RU2015824C1 - Method of continuous casting of metal - Google Patents

Abstract

FIELD: machine engineering; metallurgy. SUBSTANCE: combined mould has narrow walls and wide ones pressed against them. Metal is supplied to the combined mould, ingot is drawn at variable speed, mould is set to reciprocal motion, slag mixture is supplied to meniscus of metal, the mould is cooled by running water and the force of pressing of the wide walls against the narrow ones is measured at several levels over the length of the mould. When working pressing force is exceeded by 10-40%, flow rate of cooling agent under the mould increases by 5-20% from working value over the length of 0.8-0.2 from the ingot thickness. The walls are pressed by hydraulic cylinder, for instance. EFFECT: enhanced efficiency of casting. 2 cl, 2 dwg, 1 tbl

Description

 The invention relates to metallurgy, and more particularly to continuous casting of metals.

 A known method of continuous casting of metals, including the supply of metal to the prefabricated, consisting of four working walls of the mold and pulling from it an ingot with variable speed. In the process of continuous casting, wide working walls are pulled together by rods under the action of tightening the nuts. The tightening torque of the nuts during continuous casting is not measured. During casting, the mold is informed of reciprocating motion, the mold is cooled with running water, the slag mixture is fed to the metal meniscus, the surface of the ingot under the mold is cooled by the cooler. The flow rate of the cooler under the mold does not change (D.P. Evteev et al. Continuous casting of steel. M: Metallurgy, 1984, p. 61, Fig. 53).

 The disadvantage of this method is the unsatisfactory quality of continuously cast ingots and low productivity of the process of continuous casting of steel. This is because in the process of continuous casting, the tightening forces of the rods and the clamping of the wide working walls to the ends of the narrow working walls are not measured. In addition, during continuous casting, the flow rate of the cooler under the mold is not controlled depending on the change in the tightening forces. Under these conditions, the ingot inevitably warps along the length of the mold due to a change in the technological parameters of the casting process. As a result of the lack of regulation of the flow rate of the cooler for cooling the ingot under the mold in the event of a change in the force at the junction of the working walls, it leads to breakthroughs of the metal under the mold due to thermal stresses and temperature gradients exceeding the permissible values in the shell of the ingot, as well as an increase in the pulling forces of the ingot from the mold, this unpredictable contact of the shell with the walls of the mold during warpage of the ingot leads to a local decrease in the thickness of the shell and that causes it to break.

 The closest in technical essence is the method of continuous casting of metals, comprising supplying metal to a prefabricated mold consisting of four working walls, and drawing an ingot from it at a variable speed. During continuous casting, the wide working walls are pulled together by rods, while the wide working walls are spring-loaded using a set of Belleville springs. The pulling force of the rods during continuous casting is not measured. During casting, the mold is informed of reciprocating motion, the mold is cooled with running water, the slag mixture is fed to the metal meniscus, the surface of the ingot under the mold is cooled by the cooler. Cooler costs under the mold do not change. (A.I. Tselikov et al. Machines and Units of Metallurgical Plants, Volume 2, Moscow: Metallurgy, 1978, p. 151, Fig. IV.15).

 The disadvantage of this method is the unsatisfactory quality of continuously cast ingots and low productivity of the process of continuous casting of steel. This is because in the process of continuous casting, the pulling forces of the rods and the clamping of the wide walls to the ends of the narrow working walls are not measured. In addition, during continuous casting, the flow rate of the cooler under the mold is not controlled depending on the change in the tightening forces. Under these conditions, the ingot inevitably warps along the length of the mold due to a change in the technological parameters of the casting process. As a result of the lack of regulation of the flow rate of the cooler for cooling the ingot under the mold in the event of a change in the force at the junction of the working walls, it leads to breakthroughs of the metal under the mold due to tensile bending and thermal stresses and temperature gradients exceeding the permissible values in the shell of the ingot. This increases the efforts of pulling the ingot from the mold, locally decreases the thickness of the shell of the ingot, which causes its rupture.

 The technical effect when using the invention is to improve the quality of continuously cast ingots and increase the productivity of the process of continuous casting of metals.

 The indicated technical effect is achieved by the fact that metal is fed into a four-wall prefabricated mold, the ingot is pulled from it at a variable speed, reciprocating motion is conveyed to the mold, slag mixture is fed to the metal meniscus in the mold, the mold is cooled by running water, cooled the surface of the ingot under the mold cooler, carry out the pressing of wide walls to the ends of the narrow working walls along the length and width of the mold using, for example, hydro cylinders.

