CN1072535C - High-speed continuous casting equipment for high-quality steel thin slabs - Google Patents

Abstract

A high-speed continuous casting device for steel sheet billets comprises a crystallizer, a submerged nozzle and a vibrating device, wherein the distance between the submerged nozzle and a copper plate is constant in the middle area of the horizontal section of the crystallizer at a meniscus; the ratio of the area of the middle zone corresponding to the horizontal section of the crystallizer at the meniscus, which is closed between the larger side walls of the crystallizer and the submerged entry nozzle, to the total length of the outside of the crystallizer corresponding to said area, is 0.9 ÷ 1.1 times the ratio of the remaining surface area of the horizontal section of the crystallizer at the meniscus to the total length of the outside of the crystallizer corresponding to said area; the perpendicular distance between each point of the inner surface of the mold wall and the ideal envelope surface of all the ends of the cooling tube is fixed.

Description

The high-speed continuous casting equipment of high-quality steel sheet billet

The present invention relates to a kind of high-speed continuous casting equipment that is used for high-quality sheet metal base.

People know that the continuous casting of so-called " sheet metal base " (thickness is below 80 millimeters) can run into some quality problems, and particularly (for example poring rate is more than 4.5 meters/minute) are especially true under the situation of cast at a high speed.

These problems may go up at steel slab surface (that is, the what is called " solidification layer " that forms gradually in crystallizer) and form some defectives, and these defectives comprise:

-owing to the longitudinal crack that forms of gathering of cast powder;

-producing the vertical and horizontal crackle owing to lacking by so-called " slag " formed lubricating film and thermal isolation film, " slag " speech refers to the fusing of cast powder and solidifies the resulting product in back again;

-because the formed longitudinal crack of thermal stress; And

-owing to the copper cooling surface is the discontinuous longitudinal crack that forms.

These quality problems mainly can cause some influences to special steel, and can solve these quality problems at least in part by reducing poring rate, but can reduce productivity ratio like this, thereby the economic benefit of factory is descended.Another kind of adoptable solution is to use the calutron of a kind of being called as " EMBR " (electromagnetism viscous motion adjusting device), this device can make the fluctuation at molten steel meniscus place in crystallizer obtain relaxing by reducing the liquid steel level height, but a kind of like this device is very expensive and can only partly addresses the above problem.In addition, the other problem that brings owing to the geometry in the crystallizer and mobility status also may reduce the service life (the described mouth of a river is immersed in the liquid metals, is commonly called " immersion mouth ") at the mouth of a river and reduce production efficiency.

At present, independently of each other crystallizer, submersed nozzle and mould vibration device are improved obviously and can not address the above problem in the mode of satisfactory and system.Therefore these three parts that work for continuous casting connect each other and have formed one " apparatus for pouring " together, have only whole device is done as a whole the improvement just to find a kind of solution effectively.

The objective of the invention is to, a kind of casting equipment that can overcome above-mentioned defective when pouring into a mould sheet billet with higher poring rate is provided.

Briefly say, the present invention relates to a kind of equipment that particularly under the situation of producing low thickness slab and cast at a high speed, is used for steel sheet base continuous casting, described equipment comprises that one is used for the crystallizer of continuous casting, feeding outlet and vibrating device that is driven by the hydraulic servo control device that has submersed nozzle, described crystallizer is to be limited by the copper coin wall in its bigger side, it is characterized in that, at least in the zone line of the crystallizer horizontal cross-section at meniscus place, the spacing of submersed nozzle and copper coin is a constant; Corresponding to being at the residual surface area of the crystallizer horizontal cross-section at meniscus place and corresponding to 1.1 times of 0.9 ÷ of the ratio between the outside total length of the crystallizer of described area at the area of the zone line of the crystallizer horizontal cross-section at meniscus place and corresponding to the ratio between the summation of the crystallizer peripheral length of described area, the area that wherein said area is surrounded between the major lateral wall of crystallizer and submersed nozzle; Vertical range between the desirable enveloping surface of the every bit of crystallizer wall inner surface and all ends of cooling tube remains constant.

Below with reference to accompanying drawings a preferred embodiment (non-limiting embodiment) is described in detail, therefrom can find out these and other objects, advantage and the feature of casting equipment involved in the present invention significantly, in the accompanying drawings:

Fig. 1 is a side view of apparatus for pouring involved in the present invention;

Fig. 2 is the resulting view of arrow II direction in Fig. 1, wherein only shows the top and the submersed nozzle of crystallizer;

Fig. 3 a, 3b, 3c are the resulting sectional views at the meniscus place of III-III line in Fig. 2, this be for illustrate respectively the crystallizer that meets in the casting equipment involved in the present invention and submersed nozzle the various piece of the geometrical relationship that must satisfy;

Fig. 4 is a plane of identical crystallizer, and this figure utilizes Descartes's three-axis reference to represent;

Fig. 5 a and 5b are two sketches of crystallizer shown in Fig. 4, wherein show respectively on passing a longitudinal cross-section that is parallel to y axle and z plane that axle forms among Fig. 4 and the resulting cooling system pipeline of B-B line external envelope face in Fig. 5 a.

