CN111745136B

CN111745136B - Crystallizer

Info

Publication number: CN111745136B
Application number: CN202010652219.5A
Authority: CN
Inventors: 刘强; 韩志伟; 邓比涛; 孔意文
Original assignee: CISDI Engineering Co Ltd; CISDI Research and Development Co Ltd
Current assignee: CISDI Engineering Co Ltd; CISDI Research and Development Co Ltd
Priority date: 2020-07-08
Filing date: 2020-07-08
Publication date: 2022-06-10
Anticipated expiration: 2040-07-08
Also published as: CN111745136A

Abstract

The invention relates to a crystallizer, and belongs to the field of metal continuous casting. The copper pipe comprises a copper pipe formed by encircling four copper plates, wherein two copper plates arranged in opposite directions are wide panels, and the other two copper plates arranged in opposite directions are narrow panels; along the casting direction of the crystallizer, the plate surface of the wide panel is in curve change, and the curvatures at the inlet end and the outlet end of the wide panel are not 0; along the horizontal direction of the crystallizer, the plate surface of the wide panel is changed in a piecewise function curve mode. The design can ensure that the integral strain of the casting blank shell of the casting blank is small in the limited length of the crystallizer, and the quality of the casting blank is improved. The problem that the strain rate of a casting blank shell of the traditional thin slab crystallizer in the crystallizer is too high is solved. The strain rate is reduced, the crack defects on the surface of the casting blank are improved, and the abrasion of the casting blank on the crystallizer copper plate coating is reduced. The concave curve of the crystallizer is provided with a certain depth at the outlet, so that the service life of the crystallizer is prolonged, and the processing difficulty of equipment is reduced.

Description

Crystallizer

Technical Field

The invention belongs to the field of metal continuous casting, and particularly relates to a crystallizer.

Background

The continuous casting and rolling process of the sheet billet can more flexibly face the market due to the advantages of simplified process, short production flow, less equipment, energy conservation, high yield and the like, and becomes a key investment object of steel production companies in recent years. The most important difference between the continuous thin slab casting and rolling technique and the conventional continuous casting technique is the crystallizer. As is well known, in order to solve the problems of molten steel flowing in the gap between the mold and the nozzle, the mold is designed into a funnel shape with a large top and a small bottom, but the design makes the shell of the billet subjected to additional stress in the mold to easily cause crack defects, so the shape curve of the inner cavity of the mold is of great importance, and as a core technology of continuous casting of thin slabs, the design of the shape curve of the inner cavity of the mold has been paid great attention by those skilled in the art.

In the prior art of thin slab funnel-shaped crystallizers, the transverse and longitudinal curves comprise: the curve is formed by connecting a plurality of sections of straight lines, connecting the straight lines with circular arcs, and forming a double arc and an ellipse or combining polynomial curves. The boundary conditions of the constraint curve include: the curve end point value, the curve first derivative is continuous, the curve second derivative is continuous, the curve third derivative is continuous, the curve curvature is constant, the curve curvature change rate is minimum, the curve curvature change rate is constant and the like, so that the final curve equation is solved.

A Chinese patent application with the application number of 201910263801.X, namely a thin slab funnel-shaped crystallizer wide-surface copper plate based on a relaxation curve and a preparation method thereof, discloses a funnel-shaped crystallizer cavity curve based on a relaxation curve, wherein the curve is expressed as a curve in the horizontal direction of a crystallizer

In the casting direction of the mold, the curve is expressed as

The boundary condition of the constraint curve is the numerical value of the inlet and outlet of the crystallizer, etc.

The chinese patent application No. 200410015897.1, a water-cooled continuous metal casting mold, discloses a cavity curve of a funnel-shaped mold, the equation of the curve part of the cross-sectional profile curve is expressed as f (x) a in the horizontal direction of the mold₀+a₁x+a₂x²+a₃x³+a₄x⁴+a₅x⁵+a₆x⁶In the casting direction of the mold, the equation for the curve portion of the longitudinal section profile curve is expressed as f (z) ═ b₀+b₁z+b₂z²+b₃z³+b₄z⁴+b₅z⁵The boundary condition of the constraint curve is that the reciprocal of the curve is continuous above the third order, and the like.

In the article "obtaining the curved surface of the wide surface part of the inner cavity of the crystallizer for continuous casting of an ideal thin slab", it is disclosed that the crystallizer adopts a curve in the casting direction of

The boundary conditions for the constraint curve are that the first and second derivatives of the curve at the end points are both zero and that the maximum value of the rate of change of curvature is minimal.

