SU1366282A1 - Mould for continuous casting of metals - Google Patents

Abstract

The invention relates to metallurgy and can be used in machines for continuous and semi-continuous casting of metals in the casting of multi-faceted INGOTS; The aim of the invention is to improve the quality of the ingot. The mold contains a housing 1 and working walls 2 in the form of a polyhedron with channels 3 for cooling the building walls. The distance from the channels to the working surface of the wall increases uniformly from the middle of the face to its edges. Improving the quality of the ingot is achieved by equalizing the rate of growth of the ingot peel along the perimeter, thereby eliminating the reasons for the rise of longitudinal angular and transverse cracks. 1 il. § (L

Description

This invention relates to metallurgy and can be used in continuous and semi-continuous casting machines for casting multi-faceted ingots.

The aim of the invention is to improve the quality of the ingot.

The drawing shows schematically the mold, top view.

The mold includes a housing 1 and working walls in the form of a polyhedron 2 with channels 3 for cooling, made at a distance from the working surface of the polyhedral facing, increasing from the middle of each face to its edges (corners of the corners at the junction of faces).

This arrangement of channels creates conditions for reducing heat transfer at the vertices of the corners with a gradual increase in the intensity of heat transfer towards the middle of each face.

The expression dp for determining gradually increasing from the middle of the face to its edges the distance of each channel for cooling from the working surface of the multifaceted lining has the form

.,,

(one)

de (j is the distance from the i-ro channel to

working surface of the wall; , is the distance from the (i-l) -ro channel to the working wall surface;

i is the sequence number of the cooling channel within half of the face, counting from the middle of the face to its edges; d is the value, is equal to the difference of the distances i-ro and (i-l) -ro of the channels to the working surface of the wall and is determined from

. equations

.- (2)

n - 1

de c /; - distance — from the first channel of each face, counted from its center to the working surface of the wall; cf is the distance from the last by. this half of the channel edge to the working surface of the wall;

n is the number of channels for cooling, which are filled in half of the face.

The magnitude of the distance ff is taken constructively in the design and

This is one of the initial data for further calculations of the mold.

The distance from the cooling channel to the working surface of the lining depends on the effective heat transfer coefficient and is determined from the expression (I)

TO

1 s / 1

 at

(3)

where K is the effective coefficient of tep-g

lope;

0 - effective heat transfer coefficient from ingot to the wall of the mold; c / is the distance from the cooling channel to the working surface of the wall; L - coefficient of thermal conductivity

wall material; ofg - heat transfer coefficient from the wall to the coolant.

From the expression X. we find the formula for determining the distance from each channel to the working surface of the wall with the known effective heat transfer coefficient K (- --- -, -). (four)

Is.- m 6

To determine the distance / from the last on a given face of the channel for cooling I to the working surface

wall expression (4) takes the form

 .- -,--), (five)

. m "6

where K is the effective heat transfer coefficient at the place of the latter on a given face of the cooling channel, i.e. in the area adjacent to the top of the corner.

The cooling of a multi-faceted ingot is characterized by the fact that the heat fluxes in the faces become two-dimensional, as a result of which, at a CONSTANT heat transfer coefficient, the cooling rate of the top of the corner and the areas of the faces adjacent to it will be greater. To equalize the cooling rate, and, consequently, the ingot temperature around the perimeter, the heat transfer coefficient must be variable. Since mutual

the effect of two adjacent faces (with a constant heat transfer coefficient along the face) on their cooling rate depends on the angle formed by these faces, to equalize the cooling rate and ingot temperature along the perimeter, the heat transfer coefficient K at the vertices of the corners, depending on the angle Life is determined empirically, for example, using a hydraulic integrator.

With sufficient accuracy for practical design of multifaceted crystallizers, the coefficient of heat transfer to KB vertices of corners can be determined by interpolation.

Dp alignment of the temperature of the faces of the ingot, forming an angle of 90 °, at the tops of the corners it is necessary to reduce the heat transfer coefficient by 2 times compared to the middle of the face.

Based on this, for an angle equal to 90, one can write

determine the coefficient for between facets from 90 to 180

. " one

90 I 80

where l is the angle between adjacent faces of the mold.

