JPS5950958A - Cooling method in twin roll type continuous casting device for steel - Google Patents

Abstract

PURPOSE:To produce directly a thin sheet having a beautiful surface in a twin roll type continuous casting device by cooling the inside surface of rolls through forced circulation of a refrigerant, and immersing the corresponding part on the outside circumference into molten metal. CONSTITUTION:Molten metal is supplied from a nozzle 14 and rolls 11, 11' are rotated in arrow directions, whereby the molten metal is cast. Since the casting speed is high, the position of the molten metal on the rolls 11, 11' is detected and the roll speed is changed by automatic control. The speed is fed back to the supply rate of the molten metal so that said speed is maintained at the planned casting speed. The rolls 11, 11' are provided internally with water cooling mechanisms so that the cooling water is passed in the cooling grooves on the inside circumference of the rolls to cool the copper sleeves. The molten metal in a metal well 21 is supplied by a circulation pump 22 to the coolers 19 on the outside circumference of the rolls 11, 11' and is cooled with a heat exchanger 20. A billet 13 is coiled on a roll 25 through auxiliary rolls 23.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling method in a twin-roll continuous casting apparatus for steel.

A method of manufacturing a preparation by continuous casting by pouring a molten steel stream into the gap between a pair of rolls is already well known.

In other words, Bessemer proposed continuous VJ construction for the first time before 100 years ago, and the hole was opened upside down. However, this method has not seen much improvement, and the improved continuous casting method of Junghans and Lodge et al. is mainly used for casting steel. In the current method, in order to make a thin plate with a thickness of about 2 mm, for example, a slab with a thickness of 200 to 300 mm is made using a continuous casting machine at a casting speed of 0.6 to 2 degrees of convergence.
This is rolled in a hot rolling mill to form a hot rolled thin plate. When using the twin roll method, plates of about 2 to 9 inches can be directly produced. Despite these advantages, the reason why this method has not been neglected is that when it is applied to steel,
This is believed to be because the high melting point of steel imposes a large heat load on the rolls, making it impossible to cast stably and therefore making it impossible to obtain excellent surface quality.

The present inventors conducted an experiment using a twin-roll continuous casting machine consisting of a pair of rolls of 500 trsφ x 1 m length, and found that in this equipment, the rolls received an extremely large thermal load. We discovered that it is essential for operation and maintenance of material quality, and adopted a new cooling method to obtain thin sheets of excellent quality.

Several considerations in implementing twin roll casting are achieving high pouring speeds. If the above-mentioned conventional continuous casting machine were to cast, for example, a 250 mm thick slab at a rate of 1.2 m/min, the production rate would be approximately 250 t/11, but with a twin roll machine, for example, To obtain the same capacity with a thin plate between 2.5 m and 7 seconds, it would be necessary to cast 2.5 m in 7 seconds. Since it is attractive as a production facility, it is expected that it will be about this level, or at least a fraction of that. From this point of view, 0.25 m1 second to 0.75 m1
A casting test was carried out on a thin plate measuring 2 mm x 500 mm at a casting speed of 2 seconds.

The above-mentioned 7 rolls are cast steel rolls with 1' and 30 r
It is made by shrink-fitting a Ml copper sleeve, and water is supplied and distributed from the central shaft to forcibly cool the copper sleeve. This is shown in Figure 1.

FIG. 1 is a sectional view of a roll used in the present invention.

1 (rJ, roll body made of 611 steel etc., 2
is a sleeve made of copper or the like. A water supply and drainage main pipe 3 is opened at the center of the roll body, and distributed around the outer periphery through four to eight distribution pipes 4. The header 5 is formed along the circumference of the roll body, and the cooling channels 6 are formed of multiple shallow channels several millimeters deep at narrow intervals, thereby cooling the copper slig. The slab 7 is cast into the portion where the cooling channel is formed, which is indicated by the two-dot thin line.

Using this roll, 0.25 m/paper, 0.375 m/
seconds, 0.5m/second, 0.625 m7 seconds, 0.75m/
At a casting speed of seconds, C0.05%, Mn 0.35%,
A casting test of molten annealed copper of St 0006 was conducted.

Molten metal is supplied from a 100 kg high frequency melting furnace. The twin roll casting machine is as shown in FIG.

In Figure 2, 11.11' is a casting roll, 12°12
' is a limiting plate that limits the roll cooling range, 13 is a slab, 1
Reference numeral 4 represents a nozzle for supplying molten metal, and reference numerals 15 to 17' represent drive devices for the restriction plates. 18.18' is connected to the roll drive by a roll neck. A cooling device is used for 19 tons to form a seal around the entire circumference and press it onto a roll to form a semi-closed space. This cooling device uses molten metal such as sodium as a cooling medium, and the molten metal enters through pipe 27 and exits through 28, is cooled by heat exchanger 20, enters metal reservoir 21, and is circulated by pump 22. Heat from the molten metal is recovered from boiler 29.

The slab tri, M is wound up by a winding roll 25 via an auxiliary roll 23 and a bending roll 24.

Most of the equipment is in a space (casting chamber) that is sealed from the surroundings 26
is formed, and nine layers are introduced here to prevent the slab from forming into one condyle.