However, the above curves all have the following disadvantages:

1) due to the problems of 'curvature of curves at an inlet and an outlet of the crystallizer in the pouring direction is 0', or 'longitudinal curves are transited through arcs in a short interval', or 'curvature change rate in the crystallizer is large', and the like, the strain rate of a casting blank in the limited length of the crystallizer is increased, and the stress strain of a continuous casting blank shell in the crystallizer is increased.

2) The funnel-shaped region usually ends in a position such as "lower middle crystallizer", "crystallizer outlet" or "extension into the guide section"; whereas ending in the middle-lower part of the crystallizer necessarily results in a short funnel region, increased strain and strain rate; the copper plate at the outlet of the crystallizer is easy to wear after the outlet of the crystallizer is finished, and the online service life of the copper plate is shortened; and the guide section is finished, and the guide section needs to be made into a groove roller, so that the processing difficulty is increased.

Disclosure of Invention

In view of the above, the present invention is directed to a mold for overcoming the problem of excessive strain rate of a thin slab shell in the mold.

In order to achieve the purpose, the invention provides the following technical scheme:

a crystallizer comprises a copper pipe formed by encircling four copper plates, wherein two copper plates arranged in opposite directions are wide panels, the other two copper plates arranged in opposite directions are narrow panels, and the width of each wide panel is larger than that of each narrow panel; along the casting direction of the crystallizer, the plate surface of the wide panel is in curve change, and the curvatures at the inlet end and the outlet end of the wide panel are not 0; along the horizontal direction of the crystallizer, the plate surface of the wide panel is changed in a piecewise function curve mode.

Further, the narrow panel is a smooth flat or curved surface.

Further, the narrow panel is a semi-cylindrical curved surface.

Further, the wide panel is a concave curved surface with an inlet and an outlet in concave shapes; wherein the depth of the recess at the outlet is not more than 10 mm.

Further, along the casting direction of the crystallizer, the surface curve of the wide panel is as follows:

wherein n is greater than 2; a is_iIs a coefficient; z is a coordinate value in the casting direction z in mm.

Further, the wide panel is bilaterally symmetrical along the center of the panel surface.

Further, the center of the board surface of the wide board is taken as a boundary, and the piecewise function curve at one side of the wide board is as follows:

wherein: y is the y-direction coordinate value of the wide panel corresponding to a certain coordinate position in the z height position and the x direction of the crystallizer in unit mm;

unit mm;

unit mm;

x is a coordinate value in the x direction in the horizontal direction and the unit is mm;

C₁、C₂、C₃are the boundary points of the piecewise function.

The invention has the beneficial effects that:

the wide panel plate surface of the copper pipe in the crystallizer is an inwards concave curved surface, and the wide panel plate surface of the crystallizer is designed into a longitudinal inwards concave curve, and the curvatures of the inwards concave curve at an inlet and an outlet of the inwards concave curve are not 0, so that the whole strain of the crystallizer and a casting blank shell within a limited length is small, and the casting blank quality is improved. The problem that the strain rate of the casting blank shell of the traditional sheet billet crystallizer in the crystallizer is too high is solved. The strain rate is reduced, the crack defects on the surface of the casting blank are improved, and the abrasion of the casting blank on the crystallizer copper plate coating is reduced. The concave curve of the crystallizer is provided with a certain depth at the outlet, so that the service life of the crystallizer is prolonged, and the processing difficulty of equipment is reduced. And in the direction perpendicular to the pouring direction, the casting blank stress concentration caused by the curved surface form can be relieved by adopting the piecewise function, and the function of reducing crack defects is played to a certain extent.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a three-dimensional view of a funnel crystallizer;

FIG. 2 is a top-bottom comparison view of a funnel crystallizer;

FIG. 3 is a top and bottom enlarged comparative view of a funnel crystallizer;

FIG. 4 is a diagram illustrating a parameter derivation process;

FIG. 5 is a graph showing the variation of the depth of the inner recess along the center line of the mold in the casting direction;

FIG. 6 is a graph showing the variation of the radius of a concave curve along the casting direction;

FIG. 7 is a graph showing the change of curvature of a concave curve along the casting direction.

