withdrawing speed from the initial speed zero to the first casting speed V ₁ Hayashi, after holding the first casting speed V ₁ given time, in the vicinity of the time T ₁ in which the dummy bar head is passed through the mold bottom
In 0.6 m / min ² or more constant acceleration a linearly rising Hayashi, occupies lead to steady casting speed V _c. If necessary, as shown in FIG. 5, a heat-generating powder is used as the powder for covering the molten metal surface in the mold from the start of the molten metal injection until the steady pouring speed is reached. Further, when removing the dummy bar, the dummy bar is transferred to the dummy bar table at a predetermined position after the roller apron, and when the tip end of the slab reaches a fixed position, the dummy bar table is raised and the dummy bar is pulled out obliquely.

The dummy bar is placed in the mold at the start of casting and is provided with a groove connected to the solidified shell of the molten metal, as shown in FIG.
The concave grooves are arc-shaped hook-shaped grooves that bite in the direction of the center of curvature of the casting line, and the radii Ri, Ro of the circular arc surfaces of the concave grooves.
Where Ri = t + α, Ro = t + β, t ≦ α ≦ β, α ≦ β
≦ 1.5t ( Ri: radius of the inner arc surface of the concave groove, Ro: concave
The radius of the outer arc surface of the groove, t: slab thickness).

[0023]

In the above configuration, the first casting speed V ₁
Is held for a certain time (T ₁ −T ₀ ), and the first casting speed V ₁ is held until immediately before the dummy bar head passes the lower end of the mold, whereby a solidified shell having a sufficient thickness is formed, and the dummy bar head is formed. The seal leakage between the mold and the wall of the mold is prevented, and as shown in FIG. 2, a decrease in the temperature of the molten metal in the mold is suppressed, and the occurrence of breakout or the like due to uneven solidification is prevented.

Furthermore, since the cooling of the tip of the slab at the joint between the slab and the dummy bar head is completed, the tip of the slab cooled by the concave groove of the dummy bar head is extended by the pulling force of the dummy bar. Is prevented.

By increasing the slab drawing speed from V ₁ to V _c at a constant acceleration a, the temperature of molten steel in the mold rises as shown in FIG. To prevent the deformation of the slab shape due to the overcooling of the slab and to prevent the surface defects of the slab top due to the overcooling (FIG.
reference). Further, as the throughput of molten steel at the immersion nozzle is increased, the temperature of molten steel in the mold is continuously increased, and the floating of inclusions and the formation of powder in the meniscus are promoted, so that the internal quality can be improved ( (See FIG. 3).

By using the exothermic powder from the start of the molten metal injection until the steady casting speed is reached, the heat removal from the meniscus of the molten steel in the mold during the period from the start of the molten metal injection to the steady casting speed is reduced. As shown, the temperature of the entire molten steel in the mold is prevented from lowering. Incidentally, the range of use of the heat generating powder, as shown in FIG. 6, also on an enlarged scale in T ₃ time points after reaching a steady casting speed, improvement of the temperature difference hardly be until T _2.

The radius t of the dummy bar head is in the shape of an arc hook.
+ Α, t + β increases the contact surface area between the tip of the slab and the dummy bar head and approaches an angle perpendicular to the drawing direction, and the slab and the dummy bar are combined with complete cooling of the tip of the slab. Are firmly connected. Thereby, even if the dummy bar is pulled out at a relatively high acceleration, it is possible to prevent the slab and the dummy bar from separating in the roller apron by overcoming the frictional resistance generated between the slab and the roll. Further, at a predetermined position of the exit of the pinch roll, the dummy bar head can be easily detached from the cast piece by simply raising the dummy bar upward, and can be easily lifted obliquely.

