0 Introduction The damage of the refractory material of the converter lining is related to the thermal stress caused by the heat load, and the thermal stress received by the lining work process is closely related to the setting of the lining expansion gap. The expansion gap is too large, the furnace lining is subjected to small thermal stress, but the furnace lining structure is unstable; the lining expansion gap is set too small or not, and the lining structure is stable, but the furnace lining is subjected to large thermal stress. In order to analyze whether the lining is reasonable and the thermal stress of the lining work process, it is necessary to understand the influence of the expansion gap on the contact pressure between the lining and the furnace shell. The contact pressure between the furnace lining and the furnace shell is solved, and the temperature distribution of the lining structure is the basis. Since the physical property parameter values â€‹â€‹of the lining materials involved in the calculation are changed with the temperature, and the shape of the furnace body and the complexity of solving the boundary conditions, the contact pressure and temperature field between the lining and the furnace shell are determined according to the analytical method. Very difficult, and sometimes impossible, the development of finite element methods provides an effective tool for solving this problem.

1.1 Converter structure and heat load characteristics The converter furnace body is composed of a furnace shell and a furnace lining. The furnace shell is welded by steel plates, and the furnace lining is composed of a working layer and a permanent layer. The working layer is directly in contact with the liquid metal, slag and furnace gas in the furnace, and is gradually corroded during work; the permanent layer is closely attached to the furnace shell to protect the furnace shell steel sheet.

In addition to the taphole, the furnace structure is a rotationally symmetrical structure with the centerline as the axis. Since the furnace structure is basically a rotary symmetrical structure with the center line as the axis, and in the smelting process, each furnace can be divided into four working conditions of empty furnace, iron and steel scrap, blowing and tapping. During the first three working conditions, the heat load of the converter is axisymmetric. The furnace shell will be exposed to the heat radiation of the ladle only during tapping. The temperature on the side will rise slightly, but the tapping time is generally only 5 min. The load is axisymmetric, and the first three conditions account for about 90% of the total time. Therefore, when the heat transfer analysis of the furnace body is performed, it can be simplified into an axisymmetric body.

After the new lining is completed, the heating oven must be carried out before the normal smelting, so that the refractory bricks are closely sintered to form a whole for smelting. The oven is carried out according to a certain heating and heating system. Since the temperature inside the furnace body is constantly rising and changing, the temperature change of the converter furnace body is a transient heat transfer process during the heating oven.

After the end of the oven, when the steelmaking production begins, the temperature of the shell gradually increases. After about 80-120 hours of production, the temperature distribution of the lining tends to be stable. During smelting, the feeding, sampling, tapping and other operations will cause changes in the temperature inside the furnace. However, due to the short duration of these operations, the thermal inertia of the furnace is large, and the temperature level of the lining and the furnace shell will not be greatly affected. The temperature field formed by the furnace body can be regarded as a steady state temperature field.

1.2 Mathematical model The temperature control equation is established according to the Fourier heat conduction law. When establishing the thermal physical model of the furnace body, the furnace body is set to a plane axisymmetric model according to the above structural characteristics and thermal load conditions, and is in a steady temperature field.

1.3 Finite element model and solution results Since the converter is a whole structure composed of the furnace shell and the furnace lining, when analyzing the temperature field of the furnace lining, it should be analyzed according to the overall structure. When the axial symmetry plane of the intercepting furnace body is meshed, according to the usual division rule, the mesh is relatively coarsened in the gradual structure of the structure, and the structural transition portion is appropriately refined. The furnace body is composed of three materials with different characteristics due to the work requirements. However, when the model is built with finite elements, the lining and the furnace shell are considered as a continuous whole, and the working layer, the permanent layer and the furnace shell are respectively designated according to different materials. The material properties should also take into account the material properties as a function of temperature. The model uses a plane axis symmetry.

