WO2004012882A1

WO2004012882A1 - Method of continuous casting and machine for implementation of this method

Info

Publication number: WO2004012882A1
Application number: PCT/CZ2003/000040
Authority: WO
Inventors: Vadim Michajlovic LYUDKOVSKIJ; Aleksandr Nikolajevic BURAKOV; Aleksandr Aleksejevic POLENOV; Karel KLIMEK; Petr BAJTEK; Ondrej KULLA; Michal ADAMÍK; Bohuslav KOTAS; Jaroslav Pindor; Jirí MUSÁLEK; Lubomír LACINA; Gennadij Abramovic BURJAKOVSKIJ
Original assignee: Trinecke Zelezarny AS
Current assignee: Trinecke Zelezarny AS
Priority date: 2002-08-01
Filing date: 2003-07-25
Publication date: 2004-02-12
Anticipated expiration: 2005-02-01
Also published as: CZ300713B6; CZ20022649A3

Abstract

The method of continuous casting of metals, especially steel, wherein the melted metal is continuously poured to the inlet of the mold, where it gradually cools down and from where solidified semi-product moves to further processing through its outlet, whilst the auxiliary coolant in the form of at least one wire, band, or bar from material similar to the continuously cast material is loaded to the mold inlet. The loaded auxiliary coolant is disposed by electromagnet with the forced harmonic oscillation, wherein amplitude, frequency, and wavelength vary in relation to physical-chemical parameters of continuously cast metal and technological conditions of casting process.

Description

METHOD OF CONTINUOUS CASTING AND MACHINE FOR IMPLEMENTATION OF THIS METHOD

Field of the Invention

The invention relates to the method of continuous casting of metals, especially steel, with auxiliary loading of coolant to the molds and machine for implementation of this method.

Background of the Invention

5 During the continuous casting of metals, melted metal is continuously cast to the inlet of the mold, where it gradually cools down; the semi-product is solidified at the outlet, it is continuously withdrawn and then usually cooled by the water spray to the 0 ambient temperature. Melted metal is usually cast to the mold from the ladle through the tundish and submersing nozzle, whilst the mold is intensively cooled by water. In the mold, 10 to 30% of entire heat of incipient semi-product is dissipated, whilst equal 5 and sufficient cooling of the semi-product is the matter of its homogenous structure.

Pursuant to the document US 3,726,331 the method of continuous casting is also known, where also the auxiliary coolant in the form of at least one wire or 0 bar of the material of similar composition as the continuously cast metal is led to the inlet of the mold in the direction of casting in order to decrease the temperature gradient between the center of continuously cast material and outer surface of the semi-product emerging in the mold. The auxiliary- coolant is hereat led to the mold of the continuous casting machine from the unwinding device through the system of driving and guiding rollers .

Though, achieving of requested homogenous inte'rnal structure of the semi-product by this method is considerably problematic, because in the course of leading of the coolant to the mold in the area of the meniscus the slag and non-metallic inclusions are freezing on it and within further movement of consumed coolant inside the melt the slag and non-metallic inclusions are melting and contaminating the melt. The high axis segregation is rising in the zone of crystallization, because the material of consumed coolant is unequally diffusing, which results in non-homogenous structure of the semi-product, in unequal allocation of alloys as well as to increased pollution by non-metallic inclusions.

From the Ukrainian patent document UA No. 40053 is also known the continuous casting machine with the device for leading of auxiliary coolant to the mold, by which means are also led electro hydraulic stroke impulses in the direction of the movement of consumed coolant. Also in this case the castings with stable structure are not guaranteed; this is caused by the fact that within leading of electro hydraulic stroke impulses to the melt through the consumed coolant the energy is distributed unequally in the entire dip. Besides that the unit of energy lead into the melt in the time unit is inconstant unit, this is caused by the fact that the amount of energy led through the consumed coolant gradually decreases from impulse to impulse and in the moment of next impulse it virtually equals to zero. By this fact the slag and non-metallic inclusions freeze to the consumed coolant, whilst within next movement of consumed coolant and leading of next stroke impulse the slag and non-metallic inclusions get into the melt and pollute it with negative consequences to the quality of the continuous casting.

From the Japanese document No. 56-4133 the solution is known, where the ultrasound vibration is led to the melt in the mold through the consumed coolant. Also with regard to maximum amplitude 2 to 10 jam of this vibration, this solution does not provide sufficient amount of energy, which can ensure stable structure of the casting. Therefore, even in this case the continuous casting is not homogenous, alloys are not distributed equally and it is polluted by non-metallic inclusions.