With reference to accompanying drawing, Fig. 1 is a sketch of casting equipment involved in the present invention, this apparatus for pouring has a crystallizer 1, a submersed nozzle 2 and a vibrating device 3, described vibrating device 3 is hydraulically powered, in the present embodiment, described vibrating device 3 is fixed on the crystallizer, obviously so can not influence teeming line.Fig. 1 also shows the cross section that molten steel flows through, promptly formed two " passages " 4 between submersed nozzle 2 and the solidification layer that forms gradually along the copper crystallizer wall.

Apparatus for pouring for routine, the subject matter that crystallizer is run into when the cast sheet billet is, when molten steel flow speed is identical, reduce slab thickness and will be increased in the steel slab surface that contacts with crystallizer wall in the unit interval, thereby just increased " slag " lubricated demand, the notion of " slag " limits in front.In fact, T1, W1, V1 represent a kind of thickness, width and average poring rate of normal thick slab respectively, T2=T1/a (a＞1), W2=W1 and V2＞＞V1 then represents a kind of relevant parameter of sheet billet, under the identical situation of molten steel flow speed, has such relational expression:

T2·W2·V2＝T1·W1·V1 (I)

Therefore, the slab area of cast is in the unit interval: 2 (T2+W2) V2, if the thickness of sheet billet is insignificant with respect to its width, 2 (T2+W2) V2 approximates 2W2V2 so.Utilization replaces W2V2 from the value that relational expression (I) draws, and then has such relational expression:

2·W2·V2＝2·(T1/T2)·W1·V1＝a·(2·W1·V1) (II)

Because a＞1, above-mentioned relation formula (II) has clearly illustrated and has formed the importance that can cover the lubricated molten slag layer of slab and crystallizer contact surface, slab and crystallizer contact surface were inversely proportional to slab thickness in the unit interval, and the big more then slab thickness in this surface is thin more.On the contrary, because formed slag layer thickness is very little, the interface between molten steel in the crystallizer and the cast powder has less area in meniscus surface area that forms molten slag layer and the zone line with respect to submersed nozzle.

Although by using the cast powder that can strengthen slag formation partly to address this problem, but what must consider is to make the immersion outlet of known structure keep being melted formed molten slag and being penetrated into the required balance between the back slag that is consumed between meniscus and the crystallizer wall by powder in all meniscus surface areas.

According to the present invention, thin crystallizer can hold one reliably (promptly, enough thick) submersed nozzle, the big copper coin of described crystallizer accurately cooperates with the profile of submersed nozzle in described horizontal plane in the profile in the horizontal plane of meniscus horizontal level, thereby the every bit place in described zone line remains unchanged the spacing of submersed nozzle and crystallizer wall.Referring to Fig. 3 a, 3b and 3c, select the value of this above-mentioned distance to make ratio A 1/S1 and A2/S2 roughly the same, wherein area A 1 is corresponding to the mid portion in the crystallizer horizontal cross-section of falcate apparent height position, and this area is the area that is surrounded between a bigger side and submersed nozzle; And S1 is the periphery of crystallizer, and the periphery that is equivalent to area A 1 is long, deducts the length of the dual-side that joins with the area A 2 that defines later; Area A 2 is the horizontal sectional areas that limited by this two plate outside central area A1, is positioned at falcate apparent height position; S2 is the appropriate section of crystallizer periphery, i.e. the outer perimeter of area A 2 deducts the length of the dual-side that joins with central area A1.Ratio A 2/S2 measures (seeing Fig. 3 c) outside the submersed nozzle zone.Thereby the equation that requires to satisfy is:

(A1/S1)/(A2/S2)=0.9 ÷ 1.1, best=1

For example, for one 1300 * 65 millimeters crystallizer, and this crystallizer to have width be 300 millimeters submersed nozzle (as shown in Fig. 3 b and Fig. 3 c, described submersed nozzle has 60 millimeters reliable thickness), optimum ratio is that A1/S1=A2/S2 equals 30 millimeters.For example behind the thickness of the size of determining submersed nozzle and the less sidewall of crystallizer, this ratio can be used for determining the profile of crystallizer in meniscus position horizontal plane of living in, perhaps under the known situation of described crystallizer appearance and size, can utilize this ratio to determine the profile of immersion outlet, do so equally in order to guarantee that lubricated slag reaches good balance in the amount on whole crystallizer profile.

