JPS619946A - Method and device for continuously casting metallic molten metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for continuous casting of metals, particularly high melting point alloys such as sea bream.

BACKGROUND OF THE INVENTION During the solidification of molten metals, in particular alloys, so-called segregation occurs, ie different chemical or physical compositions occur in the cross-section and, where appropriate, in the longitudinal section of the solidified copper ingot or continuous slab. In order to prevent or reduce this type of segregation, it is known in copper ingots and continuous slabs to move the molten metal within the mold during solidification. In this case, the molten metal can be rotated, for example by means of an electromagnetic stirring device, in the pouring direction or in the longitudinal direction of the mold, or can be caused to flow from the outer mold edge to the mold inner edge. Such a flow can be obtained by suitably equipped electromagnetic stirring devices and suitable control devices.

However, melt flow starting before the crystallization front can give rise to inhomogeneities or segregation bands. These known negative segregations (white bands) significantly impair product quality.

A vertical continuous casting method is known from DE 29 03 234 A1, in which the bath water enters the mold from a molten metal container via a tap pipe. An electromagnetic stirring device is provided around the tap pipe, and the molten metal can be stirred by this electromagnetic stirring device, so that the molten metal is already given a superimposed movement in addition to the flow direction initiated by the mold. ing.

In horizontal continuous casting, it is already known to provide a talking valve in the molten metal supply line in front of the mold in order to prevent the molten metal from flowing out.

The problem that the invention seeks to solve The invention provides a method for producing a metal with a particularly high surface quality, which minimizes equipment costs, allows an energy-saving operation and significantly increases the internal quality of the continuous slab. I! It is an object of the present invention to provide a method and an apparatus for horizontally continuous casting of molten metal, in particular high melting point alloys such as steel.

molten metal is fed via at least one molten metal supply line from a molten metal container, ladle, etc. to a preferably liquid-cooled mold which is arranged horizontally and is connected in a liquid-tight manner to the molten metal container;
From this mold, the partially solidified continuous slab is gradually
The method according to the invention for the continuous casting of molten metals, in particular high-melting point alloys, e.g. A rotation of the molten metal is generated and the already rotating molten metal is introduced into the mold via an orifice which preferably has a smaller cross-sectional area than the mold. In such a method, the molten metal enters the mold while already rotating, so that the boundary layer or surface layer, which may have notches, for example when gradually withdrawing a continuous slab, has a particularly high homogeneity and is simultaneously An additional acceleration is produced in the direction of flow of the molten metal through the area change. A further advantage consists in the fact that a rotating flow of the molten metal is obtained even at the beginning of the continuous slab solidification shell formation.

If the melt supply line has at least two different cross-sectional areas and the corresponding parts of the melt supply line open tangentially to each other, stirring movements in the melt can be carried out without new energy consumption and expensive equipment. realizable.

If the melt supply line has at least two mutually succeeding parts with different cross-sectional areas and the melt is preferably introduced approximately tangentially from the part with the smaller cross-sectional area to the part with the larger cross-sectional area, the flow direction The rotation of the molten metal around can be realized without additional energy, for example by means of electromagnets, with the entire metal stream being moved at the same time.

A particularly homogeneous continuous slab is obtained in which the flow rate of the Wg melt at each point of the melt supply line remains constant on average over time.

When the molten metal is led out from the molten metal container from a molten metal supply pipe arranged almost vertically to a short molten metal supply pipe arranged at an angle as close as possible to the molten metal supply pipe, the molten metal in the molten metal container is A very slight overheating of the molten metal can be strictly observed.

The molten metal flows faster in the molten metal supply pipe arranged almost vertically than in the molten metal supply pipe arranged at an angle with respect to the molten metal supply pipe, and the melt flows faster in the molten metal supply pipe arranged at an angle with respect to the molten metal supply pipe arranged in the latter molten metal supply pipe. Short melt supply lines can be obtained by introducing the melt approximately tangentially to the cross section of the melt.

Molten metals, in particular refractory metals and alloys, with an lR9 vessel, an approximately horizontally arranged preferably liquid-cooled mold, at least one melt supply line arranged between them and a continuous slab withdrawal device. , for example, an apparatus for continuous casting of steel, in which the molten metal supply line essentially has at least two successive parts with different cross-sectional areas, the first having the smallest possible cross-sectional area as viewed in the flow direction of the molten metal. This consists in that the part opens approximately tangentially into the part following it.

