The invention relates to a method for setting a conicity of a die of a strand casting installation, in particular a slab strand casting installation, during a casting procedure, comprising the following method steps: measuring temperature values along at least one centric measuring path running in a casting direction along an adjustably disposed die wall; and measuring temperature values along at least one peripheral measuring path running in a casting direction along the adjustably disposed die wall, wherein the peripheral measuring path runs between the centric measuring path and a lateral periphery of the die wall, and a spacing of the peripheral measuring path from said lateral periphery of the die wall is smaller than a spacing of the centric measuring path from the other lateral periphery of the die wall.
The invention furthermore relates to a device for a strand casting installation, in particular a slab strand casting installation, comprising: at least one die having mutually opposite, adjustably disposed die walls; at least one adjustment mechanism for adjusting the die walls; at least one actuation electronics system for actuating the adjustment mechanism; at least one centric sensor installation, connected to the actuation electronics system, for measuring temperature values along at least one centric measuring path running in a casting direction along one of the adjustably disposed die walls; and at least one peripheral sensor installation, connected to the actuation electronics system, for measuring temperature values along at least one peripheral measuring path running in a casting direction along the adjustably disposed die wall, wherein the peripheral measuring path runs between the centric measuring path and a lateral periphery of the die wall, and a spacing of the peripheral measuring path from said lateral periphery of the die wall is smaller than a spacing of the centric measuring path from the other lateral periphery of the die wall.
A respective method and a respective device are known from DE 10 2014 227 013 A1.
In the strand casting of metals in a strand casting installation, the strand width of a cast strand can be set by way of adjustable die walls on mutually opposite narrow sides of a die. The die comprises a casting passage that continues from an inlet end by way of which a metal melt is cast into the die, to an outlet end from which a strand having a strand shell and a liquid core exits, said casting passage in the cross section perpendicular to a casting direction which is defined as the direction of the metal melt flowing through the die having a rectangular shape. The strand can be configured as a slab, for example.
During cooling of the metal melt within the die, a loss of volume arises, this meaning that a cross-sectional area of the metal melt, or of the strand created therefrom, respectively, is larger at the inlet end of the die than a cross-sectional area of the metal melt, or of the strand, respectively, at the outlet end of the die. In order for a desired guiding of the metal melt, or of the strand, respectively, to be guaranteed by way of a contact with the die across the full area, the casting passage of the die is configured so as to conically taper in the casting direction. The conicity of the casting passage of the die is usually set by way of a variation in the incline of the die walls adjustably disposed on mutually opposite narrow sides. Without such a conical configuration of the casting passage of the die, the strand would no longer be guided in the lower region of the die, or in the region of the outlet end, respectively. In this instance, a controlled dissipation of heat from the strand to the usually water-cooled die walls is no longer possible. For the sake of simplicity, the conicity of the casting passage of the die in the context of the present application is referred to as the conicity of the die.
FIG. 1A shows a result in the case of an optimal conicity of a die 1. Shown is a lateral portion of the die 1 in the cross section perpendicular to the casting direction, said die 1 having two mutually opposite die walls 2 which are in each case assigned to one broad side of the die 1. Moreover, the die 1 has two mutually opposite, adjustably disposed eyeballs 3 which in each case are assigned to a narrow side of the die 1, and of which only one die wall 3 is shown in FIG. 1A. A strand 4 which has a strand shell 5 and a core 6 of liquid metal is guided through the die 1. The strand 4 bears on the entire area of the die walls 2 and 3, and on account thereof is guided in an optimal manner and simultaneously cooled by means of the die walls 2 and 3.
FIG. 1B shows a result in the case of an inadequate conicity of a die 1. On account thereof, the strand 4, or the strand shell 5, respectively, bulges outwards on the narrow sides, and the strand 4 simultaneously flattens towards the periphery, thus having a lesser thickness at said periphery than in a central region. Moreover, the periphery of the strand 4 no longer bears on the die walls 2 and 3 across the entire area such that the strand 4 is not guided in an optimal manner and is non-uniformly cooled by means of the die walls 2 and 3.
FIG. 1C shows a result in the case of an excessive conicity of a die 1. On account thereof, a concavity 6 arises on a narrow lateral face of the strand 4, or of the strand shell 5, respectively, and longitudinal depressions 7 near the periphery, the so-called rain gutters, arise on the broad sides of the strand 4. On account thereof, the narrow sides and the peripheral portions of the broad sides of the strand 4 no longer bear on the die walls 2 and 3 across the entire area such that the strand 4 is not guided in an optimal manner and is non-uniformly cooled by means of the die walls 2 and 3. On account of the inadequate cooling on the narrow sides of the strand 4, the strand shell 5 on the narrow sides of the strand 4 is not configured so as to be sufficiently strong. On account thereof, bulges are formed on the narrow sides of the strand 4 after the strand 4 has exited the die 1 and is in a secondary cooling in a strand casting installation.
The formation of concavities on the narrow sides of a strand can conventionally be minimized or eliminated, respectively, by reducing the conicity of the die. By contrast thereto, if it is established that the strand after passing through the die has bulges on the narrow sides, the conicity of the die is usually increased. However, if the bulges on the narrow sides of the strand are caused by an excessive conicity of the die according to FIG. 1C, the defect pattern of the longitudinal depressions on the broad sides of the strand are amplified on account of the further amplification of the conicity of the die for the intended reduction of the bulges, as is shown in FIG. 1D. This can lead to fissures on the strand shell on the base of the respective longitudinal depression, and under certain circumstances can lead to strand breakages in the region of the respective longitudinal depressions. The overall quality of the strand is reduced on account of the longitudinal depressions.