RU2252107C2 - Machine for continuous casting of slab billets with two-side drawing - Google Patents

Abstract

FIELD: metallurgy, casting of steels and alloys in machines for continuous casting of slab billets, particularly in machines with two-side drawing.

SUBSTANCE: melt metal is introduced into mold through casting nozzles arranged in narrow mutually opposite faces of mold in such a way that axes of nozzles are directed one towards other along the same axis or at mutual shifting. It provides crosswise breaking of slab envelope at casting in space between casting nozzles inside mold.

EFFECT: possibility for producing thin high- quality slabs with enhanced micro-structure and improved surface.

5 cl, 3 dwg

Description

The invention relates to metallurgy and can be used in the casting of steel and alloys on continuous casting machines of slab billets with double-sided stretching (CCM).

Currently, up to 60% of smelted steel is produced in sheets. In industrialized countries, slabs cast in continuous casting machines, and to a lesser extent slab ingots, are mainly used as blanks for sheet production. The thickness of the slabs cast on the continuous casting machine is mainly (200-300) mm, and the ingots are much larger.

In modern engineering, a significant part of the consumed products is made up of sheets with a thickness of 0.5 to 10 mm.

To ensure proper crimping, the above thicknesses are not required. For this assortment, it is enough to cast thin slabs with a thickness of 40-100 mm. The production of these slabs is fundamentally possible at CCM. However, the technology itself in operation is complex and cannot service the entire existing grade of steel.

In this regard, there is an urgent need to find new solutions that open up simpler and more reliable methods of industrial production of thin slabs in continuous casting machines.

A solution is known for producing thin slabs with a thickness of (50-100) mm, which is based on the principle of local expansion of the mold in the area of the placement of the casting cup with subsequent deformational elimination of the thickening in the casting when drawing the billet from the mold (Ferrous metals, 2001, July-August. G. Brasculi, A. Mascanzoni and others. “The first industrial unit CSP for corrosive steels in factories of the company“ AST-ACCIAI SPECIALI TERNI ”, p. 38-46).

The disadvantages of this solution are:

- its inapplicability for steels having low hot ductility in the range near the crystallization temperature of the metal, and as a result - the possibility of tearing the shell of the casting when drawing from the mold in the forming billet;

- the need for increased accuracy of heating of the cast metal.

Known methods for producing ultrafine tapes in rolls-crystallizers (Ferrous metals, 1998, September - October. D. Xena, M. Espehan, V. Schmitz and others. “Properties of continuously cast steel strips made by two-roll casting method.” C. 51-56).

The disadvantages of these methods is their technological imperfection, which does not ensure the stable production of thin ribbons. As a result, the production of tapes in an industrial way using this kind of technology remains very problematic.

The main difficulties in obtaining generally thin slabs are due to the mismatch between the sizes of the nozzle and the section of the mold cavity. By reducing the living section in the pouring cup, it is impossible in all cases to reliably solve the problem, because at small sections, it is almost impossible to pour even a small mass of melting.

A known method of continuous casting of steel with two-sided stretching of the billet from the mold with the supply of liquid metal through the upper face (ed. Certificate of the USSR No. 1677923 A1, 01/13/89). However, when liquid metal is introduced through the upper face of the mold, the following disadvantages are found:

- direct effect of the leaking jet on the opposite closely lying face of the mold, reducing its service life;

- uneven heat removal through the upper edge of the mold: directly under the mold wall, the heat sink is maximal, and under the pouring nozzle it is practically zero.

This circumstance gives rise to heterogeneity of the macrostructure and affects the surface quality of the slab.

The closest in technical essence and the achieved result is a machine for continuous casting of ingots (slabs) with double-sided pulling, containing a mold with a mechanism for pulling it, a metal detector with a metal wire connected to the mold in a single mechanism for pulling the ingot (slabs) (SU 1311845 A1, IPC V 22 D 11/14, 05.23.1987).

The task of the invention is to provide a method for producing thin, high-quality slabs on continuous casting machines with double-sided stretching with improved macrostructure and surface quality of the workpieces.

The problem is solved in that in a continuous casting machine for slab billet with double-sided stretching, containing a system for supplying liquid metal through a single casting unit in the form of a structurally rigid connection of a device with a crystallizer, a swing mechanism for a single casting unit, a system for pulling a workpiece from a mold and a secondary cooling system, it contains mechanisms that change the geometric dimensions and the taper of the cast billets during the casting process, and structurally rigid is connected Another device with a crystallizer is made in the form of two pouring nozzles installed in narrow opposite sides of the mold coaxially or whose axes are offset and directed towards each other to ensure a transverse gap in the shell of the workpiece during casting in the space between the pouring nozzles, the axes of the nozzle are offset no more than 3 thicknesses of the holes of the nozzles, and the cross-section of the inner hole of the nozzle is round, rectangular or ellipse bottom shape, the major axis of which is located in the direction of drawing the workpiece and the inner hole of the casting cup is made with a taper of (-15) - (+15) °, when casting thin slabs, the narrow edges of the mold in the places of placement of the casting cups are made with a thickening to the size of the cup, the axis which are perpendicular to the directions of drawing the workpieces, with the reduction of the thickness from the ends of the glasses along the conical inclined planes to the thickness of the cast workpiece.

