JPS61226151A - Continuous casting method for metal and particularly steel - Google Patents

Abstract

PURPOSE:To prevent the cracking of a steel ingot by the constitution consisting in transmitting the overheating energy and solidification energy emitted from a casting by the spontaneous radiation of heat so that the casting shell in a secondary cooling region grows slowly. CONSTITUTION:The casting 1 is formed with the casting shell 1a by a cating mold 2 in a primary cooling region 2a and is guided by a supporting mechanism 3 consisting of supporting rollers 3a in a secondary cooling region 2b, by which the casting is fed to a rolling mechanism. The overheating energy and solidification energy emitted from the casting 1 are transmitted only by the radiation of the heat so that the casting shell 1a in the cooling region 2b grows slowly. The casting 1 solidifies thoroughly during this time and is maintained at the temp. corresponding to the heat capacity necessary for the rolling process at the terminal of a track 5. The cracking of the steel ingot is thus prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for continuous casting of metals, particularly steel, by primary cooling of a molten metal within a continuous casting mold followed by secondary cooling outside the continuous casting mold.

BACKGROUND OF THE INVENTION In conventional continuous casting methods for metals, particularly steel, the cast body is cooled by injecting water in a secondary cooling zone following the continuous casting mold.

Problems to be Solved by the Invention According to the above-mentioned conventional structure, during cooling with water (secondary cooling), supercooling of the material surface actually occurs, and this, together with stress in the casting material, causes damage to the cast body. A middle 1q crack occurs.

During field work, experiments were conducted to alleviate the rapid cooling effect of water. However, in all cases an increasing and decreasing temperature course still occurred, leading to a dangerous expansion of the liquid inside the casting body. In addition, the temperature transfer from the liquid inside the cast body to the solidified surface of the cast body was extremely insufficient. The cast body at the end of the continuous casting mold has a temperature of 15 at 1800°C core.
00°C), and at the end of the continuous casting machine approximately 120°C
The surface temperature is 0°C, and at this time the core of the cast body has just solidified. This method requires a relatively long coagulation interval.

An object of the present invention is to provide a method for continuous casting of metal, particularly steel, which eliminates the above-mentioned problems.

Means for Solving the Problems In order to solve the above problems, the continuous casting method for metals, particularly steel, of the present invention provides a method for continuously casting metals, particularly steels, by primary cooling within a continuous casting mold followed by secondary cooling outside the continuous casting mold. , especially a continuous casting method for steel, in which the superheating energy and solidification energy emanating from the casting body in the secondary cooling zone and the continuous casting mold and the end of the casting guide track slow down the growth of the casting shell. At this time, the superheating energy and coagulation energy are transferred exclusively through thermal radiation.

Further, the temperature of the cast body at the end of the cast body guide track is set to a temperature corresponding to the heat capacity required for the subsequent rolling process.

The underlying problem of the invention is to avoid thermal loading of the casting cross-sectional area and thus eliminate dangerous thermal stresses that can lead to internal and surface cracking of the casting material.

This problem is solved by the present invention as follows. In other words, overripe energy and solidification energy are removed from the cast body in the secondary cooling area.

To this end, the growth of the cast shell is slowed down between the continuous casting mold and the end of the casting guide track, and in this case, the superheating energy and solidification energy are transferred exclusively by heat radiation, and the end of the continuous casting device and the rolling mechanism are The temperature at the end of the casting guide track is such that it corresponds to the heat capacity required for the rolling process, taking into account the energy addition corresponding to the loss during the residence time during the flow into the casting body. This type of cooling is not rapid in the sense of jet water cooling, but is gentle, with heat removal through natural thermal radiation.

This cooling increases the absolute final temperature at the end of the continuous caster, so that additional heating for the immediate rolling process can be omitted. Furthermore, the temperature gradient is reduced over the entire cross-section of the casting. This causes unfavorable dendrites in the casting structure to recede.