Based on (O, (2), (5), (7) and (8), after substitution, we obtain the dependence for determining the distance from each channel for cooling to the working surface of the mold wall., 180 ° 1 J D v.vJ) °

f, /. (9)

n - 1

An example of a specific implementation of the proposed crystallizer. Baseline: octahedral facing of the mold is made of copper; the number of channels in the half face of n 4; channel diameter d 0.01 m; the distance from the first channel to the working surface of the mold wall is 0.01 m.

CP

0.5-K general view

To "tk", de

(6)

(6)

take the form

(7)

.the heat transfer coefficient at the vertices of the corners; heat transfer coefficient in the middle of the face; coefficient depending on the angle between the faces. . If the edges form an angle equal to 180 °, i.e. for flat wall

K, m and L L 320 kcal / m h hail; kcal hch-grad; o g l8700 kcal / m-h-gra angle, formed by neighboring grams of the crystallizer. For an eight gram A 135.

coefficient m 1. Therefore, when

changing the angle between adjacent gran - 40 135 °.

mi from 90 to 180 ° coefficient m change - Heat transfer coefficient in

you

.-4l 0.01. 2.02§lO.Oi 0.032 m;

. . 0.032. zfEpi 0.054 m.

Due to the fact that in the proposed ribs and the crystallizer, which can be determined from the given mom, the cooling and mathematical dependences (9) ensured that the conditions for cooling the barrel surface of the walls are increased, while increasing the intensity of the multi-faceted ingot. - schims from the middle of each facet to its heat transfer at the vertices of the corners and

five

The distance from each of the subsequent channels to the working surface of the mold wall is determined from 0 of the following relationship:

,-with/,

/. /.

Where

f.

n - 1 .180 °

one

one

Well L L 320 kcal / m h hail; kcal / m hch-grad; o g l8700 kcal / m - h; angle formed by the adjacent faces of the mold. For the octahedron A 135.

heat transfer coefficient in

channel can be determined from

place expresses 1562 kcal / m h-grad;

in the areas of the edges adjacent to them, significantly less than in the middle of the face, which, from the two-dimensional heat flux character, allows to equalize the rate of ingot peel growth along the perimeter, its shrinkage, the formation of a gap between the working surface of the wall and the ingot crust as well as the temperature of the multi-faceted ingot peel around the perimeter. As a result, the reasons for the occurrence of longitudinal angular and transverse cracks, the quality of ingots are improved, and the casting process is stabilized.

By improving the quality of ingots, with a production volume of 40 thousand tons of ingots per year, the economic effect will be 51, ji thousand rubles.

In addition, due to the stabilization of the casting process and the reduction in the number of breakthroughs of the liquid metal under the mold, the machine’s downtime and costs required to eliminate the effects of the breakthroughs are reduced.

Form m a la invention

Mold for continuous casting of metals, comprising a housing and working walls in the form of a polyhedron with cooling channels, o. t is characterized by the fact that, in order to improve the quality of the ingot, the channels for cooling are located relative to the working surface of the wall with increasing distance from its middle to the edges, determined from the relation:

. (180 ii)

K 1 / i C (m V

P

one

where cC, c /. is the distance from the channels to the working surface of the wall, with the first channel located -. wives in the middle of the wall;

And - coefficient of thermal conductivity of the material of the wall;

.K - effective heat transfer coefficient in the first channel;

otf is the effective heat transfer coefficient. from ingot to wall;

 - coefficient of heat transfer from the wall to the coolant; ft is the angle formed by the adjacent faces of the mold; . n is the number of channels formed in half of the wall.

Claims (1)

FORMULA OF THE INVENTION A mold for continuous casting of metals, comprising a housing and 30 working walls in the form of a polyhedron with cooling channels, about. t characterized by the fact that, with an increase in magnitude to the edges, bridges: the distance from its determined — from the front dependent = l_ _1 ____ η - T where, sA. „</; - the distance from the channels to the working surface of the wall, while the first channel is located. wives in the middle of the wall; A is the coefficient of thermal conductivity of the wall material; K ₇ is the effective heat transfer coefficient at the site of the first channel; - effective heat transfer coefficient. from ingot to the wall; ά _β is the heat transfer coefficient from the wall to the coolant; / 4 is the angle formed by adjacent faces of the mold; . η is the number of channels made in half of the wall.