Summary of the Invention

The above mentioned disadvantages of the actual technology state are in a great extent eliminated by the method of the continuous casting of metals especially of steel and by device of implementation of this method according to submitted invention.

As it is known from the present state of technology, within the continuous casting, the melted metal is poured into the inlet of the mold, where it gradually cools down and from where solidified semi-product goes to further processing, whilst auxiliary coolant in the form of at least one wire, band, or bar made of material of similar chemical composition as the cast material, led through the mold inlet to the melt and it is continuously consumed in the melt. The principle of the invention consists in the fact that loaded auxiliary coolant is electro-magnetically stimulated by the harmonic oscillation with the amplitude, frequency, and wavelength varies especially in relation with physical-chemical parameters of melted metal and technological conditions of the process of casting.

The principle of the method according to the invention further consists in the fact that the amplitude of oscillation of loaded auxiliary coolant advantageously ranges from 0.5 mm to 15.0 mm.

The frequency of the oscillation of loaded auxiliary coolant advantageously ranges from 10 to 1000 Hz.

Also, the wavelength of loaded auxiliary coolant advantageously ranges from 200 to 800 mm.

The chemical composition of loaded auxiliary coolant, for example the steel band, is advantageously such, as the temperature of the liquidus of the band is equal or lower than the temperature of liquidus of cast steel, though maximally by 150 °C. Using of rectangular loaded band is optimal, whilst the ratio of width and thickness of the band usually ranges from 5 to 80 : 1. The specific weight consumption of the band ranges from 1.5 to 20 kg per 1 ton of cast steel. The speed of loading of the band is depending on the size of the band and its required consumption, whilst the band is led to the mold in the angle from 0 to 60° to the vertical axis of the mold. The device for implementation of this method consists of the casting -unit of liquid metal to the mold and feeding unit of auxiliary coolant, loaded into the mold as well as of the source of creation of forced harmonic oscillation of auxiliary coolant loaded to the mold, whilst the principle of the invention consists in the fact that the source of force harmonic oscillation is created by contactless electromagnetic vibrator with the slot of the ' ' shape in the horizontal surface, which is equipped by front and rear guiding rollers, located in the direction of movement of the auxiliary coolant in front and behind the system of electromagnets. The distance of front guiding rollers, located in front of the electromagnets and the distance -L of rear guiding rollers behind the electromagnets of the contactless electromagnetic vibrator from the axis of the electromagnets is determined by the equations:

and

L₂ = (2n - 1) ^• λ / 4 (b) where n - any integer number (1, 2, ..., k) λ - length of the wave of oscillation of auxiliary coolant (mm)

In the advantageous ^"device according to the invention, the slot of the π shape in the horizontal surface is designed with possible regulation of 2 to 15 multiple of the thickness of auxiliary coolant loaded into the mold. By this design of the slot, necessary amplitude and frequency of the oscillation of consumed auxiliary coolant are guaranteed. Slot of smaller dimensions does not provide stable function of electromagnetic vibrator and causes considerable noise effects . For bigger dimension of slot, the amplitude of oscillation of consumed auxiliary coolant considerably decreases due to significant losses of inductivity in the electromagnetic vibrator.

The principle of the device consists according to the invention also in the fact, that the auxiliary coolant feeding unit is equipped with the feeding mechanism with at least two pairs of traction rollers, placed in the distance L 3 from the axis of contactless electromagnetic vibrator given in the equation:

L₃ = (2n - 1) • λ / 4 (c) where n - any integer number (1, 2, ..., k) λ - length of the wave of oscillation of auxiliary coolant (mm)

The feeding mechanism of the feeding unit is also advantageously equipped with the traction control unit coupled with the unit of traction of pulling mechanism of the continuously casting machine with the possibility of automatic change of specific consumption of the coolant of auxiliary coolant loaded into the mold.

Compared to the recent state of the technology, continuously cast semis achieve homogenous structure and equal distribution of the segregations within their entire volume, because the loaded auxiliary coolant into the melted metal has also a function of the waveguide, which transfers the energy into the melt. In so doing, the energy is equally distributed in the whole melt and the stirring of the melt increases. This helps the equal dispersion of consumed coolant inside the melt and due to lower temperature gradient; the crystallization of the melt is accelerated. The central zone of creation of parallel axis crystals and it causes reduction of central liquation. All of this is instrumental to elimination of axis segregation and to the equal distribution of segregation within the whole volume of the metal . Beside that, freezing of slag and non-metallic inclusions in the area of meniscus is suspended, because consumed coolant is in the state of oscillation at any moment and the amplitude is sufficient to guarantee necessary conversion of the matter in the melt .