Generation of globolite structure, which is advantageous for reprocessing, is promoted.

In the refinement of the invention, the extraction of superheating energy and coagulation energy is controlled by reflection of thermal radiation. This results in slow cooling, but evenly throughout the entire casting cross-section, thus avoiding the formation of single cracks.

Furthermore, it is proposed to control the reflection of thermal radiation by varying the heat absorption within the support mechanism of the secondary cooling.

It can be done conveniently.

The device for carrying out the method according to the invention furthermore has the support spacing of the support mechanisms of 80 to 120111, reducing the spacing between the support mechanisms to a minimum, and covering the surfaces of the rollers constituting the support mechanisms with an insulating layer. Covered.

It is proposed that the insulating layer consists of a metal-ceramic coating. The required slow heat dissipation is controlled by the insulating layer of the rollers of the support mechanism, so that an equalization of the temperature gradient occurs over the entire casting cross section and crack-free cooling is achieved.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. The cast body (1) is cooled in the continuous casting IM (2), i.e. by the circulation of cooling water behind the steel walls forming its mold (2), forming a cast shell (1a), which is further The continuous casting mold (2) surrounding the liquid core α is in the -secondary cooling zone (2a).
A support mechanism (3) consisting generally of support rollers (3a) outside the continuous casting mold (2) forms a secondary cooling zone (2).
It is in b). The cast body (1) has a diameter of about 1800" C1 on its surface at the exit of the continuous casting mold (2).
With a temperature of 500'C, field experimental studies indicate that radiative heat removal provides sufficient cooling. Cast shell (1
a) grows from the outside to the inside, so that the casting (1) completely solidifies while moving along its trajectory (5). Orbit (
At the end (not shown) of 5), the cast body (1) still has a heat capacity, which is given by taking into account the heat losses that occur during the residence time between the end of the continuous casting device and the rolling mechanism. Moreover, the cast body (1) is divided according to the length of the rolled material. Control of heat removal in the secondary cooling zone (2b) is regulated by heat absorption in support machine #i (3). That is, the amount of heat of the cast body (1) to be discharged is adjusted according to the superheating energy and solidification energy that are known in advance, and therefore the amount can be calculated.

The amount of energy applied to one support mechanism (3) can be calculated by the diameter "Dll", the support spacing "Y" and the gap @X11 between each two support mechanisms (3). The distance 1Y' is between 80 and 120 degrees, and the distance between the surfaces of the support rollers (8a) is reduced to a minimum gap of 2''. The supporting roller (3a) is provided with an insulating layer (6), and the HJ (6) consists of a metal-ceramic coating in the embodiment. This insulating layer (
6) is heated by the hot casting body (1) until safety against wear and/or cracking is guaranteed. The thermal energy of the casting (1) is also discharged by a cooling medium (7), for example cooling water, which passes through the support mechanism (3). The casting body (1) moves in a hot state and the temperature gradient from the casting body center (8) towards the casting outer region (9) is low. The bearing αO supporting the support roller (3a) is cooled by a cooling medium (7). It is therefore protected from radiant heat.

The above-mentioned continuous casting apparatus is a so-called dry operation continuous casting apparatus, in which cooling water is injected toward the cast body (1) from the separated support roller (8a) III, except for cooling the support mechanism (3) or bearing αO. That is unnecessary. Such dry continuous casting apparatuses are of special significance because, on the one hand, the continuous casting apparatus requires fewer operations and, on the other hand, significant energy savings are achieved. This means that no thermal energy is required for rolling the cut continuous cast pieces and no heating in special preheating furnaces is necessary.

The heat load is as is clear from FIG. 3, and the basis of curve 1 of the comparative example is the injection water cooling with a high heat load of the casting material at the surface. Comparative curve 2 provides gentle cooling with a much lower temperature heat load, but even this cannot completely eliminate surface cracking in special cases in the field. In contrast, the embodiment of the present invention, as shown by curve 8, shows a negligibly small heat load, in which case the absolute temperature is relatively high. The individual cooling methods at the ends (1', 2', 8') of the cast rod guide track (5) are (El)
, (E2).

