JPH04322842A - Mold for continuously casting molten metal - Google Patents

Abstract

PURPOSE:To enlarge molten powder flow passage and to obtain a cast slab having good surface characteristic by including electromagnetic induction coil in inner part of a mold and applying ceramic lining on inner wall surface of the mold. CONSTITUTION:In the mold, the electromagnetic induction coil 10 is included so as to surround molten metal incorporated in the inner part and further, the ceramic lining 14 is applied on the inner wall surface of mold. The ceramic lining 14 is set at position corresponding to meniscus of the molten metal poured in the inner part and is desirable to be material having difficult-to-erode with the molten powder material and alumina-graphite series, BN series or Si3N4 series ceramic, is used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used in continuous casting of molten metal such as steel.

0002

2. Description of the Related Art FIG. 3 is an explanatory diagram of a conventional continuous casting mold. The molten metal 2 to be injected is injected below the meniscus 3 of the molten metal in the water-cooled mold 1 using an immersion nozzle 9. A powder agent 8 is placed on the meniscus 3 of the molten metal. The molten metal inside the mold is cooled along the wall surface, and becomes a semi-solid slab with a solidified outer shell. The semi-solid slab is pulled out in the direction of arrow 6 by pinch rolls 5. 4 is cooling water spray,
The semi-solidified slab after coming out of the mold 1 is cooled to promote solidification. The mold 1 is periodically vibrated in the direction of arrow 7. The powder agent 8 is melted, and the molten powder agent flows into the gap between the inner wall surface of the mold 1 and the meniscus 3 of the molten metal, and lubricates between the inner wall surface of the mold 1 and the semi-solid slab.

JP-A-52-32824 relates to a method for improving the lubricity of powder agents. That is, an electromagnetic induction coil 10 is built into the mold 1, and an alternating current of low to medium frequency is applied to the coil. Due to this energization, the meniscus 3 of the molten metal is curved to a middle height as shown by a dotted line 13. This curvature makes it easier for the molten powder to flow into the gap between the inner wall surface of the mold 1 and the meniscus 13 of the molten metal, improving the lubrication between the inner wall surface of the mold 1 and the semi-solid slab, and improving the lubrication between the inner wall surface of the mold 1 and the semi-solid slab. The surface quality becomes better.

For example, in continuously cast slabs for producing bright annealed finished steel sheets, it is important that the surface has extremely high cleanliness. However, according to the findings of the present inventors, the method of JP-A-52-32824 does not sufficiently improve the surface properties.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a continuous casting mold suitable for producing slabs with extremely excellent surface properties.

[0006]

[Means for Solving the Problems] The present invention has an electromagnetic induction coil built in so as to surround the molten metal inside the mold, and a ceramic lining on the inner wall surface of the mold at a position corresponding to the meniscus of the molten metal. This is a mold for continuous casting of molten metal, which is characterized by:

FIG. 1 is an explanatory diagram of a longitudinal section of a mold according to the present invention. The body of the mold of the present invention is made of water-cooled copper. Figure 1
, the description of water cooling piping, etc. is omitted. The mold of the present invention incorporates an electromagnetic induction coil 10 so as to surround the molten metal contained therein. This electromagnetic induction coil has 10~
An alternating current of 500 Hz is applied to form an electromagnetic field with a magnetic flux density of 100 to 3,000 Gauss or more at the center of the cross section at the height of the upper end of the coil. As described later, in the present invention, the meniscus of the molten metal in the mold is curved into a medium-high shape. If the frequency is less than 10Hz, the flow of the molten metal becomes too intense,
When the frequency exceeds 500 Hz, the penetration depth of the eddy current generated in the molten metal is shallow and the bending effect is small.

The mold of the present invention further includes a ceramic lining 14 on the inner wall surface of the mold. The ceramic lining 14 is provided at a position corresponding to the meniscus of the molten metal poured inside. In normal continuous casting, the meniscus of the molten metal is operated so that the height from the lower end of the mold is 2/3 or more of the total height of the mold. Therefore, for example, if a ceramic lining 14 is applied to a range of 1/3 of the total height of the mold from the upper end of the mold, the ceramic lining is always applied to the inner wall surface of the mold corresponding to the molten metal meniscus. The ceramic used for the lining is preferably a material that is not easily corroded by the molten powder material, and for example, alumina graphite-based, BN-based, or Si3N4-based ceramics can be used.

[0009]

[Operation] In conventional continuous casting of steel, a lubricant such as continuous casting powder is put into the mold. This lubricant, such as powder, improves the lubrication between the slab and the mold when drawing the semi-solid slab, reduces wear on the mold walls, and at the same time alleviates various thermal stimuli on the mold surface, suppressing the occurrence of surface defects. It also has the role of protecting against mechanical wear and tear. In addition, when drawing a slab, the mold constantly moves up and down by several millimeters or tens of millimeters dozens of times per minute, which makes it easier to pull out the slab. is a groove-shaped afterimage (hereinafter referred to as oscillation mark) on the surface of the slab.
This caused the surface quality of the slab to deteriorate.