This geometry also is important for molten steel flowing in meniscus surface area; this be because be formed on submersed nozzle and be formed on gradually described " passage " between the solidification layer on the copper crystallizer wall (in Fig. 1 by Reference numeral 4 expressions) will be enough greatly to prevent to produce because the liquid of assembling to middle section from the less sidewall of crystallizer flows the eddy current that acceleration forms; described eddy current can make the cast powder accumulate in the meniscus surface area usually, thereby forms above-mentioned defective.

It should be noted, used preferably a kind of crystallizer that has variable flexibility in the vertical of crystallizer in casting equipment involved in the present invention, this is the theme of the applicant in European patent EP 0705152, for the mouth of a river is set better, the top of this crystallizer has and is almost infinitely-great bending radius, while is on arc cast leader rather than provide an outlet for the plate bending that is formed on crystallizer inside gradually on vertical cast leader, help reducing the height of this casting equipment like this, thereby can reduce the danger of ferrostatic pressure and slab protuberance.According to above-mentioned patent application, from the infinite radius of crystallizer porch to (Fig. 1) corresponding to the bending radius (R0) of cast leader, the flexibility of crystallizer is that a kind of progressive and uniform mode distributes, thereby prevents incomplete contact of appearance between the solidified shell that forms excessive stresses on the solidified shell of slab and prevent described slab and copper crystallizer wall.

In order to solve related technical problem, it is very important being used for the device that the crystallizer wallboard cools off, described cooling device must be able to bear the required high heat-flux (its mean values is up to 3MW/m2 on the whole cooling surface of crystallizer) of sheet billet cast, this cooling device has good cooling effect to prevent the copper coin cracking in meniscus surface area, yet for the slab that prevents to form gradually produces thermal stress, the cooling around the crystallizer should be enough uniform.

Referring to Fig. 4, when considering that specified between cast product surface and crystallizer is than heat flux (dqn), should satisfy the following relationship formula:

dqn＝dq/dA[W/m ²]

This heat flux still is a function of the local surfaces temperature on the copper coin hot surface, and described local surfaces temperature depends on and flow through distance between the cooling pipe of cooling water.

As shown in Figure 4, utilize a cartesian coordinate system x, y, z (wherein the z axle is towards the below or towards the bottom of crystallizer) and consider by the formed complex surface f of crystallizer (x, y, z)=0, then the local surfaces temperature along with t=t[f (x, y, z)] change.

Because heat flux dqn must remain unchanged on a horizontal line (wherein z=z0) direction of crystallizer surface as much as possible, promptly temperature t must remain unchanged along such horizontal line, thereby:

t＝t[f(x，y，z0)]＝t0

According to the present invention, this is to remain unchanged by the vertical range Nd between the desirable enveloping surface E (seeing Fig. 5 a and 5b) of all ends of every bit that makes the copper coin hot surface and cooling tube W to reach, and described vertical range Nd is perpendicular to described hot surface.Like this, Nd must be a constant, and in order to make described cooling system satisfy above-mentioned condition, can find by experiment, and the optimal values of this constant must be in 10 to 25 millimeters scope.

For submersed nozzle, except relate to previously and crystallizer between relative size, must be able to make the MOLTEN STEEL FLOW situation reach best, also to consider the solidification layer that forms gradually and the service life of submersed nozzle itself simultaneously.In fact, people know, when slab thickness reduces, the problem that relates to liquid motion in the crystallizer will increase, this may cause forming standing wave in meniscus surface area, thereby the thickness part of molten slag is reduced, like this will be to the lubricated and heat insulation generation harmful effect of the slab solidification layer that forms gradually.

The submersed nozzle that is used for sheet billet is the theme of patent application PCT/IT-97/00135 of the applicant, except in crystallizer, having a kind of improved fluid level control device, these some geometric properties that are used for the submersed nozzle of sheet billet can make in the lower and liquid part at slab of the cast energy in the exit has higher loss probability, utilizes the sidewall shape that immerses part to improve the liquid flow guiding gathering of eddy current and cast powder (thereby prevent to form) like this.In addition, feed is stable, and liquid stream is divided into two strands and the initial surface of described submersed nozzle inside is protected basically, and keeping and the identical shape of shape when continuous casting begins, this is that deposition because of oxide can be left in the basket; These good flox conditions are reduced the exterior mechanical erosion degree in meniscus surface area in addition.

