JPS5924901B2 - How to control the cooling efficiency of assembled molds in continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling the cooling efficiency of assembly casting in continuous casting, by controlling the width and width of the respective wide and narrow side walls of the mold assembled by a wide plate-like body and a narrow plate-like body. the quality of the steel and the slab by sandwiching the other end wall between the side walls of the slab and converging the hollow spaces between each of said end walls in the direction of travel of the slab before starting casting. The present invention relates to a method for controlling the cooling efficiency of the end wall by providing a mold with a taper that matches the width of the end wall.

In the continuous casting of steel, an effort is made to remove heat as uniformly as possible on all sides of the slab inside the mold, so that when the slab leaves the mold the shell thickness is as uniform as possible over all sides. .

In the case of slab casting, the shrinkage values of the slab shell on the narrow and wide sides of the mold vary depending on the dimensions of the slab. Contacts to the sides are no longer equivalent.

Furthermore, the contact of the slab shell to the mold wall is also influenced by the expansion, especially on the wide sides.

The narrow sides of the mold cavity are provided with a casting taper (GiessKonus) or mold taper converging in the direction of the mold outlet, and the wide sides of the mold cavity are provided with parallel sides or with a different taper from the narrow sides. Generally, it is a cast surface.

Adjustable plate for adjusting the end wall according to different slab widths and at the same time varying the taper of the mold cavity between the narrow walls by means of a predetermined shrinkage value depending on the width of the slab. Shape assembly molds are known.

However, the adjusted mold taper is only optimal for a narrow range of casting speeds and temperatures.

The contact of the solidified shell and the amount of heat absorbed thereby are optimal only at these values.

Changes in casting speed and/or casting temperature also change the shrinkage, resulting in non-uniform cooling and solidification of the slab shell.

Such irregularities can cause cracks and
There is more risk of outs and mold wear.

It is a plate assembly mold that is divided into two parts across the direction in which the slab runs, the upper part has no mold taper, and the lower wall is elastically pressed against the surface of the slab. Plate assembly molds are also known.

Between the walls arranged below and adjacent to each other, gaps are provided which allow the walls to move freely and without interfering with each other.

The elastic forces acting on these walls must withstand the forces created by the static pressure of the iron, while on the other hand they must not deform the thin slab shell.

This equipment is unsuitable for casting where casting factors such as casting speed and casting temperature vary.

This is because the elastic force cannot be adapted to different shell thicknesses, ie shell strengths.

Moreover, walls that are pressed against such elastic forces wear out very quickly.

Furthermore, such an end wall is not sandwiched between side walls, which precludes the use of the device in the area of the liquid level of the bath.

In order to adjust the dimensions of the plate assembly mold when no casting operation is being carried out, the end wall of the mold is first displaced without changing the taper of the mold, and then fixed according to the desired shape of the slab; There is also known an apparatus for adjusting the shape of a plate assembly mold that subsequently adjusts the taper of the mold by a desired amount.

With this device uniform cooling is taken out of consideration when casting factors change during the molding process.

The problem on which the invention is based is to provide a method in which uniform and optimal cooling occurs inside the mold when the casting factors change, in particular when the casting speed and the casting temperature change.

According to the invention, this problem is solved by further adjusting the taper of the mold to a theoretical value corresponding to a predetermined casting speed and/or casting temperature before starting the casting, and during the casting operation to adjust the casting speed to a theoretical value corresponding to a predetermined casting speed and/or casting temperature. When the casting temperature and/or the casting temperature change, this is achieved by changing the taper to a predetermined theoretical value corresponding to these changing casting factors.

In particular, the taper readjustment is carried out on the basis of continuous measurements of the cooling efficiency of said end wall and a comparison with a reference value representing the cooling efficiency corresponding to the actual value of the casting speed and/or the casting temperature. A feature of the present invention is a method for controlling.

By using this method, it is possible to create an optimal cooling efficiency relationship for the narrow side of the slab in the plate assembly mold, even when the casting speed, casting temperature, etc. fluctuate drastically.
It becomes possible.

For example, when continuously casting slabs at a high casting speed of 2 m/min, it is possible to set the cooling efficiency between the same castings in advance and run within a speed range of 1 m/min. This creates the possibility of casting slabs of optimum quality and without the risk of breakout.

There are many reasons for casting at various casting speeds in such equipment.

Examples include slow pouring, interruption of the metal feed between the intermediate vessel and the mold or between the ladle and the intermediate vessel, adaptation of the casting time to the converter cycle, At the end, the casting speed decreases.