With requested placement of guiding rollers, the nodes and loops of the waves of forced harmonic oscillation of auxiliary coolant are distributed in the manner that the maximum amount of energy is led to the dip.

The front guiding rollers placed in front of the electromagnets of the contactless electromagnetic vibrator also guarantee the attenuation of auxiliary coolant between the vibrator and feeding unit . As the front guiding rollers are situated in longer or shorter distance than L pursuant to the equation (a) , the attenuation of auxiliary coolant is not provided and oscillation will pass to the feeding mechanism as well as to other mechanisms of the feeding unit, which will destabilize the whole unit.

With placement of rear guiding rollers behind the electromagnet of the contactless electromagnetic vibrator in distance different from L pursuant to the equation (b) , the energy is dissipated or absorbed, which results in not possible directionality in loading the energy and in deterioration of the semi-product structure.

Placement of minimum of two pairs of traction rollers of feeding mechanism in the distance L pursuant to the equation (c) from the contactless electromagnetic vibrator is necessary so that the residual oscillation in the reverse direction from the electromagnetic vibrator could not have a negative impact to the function of the feeding unit. Especially using the equation (b) guarantees stable feeding of auxiliary coolant to the mold, which provides the quality of continuously cast semi-products.

The fact that the control unit of the traction of the feeding mechanism is coupled with the control unit of traction mechanism of the continuous casting enables automatic change of speed of loading the auxiliary coolant in relation to the linear casting speed. Withal, the loading of auxiliary coolant is provided in the amount necessary and sufficient for decreasing the temperature of the dip to the value, when the optimum conditions of creation of equal axis crystal in the mold are provided.

Brief Description of the Drawings

The invention is explained in more details on the drawings of exemplary implementation of the device according to the invention, where: Fig. 1 is the configuration of the whole device of continuous casting Fig. 2 is the cross section of the electromagnetic vibrator

Description of the Preferred Embodiment

The device for implementation of the method of the continuous casting according to the invention depicted of Fig. 1 consists of the unit 8. casting the liquid metal to the mold 10. created by the ladle not depicted at the drawing and by the tundish 7 with submersing nozzle 9. falling into the inlet of the mold 10. The feeding unit of the auxiliary coolant 2 delivered to the mold 10. is created by unwinding barrel 1, where the auxiliary coolant 2 is delivered through the feeding mechanism 3. with straightening rollers 16 and traction rollers 15., then through the lead 5 and contactless electromagnetic vibrator 6 with adjustable slot of PI shape in the horizontal surface which is the source of forced harmonic oscillation of auxiliary coolant 2 to the inlet of the mold 10. Behind the feeding mechanism 3 in the direction of movement of the auxiliary coolant 2 are installed shears 4.

As it is depicted on Fig. 2, the contactless electromagnetic vibrator 6 is equipped with front and rear guiding rollers 11, 14 located in front and behind the system of electromagnets 13. Front guiding rollers 11 placed in front of the electromagnets 13 are from the axis of electromagnets 13 in the distance L^ and rear guiding rollers 14 placed behind the electromagnets 13. of the contactless electromagnetic vibrator 6 are from the axis of the electromagnets 13 in the distance L . Between the front guiding rollers 11 and electromagnets 13 are in the electromagnetic vibrator £ supporting rollers 12..

Two pairs of traction rollers lϋ of feeding mechanism 3 on the Fig. 1 are situated in the distance L₃ from the axis of contactless electromagnetic vibrator 6.

Feeding mechanism 3. of feeding unit is also equipped with the control unit of its traction, which is coupled with the control unit of traction mechanism of the continuous casting machine with the possibility of automatic change of specific consumption to the mold 10 of loaded auxiliary coolant 2.

The method of the continuous casting according to the invention can be used for continuous casting of steel with the carbon content of 0.40 % in weight with the casting speed of 0.43 to 0.44 m/min. During the process of continuous casting, the auxiliary coolant

2 in the form of steel band of cross section of

3 x 80 mm is loaded into the mold 10 with the speed of 4.1 m/min. The content of carbon in the steel band is

0.35 % in weight. The transverse harmonic oscillation of the frequency 95 to 100 Hz, wavelength of 540 mm, and amplitude of 4.0 to 5.0 mm in auxiliary coolant 2 is evoked by the contactless electromagnetic vibrator 6.