 In the process of continuous casting, the force of pressing the wide working walls to the ends of the narrow walls is measured at least at two levels along the length of the mold, while increasing the pressing force at least at one of the measurement levels by 10 ... 40% of the working value, increase the specific cooler costs under the mold by 5–20% of the operating value over a length equal to 0.8–0.2 of the thickness of the ingot, and at large values of the change in force, the process of pulling the ingot is stopped.

 Improving the quality of continuously cast ingots will occur due to the timely increase in the specific consumption of the cooler under the mold in case of a change in the force of pressing of the wide working walls to the ends of the narrow working walls. Under these conditions, the heat sink from the ingot is aligned along its length and perimeter, which eliminates the warpage and lead of the ingot in the mold. In this case, thermal stresses and temperature gradients in the shell of the ingot under the mold are reduced, as well as the friction forces of the ingot against the walls of the mold. The aforesaid leads to a decrease in warpage of the ingot and to a reduction in the marriage of ingots along internal and external cracks, which helps to reduce breakthroughs of the metal under the mold and, thereby, increase the productivity of the process of continuous casting of metals.

 The measurement of the efforts of pressing the wide working walls to the ends of the narrow working walls at least at two levels along the height of the mold is explained by the need to control the warpage of the ingot along the length of the mold. In the general case, the higher the level of measurement of the forces of pressing the walls, the more accurately you can control the process of warping of the ingot along the length of the mold.

 The range of increase in the efforts of pressing wide walls to narrow walls within 10 ... 40% of the working value is explained by the regularities of the ingot deformation in the mold in the longitudinal and transverse directions. At lower values, the process of deformation of the ingot in the mold will not affect the quality of the ingots and breakthroughs of the metal. At large values, the friction forces of the ingot against the crystallizer walls increase significantly, which is accompanied by rupture of the ingot shell and breakthroughs of the metal.

 The termination of the process of pulling the ingot when changing the pressure force of the walls by more than 40% of the working value is explained by the fact that under these conditions, the efforts of pulling the ingot from the mold will exceed the permissible values. Under these conditions, breakthroughs of the metal under the mold will be inevitable.

 The specified range is set in direct proportion to the working value of the pressure of the walls.

 In the process of continuous casting, a decrease in the wall pressing force at one of the measurement levels leads to a corresponding increase in the wall pressing force at another measurement level.

 The range of increase in specific consumption of the cooler under the mold by 5 ÷ 20% of the operating value is explained by the laws of heat removal from the ingot under the mold under the action of the sprayed cooler, as well as the patterns of bending of the shell of the ingot in the lower part of the mold and directly below it. At lower values, the effect of an increase in the specific consumption of water will not affect the improvement of the quality of ingots and breakthroughs of the metal. At high values, supercooling of the surface of the shell of the ingot will occur, which will lead to the rejection of the ingots along internal and external cracks, as well as to breakthroughs of the metal.

 The specified range is set in direct proportion to the working flow of the cooler under the mold.

 The range of the length of the ingot under the mold, which increases the flow rate of the cooler, within 0.8 ÷ 0.2 of the thickness of the ingot is explained by the laws of heat removal from the ingot due to the sprayed cooler and the intensity of alignment of the shell thickness around the perimeter of the ingot when it leaves the mold. At lower values, the gaps of the shell of the ingot will not have time to be eliminated and its thickness will be leveled. At large values, supercooling of the surface of the ingot will occur, which will lead to the rejection of the ingots by internal and external cracks.

 The specified range is set in direct proportion to the speed of drawing the ingot.

 The analysis of patent and scientific and technical literature shows the lack of coincidence of the hallmarks of the proposed method with the hallmarks of the known technical solutions. Based on this, it is concluded that the claimed technical solution meets the criterion of "inventive step".

 In FIG. 1 shows a mold, cross section; figure 2 is a section aa in figure 1.

 The mold for implementing the method of continuous casting of metals consists of wide 1 and narrow 2 working walls with channels 3, base plates 4 and 5 of the mold body, rods 6, hydraulic cylinders 7 with pistons 8.

 The method of continuous casting of metals is as follows.

