RU2079390C1 - Apparatus for continuous casting of blanks - Google Patents

Abstract

FIELD: metallurgy, metals continuous casting. SUBSTANCE: aim is to increase productivity of blanks continuous casting process. Apparatus for blanks continuous casting has prefabricated crystallizer, that has four longitudinally located operational walls. First pair of operational walls is capable to exercise rotation in process of operation and in the case inclination angle to the vertical of operational walls upper widened section operational surface is α = 7...30 deg. Value of the angle is taken in inversely proportional dependence to value of received blanks metal thermal conductivity factor. Besides, in apparatus for blanks continuous casting height of vertical lower section "h", widened upper section to vertical lower section transition area curvature radius R, before vertical lower section shaping initial height "h'" are connected to each other by following ratios: h / R = 0.1 - 0.6; h/h' = 0.45 - 0.85. EFFECT: increased productivity of blanks continuous casting process. 2 cl, 3 dwg

Description

 The invention relates to metallurgy, namely to the continuous casting of billets.

A prototype of the technical nature of the claimed invention is a mold for continuous vertical casting of steel strip, containing cooled wide and narrow walls, the wide side walls of which are made in the upper part with an inclination angle to the vertical of less than 10 ^o , taper down to the size of the resulting tape and form a working cavity conical shape, the end sections of the wide side walls are made parallel, and their width is equal to at least the thickness of the resulting tape. In addition, in the mold [1], the wide side walls of the conical part are arcuate, and the narrow walls are movable in the area of parallel sections of the wide walls.

The disadvantage of the mold for continuous vertical casting of steel strip is the possibility of its use only for steel strips. In addition, the implementation of the wide side walls of the mold with an angle of inclination to the vertical of less than 10 ^o does not provide the opportunity to obtain high-quality continuously cast billets from metals with different values of the thermal diffusivity.

 The inventive device is aimed at creating a high-performance process for producing continuously cast billets.

The technical result obtained by the implementation of the inventive device is:
increasing the productivity of the process of producing continuously cast billets;
improving the reliability of the device;
increase in metal yield;
energy saving;
improving surface quality and internal structure of the workpiece.

 The inventive device is characterized by the following essential features.

 Restrictive signs: four pairwise located longitudinal working walls; the first pair of water-cooled working walls is made with the upper extended to the vertical and vertical lower sections of the working surface; the transition section from the expanded upper to the vertical lower section is made curved with a certain radius of curvature; the second pair of water-cooled working walls is made with the possibility of reciprocating motion.

Distinctive features: the first pair of working walls is made with the possibility of performing in the process of work rotational movement; the angle of inclination to the vertical of the working surface of the upper expanded portion of the working walls is α = 7-30 ^{°; the} angle of inclination α is chosen inversely proportional to the value of the thermal diffusivity of the metal of the obtained workpieces; the height of the vertical lower section “h”, the radius of curvature “R” of the transition region of the expanded upper to the vertical lower section, the initial height of the vertical lower section “h” prior to profiling is interconnected by the following relationships:
h / R 0.1-0.6; h / h '0.45-0.85.

 A causal relationship between the set of essential features of the claimed device and the achieved technical result is as follows.

 The execution in the process of working the walls of the first pair of rotational motion provides the conditions for the capture, compression and pushing of the metal to the exit of the mold. At the same time, there is no need for an additional device for pulling the workpiece, and accordingly, the time spent on servicing the device is reduced, and its reliability is increased.

When casting metals in a mold with two pairs of walls, the angle of inclination of the working surface of two walls in the upper expanded section to the vertical is ultimately determined by the physical parameters of metals: these basic parameters include: l metal thermal conductivity, W / (mK); C specific heat, J / (kgK) and r metal density, kg / m ³ . The ratio of parameters a = λ / ρc is the thermal diffusivity of the metal, which characterizes the rate of temperature equalization in it during cooling.

For poured metals, the thermal diffusivity coefficient a is different. The maximum value of the coefficient a = 95x10 ^-6 and 113x10 ^-6 m ² / s are copper and aluminum, respectively.

The minimum values of the coefficient a = 6x10 ^-6 and (7.5-9) x10 ^-6 m ² / s have titanium and low-carbon (low alloy) steel.

Based on the characteristics of the thermal diffusivity coefficient, it follows that the minimum value of the angle of inclination α _{min of the} working surface of the mold wall in the upper expanded section corresponds to casting aluminum and copper into the mold, and the maximum possible angle α _max
during casting of titanium and low carbon (low alloy) steel.

In addition, based on the fact that the first pair of working walls in the expanded (inclined) upper section causes compression (deformation) of the metal, the conclusion made about the values of α _min and α _max becomes valid for the following reasons.