Adapting the taper of the mold while or immediately after the casting speed, casting temperature or other casting factors affecting solidification is changed can be accomplished in a number of ways.

For example, the optimal value of the taper between the two end walls depending on the casting speed and/or casting temperature can be determined by empirical exploration.

In principle, such optimum values are determined with respect to uniform solidification of the outer shell of the slab.

In this case, the taper of the mold is adjusted to the varying casting speed and/or
Alternatively, it can be adapted to varying casting temperatures and to predetermined theoretical values.

The theoretical value for the taper K of the mold is expressed in coefficients per meter.

It is also possible to adjust the desired theoretical value of the cooling capacity of the end wall as the basis for adjusting the taper.

Not only casting temperature but also casting speed are casting factors that affect the cooling efficiency of the mold wall.

According to another feature of the invention, the cooling efficiency of the end wall is continuously measured and this measured value is compared with an actual value of the cooling efficiency that corresponds to the actual value of the casting speed and/or the actual value of the casting temperature. Therefore, if there is a deviation between the theoretical and actual cooling efficiency, the taper of the mold can be varied until the theoretical cooling efficiency is achieved.

The cooling efficiency of the end wall, as well as the casting speed and temperature, is influenced by the inflow into the riser section, the type and amount of powder slag in the casting, and the bending moments generated by irregular cooling of the slab.

Another advantageous method for adapting the taper of the mold when the casting factors affecting the cooling efficiency of the end walls change is, according to the invention, to continuously measure the specific cooling efficiency of the end walls and the side walls, and to The measured values are compared with each other for the end wall and the side wall, and the actual cooling efficiency relationship between these two types of walls is distinguished from the predetermined theoretical cooling efficiency relationship, and the actual cooling efficiency relationship is If there is a deviation between the theoretical efficiency-to-gravity relationships, this can be achieved by changing the taper of the casting until the theoretical efficiency-to-gravity relationship is achieved.

According to this method, the absorption of heat from the slab, that is, the growth of the shell of the slab, is controlled as the sum of casting factors that are standard for the method.

At the same time, all casting factors and all uncontrollable influencing factors, such as bending moments of the slab generated by expansion or secondary cooling inside the mold, are taken into account.

When the cooling efficiency of the end wall is continuously measured, the variation in cooling efficiency ΔQ (Kca
l /ai・5ec) is the change in taper ΔK (%/m
) and determining from the characteristics of the curve of the theoretical shape of the taper attached to the theoretical value of the cooling efficiency, the theoretical shape of the taper for a given casting factor can be advantageously found during a casting operation.

The theoretical value of the cooling efficiency, that is, the theoretical shape of the taper, lies in the transition region between the two.

For this purpose, while the casting continues, the forces for adjusting the taper of the mold cavity between the two end walls are selected to be minimal, resulting in dimensionally accurate slabs at varying casting speeds. Another characteristic of the invention is that the dimensions of the mold cavity are adjusted in accordance with another characteristic of the invention in adapting the shape of the taper of the casting, in order to allow the production of is held between the two end walls at the outlet of the mold, corresponding to the nominal dimensions of the slab.

In this case, the pivotable connection of the taper-adjusting plate is determined by an axis extending parallel to the end wall and located close to the plane formed by the outlet of the mold. In principle, the mold is equipped.

In order to keep the forces for adjusting the taper relatively small during the casting operation and to prevent scraping of the side wall steel plates, another feature of the invention provides that the two end walls are closed during adjustment. The clamping force is reduced to a value approximately twice the reaction force exerted by the static pressure of the iron, and after adjustment is increased again to the value before adjustment.

Further elements and advantages of the invention are described below with reference to the accompanying drawings.

In FIGS. 1 and 2, a plate assembly mold for continuous casting of steel is indicated by 1.

Fixed wall 2 and movable wall 2 of the two side walls, and 2
End walls 3 define a mold cavity 4.

One end wall 3 has a copper plate 7 facing the mold cavity 4.
and a support plate 8.

The walls 2.2', 3 are supported in a support frame 5 which goes around the mold.

Due to the force of the piston-cylinder element 6, the end wall 3 is clamped between the side walls 2, 2'.

In order to adjust the mold cavity 4 for different slab sizes,
A super spindle 11 is attached to the end wall 3 and to one plate 11.
A device consisting of this spindle 11 and an adjusting gear 12 which interacts with each other is fixed.

The aforementioned spindle is hingedly connected to the end wall by a bolt 14.

The adjustment gear 12 is fixed to a plate-shaped body 17, and the plate-shaped body is connected to the support frame 5 on the side of the plate-shaped body where the joint 16 is located.