It has an energy capacity of (E3).

The invention will now be explained using the enthalpy graph according to FIG. The enthalpy of the metal melt field in the continuous casting mold (2) is expressed as E kok, and the temperature at that time is Tko.
Represented by k. - After secondary cooling (2a) and secondary cooling (2b)
The rolling loenthalpy (Ewalzanst) tte(7) j-*k ghee is taken away from the mold enthalpy (Ekok) in the region of , and thus the rolling mouth temperature (Twalzanst) is obtained.

Next, preferred embodiments of the present invention will be described.

1. A continuous casting method for metals, especially steel, characterized by controlling the absorption of superheating energy and solidification energy by reflecting thermal radiation.

2. A method for continuous casting of metals, in particular steel, characterized in that the reflection of thermal radiation is controlled by a change in the absorption of heat into the support structure of the secondary cooling zone.

8. The support spacing (T) of the support mechanisms that make up the casting rod guide track is reduced from 80 to 1201EII, the spacing between the support mechanisms is reduced to the minimum spacing, and the surfaces of the rollers that make up the support mechanism are insulated. Apparatus for continuous casting of metals, especially steels, characterized in that they are coated with a layer.

4. An apparatus for continuous casting of metal, especially steel, characterized in that the insulating layer consists of a metal-ceramic coating.

Effects of the Invention As described above, according to the present invention, superheating energy and solidification energy are removed from the cast body in the secondary cooling region, and therefore the casting shell growth is prevented between the continuous casting mold and the end of the casting rod guide track. , the transfer of superheating energy and solidification energy is carried out exclusively by means of thermal radiation, and the additional energy corresponding to the losses during the residence time between the end of the continuous caster and the entry into the rolling mechanism is taken into account. At the end of the casting rod guide track, the temperature of the cast body corresponds to the heat capacity required for the subsequent rolling process. This type of cooling is not rapid in the sense of jet water cooling, but is gentle, with heat removal through natural thermal radiation. This cooling increases the absolute final temperature at the end of the continuous caster, so that additional heating for the immediate rolling process can be omitted. Furthermore, the temperature gradient is reduced over the entire cross-section of the casting. As a result, unfavorable dendrites in the casting structure recede, and the formation of a globolite structure, which is advantageous for reworking, is promoted. Also, the extraction of superheating energy and coagulation energy is controlled by reflection of thermal radiation. This results in slow but uniform cooling over the entire casting cross-section, thereby avoiding crack formation.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical cross-sectional view of a curved continuous casting device, Fig. 2 is a view taken along the line ■-■ in Fig. 1, Fig. 3 is a graph regarding the surface temperature progression in three types of cooling methods, and Fig. 4 is It is an enthalpy graph showing the relationship between steel and temperature. (1)... Cast body, (2)... Mold, (2a)...
...-Next cooling region. (2b)...Secondary cooling area, (3)...Support mechanism, (
5) ...Orbital Agent Yoshihiro Morimoto Figure 1 Figure 3 1'2'3' 1 Am-IL (Honrai Ensho Mimane Figure 4

Claims (1)

[Claims] 1. Continuous casting method for metals, especially steel, by primary cooling within the continuous casting mold followed by secondary cooling outside the continuous casting mold, in which the superheating energy emitted from the cast body in the secondary cooling area and The solidification energy is removed between the continuous casting mold and the end of the casting guide track by slowing the growth of the casting shell, and at this time, the superheating energy and solidification energy are transferred exclusively by thermal radiation, and the casting body A continuous casting method for metals, etc., and steel, characterized in that the temperature of the cast body at the end of the guide track is set to a temperature corresponding to the heat capacity required for the subsequent rolling process.