RU2320452C2 - Ingot for rolling production method and ingot mold for casting such ingot - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method comprises steps of pouring melt to ingot mold in the form of sleeve to bottom of which hollow tube-shaped insert is secured for producing ingot in the form of tube; at crystallization of melt cooling outer wall of ingot mold and treating ingot in force fields. In process of ingot crystallization inclusions are displaced towards ingot surface adjacent to tube-shaped insert. Inner opening of produced ingot is drilled in radial direction by depth of displacing inclusions by crystallization front. Then ingot is cut in lengthwise direction by segments to be subjected to rolling.

EFFECT: production of ingot with uniform structure.

4 cl, 7 dwg

Description

The invention relates to metallurgy and relates to the production of a tubular form of ingots with a high degree of purification from accidental inclusions and greater uniformity of structure.

The value of the process of solidification of melts on the quality of castings, especially pre-rolling, is much greater than is commonly believed in practical metallurgy. With a rather significant variety of technical solutions, the essence of the process in most cases comes down to the selection of heat in one way or another. Moreover, as a rule, they vary with two process parameters - the direction of heat removal and its intensity. The direction of heat extraction, as well as the creation of nuclei and crystallization front (s), is determined by the shape of the working cavities of the molds and molds. The intensity of the process is set using air or liquid cooling flows. In most cases, industrial water is used. In this case, the possibility of displacement by the crystallization front of inclusions not demanded by the crystallization process is forcibly ignored. Moreover, in a number of technological processes adopted in industry, heat is taken out in the incident liquid melt stream by industrial water supplied to the peripheral parts of the feeders, i.e. an annular front of initiated crystallization is created. As a result of such and similar fronts, all the "excess" is driven into the casting. In some forms of castings, due to the opposition of internal heat, the direction of motion of the crystallization front changes, and the speed of movement slows down, an inhomogeneous grain structure is formed, etc. As a result, the quality of the pre-rolling material generally decreases. The pre-rolling machining of the resulting castings such as "pillars" and flat slabs requires the use of sophisticated techniques for the use of cutting tools.

A known method of producing steel ingots, which consists in pouring the melt into the mold with subsequent crystallization of the melt in the heated mold, and before the melt is cast, the inner surface of the mold is heated (SU ed. St. No. 1323223, B22D 7/00, publ. 15.07.2987).

From the same source, a mold is known, which is a body of revolution in the form of a glass, the inner surface of which is protected by a heat-resistant material.

This decision was made as a prototype for both declared objects.

A feature of this method is that due to the heating of the internal walls of the mold, the crystallization front is directed not from the wall to the center, but from top to bottom, as a result of which unclaimed inclusions are lowered into the mold bottom zone in the shrink shell, i.e. in the lower part of the ingot, thereby eliminating an altered state of the structure of the core of the ingot.

This method allows you to obtain the desired result in terms of ensuring an almost constant structure of the ingot over the cross section, but it requires high energy consumption and mathematical accuracy in heating the mold walls depending on its height (the mold is heated by increasing the temperature for every 10% of the mold height by 55-85 ° FROM). Naturally, energy costs will be decisive in the cost of such an ingot. In addition, the obtained ingot must be subjected to pre-rolling machining, that is, removing a small outer layer to give the ingot a cylindrical shape and cutting off the end part in which unclaimed inclusions are collected. Since both operations are carried out on different cutting equipment, the process of pre-rolling machining becomes time-consuming, significantly affecting the cost of the ingot prepared for rolling. In addition, despite the fact that the crystallization front moves vertically, it is not possible to maintain the stability of the process in the direction from the periphery to the center, as a result of which the middle part of the ingot is nevertheless obtained with obvious signs of a changed structure.

The present invention is aimed at solving the technical problem of giving the ingot a tube-like shape in which a crystallization front of a ring shape is formed with a technologically quasi-uniform speed, which makes the structure of the ingot uniform in structure and shifts unclaimed inclusion crystallization to the edge of the ingot with the possibility of simple removal during machining, as well as to simplify the ingot.

The technical result achieved in this case is to improve the quality of the pre-rolled ingots by providing a constant thickness structure without changing zones and to simplify the process of obtaining the pre-rolled ingot through the use of simple mechanical operation such as hole bores.

The specified technical result is achieved by the fact that in the method for producing pre-rolled ingots, which consists in pouring the melt into the mold with subsequent crystallization of the melt in the mold, and by pre-rolling machining, the melt is filled into the mold made in the form of a glass with a hollow cylindrical insert attached to its bottom, to obtain an ingot in the form of a hollow pipe, during the crystallization of the melt, the external mold wall and, if necessary, the inner wall of the insert are cooled, and when prep Katni machined ingot performed bore inner hole of the ingot in the radial direction to the displacement of the solidification front depth ignored during the crystallization and separation of inclusions in the ingot segments.

These features are significant and interconnected with the formation of a stable set of essential features sufficient to obtain the specified technical result.