As shown in FIG. 12, when α> β, the dummy bar often does not separate from the slab at the dummy bar release position, so that α ≦ β, and when β> 1.5t, the dummy bar is cast in the roller apron. Since there are many accidents of detachment from one piece, β ≦ 1.5t is set.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 10 shows a general curved-type continuous casting facility in which molten steel is cast into a mold 1 from a tundish 2 through a sliding nozzle device 3 and an immersion nozzle 4, and is primarily cooled by the mold 1. After that,
A slab that has been secondarily cooled by a cooling water spray or the like by a roller apron 5 serving as a roll supporting and guiding device is pulled out by a pinch roll 6, and cut into a predetermined length by a traveling cutting device (not shown). The surface of the molten metal in the mold is covered with powder 7 to prevent quenching of the surface of the slab and trap inclusions.

Dummy bar 10 used at the start of casting
Is a flexible member in which unit blocks are generally connected by pin bonding, and is an upper part of the mold 1 (top loading type).
Alternatively, the dummy bar head 1 is loaded from the back of the pinch roll 5 (bottom loading method) or the like and located at the upper end thereof.
1 is disposed in the lower part of the mold 1. After the start of casting, it is taken out from the middle of the roller apron 5 or from the latter stage of the pinch roll 6.

In the above configuration, in the present invention, the control and operation as shown in FIG. 1 or FIG. 5 are performed at the start of casting, and the dummy bar head 11 as shown in FIG.
, The dummy bar 10 is taken out obliquely upward from the rear stage of the pinch roll 6.

The dummy bar head 11 is shown in FIGS.
As shown in FIG. 5, an inclined surface 12 and an arc-shaped hook-shaped groove 13 are formed on the upper part. The inclined surface 12 is formed on the upper surface of the connection with the slab S with a downward slope toward the outside of the center direction A of the curvature of the line (the slab thickness direction) in a state where the inclined surface 12 is located in the mold 1. Reference numeral 13 is formed so as to extend in the direction A from the outside in the direction A of the inclined surface 12 and penetrate to the center.

The concave groove 13 is formed so that the radius Ri of the inner surface in the direction A is t + α and the radius Ro of the outer surface is t + β.
Also, the center Oi of the inner surface radius Ri is near the upper end inside the curve,
The center Oo of the outer surface radius Ro is shifted to the outside.

By making the radii Ri and Ro larger than the thickness t of the slab S, the contact area with the slab is increased, and the angle is made closer to the angle perpendicular to the drawing direction, so that the slab and the dummy bar separate even with a large drawing force. Don't do it. Note that if this radius is too large, the distance becomes far from the angle perpendicular to the drawing direction, so that β ≦ 1.5t. Further, by setting α ≦ β, it can be easily separated after the drawing.

The outer surface of the concave groove 13 in the direction A is opened to form an opening 13a, and the upper part of the inner surface is formed as an inclined surface 13b inclined toward the upper part so that the groove 13 can be easily separated after being pulled out. In the slab width direction, the distance from the center is r,
The strength of the dummy bar head 11 is ensured. The upper end of the dummy bar 11 having such a structure is provided with a sealing member 14.
To prevent the molten steel from leaking.

Next, regarding the loading method of the dummy bar 6,
In the dummy bar top charging type CC, a machine mainly equipped with a drive roll after the second of the roller apron 4 is mainly used. However, since the number of drive rolls is about two to three, a large acceleration like the pull-out control of the present invention is required. Is required, the force for pulling out the slab and the dummy bar is insufficient, so that the slab cannot be pulled out. Therefore, in the present invention, a bottom loading method using a pinch roll drive is adopted.

As shown in FIG. 10, the dummy bar table 15 is placed on the pinch roll horizontal zone 16 at the subsequent stage of the pinch roll 6, and its rear end is pivotally mounted. From the position located at the exit of the vehicle to the horizontal position. Further, the dummy bar 10 on the dummy bar table 15 is loaded and moved by a driving device including a winch and a winch wire (not shown).

At the time of loading, the dummy bar table 15
Is tilted from the horizontal state, the dummy bar 10 is fed into the pinch roll 6, and the pinch roll 6 is reversely driven by the reverse rotation drive. At this time, a position sensor 17 of a photoelectric tube type or the like installed at a position where the dummy bar is detached from the pinch roll 6 exit.
, The tip of the dummy bar is detected, the moving distance is detected based on the number of rotations of the pinch roll 6, and the dummy bar insertion length with the position of the sensor 17 as the origin is measured.

