RU2038897C1 - Method of continuous casting of slabs - Google Patents

Abstract

FIELD: foundry engineering. SUBSTANCE: liquid metal feeds into crystallizer with a varying speed and solid-liquid ingot is reduced in a secondary cooling zone with the help of rollers. Ingot reducing distance is determined by the function L=(0,08-0,40)V/l, where L is distance from the lower side of crystallizer up to the starting point of ingot reducing, m; V is ingot drawing speed, m/min; l is ingot length in crystallizer, m; (0,08-0,40) is empirical coefficient considering thermal properties of casting metal, i.e. metal temperature, viscosity, heat capacity, admissible stress under high temperatures, chemical composition, l/min. EFFECT: enhanced efficiency. 1 dwg, 1 tbl

Description

 The invention relates to metallurgy, and more particularly to the continuous casting of flat ingots of small thickness.

 A known method for the continuous casting of flat ingots, including feeding metal into the mold, pulling a flat ingot from it at a variable speed, maintaining and directing the ingot in the secondary cooling zone using drive rollers, and deforming the ingot in a solid-liquid state by means of rollers.

 The disadvantage of this method is the unsatisfactory quality of continuously cast ingots and the low stability and performance of the continuous casting process, which is explained by the fact that the compression of the ingot begins to produce immediately after the ingot leaves the mold. Under these conditions, at high drawing speeds and a small thickness of the shell of the ingot, its continuity is violated, which is accompanied by breakthroughs of the metal under the mold. In addition, the deformation of the relatively thin shell of the ingot leads to its crushing, the formation of bumps, belts, etc. The foregoing leads to the rejection of ingots by surface quality, as well as to a decrease in the stability and productivity of the casting process.

 Studies have established that to improve the quality and productivity of the process of casting flat ingots of small thickness, it is necessary to begin the compression deformation of the ingot at a certain distance from the lower end of the mold after reaching a certain thickness of the ingot shell. The value of this distance is established on the basis of an empirical dependence, taking into account the thermophysical characteristics of the cast metal and the drawing speed.

 The aim of the invention is to improve the quality of flat continuously cast ingots and increase the stability and productivity of the casting process.

This goal is achieved by the fact that in the method of continuous casting of flat ingots, liquid metal is fed into the mold, an ingot is formed, it is pulled out of the mold with a variable speed, and the ingot is compressed in the solid-liquid state in the secondary cooling zone using rollers, while the ingot is pressed at a distance from the bottom end of the mold, determined by the dependence
L = (0.8-0.40) V / l where L is the distance from the lower end of the mold to the place where the ingot begins to be crimped, m;
V ingot drawing speed, m / min;
l the length of the ingot in the mold, m;
(0.08-0.40) empirical coefficient taking into account the thermophysical properties of the cast metal; metal temperature, viscosity, thermal conductivity, thermal diffusivity, heat capacity, permissible metal stresses at high chemical composition temperatures, 1 / min.

 Improving the quality of continuously cast flat ingots will occur due to the elimination of the formation on the surface of the bumps, belts, etc. as well as internal cracks.

 Improving the stability and productivity of the casting process will occur due to the elimination of metal breakthroughs at the beginning of the compression zone of the ingot compression.

 The beginning of the compression reduction of the ingot at a certain distance from the lower end of the mold is explained by the need to eliminate the violation of the continuity of the ingot shell and create conditions for increasing the thickness of the ingot shell to the required values.

 The range of values of the empirical coefficient in the range of (0.08-0.4) 1 / min is explained by the thermophysical properties of the cast and deformable metal, which determine its strength and plastic properties at high temperatures.

 At lower values, metal breakthroughs will occur due to violation of the continuity of the ingot shell due to the proximity to the mold of the beginning of the compression zone of the ingot.

 At large values, the compression zone of the ingot will be insufficient in length due to its restriction to the end of the liquid phase. Under these conditions, the marriage of ingots along internal cracks will increase due to the high degree of compression deformation in each pair of rollers in the compression zone.

 The specified range is set inversely proportional to the carbon content of the cast steel and in direct proportion to the speed of drawing the ingot.

 The following is an embodiment of the invention that does not exclude other variations within the scope of the claims.

 The drawing shows a diagram of the installation for implementing the method of continuous casting of flat ingots.

