JPS61289950A - Continuous casting method for thin sheet - Google Patents

Abstract

PURPOSE:To form a continuously cast thin sheet having no transverse cracks and bulging by detecting the reaction of the solidified shell formed on drum surfaces and controlling the space between the drums in accordance with the detected reaction in the stage of continuously casting the thin metallic sheet with a twin drum system. CONSTITUTION:A molten metal is continuously cast to the continuously cast thin sheet-like steel ingot 3 by the twin drum system having the water cooling type casting drums 1, 1' and is drawn out by pinch rolls. The reaction of the drums is detected in this case in such a manner as to satisfy the equation when the coincidence point P of the solidified shell on th surfaces of both drums is above the neutral point of both drums and when the solidification thickness at the coincidence point of the solidified shell (1.0 solid phase rate) is designated as dSmm and the space between both drums as (t)mm and also in such a manner that the coincidence point Q of the 0.2 solid phase rate region of the molten metal exists on the neutral point of the drums or above said point when the point P of the solidified shell is below the neutral point of both drums. The space between both drums is finely adjusted and the thin steel ingot 3 having no cracks and bulging is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for continuously casting thin strips of ferrous and non-ferrous metals and alloys.

In particular, the present invention relates to a thin plate continuous method using a twin drum system.

[Conventional technology]

There is a twin-drum continuous casting process in which molten metal is poured between two drums and a thin plate having a thickness of 2 to 6 mm is continuously cast.

[Problem that the invention seeks to solve]

In the twin-drum continuous casting process, when the thickness of the thin plate is 2 to 6M4, the time for the molten metal to solidify in contact with the drum, the so-called solidification time, is usually 0.5 to 2Bθ0.

Strict control of this short-time solidification is essential in order to maintain good properties of the obtained slab, but the conventional control method is to change the drum rotation speed depending on the amount of poured metal. , coagulation is not well controlled.

Horizontal cracks or bulging (bulging phenomenon in the slab) occurred in the slab, and the properties of the FA slab were not satisfactory.

The present invention aims to provide a continuous thin plate casting method that strictly controls the solidification of molten metal on the drum surface and improves the properties of slabs.

[Means for solving problems]

The present invention is a means to achieve the above object.

The point is to control the position of the matching point of the two solidified shells formed by cooling the molten metal on the drum surface.

That is, in the present invention Fi, a thin plate continuous casting method using a twin-drum method, a solidified shell is generated on the drum surface.

(1) If the matching point of the two solidified shells on the drum surface is above the neutral point of the drum, the 9th equation [However, in the above equation, d8 is the value of the solidified shell (solid phase ratio 1.0)] Solidification thickness at the matching point u).

t indicates the drum gap (frame). ] to satisfy you.

(2) If the matching point of the two solidified shells on the drum surface is below the neutral point of the drum, the solid phase ratio of the molten metal is 0.
So that the matching point of the two areas is at or above the drum neutral point.

This continuous casting method is characterized by detecting the reaction force of the drum and minutely controlling the drum gap.

〔composition〕

Based on FIG. 5, a twin-drum continuous thin plate casting apparatus suitable for carrying out the present invention will be described. This device consists of water-cooled casting drums 1, 17, .
The main components include a fixed side weir 212' that prevents the molten metal 4 from leaking between the water-cooled casting drums 1 and 11, and a tundish 5 that stores the molten metal 4 such as molten steel.

To explain this device in detail, the water-cooled drums 1, 1/
is installed horizontally and is driven to rotate (in the direction of the arrow) by a drive device (not shown). This water-cooled drum 1, 11
is made of copper, copper alloy, or steel, for example,
The drum has a fairly large diameter in order to have a large contact area with the molten metal 4, and has several built-in water cooling components.The water-cooled casting drum 1.1' has a large diameter drum at both ends.

Fixed weir 2 made of fireproof material for sealing the sides,
9. Two water-cooled casting drums 1.
Molten metal 4 is poured into the space formed by 1' and the two fixed weirs 2, 2'. The molten metal 4 comes into contact with the surface of the water-cooled casting drum 1.1' and is cooled, resulting in a solidified shell that is integrated into a slab 5. This slab is pulled out by pinch rolls 6. Note that 7 is a guide roll.