A device of this type provides a particularly simple horizontal continuous casting device, in which at the same time rotation of the molten metal entering the mold is realized, so that surface damage and segregation of the continuous slab can also be particularly reduced. .

According to another feature of the invention, the axis of the melt supply line is twisted in the range of reversal of the direction of the melt flow, preferably from I/2 to 1/6 of the internal diameter of the melt supply line with the larger cross-sectional area.
It has a standard interval of .

According to another advantageous embodiment of the invention, the melt supply line can be closed in the melt container with a plug.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below with reference to embodiments shown in the drawings.

The melt container 1 according to FIG. 1 has a melt supply line 2 which opens into a liquid-cooled mold 4 via an outlet of an orifice 3.

The minimum free IIIt cross-sectional area of the orifice is 4\ larger than that of the mold. A molten metal supply pipe protruding from the molten metal container is attached to the molten metal container via a clamp 5. The supply of molten metal to the mold can be stopped by lowering the tap 6. As can be seen from Figure 1a, the molten metal supply pipe has a monumental cross-sectional area, and the
The part 7 opens in the connection direction into the part 8 which follows it. In the area of the opening, the cross section 7 is approximately as wide as the slit.

Another cross-section of the melt supply line is shown in FIG. 2, in which a melt supply line 9 with an approximately circular cross section opens tangentially into the section 1o of the bath water supply line, and this The parts also have a circular cross section. The cross-sectional area of section 9 is approximately 15
cd, whereas the cross-sectional area of portion 10 is 43a
It is I.

The W semi-distance a is P3 of the molten metal supply pipe with the larger cross-sectional area.
It is approximately 1/4 of the diameter d.

For the horizontal continuous casting apparatus, it is further necessary to provide a continuous slab drawing device, but since this continuous slab drawing device is not a component of the present invention, a description thereof can be omitted here.

pilot! In the apparatus, iron-based alloys and charcoal** of various compositions were first cast by a horizontal continuous casting method using conventional techniques. Casting cross-sectional area is 96 mm in diameter and 100 mm in diameter.
It was square. The weight of the molten metal was 2.5 and +4 tons. The continuous slab material underwent thorough quality inspection. For this purpose, continuous slabs were examined in the transverse and longitudinal directions.

The following results were obtained from the inspection of continuous slabs cast by the prior art.

The circular continuous slabs showed different shell growth, and this immediate growth finally took on a polygonal cross-sectional shape. Furthermore, cooling stress cracks were observed, and continuous slab defects increased as the steel overheated. The shrinkage and solidification structures were eccentrically located within the continuous slab.

By using an electromagnetic field, it was possible to homogenize the crystallization shape and convert eccentric porousness to central porosity inside a continuous slab from about 1/2 radius, but not concentrically. Distributed strips of negative segregation, so-called white bands, formed.

The tests were repeated with the same alloy incorporating the apparatus according to FIG. 1 and using the method according to the invention. The following results were obtained from the inspection of continuous slabs cast by the method according to the present invention.

Example 1 25tCO of alloy slab with the following composition by weight %,
38, Si 0025, Mn 0.7, PO,02
+, SO, 012, residual iron and impurity casting speed or average slab withdrawal speed from the mold was 1.41+1/Win. The mold had a circular cross section of 96M. The superheat of the sea bream at the beginning of pouring was 758C, and the #I humidity temperature in the melt vessel was accordingly 1570C. The molten metal supply pipe is the first with an inner diameter of 40M.
, which opened tangentially into a second part of internal diameter 7j)++s. Both cross sections were circular. The standard spacing between axes arranged twisted relative to each other is 17
．． It was 5Mjl. The following results were obtained from the horizontal and vertical inspection of the continuous slab.

The cross-sectional shape of the continuous slab was circular, and the shell formation of the continuous slab in the mold was uniform. Due to the rotation of the molten metal, cooling stress cracks did not occur in the continuous slab area near the surface even during high superheating of the sea bream. The crystallized shape was sufficiently small spherical, and the eccentric distance of the casting sink could be significantly reduced by /IX.

Example 2 In another test conducted with the same brand of sea bream as in Example 1, a stirring electromagnetic field was used after the mold. Inspection of these continuous slabs revealed that the quality of the continuous slabs was significantly improved. Contrary to expectations and previous experience, no segregation streaks were formed in the continuous slab material after the mold when a moving electromagnetic field was used. The electromagnetic field produced an even greater improvement in the internal quality of the continuous slab.