Reference numerals:

wide panel I-1, wide panel II-2, narrow panel I-3, narrow panel II-4, wide panel width W₁Narrow panel width-W₂。

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustration only and not for the purpose of limiting the invention, shown in the drawings are schematic representations and not in the form of actual drawings; for a better explanation of the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

Referring to fig. 1 to 4, a crystallizer is shown, which includes a copper tube surrounded by four copper plates, wherein two copper plates disposed opposite to each other are wide plates, which are respectively designated as a wide plate i1 and a wide plate ii 2, and the other two copper plates disposed opposite to each other are narrow plates, which are respectively designated as a narrow plate i 3 and a narrow plate ii 4; width W of wide panel I1 and wide panel II 2₁Greater than the width W of the narrow panel₂. Along the casting direction of the crystallizer, the surface of the wide panel changes in a curve, andthe curvatures at the inlet (also called as an upper port) and the outlet (also called as a lower port) are not 0; along the horizontal direction of the crystallizer, the plate surface of the wide panel is changed in a piecewise function curve mode.

Specifically, as shown in fig. 1, a spatial rectangular coordinate system is established by taking the upper opening end face of the crystallizer as a horizontal plane, taking the center of the wide panel plate face as a vertical plane, and coinciding the X axis with a certain straight line segment on the inlet end of the wide panel i 1. In the rectangular spatial coordinate system, the z-axis is the casting direction, and the planes of the x-axis and the y-axis are horizontal planes (also referred to as "upper opening end faces") perpendicular to the casting direction.

In the established rectangular space coordinate system, as shown in fig. 3, the depth of the concave part at the inlet of the copper tube in the crystallizer is recorded as L_tThe depth of the recess at the outlet is recorded as L_bWherein L is_t＞L_bPreferably L_bNot more than 10mm, namely the concave depth of the lower opening of the copper pipe is not more than 10 mm. The concave curve of the crystallizer is arranged at the outlet of the crystallizer with a certain depth, so that the service life of the crystallizer can be prolonged, and the processing difficulty of equipment is reduced.

On the premise of meeting the requirements, along the casting direction of the crystallizer, the concave curved surface curve of the wide panel is as follows:

The narrow panel of the copper pipe in the crystallizer is a smooth plane or a curved surface. Preferably, the narrow panel is a semi-cylindrical curved surface, in which case the width W is₂I.e. the semi-cylindrical diameter.

Preferably, the wide panel is left-right symmetrical along the center of the panel surface. Referring to fig. 1 and 2, the wide panel I1 and the wide panel II 2 are symmetrical to each other about the plane of yoz.

The curve of the wide face plate I1 on the right side of the plane of the yoz is in a piecewise function change in the direction perpendicular to the casting direction by taking the center of the face of the wide face plate as a boundary, namely the plane of the yoz.

As shown in fig. 2 and 4, the piecewise function is divided into 4 sections, AB, BC, CD, and DE, and the y values of the different sections are represented by different functions.

For the OB' interval: y ═ y_max， ——(0)。

For the B 'C interval, any y ═ PP', given the similarity of Δ O "B 'K to Δ PP' K by the triangle-like theorem, then:

wherein: KP ' ═ x-OB ' -B ' K, — (2);

B′O″＝BO″-BB′＝r-y_max， ——(3)；

the combined vertical type (4) and the formula (5) can obtain

The joint type (1), (2), (3) and formula (6) can obtain:

for the C 'D' interval: any y ═ QQ '═ O' D '-O' D ═ r-rcos β, - (8);

and is provided with

Simultaneous reaction of (8) and (9) gives

For the D 'E' interval: y is 0, i.e. y is 0- (11).

By combining (0), (7), (10) and (11), the piecewise function y can be expressed by the following relation:

wherein: y is a function of x and z, and is a y-direction coordinate value of the wide panel corresponding to the z height position of the crystallizer and a certain coordinate position in the x direction, and the unit is mm;

r is a variable, and according to the triangle similarity principle, Δ O ' D ' N is similar to Δ O "B ' N, so that:

sinγ²+cosγ²＝1， ——(15)；

the simultaneous type (12) to formula (15) can obtain:

unit mm;

the delta E is a variable in the variable,

unit mm;

x is a coordinate value in the x direction and is in mm;

C₁is the boundary point of the piecewise function, i.e., point B' in FIG. 4; c₁May be 0, i.e., it means that the straight line segment may not be present;

C₂is the boundary point of the piecewise function, i.e., point C' in fig. 4;

C₃is the boundary point of the piecewise function, i.e., point D' in FIG. 4; x is not less than C₃The straight line segments of (a) may be absent.