[Effect]

A detailed method for maintaining the properties of the slab 5 in the twin-drum continuous thin plate casting apparatus described above will be explained in detail with reference to FIGS. 1 and 2.

FIG. 1 shows the case where the matching point (point P) of the two solidified shells is located above the neutral point υ of the water-cooled casting drum 1.11. In this case, if the solidified thickness at the matching point of the solidified shell (solid phase ratio 1.0) is d8 (■), then 1 In the present invention, the P point is controlled so as to satisfy the following equation (1). .

2 @ d8 [Friendship 1) In the formula, t is 1 between drums! J(llil)
shows. ] In the present invention, the reason why the P point is controlled so as to satisfy the above equation (1) is that if the il1 equation is not satisfied, the oversolidification state will be excessive, and rolling will occur near the neutral point of the water-cooled casting drums 1 and 11. This is because horizontal cracking occurs on the surface of the slab 5, which significantly impairs the properties of the slab.

FIG. 2 shows the case where the matching point (point P) of the two solidified shells is below the neutral point of the water-cooled casting drum 1.1'. In this case, let Q be the matching point in the 0.2 solid phase ratio region of the molten metal (if the solid phase ratio is lower than this, the shell strength will be 0 and 9 bulging will occur).1 In the present invention, the Q point is set at the drum neutral point or above the drum neutral point.

The reason why the Q point is controlled to satisfy the above-mentioned range in the present invention is that if the above-mentioned range is not satisfied, the unsolidified state becomes excessive, and the water-cooled casting drum 1.11
This is because a bulging phenomenon occurs on the surface of the slab 5 after passing through the neutral point of the slab, which significantly impairs the properties of the slab.

The present invention detects the reaction force of the drum and finely controls the gap between the drums so as to satisfy the above-mentioned conditions, thereby preventing transverse cracks on the surface of the slab 3.

This prevents the bulging phenomenon from occurring.

〔Concrete example〕

The dimensions and various conditions of the structural members in the case of casting steel are as follows.

(11 water-cooled cast drum made of steel and internally water-cooled.Drum diameter is 2000mmφ, drum width is 1200mm, dimensions of cast slab are 3mm t x 1200mm width,
The drum rotation speed (casting speed) at this time is approximately 281Ll
/min.

(2) In the case of molten normal steel, the temperature of the molten metal in the tandyer is 1520.
~1570°C. The molten metal head on the water-cooled casting drum is approximately 5 oots.

+31 Convert the solidification control P point and Q point into the limit pushing force in each range (the limit value at which transverse cracking or bulging occurs if it is more or less than this), 1 ton<F<
The gap between the drums was controlled to be within a range of 7 tons (F is pushing force).

As a result of tone casting under the above conditions, slabs with all good properties were stably obtained, with no transverse cracks or bulging on the surface.

〔Effect of the invention〕

As described in detail above, the present invention detects the reaction force of the drum and controls the gap between the drums so that the solidified shell generated on the drum surface in a twin-drum continuous thin plate casting machine satisfies the above-mentioned conditions. This produces the effect that the properties of the thin plate slab can be maintained stably and in good condition. That is, the present invention has the remarkable effect of continuously and stably obtaining a thin plate slab having good properties without surface transverse cracks or bulging.

[Brief explanation of the drawing]

Figures 1 and 2 show the coincident points of two solidified shells on the surface of the water-cooled casting drum. FIG. 5 is a vertical cross-sectional view of a twin-drum type continuous thin plate casting apparatus suitable for carrying out the present invention. Atsuo

Claims (1)

[Claims] In a twin-drum continuous thin plate casting method, a solidified shell generated on the drum surface is formed by (1) two casters on the drum surface;
If the matching point of the solidified shells is above the neutral point of the drum, then the following equation (2d_s-t)/(2d_s)≦0.
005 [However, in the above formula, d_s represents the solidified thickness (mm) at the matching point of the solidified shell (solid phase ratio 1.0), and t represents the drum gap (mm). ] In order to satisfy (2) If the matching point of the two solidified shells on the drum surface is below the neutral point of the drum, the matching point in the solid phase ratio 0.2 region of the molten metal is below the drum neutral point. A continuous casting method characterized by detecting the reaction force of the drum and minutely controlling the drum gap so that it is above the neutral point of the drum.