A support hole 20 between the pivot plate 17 and the end wall 3, which can be inserted freely depending on the shape of the slab.
is stored.

In order to adjust the taper of the mold during the casting operation, a device for adjusting the taper is arranged on the plate 17 and the support frame 5.

The spindle 21 cooperates with an adjusting gear 22 which is fastened to the support frame 5.

When the spindle 21 moves, the plate 17 moves against the end wall 17.
, about an axis 25 running transversely to the running direction 24 of the slab and parallel to the end wall 3 .

The shaft 25 is arranged close to the plane 27 formed by the outlet of the mold, and the adjusting gear 22 is arranged in front of the aforementioned shaft 25 when viewed in the running direction 24 of the slab.

Such an arrangement ensures that the dimension 28 of the mold cavity 4 between the two end walls at the outlet of the mold is adjusted during the casting operation by means of the adjusting gear 22.
is actually held equal to the nominal dimension of the slab.

The adjusting gears 12 and 22 are equipped with an electric motor, which is not shown.

Other regulating devices can be used, for example hydraulic devices.

Different solutions are illustrated in FIGS. 3 and 4.

A support frame 5 and a side wall 2 supported within the support frame 5. z
The construction of the mold for , and the piston-cylinder element 6 is the same as described in FIGS. 1 and 2.

In order to adjust the mold cavity in relation to the width of the slab, a spindle 32 is connected at one end to the plate 31 and at the other end to the support frame 5.

This spindle 32 can be driven using an adjusting gear 33.

This adjustment gear 33 is fixed to the support frame 5.

Between the plate-shaped body 31 and the support frame 5, depending on the dimensions of the slab,
A single length 20 for adjustment and support is housed.

Connected to the plate 31 is an adjusting gear 35 which interacts with the spindle 31 and serves to adjust the taper of the mold cavity between the two end walls.

In this case, the end wall 3 is pivoted about an axis 37.

The centerline of the axis 37 lies above the exit plane 27 of the mold.

A shaft 37 hinge-likely connects the side wall 3 to a plate 31 arranged between the end wall 3 and the support frame 5 .

The size 38 which determines the width of the mold cavity, ie the size of the squeeze wall 31, is at most 2 mrn larger than the end wall 3.

For this reason, the squeezing force generated by the piston-cylinder element 6 is completely absorbed by the plate-shaped body 31 while the mold is cold.

Due to the heating of the copper plate 7 during the casting operation, the gap 39 which exists when the mold is cold is closed, especially in the region of the bath level.

To prevent steel droplets from penetrating the gap 39 during casting, the butt connection can be covered with an adhesive band.

Pivoting of the end wall 3 during the casting operation is possible with this solution with low forces and without changing the pressure of the piston ring element 6.

In FIG. 5, a plate assembly mold for a slab is indicated at 50.

This mold has two side walls 2. z and two end walls 3.

The mold wall has a plurality of cooling chambers 63-70 surrounding a defined cooling area.

For simplicity, the cooling chamber is not divided in the direction of slab travel.

If desired, by dividing the cooling chamber across the direction of slab travel, the cooling efficiency can be measured separately and evaluated.

Associated with each cooling chamber 63-70 is a conduit 72 through which water enters and exits.

Measuring element 5 for determining the amount of water led into the water inflow and outflow conduits 72 of the side walls 2, 2', i.e. the cooling efficiency.
9 are connected.

An average value of the cooling efficiency of the two cooling chambers 63.64 or 65.66 is simultaneously produced in the measuring element 59 and sent to the average value generator 55.

The cooling efficiency of the two cooling chambers 67, 68 or 69, 70 is measured with a measuring element 51' or 51 and an average value of 52.
52' as a difference value former 53.54 or 53', 54
' is dispatched to '.

The output signal 74 of the average value generator 55 is further applied to the difference value generator 53, 53'.

The difference value generators 53, 53' generate difference value signals 56, 56 corresponding to the difference in cooling efficiency between the corresponding end wall and side wall.
' to create.

These signals 56° and 56' are sent to a computer 58.

The difference value generator 54, 54' generates a difference value resulting from the actual cooling efficiency of the end wall and the theoretical cooling efficiency of the end wall, which is combined with the actual casting speed and/or the actual casting temperature and is predetermined. Signals 57, 57' are produced.

Calculator 58 includes an optional mechanical adjustment member 60 that adjusts the taper of the end wall depending on whether signal 56 or signal 57 is received.
60' can be controlled.