The wide panel plate surface of the copper pipe in the crystallizer is an inwards concave curved surface, and the wide panel plate surface of the crystallizer is designed into a longitudinal inwards concave curve, and the curvatures of the inwards concave curve at an inlet and an outlet of the inwards concave curve are not 0, so that the whole strain of the crystallizer and a casting blank shell within a limited length is small, and the casting blank quality is improved. The problem that the strain rate of a casting blank shell of the traditional thin slab crystallizer in the crystallizer is too high is solved, the strain rate is reduced, the defect of cracks on the surface of the casting blank is overcome, and the abrasion of the casting blank on a crystallizer copper plate coating is reduced. And in the direction perpendicular to the pouring direction, the casting blank stress concentration caused by the curved surface form can be relieved by adopting the piecewise function, and the function of reducing crack defects is played to a certain extent.

The following is a proof of description by way of specific examples:

the continuous casting crystallizer of a certain steel mill is formed by encircling four copper plates, two wide panels and two narrow panels, as shown in figure 1, wherein the wide panel is an inwards concave curved surface, the inwards concave curved surface is in curve change along the casting direction, and the curvatures at the inlet and the outlet of the crystallizer are not 0. Perpendicular to the casting direction, the curve varies as a piecewise function curve.

Specifically, as shown in fig. 2 and 3, the inlet and the outlet of the mold are both concave, and the concave depth at the inlet is L_t＝40mm, and the depth of the concave part at the outlet is L_b0.5 mm. The curvature radius r of the curve at the inlet of the crystallizer_t16000mm, radius of curvature r at the outlet_b＝20000mm。

The concave curved surface is changed along the casting direction in a curve,

when n is 3, i.e. y isa₀+a₁z¹+α₂z²+a₃z³The constraint of the curve equation at this time is as follows:

wherein:

the equation of the curve is solved as follows:

y＝40-6.74164842e-02z+3.14503903e-05z²-1.86677142e-09z³；

when the narrow panel is a semi-cylindrical curved surface with a radius of 50mm, as shown in fig. 1, taking the curved surface of the right side panel surface of the symmetry axis of the wide panel as an example, the curve changes in a piecewise function along the direction perpendicular to the casting direction;

wherein: c₁＝AB＝90mm；C₂＝AC＝270mm，C₃＝AD＝450mm；

At this time:

then:

the curved surface of the crystallizer plate is obtained through calculation, the concave depth of the center line of the crystallizer changes along the casting direction as shown in figure 5, the radius of the concave curve changes along the casting direction as shown in figure 6, the curvature change rate of the concave curve changes along the casting direction as shown in figure 7, and as can be seen from figures 5 to 7, the curvature radius of the curve at the upper opening of the crystallizer is 16000mm, the curvature radius at the lower opening of the crystallizer is 20000mm, and the concave depth at the lower opening of the crystallizer is 0.5mm, the strain and the strain rate of a casting blank shell in the crystallizer can be greatly reduced; the quality of the casting blank is improved, and the complexity of equipment processing is reduced.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.

Claims

1. A crystallizer comprises a copper pipe formed by encircling four copper plates, wherein two copper plates arranged in opposite directions are wide panels, the other two copper plates arranged in opposite directions are narrow panels, and the width of each wide panel is larger than that of each narrow panel; along the casting direction of the crystallizer, the plate surface of the wide panel is in curve change, and the curvatures at the inlet end and the outlet end of the wide panel are not 0; along the horizontal direction of the crystallizer, the plate surface of the wide panel changes in a piecewise function curve; the narrow panel is a smooth plane or a curved surface; the method is characterized in that: the narrow panel is a semi-cylindrical curved surface, and the wide panel is bilaterally symmetrical along the center of the panel surface; the center of the board surface of the wide board is taken as a boundary, and the piecewise function curve at one side of the wide board is as follows:

unit mm;

unit mm;

C₁、C₂、C₃are the boundary points of the piecewise function.

2. The crystallizer of claim 1, wherein: the wide panel is a concave curved surface with an inlet and an outlet in concave shapes; wherein the depth of the recess at the outlet is not more than 10 mm.

3. The crystallizer according to any one of claims 1-2, wherein: along the casting direction of the crystallizer, the surface curve of the wide panel is as follows:

wherein n is greater than 2; a is_iIs a coefficient; and z is a coordinate value in the casting direction z and has a unit of mm.