The dummy bar insertion length is determined in advance by the control device C
When it matches the numerical value stored in the PU, it is determined that the charging is completed. The dummy bar head 11 is located at a predetermined position in the mold 1, and in this state, the pinch roll 6 is driven to rotate forward to start pulling. The dummy bar 11 is transferred onto the dummy bar table 15 through the inside of the roller apron 5.

At this time, the amount of movement of the dummy bar is measured by detecting the number of rotations of the drive pinch roll 6, and when the amount of movement of the dummy bar coincides with the amount of movement of the pinch roll 6 in the reverse rotation,
The dummy bar table 15 is raised, and the dummy bar 10 is pulled obliquely upward. The slab is continuously pulled out by the pinch roll 6 as it is.

Example 1 Using the steel shown in Table 1, and under the conditions shown in Table 2, after a certain period of time had elapsed since the start of the injection of the molten metal, the level of the molten metal in the mold 1 reached the control level, as shown in FIG. the cast strip withdrawing beginning T _0, to speed-up the cast strip withdrawing speed from the initial speed zero to the first casting speed V _1. Next, the first casting speed V ₁
After holding for a predetermined time, the dummy bar head 10 is linearly rising with a constant acceleration a at the time T ₁ that passes through the mold 1 lower Hayashi were controlled occupied lead to steady casting speed V _c.

[0042]

[Table 1]

[0043]

[Table 2]

FIG. 2 shows the temperature difference between the tundish and the mold from the start of drawing to the steady part, and FIG. 3 shows the number of inclusions in the slab from the tip of the slab to the steady part. 2 and 3
Thus, the temperature in the mold is clearly higher than that of the conventional method, and it is clear that the method of the present invention is effective even for inclusions in the slab.

FIG. 4 shows slab surface flaws (pinhole flaws) at the tip of the slab. Even with respect to surface flaws, there is a clear difference between the conventional method and the method of the present invention, and the effect of improving the surface quality is apparent.

Example 2 Using the same steel as shown in Table 1 as in Example 1, and under the conditions shown in Table 3, as shown in FIG. 5, as shown in FIG. _0, to speed-up the cast strip withdrawing speed from the initial speed zero to the first casting speed V _1. Then, after holding the first casting speed V ₁ given time, linearly rising Hayashi constant acceleration a at the time T ₁ in which the dummy bar head 10 passes through the mold 1 lower, arrives to a steady casting speed V _c Exothermic powder was used as the powder 7 for coating the molten metal surface in the mold from the start of the molten metal injection until the steady casting speed was reached.

[0047]

[Table 3]

FIG. 7 shows the temperature difference between the tundish and the mold from the start of drawing to the steady part, and FIG. 8 shows the number of inclusions in the slab from the tip of the slab to the steady part. 7 and 8, the temperature in the mold is clearly higher than that of the conventional method, and it is clear that the method of the present invention is also effective for inclusions in the slab.

[0049] Incidentally, FIG. 6 shows a relationship of the heating powder used ranges and tundish-mold between the temperature difference, the improvement of the temperature difference even to expand the use range of T ₂ to T ₃ is not observed Was.

FIG. 9 shows the slab surface flaws at the tip of the slab. Even with respect to surface flaws, there is a clear difference between the conventional method and the method of the present invention, and the effect of improving the surface quality is apparent.

Further, in this embodiment, the use of the heat generating powder makes it possible to improve the temperature difference between the tundish and the mold, the number of inclusions in the slab, and the surface swarf of the slab as compared with the first embodiment. Recognize.

[Embodiment 3] The same steel as shown in Table 1 was used under the conditions shown in Table 4 and the control was performed in the same manner as in Embodiment 1, and a dummy bar head 11 as shown in FIG. 11 was used. When removing the dummy bar, use a pinch roll 6
The dummy bar 10 reaching the predetermined position was transferred to the dummy bar table 15, and when the tip end of the slab reached the fixed position, the dummy bar table 15 was raised and the dummy bar 10 was pulled out obliquely.