When the adjustment member 60.60' is controlled by the signal 56.56', the cooling efficiency of the end wall is changed to a predetermined cooling efficiency between the end wall and the side wall by changing the taper of the mold. Continue to be adapted to the relationship.

This achieves a uniform cooling efficiency relationship between the end wall and the side wall of the mold.

In this way, it is also possible to create from the difference values 57, 57' a theoretical value of the cooling efficiency of the end wall, which is adapted correspondingly to one of the predetermined factors, such as the cooling rate.

When the adjusting member 60, 6σ is controlled by the signal 57°5γ, the cooling efficiency of the narrow side is continuously measured, independent of the cooling efficiency of the side wall, and corresponds to a predetermined theoretical value of the cooling efficiency. The taper of the mold is adjusted.

Since the cooling planes that follow each dimension of the slab, that is, the cooling planes of the narrow side and the wide side, are given to the calculator 58, the specific cooling efficiency (Kcal) per square area and per second is continuously calculated. be able to.

The computer can also control the mechanical adjustment member by means of a program which is optionally combined with both difference signals 56 and 57.

The described apparatus for adapting the taper of the end wall mold during a casting operation according to various casting factors operates as follows.

In a high-efficiency continuous casting machine, for example, casting is performed by multiple injections during one continuous casting period.

The dimensions of the slab are 2000x250ynm, the theoretical continuous casting speed is 2m/min, and the maximum continuous casting speed is 2.5m/min.
It is min.

Before starting casting, the taper of the mold converging in the direction of casting was adjusted to 0.9%/m in the mold cavity between the two end walls.

This taper corresponds to an initial speed of 1 m/min, slab width and steel quality.

-, which is expressed in terms of the ratio per meter of taper of the casting described above, is calculated by the following formula:

In this case, ΔB is the difference between the upper and lower widths of the tapered mold cavity, Bu is the narrower width of the mold cavity 4 m→, and L is the height of the mold cavity 4. It means H respectively.

After disconnecting the dummy bar, while the casting continues, the taper of the casting is adjusted to a value that follows the theoretical casting speed of 2 m/min.

For this purpose, prior to adjustment, the squeezing force acting on the side wall 2 is reduced to about 2 times the reaction force exerted on the side wall by the static force of the iron.
Reduce by up to 2 times.

The taper of the end wall is varied to 0.5% per meter while increasing the casting speed to 2 m/min.

After this adjustment, the squeezing force is increased again to a value that is at least 5 times the reaction force acting on the side wall.

When using the mold of FIGS. 3 and 4, it is not necessary to reduce the squeeze force during adjustment.

In the case of molds equipped with a device for measuring the cooling efficiency of the end walls, the actual value of the cooling efficiency of the two end walls, after adapting the taper of the mold to the varying casting speed, is The cooling efficiency can be compared with the theoretical value, which is predetermined by the casting speed.

If the actual and theoretical values do not match, the taper of the casting is adjusted in one or both of the end walls to the retained deflection signal.

If one has to cast at a maximum casting speed of 2.5 m/min within a certain time, for some reason, for example due to contact of the stopper, further adjustment of the pouring taper is necessary.

Prior to the end of the casting, the casting speed was adjusted to 0.8% while adapting the casting taper to a value of approximately 0.8-0.9%/m.
-1 m/min stepwise.

Adaptation of the mold taper to varying casting temperatures is done in the same way as when the casting speed is varied.

Higher casting temperatures retard solidification of the slab shell in the mold.

This is similar to when the casting speed increases.

In this case, the cooling efficiency of the end wall is increased.

The taper of the casting is adjusted so that the taper of the mold becomes smaller when the casting temperature becomes higher, and that the taper becomes larger when the casting temperature becomes lower.

The optimal value K (theoretical value) of the taper of the mold during the casting operation is:
Depending on all the influencing factors that affect casting, such as casting speed, casting temperature, slab dimensions, steel quality, type of casting powder slag, etc., it can be determined as follows:

In the graph shown in Figure 6, the cooling efficiency Q is plotted on the vertical axis.
(Kcal / crtt ・sec,), and the taper K (% per 1 m) is plotted on the horizontal axis, so as the taper K increases in the section 80, the cooling efficiency curve 85 changes from the taper 0 to the cooling efficiency. It rises to a higher value and then bends into an almost horizontal curve in section 81.

The optimum taper K (good cooling efficiency and relatively low wear) lies, as a rule, in the transition curve (section 81) from the ascending section of the curve to the horizontal section in section 82.

Characteristic curve 85 is valid for one example only.

This is because, depending on the type of mold and casting factors, the curves shown may vary and the curve area must be quickly found during the casting operation.