Installation for implementing the method of continuous casting of flat ingots consists of crystallizer 1, rollers 2, 3 and 4. 5 liquid metal, 6 meniscus of metal, 7 flat sheet, 8 shell of the ingot, l length of the section of the ingot in the mold, L length of the section of the ingot, not subjected to compression deformation, L _{1 the} length of the compression zone of the ingot, L _{2 the} length of the liquid phase of the ingot.

 The method of continuous casting of flat ingots is as follows.

PRI me R. In the process of continuous casting of flat ingots, metal 5 is fed into the mold 1 under the meniscus 6 through an elongated casting cup (not shown). The length of the plot of the ingot 7 in the mold 1 is l. From the mold 1, an ingot 7 with dimensions H x b is pulled with variable speed using drive rollers 2,3 and 4. Moreover, the compression of the casing 8 by rollers 2 is not deformed along the length of section L and the ingot 7 in this section has dimensions b and thickness H Next, on the plot L _{2, the} shell 8 of the ingot 7 is deformed by crimping with rollers 3 from a thickness H to a thickness h in a solid-liquid state. Below section L _{2, the} compression deformation of the ingot 7 by the rollers 7 is stopped both in the solid-liquid and in the solid state, and the ingot is pulled with a constant thickness h.

In the process of continuous casting, the compression compression deformation of the ingot begins to be carried out at a distance from the lower end of the mold, which is set according to
L (0.08-0.4) V / l; where L is the distance from the lower end of the mold to the place of the beginning of the compression reduction of the ingot, m;
V ingot drawing speed, m / min;
l the length of the plot of the ingot located in the mold, m;
(0.08-0.4) empirical coefficient taking into account the thermophysical properties of the cast metal: metal temperature, viscosity, thermal conductivity, thermal diffusivity, specific heat, allowable metal stresses at high chemical composition temperatures, 1 / min.

 The table shows the technological parameters of the process of continuous casting of flat ingots.

 In the first example, the length of the section L to the beginning of the compression zone of the ingot compression exceeds the permissible values, which causes a decrease in the length of the compression zone of the compression of the ingot. Under these conditions, it is necessary to increase the degree of compression reduction of the ingot in each pair of rollers 3. In this case, the marriage of ingots along internal cracks increases.

 In the fifth example, the beginning of the compression reduction deformation zone of the ingot is too close to the mold. Under these conditions, there is a violation of the continuity of the shell of the ingot, which leads to breakthroughs of the metal. In addition, due to the insufficient thickness of the shell of the ingot, the formation on the surface of the bumps, belts, etc.

 In the sixth example (prototype), due to the beginning of the compression reduction of the ingot directly under the mold (L 0), metal breakouts occur due to the small thickness of the ingot shell at the exit of the mold.

 In examples 2, 3, and 4, metal breakthroughs do not occur at the beginning of the ingot compression zone, no hoops and belts are formed on its surface due to the sufficient thickness of the ingot shell. The length of the compression zone of the ingot provides the degree of deformation of the ingot in the solid-liquid state within acceptable limits without the formation of internal cracks.

 The application of the proposed method allows to reduce the marriage of ingots for internal cracks and surface quality by 2.5% and to reduce the number of breakthroughs of metal by 1.8%. The economic effect is calculated in comparison with the base object, which is accepted as a method of continuous casting of flat ingots, used at NPO Tulachermet.

Claims (1)

METHOD FOR CONTINUOUS CASTING OF FLAT INGOTS, including feeding liquid metal into the mold, forming an ingot and drawing it out of the mold with a variable speed, compressing the ingot in a solid-liquid state in the secondary cooling zone using rollers, characterized in that, in order to improve the quality of the ingots, stability and performance of the process, the compression of the ingot is carried out at a distance from the lower end of the mold, determined by the dependence

where L is the distance from the lower end of the mold to the place where the ingot begins to be crimped, m;
V ingot drawing speed, m / min;
l the length of the ingot in the mold, m;
0.08 0.40 empirical coefficient taking into account the thermophysical properties of the cast metal: temperature, viscosity, thermal conductivity, thermal diffusivity, heat capacity, permissible metal stresses at high temperatures, chemical composition, min ^{- 1} .

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