[0053]

[Table 4]

The temperature difference between the tundish and the mold, the number of inclusions in the slab, and the slab surface flaws were all improved as in Example 1.

Further, by using the dummy bar head 11 shown in FIG. 11, even if the drawing speed is increased at an acceleration of 1.0 m / min ² , the tip end of the slab connection is not extended, and the detachment in the roller apron can be prevented. There was no operation trouble, and detachment from the slab tip at a fixed position was easy.

As shown in FIG. 12, α ≦ β, β ≦
By setting it to 1.5 t, the accidental detachment of the dummy bar in the roller apron was reduced, and the dummy bar was easily detached from the slab at the exit of the pinch roll.

[0057]

As described above, the present invention has the following configuration, and thus has the following effects.

(1) Hold at the first casting speed for a certain period of time and reach the steady casting speed when the dummy bar head has passed the lower end of the mold, so that the seal leakage at the start of drawing and the molten steel throughput are low. Nozzle clogging due to the adhesion of molten steel inside the immersion nozzle is eliminated, breakouts or the like mainly caused by uneven solidification due to a drop in meniscus temperature can be prevented, and stable operation can be ensured.

(2) By increasing the slab top to a steady casting speed with an acceleration of a fixed value or more, the slab top is prevented from being excessively cooled, and surface defects can be eliminated to improve slab surface quality.

(3) As the throughput of molten steel increases, the mold temperature continuously increases, and the internal quality of the slab can be improved by the effect of floating inclusions.

(4) By using the exothermic powder during the period from the start of pouring to the steady casting speed, the heat removal from the meniscus of the molten steel in the mold can be reduced. And the surface quality and internal quality of the slab can be further improved.

(5) By using a dummy bar head in which a concave groove having an arc surface having a radius of t + α, t + β is formed in an arc hook shape, the contact surface area between the tip of the slab and the dummy bar head is increased, and is perpendicular to the drawing direction. And the slab and the dummy bar are firmly connected together with the complete cooling of the slab tip. Thereby, even if the dummy bar is pulled out at a relatively high acceleration, it is possible to prevent the slab and the dummy bar from separating in the roller apron by overcoming the frictional resistance generated between the slab and the roll.

(6) At a predetermined position of the exit of the pinch roll,
Only by raising the dummy bar upward, the dummy bar head can be easily separated from the cast piece and can be easily lifted obliquely.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between time and a slab pull-out speed, which is a first embodiment of a control method at the time of starting casting according to the present invention.

FIG. 2 is a graph showing a temperature difference between a tundish and a mold obtained by the control method of FIG.

FIG. 3 is a graph showing the number of community inclusions in a slab obtained by the control method of FIG. 1;

FIG. 4 is a graph showing a surface flaw code of a slab obtained by the control method of FIG.

FIG. 5 is a second embodiment of the control method at the start of casting according to the present invention, and is a graph showing a relationship between time and a slab withdrawal speed, and the like.

6 is a graph showing the temperature difference between the tundish and the mold obtained by the control method of FIG. 5 while changing the range of use of the heat generating powder.

FIG. 7 is a graph showing a temperature difference between the tundish and the mold obtained by the control method of FIG. 5;

FIG. 8 is a graph showing the number of community inclusions in a slab obtained by the control method of FIG. 5;

FIG. 9 is a graph showing a surface defect code of a slab obtained by the control method of FIG. 5;

FIG. 10 is a schematic side view showing a continuous casting facility used in the present invention.

FIG. 11 is a dummy bar head according to the present invention,
(a) is a longitudinal sectional view in a mold, (b) is a longitudinal sectional view at a pinch roll outlet, and (c) is a plan view.

12 is a graph showing pass / fail when the groove radius of the dummy bar head of FIG. 11 is changed. (a) is the number of times the pinch roll exit cannot be released, and (b) is the number of times the dummy bar has been released inside the roller apron.

FIG. 13 is a graph showing the relationship between time and drawing speed by a conventional control method at the start of casting.