According to the present invention, except the related condition in front, for the optimal design mode between crystallizer and the submersed nozzle be, ratio between height of standing wave (height from the crest to the crest is represented with millimeter) and the poring rate (with the rice/expression of assigning to) is no more than 5, and its mean value is 3.3.

In addition, the sampled signal standard deviation of the casting position (ML) in the measured crystallizer (by StdDEV (ML) expression) is usually in below the scope:

StdDEV (ML)=0.7-1.5 millimeter

At last, for the quality surface of slab and the stability of casting process, the 3rd parts of this casting equipment, promptly vibrating device 3 also should be considered as a key factor.Referring to Fig. 1, described vibrating device can be made of a frame 3a, and this frame 3a is on the ground hinged and driven by a hydraulic servo controlling organization 5.Frame 3a is also hinged with a crystallizer supporting arrangement 3b, thereby has formed a kind of quadrilateral structure, and its two ends are fixed with one group of spring 3c.

Controllable deformation performance is to obtain by programmable logic control device and vibration program, and this programmable logic control device can change the vibration parameters relevant with waveform, amplitude ± 2 and ± 10 millimeters between.This control is write down the actual numerical value of poring rate serially with the parameter control vibration frequency according to the front.Because first intrinsic frequency of whole dynamical system is 16.7 hertz, the peak of vibration frequency can reach 480-520 time reciprocal/minute.Above-mentioned deformation performance refers to, and described vibration parameters is adjustable so that can obtain the lubricated and surface quality as the best of a function of poring rate for the steel of each quality.

Perhaps, described vibrating device can be so-called " resonance " type, crystallizer is directly installed on the bending spring, without any lever system, vibrate with the frequency that approaches the elastic system intrinsic frequency by a hydraulic servo control device, thus because very close to each other can the action along a point-device path.

Those of ordinary skills can improve and modification the above-mentioned embodiment that utilizes accompanying drawing to describe on the basis that does not exceed protection domain of the present invention.Particularly, as long as meet above-mentioned geometrical relationship, this can have other profile rather than in the profile disclosed in the European patent application EP 0705152 crystallizer in perpendicular, what submersed nozzle also can be with disclosed in patent application PCT/IT-97/00135 is different.

Claims (7)

1. A device for continuous casting of steel thin slabs, especially in the case of producing low-thickness slabs and high-speed pouring, said device comprising a mold (1) for continuous casting, a submerged nozzle ( 2) and a vibration device (3) driven by a hydraulic servo control device, said crystallizer (1) is defined by a copper plate wall on its larger side, characterized in that, at least in the meniscus In the middle region of the crystallizer horizontal section at the place, the distance between the submerged nozzle (2) and the copper plate is constant; the area (A1) corresponding to the middle region of the crystallizer horizontal section at the meniscus place is the same as that corresponding to the area The ratio between the sum (S1) of the mold perimeter lengths of (A1) is the remaining surface area (A2) of the horizontal section of the mold (1) at the meniscus and the mold area corresponding to said area (A2) 0.9÷1.1 times the ratio between the sum of the perimeter lengths (S3), where said area (A1) is the area enclosed between the larger side wall of the crystallizer and the submerged nozzle (2); inside the crystallizer wall The perpendicular distance (Nd) between each point of the surface and the ideal envelope (E) of all ends of the cooling tube (W) is kept constant. 2. An apparatus as claimed in claim 1, characterized in that said ratios A1/S1 and A2/S2 are substantially equal. 3. An apparatus as claimed in claim 1 or 2, characterized in that said constant vertical distance (Nd) is between 10 and 25 mm. 4. A kind of equipment as claimed in claim 1, is characterized in that, the ratio between the standing wave height that is formed on the meniscus in the crystallizer and pouring speed is less than or equal to 5, and its average value is 3.3, described The standing wave height is the height from peak to peak and is expressed in millimeters, the pouring speed is expressed in meters per minute. 5. An apparatus as claimed in claim 4, characterized in that the standard deviation of the sampled signal of the measured crystallizer position is in the range of 0.7-1.5 mm. 6. A kind of equipment as claimed in claim 1, is characterized in that, described vibration device (3) is made of four-bar linkage system (3a, 3b, 3c), and described vibration device (3) has hydraulic servo The control mechanism (5), the hydraulic servo control mechanism (5) is able to vary the amplitude between ±2 and ±10 mm. 7. A kind of equipment as claimed in claim 1, it is characterized in that, described vibrating device (3) is resonant type, crystallizer (1) is installed directly on the bending spring in the mode without clearance, and through a hydraulic servo The control device vibrates at a frequency close to the natural frequency of the elastic system.

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