A computer connected to the continuous casting equipment can also automatically determine the optimal taper-dependent cooling efficiency, taking into account all influencing factors that influence the cooling efficiency.

The invention is not limited to the embodiments described above.

The method cannot be implemented only with the apparatus described above.

For example, it is also possible to carry out the method of the invention on a mold from which the plate 17.31 described above has been removed.

The invention includes the following embodiments.

(1) In the method described in claim 1, the cooling efficiency of the end wall is continuously measured, and this measured value is
If there is a deviation between the theoretical and actual cooling efficiency compared to the actual value of the cooling efficiency that corresponds to the actual value of the casting speed and/or the actual value of the casting temperature, the taper of the mold is determined. A method characterized in that the cooling efficiency is varied until a desired cooling efficiency is achieved.

(2. In the method described in claim 1, the specific cooling efficiency of the end wall and the side wall is continuously measured, the measured values are compared with each other of the end wall and the side wall, and these two types are Distinguish the actual cooling efficiency relationship between the walls from the predetermined theoretical cooling efficiency relationship, and if there is a deviation between the actual cooling efficiency relationship and the theoretical ratio relationship, taper the mold. A method characterized by varying the ratio until a theoretical ratio relationship is achieved.

(3) Claim paragraph 1, preamble paragraphs (1) and (2)
In the method described in one or more of the following paragraphs, the cooling efficiency of the end wall is continuously measured, and the variation in cooling efficiency ΔQ (K c a l /ci-se
c) is differentiated by the taper variation ΔK (%/m), and a theoretical taper that accompanies the theoretical value of the cooling efficiency is determined from the characteristics of the curve.

(4) In the method described in the preceding paragraph (3), the method is characterized in that a theoretical value of cooling efficiency, ie, a theoretical value of taper, is selected as the functional area.

(5) Claims Paragraph 1, Preamble Paragraphs (1) to 4
In the method described in one or more of paragraphs 1 and 2, when adapting the taper of the mold, the dimensions of the mold cavity are adjusted between the two end walls at the outlet of the mold to correspond to the nominal dimensions of the slab. A method characterized by holding.

(6) Claims Paragraph 1, Preamble Paragraphs (1) to 5
), in which the force squeezing the two narrow side walls during adjustment is reduced to a value approximately twice the reaction force exerted by the static pressure of the iron. A method characterized in that the method is characterized in that the value is increased again to the pre-adjustment value after the adjustment.

[Brief explanation of the drawing]

Figure 1 is a partially cross-sectional plan view showing a part of the mold in which the plate-shaped body is assembled, and Figure 2 is l-11 of Figure 1.
3 is a plan view showing a part of a plate assembly mold according to another embodiment, FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, and FIG. 5 shows a control device. A conceptual diagram of a mold for assembling a plate-like body, and FIG. 6 are graphs showing cooling efficiency depending on the taper of the mold. 1... Assembly mold for plate-shaped body, 2... Side wall, total... end wall, 4... Mold hollow chamber, 5...
... Support frame, 6 ... Piston cylinder element, 7 ... Copper plate, 8 ... Support plate, 1
1...Spindle, 12...Drive gear, 16...Hinge, 17...Swivel plate,
21... Spindle, 22... Adjustment gear, 24... Running direction of slab, 27...
・・Mold exit plane, 31 ・・Plate body, 32・
...Spindle, 33...Adjustment gear,
36...Spindle, 50...Assembling mold of plate-shaped body, 52...Average value, 53...
- Difference value former, 55...Average value former, 56
．． 57... Difference value signal, 58... Calculator, 59... Outflow water amount measuring member, 60...
... Mechanical adjustment member, 63-70 ... Cooling chamber,
72...Conduit through which water flows in and out, K...
・Taper, Q... Cooling efficiency, 85...
curve.

Claims (1)

[Claims] 1. When controlling the cooling efficiency of the end wall sandwiched between the two side walls of the plate assembly mold for continuous casting during continuous casting, the taper angle of the end wall is adjusted prior to the start of casting, and the steel A taper is provided in the mold chamber in the casting direction that matches the quality of the slab, the width of the slab, the planned casting speed and/or the planned casting temperature, and the taper is re-applied when the casting speed and/or casting temperature changes during continuous pouring. and this taper readjustment is performed by continuous measurement of the cooling efficiency of the end wall and the casting speed and/or
or a method for controlling the cooling efficiency of an assembled mold for continuous casting, characterized in that the cooling efficiency is controlled based on a comparison with a reference value representing the cooling efficiency corresponding to the actual value of the casting temperature.