[Explanation of symbols]

T ₀ … Start time of slab withdrawal T ₁ … Time when the dummy bar head passes the lower end of the mold T ₂ … Time when the steady casting speed is reached V ₁ … First casting speed V _c … Steady casting speed 1… Mould 2 ... Tundish 3 ... Sliding nozzle device 4 ... Immersion nozzle 5 ... Roller apron 6 ... Pinch roll 7 ... Powder surface coating powder 10 ... Dummy bar 11 ... Dummy bar head 12 ... Slope surface 13 ... Groove 14 ... Seal material 15 ... Dummy bar table 16 … Pinch roll horizontal zone 17… Position sensor

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Terumi Arimoto 3rd-floor light, Kashima-cho, Kashima-gun, Ibaraki Sumitomo Metal Industries Co., Ltd. In the Kashima Works of Sumitomo Metal Industries, Ltd. (56) References JP-A-54-16332 (JP, A) JP-A-1-210157 (JP, A) Full-scale production 57-152359 (JP, U) Real-life production 49 −79617 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/20 B22D 11/08 B22D 11/10 370

Claims (4)

(57) [Claims] 1. At the time of casting slab withdrawal from the start of pouring into a mold at the start of casting in continuous casting until reaching a steady pouring speed, a slab withdrawal start time T ₀ after a certain period of time has elapsed since the start of molten metal injection. , raising the cast strip withdrawing speed from the initial speed zero to the first casting speed V ₁ Hayashi, after holding the first casting speed V ₁ fixed time, the time the dummy bar head is passed through the mold bottom T
Constant acceleration a of 0.6 m / min ² or more around ₁
In linearly ascending Hayashi, cast strip withdrawing method in casting early continuous casting, characterized in that occupied lead to steady casting speed V _c. 2. At the time of slab withdrawal from the start of pouring into the mold at the start of casting in continuous casting until the steady pouring speed is reached, a slab withdrawal start time T ₀ after a certain time has elapsed since the start of the injection of molten metal. , raising the cast strip withdrawing speed from the initial speed zero to the first casting speed V ₁ Hayashi, after holding the first casting speed V ₁ fixed time, the time the dummy bar head is passed through the mold bottom T
Constant acceleration a of 0.6 m / min ² or more around ₁
Continuous THAT linearly rising Hayashi, tighten lead to steady casting speed V _c, from the time the molten metal injection start until it reaches a steady casting speed, characterized by the use of heating powder into the mold molten steel surface coated powder A method of drawing a slab in the early stage of casting. 3. An arc-shaped hook-shaped groove that cuts into a casting line in a curved direction of a casting line when a slab is drawn from the start of pouring into a mold at the start of casting in a continuous casting process until the dummy bar is separated from the slab. Using a dummy bar head equipped with a slab, and starting to inject the molten metal and starting a slab drawing starting time T after a certain period of time
_0, the temperature of the cast strip withdrawing speed from the initial speed zero to the first casting speed V ₁ Hayashi, after holding the first casting speed V ₁ fixed time,
With time T ₁ of the dummy bar head is passed through the mold bottom
Linearly rising at 0.6 m / min ² or more constant acceleration a in the near Hayashi, tighten lead to steady casting speed V _c, from the time the molten metal injection start until it reaches a steady casting speed if necessary,
Use the exothermic powder for the powder coating in the mold,
A dummy bar is transferred to a dummy bar table at a predetermined position after the roller apron, and when the slab tip reaches a fixed position, the dummy bar table is raised and the dummy bar is pulled out obliquely. Slab pulling method in the initial stage 4. A dummy bar head provided in a mold at the start of casting and having a groove connected to a solidified shell of a molten metal, wherein the concave groove has a shape of an arc hook that cuts into the center of curvature of a casting line. And the radii Ri, Ro of the arc surface of the groove.
Ri = t + α, Ro = t + β, t ≦ α ≦ β, α ≦ β ≦ 1.5t ( Ri: radius of the inner arc surface of the groove, Ro: outer circle of the groove)
A radius of an arc surface, t: thickness of a slab).