A notable feature of the continuous slabs cast by the method according to the invention was the crystallization of the continuous slab area close to the surface and a significant improvement in surface quality. When the drawing parameters were the same, the notch was reduced and no embrittlement occurred in the hole mold #2 even if the continuous slab was highly deformed during subsequent rolling.

Example 3 An alloy with the following weight percent composition was cast:

CO,03, Sj 0.65, Mn 1.12, Cr
17.90, Ni 9.02, P O, 022 and 30.012, remaining iron casting speed is I -6 m/m
It was ln. The casting cross-sectional area was +00 square meters. The superheat of the alloy at the beginning of casting was 80°C. Accordingly, the steel temperature in the molten metal container was 1540°C.

The cross-sectional shape of the continuous slab was square, and in this case, the rotation of the molten metal did not cause cooling stress cracks in the continuous slab even when the sea bream was highly overripe. The crystallization shape was well spheroidal. It was possible to significantly reduce the eccentric distance of the casting sink, and at the same time, it was possible to significantly reduce the notches on the surface of the continuous slab. During subsequent thermal deformation, no cracks were formed after the first deformation stroke.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a horizontal continuous casting apparatus, FIG. 2... Molten metal supply pipeline, 7.8, 9, 10... Part of the molten metal supply pipeline Figure 1 Figure 1a

Claims (1)

[Scope of Claims] 1. Molten metal is supplied via at least one molten metal supply pipe from a molten metal container, ladle, etc. to a preferably liquid-cooled mold arranged approximately horizontally and liquid-tightly connected to the molten metal container. In this method of continuous casting of molten metal, the continuous slab is pulled out from the mold as gradually as possible, and in some cases partially backwards.The molten metal is stirred in the molten metal supply pipe, and the molten metal around the flow direction is drawn out. A method for continuous casting of molten metal, characterized in that rotation is generated and the already rotating molten metal is introduced into the mold via the outlet opening of an orifice, preferably with a smaller cross-sectional area than the mold. 2. Process according to claim 1, characterized in that the melt supply conduit has at least two different cross-sectional areas, and corresponding parts of the melt supply conduit open tangentially to each other. 3. The molten metal supply pipe has at least two mutually continuous parts with different cross-sectional areas, and the molten metal is preferably introduced from the part with the smaller cross-sectional area to the part with the larger cross-sectional area almost tangentially. The method according to claim 1 or 2, wherein: 4. characterized in that the flow velocity of the molten metal at each point of the molten metal supply pipe is kept approximately constant on average over time;
A method according to one of claims 1 to 3. 5. A patent claim characterized in that the molten metal is led out from a molten metal container from a molten metal supply conduit arranged substantially vertically to a molten metal supply conduit arranged at an angle preferably substantially horizontal to the molten metal supply conduit. The method according to any one of items 1 to 4 of the range. 6. The molten metal flows faster in the molten metal supply pipe arranged approximately vertically than in the molten metal supply pipe arranged at an angle with respect to the molten metal supply pipe, and the melt flows faster in the molten metal supply pipe arranged at an angle with respect to the molten metal supply pipe arranged in the latter molten metal supply pipe. 6. The method according to claim 1, wherein the method is introduced approximately tangentially to the cross section of the road. 7. An apparatus for continuously casting molten metal, comprising a molten metal container, a liquid-cooled mold arranged substantially horizontally, at least one molten metal supply pipe arranged between these, and a continuous slab drawing device. , the molten metal supply pipe (2) has at least two mutually succeeding parts (7, 8, 9) with different cross-sectional areas, the first part (7, 9) following in the direction of flow of the molten metal; An apparatus for continuously casting molten metal, characterized in that the opening is substantially tangential to (8, 10). 8 The cross-sectional area of the first part (9) is the same as that of the next part (10
7. Device according to claim 6, characterized in that the cross-sectional area of the device is smaller than the cross-sectional area of ). 9 The axis of the molten metal supply pipe is twisted in the range of turning the direction of the molten metal flow, and the standard interval (a) is 1/2 to 1/6 of the inner diameter (d) of the molten metal supply pipe with the largest cross-sectional area.
Device according to claim 7 or 8, characterized in that it has: 10. 1 of claims 6 to 8, characterized in that the melt supply line (7) can be closed in the melt container (1) with respect to the inlet opening by a stopper (6). The device described in. 11. The molten metal supply pipe (7) has two parts standing approximately perpendicular to each other, one part is connected to the mold,
11. Device according to one of claims 7 to 10, characterized in that the other part is connected to a melt container.