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THE ARTICLE А.U.Tsuprun, А.N.Smirnov. Optimization of parameters of bend and razgiba of continuously poured slyaba. "Сталь". №8. 2006г.
OPTIMIZATION OF PARAMETERS OF BEND AND RAZGIBA OF CONTINUOUSLY POURED SLYABA
Presently for new slyab MNLZ (thickness of bar 150 - 300 mm) the following elements of their construction are selected: vertical kristallizator long 0,8 - 1,0 m (depending on the section of bar); kristallizator with possibility of change of width of slyaba in the process of pouring: sheeting on the internal surface of kristallizatora; vertical area under kristallizatorom long 1,5 - 1,7 m ; section of bend of bar and reduction of base radius to 7 - 8 m; dynamic case frame by the process of cooling of bar in ZVO; area of razgiba of bar; area of the "soft wringing" out, which provides upgrading internal area of purveyance.
At establishment of rollers in ZVO with growth of correlation of step of rollers and width of area of liquid phase in the bar of lr / b₁ the horizontal bending moments caused by ferrostaticheskim pressure, at first become level on the value with vertical, and then excel them. Equality of moments takes place at lr / b₁=0,78.
In practice of the continuous casting of lr / b₁ generally use considerably less 0,78. At the same time in most cases lr/b₁<1/3. Therefore the locations of rollers determine vertical tensions.
If the thickness of crust in ZVO is known, it is possible to calculate the location of rollers.
Coefficient which determines vertical moments is evened
where h - height of hardening layer; p - ferrostaticheskoe pressure.
Knowing the value of , we determine distance between rollers in ZVO.
If lr / b₁<1/3, that value of coefficient of is found in limits
In this case it is possible to find analytical expression for computation of step of rollers (м) in ZVO.
Taking on a value we get
where
We accept that
where L'' - distance on the arc of the R radius from the meniscus of bar to the place of establishment of rollers, m;y = pg (g - closeness of steel).
Step of rollers on the MNLZ radial type
With growth of size the L''/R value grows, that is, between rollers along radial MNLZ it can multiply distance even then, when
From marked clearly, that heavier to pick all up mode of cooling and construction which supports the crust of bar directly under kristallizatorom, especially on the MNLZ radial type.
The generally accepted "safe even deformations" and those which are often led in literature, make 1,25% for a surface and 0,2 - 0,25% for megfaznoy deformation. Maximum relative lengthening at 1430 - 1470°S makes 0,3 - 0,4%.
In computations of possible radiuses of bend and razgiba of bar with liquid serdtsevinoy it follows to take into account the possible relative lengthening not on verge of front of consolidation, and on some removal from him (13 - 15 mm).
Plasticity of steel in a range 1300 - 1400°S considerably below 1%. Oscillation of plasticity of steel relies on the method of research (method of receipt of standards, speed of deformation, sizes of standards, method of measuring of temperature of standards). Consequently, literary data about plasticity of steel can be used only taking to account that they have an approximate character.
For approximate computations the critical values of coefficient of the relative lengthening can be found within the limits of 0,2 - 0,25%. Stalling speed of deformation is here found within the limits of 10^-2 - 10^-4 s^-1, and the border of durability of hard crust makes 10 - 20 MPa (for some staley 4 - 6 MPa).
For carbon the staley legitimate measured critical values of tension of bar ( razgib - bend, thermal tensions and consolidations) must not exceed 0,7%.
For implementation of project computation the technological line MNLZ is broken up on the following areas ( picture ): vertical kristallizator of lver, vertical area under kristallizatorom of lkr, area of multiof thread bend of ldugi, radial area, area of multiof thread razgiba of lroz, horizontal area Lgor.
Initial stage of planning - choice of base radius of the machine R0, on which the described wall of technological channel of machine, including kristallizator and arc area of area of the second cooling.
On the basis of theoretical analysis and experience of exploitation of many machines of curvilinear type the developed recommendations on limitation of base radiuses within bounds of 25 - 35-multiple thickness of purveyances which pour off.

Picture - Chart of the MNLZ curvilinear type with vertical one by kristallizatorom
Knowing the quantity of points of bend and step of rollers on the curvilinear area of bend, it is possible to define complete length of area of the Lzag bend. By a basic factor which determines length of multiof thread bend at the known step, there is the requirement of not exceeding by the size of relative deformation of bend on each of rollers of critical values of index of plasticity of
The area of bend can be built on a curve with permanent reduction of radius of curvature from endlessness at the beginning to the base radius R0 in the end. The accumulated complete relative deformation on all area of it is determined as
where x₀ - thickness of slyaba, m.
Then common quantity of points of bend
Relative deformation of bend on each of rollers of is determined as a relation of complete relative deformation to the common quantity of points of bend of n_zag.
For the radius R_zag.i on every roller I will have a kind
where i = 1,…,n_zag.
The area of razgiba must be built on a curve with the radius of curvature, which is constantly multiplied from R0 for ever and ever. Total complete relative deformation on the area of razgiba is determined as
Common quantity of points of razgiba
The radius of curvature of razgiba on each of rollers is determined as
where i = 1,…,n_заг.

Information from the internet

Keyword	It is found references	It Is Looked Over	Useful
"Production of slyab"	52578	300	45
"Bend of slyab"	92	92	14

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