[0010] However, in any of the above cases, such as the phenomenon of the lubricant, such as powder, flowing into the surface of the cast slab, or the phenomenon of the formation of oscillation marks, physical properties such as the surface tension of the molten metal or the lubricant, such as powder, It is already well known that the molten metal temperature, oscillation mode, drawing speed, etc. are important factors that define the above-mentioned phenomena, and on the other hand, the molten metal temperature, oscillation mode, drawing speed, etc. are important factors.

[0011] In addition to the above, in order to hold the molten metal meniscus within its vertical range, a continuous casting device is used, which is equipped with an electromagnetic coil device surrounding the mold.
Performs continuous casting of molten metal. At this time, by applying electromagnetic force to strongly curve the molten metal meniscus area, especially the meniscus area between the mold wall and the molten metal contact area, the oscillations that occur in the slab when the mold oscillates,
It is possible to reduce marks, promote good flow of molten powder, reduce surface flaws, and improve the surface properties of the slab.

However, in this case, the lubrication improvement effect is not sufficient, and the degree of improvement in the depth of the surface oscillation mark varies in the cross-sectional and circumferential direction. That is, due to the curvature of the molten metal meniscus, the flow path of the molten powder temporarily widens, but due to the widening, the mold side of the molten powder is cooled, and a fixed powder (hereinafter abbreviated as a fixed substance) is formed. Therefore, the molten powder flow path is narrowed again and the lubrication promoting effect is halved. Further, since the adhered substances are not generated uniformly within the cross section, variations in the circumferential direction of the molten powder flow path appear, and the above-mentioned phenomenon occurs.

FIG. 2(B) is an example of the present invention. In the mold of the present invention, a ceramic lining 14 is provided on the inner wall surface of the mold at a position corresponding to the meniscus of the molten metal. On the other hand, in the conventional example shown in FIG. 2(A), the molten powder 8 comes into contact with the inner wall surface of the water-cooled copper mold, and because the temperature of the inner wall surface of the water-cooled copper mold is low, A solid substance 16 is generated on the inner wall surface of the mold. In the present invention shown in FIG. 2(B), the molten powder 8 is
However, since the surface of the ceramic 14 has a high temperature, the generation of fixed substances 16 can be prevented.

In the present invention, the electromagnetic induction coil 10 is used to curve the meniscus of the molten metal to a middle height as shown in 13.
By curving, the molten powder 8 smoothly flows into the gap between the solidified shell 15 and the mold 1. Furthermore, since there is no fixed object 16 in the mold of the present invention, the flow path 11 for the molten powder 8 is wider than in FIG. It's even smoother.

[0015] In conventional continuous casting operations, various powders with different components were prepared and used by selecting them to suit the operation. Moreover, it has not been easy to operate to reduce non-metallic inclusions caused by powder. However, by using the mold of the present invention, these conventional problems can be significantly improved.

[0016]

[Example] SUS304 steel was continuously cast under the following conditions. That is, the slab size is 200 mmφ, and the drawing speed is 2.
Powder casting was performed at m/min and mold oscillation of 6 mm x 100 cycles. Electromagnetic field (1,3
00 Gauss) is applied to the mold (height 600 mm). When the mold (height 600 mm) is lined with ceramics (alumina graphite type) to a depth of 200 mm from its upper end (invention). ■ When no lining is applied (comparative example). ) and compared the circumferential distribution of oscillation mark depth. As a result, the distribution width in the comparative example was 100 to 250.
(2) In the present invention, it was 50 to 130 μm, and good surface quality with little variation was obtained in the present invention.

[0017]

[Effects of the Invention] By using the mold of the present invention, it is possible to produce slabs whose surfaces are even more clean than those of the prior art.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a vertical cross section of the mold of the present invention, FIG. 2 is an explanatory diagram of the operation of the present invention, and FIG. 3 is an explanatory diagram of a conventional continuous casting mold.
It is.

[Explanation of symbols]

1: water-cooled mold, 2: molten metal to be poured, 3: meniscus of molten metal, 4: cooling water spray, 5: pinch roll, 6: drawing direction of slab, 7: vibration direction of mold, 8: powder agent (melting powder),
9: Immersion nozzle, 10: Electromagnetic induction coil, 11
: Flow path of molten powder, 12: Injected molten metal,
13: Meniscus of molten metal, 14: Ceramic lining, 15: Solidified shell, 16: Fixed substance.

Claims (1)

[Claims] 1. A molten metal continuum, characterized in that an electromagnetic induction coil is built in so as to surround the molten metal inside the mold, and a ceramic lining is applied to the inner wall surface of the mold at a position corresponding to the meniscus of the molten metal. Casting mold.