In this particular example, the distance is 270 mm (n=l) , ₂ is 135 mm (n=l) and L₃ is 2 295 mm (n=9) .

The width of the slot in the electromagnetic vibrator 6 is 30 mm, which is ten times more than the thickness of the auxiliary coolant 2 . With this technology, which uses the method of continuous casting and device for implementation of this method according to the invention, the auxiliary coolant 2 is fully dissolved and the structure of continuously cast semi-products significantly improves. The axis segregations drops from 3 grades to 1 - 1.5 grades, the central zone of parallel axis crystals increases from 15 % - 20 % to 40 % to 45 % of the semi-product cross section, which is characteristic for significant decrease of the central segregation.

Field of the Application

The method and device according to the invention can be use in any plant of continuous casting of metals.

List of reference sign

1 - unwinding device

2 - auxiliary coolant

3 - feeding mechanism

4 - shears

5 - conveyance

6 - electromagnetic vibrator

7 - tundish

8 - liquid metal

9 - submersing nozzle 0 - mold 1 - front guiding rollers 2 - supporting rollers 3 - electromagnets 4 - rear guiding rollers 5 - traction rollers 6 - straightening rollers

Claims

P A T E N T C L A I M S

1. The method of continuous casting of metals, especially of steel, when the metal is continuously poured to the inlet of the mold, where it gradually cools down and from its outlet solidified semi-product moves to further processing, whilst the auxiliary coolant in the form of at least one wire, band or bar from the material similar to the continuously cast material is loaded to the inlet of the mold, characterized by the fact, that loaded auxiliary coolant is disposed with forced harmonic oscillations, which amplitude, frequency, and wavelength vary in relation to the physical - chemical parameters of cast metal and technological conditions of the casting process.

2. The method according to the claim 1, characterized by the fact, that the amplitude of the oscillation of .loaded auxiliary coolant ranges from 0.5 mm to 15 ,.-Q. mm.

3. The method according to the claim 1 , characterized by the fact, that the frequency of the oscillation of loaded auxiliary coolant ranges from 10 to 1000 Hz.

4. The method according to the claim 1, characterized by the fact, that the wavelength of the oscillation of loaded auxiliary coolant ranges from 200 to 800 mm. The device for implementation of the method according to the claim 1, consisting of casting unit of liquid metal (8) to the mold (10) and feeding device of auxiliary coolant (2) loaded into the mold (10) as well as from the source of forced harmonic oscillation of the auxiliary coolant (2) loaded into the mold (10) , characterized by the fact, that the source of creation of the forced harmonic oscillation of the auxiliary coolant (2) comprises of contactless electromagnetic vibrator (6) with the slot of the fl shape in the horizontal surface and equipped with front and rear guiding rollers (11,14) placed in front of and behind the system of electromagnets (13) whilst the distance L of front guiding rollers (11) placed in front of the electromagnet (13) and the distance ₂ of rear guiding rollers (14) placed behind the electromagnets (13) of the contactless elektromag- netic vibrator (6) from the axis of the elektromag- nets (13) is given by the equations:

Li = n • λ / 2 (a) and

L₂ = (2n - 1) • λ / ⁽b⁾ where

n - any integer number (1, 2, ..., k) λ - length of the wave of oscillation of auxiliary coolant (mm)

6. Device according to the claim 5, characterized by the ^• fact, that the slot of the PI shape in the horizontal surface is designed for possible regulation in range from multiple of 2 to multiple of 15 of the thickness of the auxiliary coolant (2) loaded into the mold (10) .

7. Device according to at least one of previous claims 5 or 6, characterized by the fact, that the feeding unit is equipped with the feeding mechanism (3) with at least two pairs of traction rollers (15) , which are situated in the distance L 3 from the axis of contactless electromagnetic vibrator (6) , which is given by the equation:

I* = (2n - 1) ^■ λ / 4 (c) where n - any integer number (1, 2, ..., k) λ- length of the wave of oscillation of auxiliary coolant (mm)

8. Device according to at least of previous claims 5 to 7, characterized by the fact, that the feeding mechanism (3) of the feeding unit is equipped with the control unit of its traction, which is coupled with the control unit of the traction of the continuous casting machine with the possibility of automatic change of specific consumption of auxiliary coolant (2) loaded into the mold (10) .