 In the process of continuous casting, mold 3SP steel is fed into the working cavity of the mold formed by wide 1 and narrow 2 working walls and the ingot 9 is pulled at a variable speed. Through channels 3 in the working walls 1 and 2 serves flowing cooling water. The mold is informed of reciprocating motion and a slag mixture is fed to the metal meniscus in the mold. The working walls 1 and narrow walls 2 are attached with pins to the base plates, respectively 4 and 5 of the mold body. The wide walls 1 are pressed against the ends of the narrow walls 2 using rods 6, passed through holes in the base plates 4. The rods 6 are simultaneously the rods of the hydraulic cylinders 7 and are connected to the pistons 8.

 The surface of the ingot under the mold is cooled by water sprayed by nozzles. The specific consumption of water is distributed along the secondary cooling zone according to the exponential law from the maximum value under the mold to the minimum at the end of the cooling zone.

 In the process of continuous casting, the compressive force of the wide working walls is measured at least at two levels along the length of the mold, while increasing the compressive force at least at one measurement level by 10 ... 40% of the operating value increases the flow rate of the cooler under the mold by 5 ... 20% of the working value over a length equal to 0.08 ÷ 0.2 of the thickness of the ingot, and at large values of the change in effort, the process of drawing the ingot is stopped.

 The fluid pressure in all hydraulic cylinders 7 is measured in the supra-piston cavity.

 The table shows examples of the method of continuous casting of metals with various technological parameters.

 In these examples, the measurement of the pressing forces of the wide walls is carried out at three levels along the length of the mold equal to 1.2 m. The step between the levels of measurement of effort is 400 mm

 In the first example, due to a slight increase in the force of pressing the wide walls to the ends of the narrow walls, the latter deform with the formation of gaps between the walls, which causes metal breaks. In addition, due to a significant increase in the flow rate of water under the mold and the length of the ingot with an increased flow rate of the water, the stability of the formation of the ingot occurs, its cooling occurs, which leads to the rejection of the ingots by internal and external cracks, as well as by the quality of the macrostructure.

 In the fifth example, due to a significant increase in the efforts of pressing the wide walls to the ends of the narrow walls, dents occur on the surface of the wide walls, which causes them to fail, the process of pulling the ingot is stopped. In addition, due to a slight increase in the flow rate of water under the mold and the length of the ingot with an increased flow rate of water, metal breakthroughs occur under the mold.

 In the sixth example (prototype), due to the lack of regulation of the flow rate of water under the mold, depending on the change in the pressure forces of the wide walls to the ends of the narrow walls, internal and external cracks form in the shell of the ingot in the mold. In addition, when the ingot warps under conditions of constant water flow under the mold, in the places where the shell contacts the walls of the lower part of the mold and where it leaves the walls in the shell, temperature gradients and thermal stresses exceed the permissible values, which causes the ingots to become defective in terms of macrostructure quality.

 In examples 2 ... 4, due to the change in the flow rate of water under the mold along the length of the ingot in the optimal range, if the pressure of the walls changes along the height of the mold, the temperature field is aligned along the perimeter and length of the ingot in the lower part of the mold, which prevents the development of the warpage of the ingot in the mold . Under these conditions, breakthroughs of metal under the mold are prevented, and the quality of continuously cast ingots improves.

 The application of the method allows to reduce the marriage of ingots by 1.7% and to increase the productivity of the process of continuous casting of metal by 2.3%.

Claims (2)

 1. METHOD FOR CONTINUOUS METAL CASTING, which includes supplying metal to a prefabricated catalyst, consisting of narrow walls and wide walls pressed against their ends, drawing an ingot from it at a variable speed, communicating to the mold reciprocating motion, feeding slag mixture to the meniscus, characterized in that the walls of the mold are cooled by running water, and the surface of the ingot under the mold is cooled, and the force of pressing the wide walls to the ends of the narrow walls is measured by at least two x levels along the length of the mold, while with an increase in the pressing force of at least one of the measurement levels by 10 - 40% of the operating value, the specific consumption of the cooler under the mold increases by 5 - 20% of the working value in a length of 0.8 - 0 , 2 thickness of the ingot, and at large values of the change in effort, the process of pulling the ingot stops.  2. The method according to claim 1, characterized in that the pressing of the wide walls to the ends of the narrow is carried out using hydraulic cylinders.

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