An analysis of the operation of CCM with double-sided stretching showed that when casting slabs with a developed width, when supplying liquid metal through the upper face of the mold, there are almost insurmountable difficulties in breaking the shell of the casting. The inventive CCM with a rupture of the shell with a two-sided supply of metal is free from this drawback. It is noted that in the production of slabs based on this machine, the following advantages take place:

the ability to perform many technical solutions based on the supply of liquid metal to the side faces of the mold, including:

- cast steel without an open metal surface in the mold;

- without the use of slag protection;

- to obtain a more uniform macrostructure and high quality surface castings;

- reduce secondary oxidation and metal contamination with nitrogen;

- reduce the thickness of the cast billets;

- provide symmetrical spacing of the contact zone of the glasses with narrow side faces;

- change the conditions for introducing liquid metal into the mold due to the displacement of the axes of the glasses.

On figa, 1b, 1c, 1d, 1d and 1e shows the schematic diagrams of continuous caster with two-way pulling and, accordingly, the nodes of the machine, and on figa, 2b, 2c and 2g presents the dynamics of the movement of metal flows. On figa, 3b and 3c shows a well-known caster with a supply of liquid metal to the upper plane of the mold.

The composition of the elements shown in these figures is presented below:

1 - mold; 2 - permeability; 3 - cast billet; 4 - refractory wiring; 5 - a single casting unit, consisting of capacity, wiring and mold; 6 - node input metal into the mold; 7 - a glass introducing liquid metal into the mold; 8 - direction of metal supply; 9 - the direction of drawing the blanks; 10 - direction of swing of the mold; 11 - liquid metal slabs; 12 - hardened shell; 13 - a stream of metal from pouring glasses; 14 - tear cast billet; 15 - displacement of the axes of the filling glasses; 16 is the area of alignment of the thickness of the workpieces.

The operating mode is as follows:

A fully assembled caster with a heated capacity of 6, wires 5 and seeds introduced into the mold 1 (if the mold consists of 2 half-sections, then after fitting the planes at the junction of the half-sections), the capacity 5 is filled to a predetermined level and then the metal is fed from 2 sides to crystallizer 1. Immediately and gradually start with the speed of the hood 9 in opposite directions of the workpiece with the simultaneous inclusion of swings 10 of the mold 1. The frequency and amplitude of the swing in the initial period can be increased, and then up to 0.5-2.0 mm at Vyshen sweep to 200-400 oscillations per minute. At the same time, and in the process of casting, the metal is heated in the tank 5, maintaining the set temperature. To protect the metal from oxidation and heat loss, slag-forming compositions are induced on the metal mirror and a neutral gas or a limited passive nitrogen gas is supplied.

As the workpiece is drawn, a device for cutting measured workpieces is turned on.

CCM can work in a block with rolling stands with all the equipment appropriate for this mill, i.e. according to the scheme "casting and rolling complex" (LPS).

Thus, the inventive CCM is a further continuation of the development of the known CCMs, while maintaining the ability to work in the LPS system and allowing to obtain thin and thick slabs.

Claims (5)

1. Machine for continuous casting of slab billets with double-sided stretching, comprising a system for supplying liquid metal through a single casting unit in the form of a structurally rigid connection of the industrial device to the mold, a swing mechanism for a single casting unit, a system for drawing the blanks from the mold and a secondary cooling system, characterized in that it contains mechanisms that change the geometric dimensions and the taper of the cast billets during the casting process, and structurally rigid connection industrial va a mold formed by two nozzles installed in the narrow faces of the mold protivoraspolozhennyh coaxially or axis which is offset from and directed toward each other with the provision of transverse rupture coated workpiece in the casting and in the space between the nozzles. 2. The machine according to claim 1, characterized in that the axis of the nozzles are offset by a distance of not more than 3 thicknesses of the holes of the nozzles. 3. The machine according to claim 1, characterized in that the cross section of the inner hole of the casting nozzle is made round, rectangular or ellipsoid in shape, the major axis of which is located in the direction of elongation of the workpiece. 4. The machine according to claim 1, characterized in that the inner hole of the nozzle is made with a taper of (-15) ° - (± 15) °. 5. The machine according to claim 1, characterized in that when casting thin slabs, the narrow edges of the mold in the places of placement of the casting glasses are made with thickenings for the dimensions of the glass, the axis of which is perpendicular to the directions of drawing the blanks, with the reduction of the thicknesses from the ends of the glasses along conical inclined planes on the thickness of the cast billet.

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