The metal compression pressure (during pressure welding) in the range of plastic deformation temperatures (0.8 t _pl , where t _pl metal melting temperature) is: for aluminum and its alloys, respectively -120-150 and 130-200 MN / m ² , copper 250- 400 MN / m ² , while for titanium and low-carbon (low alloyed) steel, respectively, only 30-60 and 80-100 MN / m ² .

 That is, lower values of the coefficient of thermal diffusivity of the metal and compression pressure allow it to be cast in a mold with a higher value of the angle of inclination of the working surface on the upper section of the wall. In this case, it is possible to increase the amount of simultaneously deformable metal and reduce the requirements for the accuracy of maintaining the temperature of the metal in the upper part of the mold compared to casting a metal with a higher value of the thermal diffusivity and compression pressure.

 The determination of the angle of inclination of the working surface of the wall during casting of a given metal can be determined from the solution of the inverse heat conduction problem [2, 3] in which the corresponding boundary conditions (the shape and size of the working surface of the mold wall) are determined from the given distribution of metal temperatures.

For technological reasons, the minimum value of the angle of inclination of the working surface of the wall to the vertical is α _min = 7 ^° (when casting aluminum and its alloys). This is due to the fact that, at an angle α less than 7 ^° (α <7 ^° )), the conditions for pouring the metal through the immersion cup and maintaining it at a predetermined level in the mold are hindered, which is especially evident when preparing blanks with a small thickness (δ <10 mm).
The maximum value of the angle of inclination of the working surface to the vertical when casting low-carbon steel is α _max = 30 ^°. An increase in the angle α> 30 ^° leads to an increase in the surface of the mirror of liquid metal in contact with air, and as a result, an increase in the amount of heat removed from the metal and its additional oxidation . In addition, metal compression deteriorates due to the redistribution of normal stresses to the upper part of the mold (i.e., O ₁ and O ₂ in FIG. 2) and the need to increase drive power (power consumption) for metal compression due to an increase in the thickness of the deformable metal at a given height h (δ ₂ > δ ₁ in Fig. 2).

 The ratio of the height of the vertical lower section of the wall h to the radius of curvature R of the transition region of the expanded upper to the vertical lower section is h / R = 0.1-0.6. An increase in the ratio h / R> 0.6 leads to the need to increase the height of the mold by increasing the height of the calibration (lower vertical) section and the zone of liquid metal in the upper part of the mold.

 With a decrease in the ratio h / R <0.1, the force that goes to deform and push the workpiece increases significantly.

 The ratio of the vertical lower (calibration) section to its initial height before surface profiling (transition area) is h / h '= 0.45-0.85. When h / h '> 0.85, the surface quality of the resulting workpiece deteriorates. The decrease in the ratio h / h '<0.45 increases the resistance to pushing the workpiece by increasing the friction force, and accordingly increases the drive power and power consumption.

 In FIG. 1 shows the appearance of one working wall of the mold in a vertical plane with a different angle of inclination of the working surface to the vertical and the transition area from the expanded upper to the vertical lower section; FIG. 2 shows the appearance of a mold with a pair of working walls with inclined (expanded) sections in a vertical plane, illustrating the operation of the device (the direction of normal stresses σ to the surface and the thickness s of the crimped metal at a given height h are shown); FIG. 3 - the appearance of the mold in the horizontal plane.

 The inventive device for continuous casting of blanks (mold) in FIG. 1, 2 and 3 consists of a pair of working walls 1, 7 with expanded (inclined) 2 and vertical 3 sections with a transition (profiling) region 4, the actual mold 5 and a pair of vertical walls 6.

 The operation of the device is as follows.

 Before casting the metal, the mold is heated to the required temperature, and its lower part is blocked by a special device (seed), which prevents the pouring of the melt. Liquid metal through a submersible pouring cup enters the mold 5 through its upper part along the extended section 2. In the process, the walls 1, 7 perform a complex rotational movement with compression of the metal in the transition region 4 and its pushing to the lower vertical (calibration) section 3. Walls 6 perform an antiphase to the walls 7 reciprocating motion.

Claims (2)

1. Device for continuous casting of preforms, comprising a prefabricated mold, consisting of four longitudinally arranged pairwise working walls, in which the first pair of working walls is made with upper and vertical lower sections of the working surface expanded at an angle to the vertical, and the second pair of working walls is made with the possibility of reciprocating movement, while the transition section from the expanded upper to the vertical lower section is made curved, characterized in that the first pair of working stations The calf is made with the possibility of rotational movement during operation, while the angle of inclination to the vertical of the working surface of the upper expanded section of the working walls is α = 7 ... 30 ^° , the value of which is selected inversely proportional to the value of the thermal diffusivity of the metal of the obtained workpieces. 2. The device according to claim 1, characterized in that the height of the vertical lower section h, the radius of curvature R of the transition region of the expanded upper to the vertical lower section, the initial vertical height of the lower section h 'prior to profiling, is interconnected by the following relationships:
h / P 0.1 0.6, h / h '0.45 0.85.

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