The present invention is illustrated by a specific example, which, however, is not the only possible, but clearly demonstrates the possibility of obtaining the desired technical result.

Figure 1 - mold for tubular ingots;

figure 2 - the process of crystallization of the melt in the mold;

figure 3 - demonstration of displacement by the crystallization front of ignored inclusions;

figure 4 is an ingot to pre-rolling machining;

5 is an ingot after segmentation;

6 is a process of straightening segments;

7 is an embodiment of a mold with a rotating platform.

According to the present invention, it is proposed to cast ingots in ring molds (FIG. 1), and heat removal during melt crystallization by any known method in radial directions (FIG. 2).

The mold (Fig. 1) is a deep-sea vessel in the form of a body of revolution, for example, in the form of a glass 1 of a metal sheet, the inner surface of which is protected by a heat-resistant material, for example refractory brick, coated with a glassy mass. The vessel is equipped with a hollow tube-shaped insert 2 attached to the bottom of the glass, also made of a metal sheet, while the outer surface of the insert is also protected by a heat-resistant material, which is used to protect the glass. Thus, the made mold allows obtaining tube-shaped ingots 3. In addition, additional heat extraction (cooling supply 4) can be easily brought to such a mold, for example, by treating the outer wall of the vessel with industrial water or gas. In this case, it is also possible, if it is technologically necessary, to carry out additional heat removal (cooling supply 5) from the inner wall of the insert (Fig. 2) (simultaneously with external cooling). With such two-sided heat removal, it is possible to organize variable temperature parameters of the melt in the direction from the outer wall of the vessel to its insert, which is essential for controlling the movement of the crystallization front 6.

With an external heat sink (that is, when heat is removed or the outer wall of the vessel is cooled), the crystallization front 6 propagating in the radial direction 6 unclaimed inclusions 7 moves to the edge of the casting to the insertion location zone (Fig. 3). Thus, upon completion of the crystallization process in the zone adjacent to the insert, an ingot structure is formed in the form of an annular zone 8 of depth Δ, in which the displaced inclusions ignored during crystallization are concentrated, displaced by the crystallization front. With this form of the ingot, conditions are created for the removal of these inclusions during subsequent machining by removing the entire contaminated zone, that is, part of the metal to a depth Δ of these inclusions. More economically sound is the direction from the periphery to the center. Moreover, the greater the ratio of the radius of the casting to the thickness of the ingot, the more uniformly, organizedly and quickly the crystallization front moves along the thickness of the ingot due to a decrease in the counteraction of the internal heat of the ingot. All this taken together leads to a significant improvement in the quality of the casting.

Moreover, by rotating the mold with the melt during crystallization at any speed around its longitudinal axis (Fig. 7), for example, from the electric drive 9, it is possible to expose the melts during crystallization to any action from a fixed source of such action (Fig. 3), for example, ultrasonic , magnetic, microwave or other force field. You can carry out and heat removal. With this implementation of the method, it is possible to use local units for supplying refrigerant or other effects, and by changing the speed of rotation of the platform on which the mold is located, regulate the crystallization process. With sufficient speed of the mold platform, the melt can be processed during crystallization by centrifuge force fields, i.e. gravitational or quasi-gravitational fields.

Received pre-casting in the form of rings or hollow pipes (figure 4) is easier to machine. From the theory of metal cutting with a cutting tool, it is known that the processing of bodies of revolution is the simplest and most economical with a high surface quality. Such processing is easier to automate and does not require additional operations for lifting, moving and positioning the ingot from one machining station to another. Thus, the obtained ingot is subjected to boring of the inner hole of the ingot in the radial direction to a depth Δ of displacement by the crystallization front of inclusions ignored by the crystallization process. After boring we get an ingot without sections of a technologically unacceptably altered structure.

The subsequent division of the casting into segments 11 (cutting in the longitudinal direction into arcuate parts-segments (Fig. 5) and, if necessary, the straightening of the parts (Fig. 6) are carried out depending on the tasks facing the caster and are not difficult.

The present invention is industrially applicable, as it can be implemented using existing foundry tools and methods. The novelty of the claimed invention lies in a new approach to the formation of the shape of the ingot to provide a better crystallization process, simplify the processing by various force fields and conduct pre-rolling machining in the simplest way.

Claims (4)

1. A method of producing pre-rolled tubular ingots, comprising pouring the melt into the mold, made in the form of a glass with a hollow tube-shaped insert attached to its bottom, and crystallizing the melt, characterized in that during crystallization of the melt, the outer wall of the mold is cooled and the ingot is treated by force fields, and then pre-rolling machining of the ingot is carried out by boring the inner hole of the ingot in the radial direction to the depth of displacement by the crystallization front of inclusions. 2. The method according to claim 1, characterized in that after boring the inner hole, the ingot is divided into segments for their subsequent straightening. 3. The method according to claim 1, characterized in that during crystallization, the mold is rotated around its longitudinal axis. 4. The method according to claim 1, characterized in that during crystallization of the melt, the inner wall of the mold insert is cooled.

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