The molten metal is supplied from the nozzle 14, and the rolls 11 and 11' are rotated in the direction of the arrow to perform lj construction. Since the casting speed is fast, the position of the molten metal on the roll], 1, 11' is detected and the speed of the roll is changed by automatic control 1 to 1 degree.
Feedback is made to the molten metal supply amount so that the casting speed reaches 11 points. °Roll] 1 and 11' are equipped with a water cooling mechanism as shown in Fig. 1, and the cooling water flows through the cooling grooves around the roll at a flow rate of about 5FM/sec to 101υH). ?4 Cool 2).

The slab 13 is wound up onto a cooling tongue-up roll 25 by heat transfer to the lower auxiliary roll 23 and radiation into space. At this time, the rolls 11 and 11' are cooled from the outer periphery with molten metal in the case of wood and light. As shown in FIG.
, 11' is cooled by supplying the molten metal to a cooling device 19 sealed by jetting or pressing the molten metal stream against a roll. The molten metal is supplied from the metal reservoir 21 to the roll cooling via the circulation pump f22, and then to the heat exchanger 20.
It is configured so that it returns to the metal reservoir 21 via (□).

Casting chamber 16 contains 11 parts of sodium as molten metal.
Be careful not to let air or moisture get inside. n) IJum was circulated at a rate of 1.8t/hour.

When a casting test was conducted in this way, the result was 0.75m.
It is possible to work stably up to the casting speed of 100% from the furnace.
It was found that it was possible to process kg of molten metal. In addition, the surface quality of the obtained slab is good up to 0.6252?1/sec,
It was found that the speed deteriorated slightly at 0.75 m/sec and was almost at its limit.

In order to plan such table results, we measured the inflow and outflow degrees of cooling water from the rolls and molten metal for cooling the outer surface, and investigated the amount of heat absorbed by each. The results are shown in Table 1.

The fever in Table 1 is calculated by dividing it by the number of days it was created. As seen from this 1, it can be seen that the ratio of cooling by the liquid metal externally cooled by the roll increases as the forming speed increases.

From the above results, it was found that external cooling of the roll with molten metal is advantageous in many respects. In other words, the casting speed can be increased, and the surface quality of the slab T[
and to obtain it without converting the slab into 61 (
l″l: As already mentioned in the text.Furthermore, this device is C) As you can see, it is possible to recover heat from a single piece of the sheath, d, and a large actual machine W.
λ(+it+ would be a big advantage.This JA
As can be seen from Table 1, it is essential to use in-roll cooling.

Note that since the heat load of cooling inside the roll is high as described above, it is also possible to use a single liquid metal.

This makes it possible to recover most of the heat from the molten metal being poured. Molten metal is 300℃ to 400℃ for both internal and external cooling.
5 to 10 kvC via a heat exchanger to raise the temperature to
It is possible to recover more than rn vapor.

Based on the above experimental results, we investigated the case of applying it to large-scale equipment. In the actual machine, the core wall is to manufacture thin plates with a width of 1 to 2 m. In this case, the diameter of the casting roll is also increased, but since the heat load per unit area can be made the same, the casting speed can be approximately increased in proportion to the diameter of the roll. Therefore, for example, roll diameter 2
It can be estimated from the results of this experiment that a casting speed of 2.5 ml/sec for the front edge can be achieved at mφ.

Since a copper mold was used in the experiment, sodium was used as the molten metal, but considering the safety of a large actual machine, lead, lead-
It is preferable to use alloys such as blue lead and lead-tin. When using such a material, it is necessary to use a material other than copper plate as the sleeve material for the roll. Such materials include nickel, mild steel, etc., but molybdenum is the most preferable material. Unlike general rolls, they are exposed to temperatures up to about 500°C as molds, so they must have sufficient rigidity and as good thermal conductivity as possible up to this level of τ quality. Nickel, mild steel, etc. are selected, but molybdenum in particular has these characteristics. However, they still lack corrosion resistance to lead alloys.

According to the present invention, thin plates can be directly cast, and when cast under the conditions of the present invention under proper cooling conditions, the cooling chamber for the slab is non-oxidizing, and a base plate with a beautiful surface is formed. can get. The sheet obtained according to the present invention had no freezing problem when used in a conventional cold rolling process.

In this specification, it is sometimes referred to as a slab and sometimes as a cast thin plate, but unlike conventional continuous casting methods, the present invention is mainly intended for thin plate-shaped pieces. It is not suitable for manufacturing rods or single wire H.

Embodiments of the present invention are listed below.

(1) Form a sealed space between the rolls and
A method according to the claims, in which molten metal is forcedly circulated.

(2) Cooling in the rolls is also a conventional method by forced circulation of the molten metal.

(3) The method according to the claims, wherein the casting roll of the twin roll casting machine has an outer periphery of copper or a copper alloy, and the molten metal is an alkali metal.

(4) The method according to the claims, wherein the casting roll of the twin roll casting machine has an outer circumference of molybdenum, and the molten metal is lead or a lead alloy.

(5) A method according to the claims, in which heat is recovered from a continuous casting machine using molten metal.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a roll used in the method of the present invention, and FIG. 2 is an explanatory diagram of a continuous casting apparatus that uses the method of the present invention. Patent applicant Nippon Steel Corporation

Claims (1)

[Claims] In a continuous casting machine that produces steel billets by casting molten steel into the gap between a pair of rolls and drawing it out at high speed, the rolls are cooled by forced circulation of a refrigerant on their inner surfaces, and a considerable portion of the outer periphery is poured into the molten metal. A method of cooling copper in a twin-roll continuous casting machine, characterized by immersion in a copper bath or injection of molten metal.