When using the finite element method for analysis, the boundary conditions are usually considered in two ways: one is to specify the temperature of the inner surface of the lining to be 1600 Â° C, according to the first type of boundary conditions; the other is to change the outer surface of the furnace shell by experiment The thermal conditions are considered according to the third type of boundary conditions, and then the heat transfer conditions are corrected according to the measured results of the outer surface of the furnace shell, so that the obtained finite element heat transfer model can truly reflect: the furnace lining expansion gap to the furnace lining The contact pressure with the furnace shell affects the actual working process. The thermal properties of the working layer (magnesium carbon brick), permanent layer (magnesium brick) and furnace shell (steel) used in the finite element calculation are mainly based on the composition of the refractory used in the converter.

After finite element calculation, the temperature field distribution of the furnace body and the lining, the temperature distribution of the outer surface of the lining is lower and higher, and the change of the geometry of the lining surface will have a certain influence on the temperature distribution. In addition, at the transition between the bottom of the furnace and the shaft, due to the change of geometry, there is also a sudden change in the temperature. The temperature distribution curve of the lining has a large slope, and the lowest point of the lining temperature is at the junction of the bottom of the furnace and the cone of the lower cone. .

2 The contact pressure between the different expansion gap lining and the furnace shell 2.1 The physical model contact problem is a kind of complex nonlinear problem, which belongs to the boundary condition nonlinear problem. Its complexity mainly comes from the change of system state, that is, the separation and contact between objects. In the contact problem, the contact surface between the two contact bodies is usually unknown in advance, and the boundary conditions are not given before the calculation, but are given by the calculation results. The area and pressure distribution of the contact surfaces between the two contacts vary with the external load and the initial gap and are related to the rigidity of the contact body. When the gap between the contact surface and the target surface is greater than zero, it is an open contact; when it is less than zero, it is a closed contact. Contact permeability is represented by the value of the gap, which occurs when the point of contact penetrates the target surface.

2.2 Construction and solution of contact finite element model The contact finite element model is based on solving the finite element model of temperature field. Using the ANSYS finite element thermal-structural coupling relationship, the above-mentioned temperature field is coupled to the contact finite element model, and at the same time, the contact unit is added between the lining and the inner surface of the furnace shell. The material elastic modulus, Poisson's ratio and thermal expansion coefficient physical property parameters involved in the calculation are determined, and the boundary condition parameters are determined according to the normal operating conditions of the converter site. When considering the expansion of the lining, the following assumptions are made: (1) the thermal expansion coefficient of the refractory material is the same in three dimensions; (2) It is assumed that the circumferential expansion gap between the refractory brick and the refractory brick only affects the stress of the refractory brick without affecting the lining and furnace Contact pressure between the shells. When calculating the contact pressure between the lining and the furnace shell, only the radial expansion gap between the lining and the furnace shell (hereinafter referred to as the expansion gap) is considered; (3) according to the actual working conditions, in the establishment of the contact model, from the bottom of the furnace to An expansion gap is provided between the furnace lining of the furnace cone and the furnace shell, and the expansion gaps of different parts are different.

At the beginning of the analysis, first consider the condition that the radial expansion gap of the lining is zero, and then calculate according to the actual expansion gap, and compare the two. The contact positive pressure distribution between the lining and the furnace shell when the refractory brick is not provided with the radial expansion gap is obtained. In order to specifically show the magnitude of the contact positive pressure at different locations, the length between the inner wall of the furnace shell at the lowest point of the furnace bottom and the inner wall surface of the furnace shell at the furnace mouth is taken as the equivalent height. Taking the equivalent height as the abscissa and the contact pressure as the ordinate, the actual value of the contact positive pressure without the radial expansion gap along the equivalent height distribution such as the gap is obtained, and the contact pressure along the lining and the furnace shell is obtained. The distribution of equivalent heights.

3 Conclusions (1) The solution of the temperature field of the refractory material of the converter lining is the basis of the lining stress analysis. Since the furnace lining is inside the furnace shell, the temperature field distribution of the lining material is not easily obtained by the actual measurement method. Moreover, the heat transfer coefficient of the furnace material changes with temperature, and it is difficult to calculate the temperature distribution of the overall lining by a theoretical method. The finite element method is used to calculate the temperature field distribution of the refractory material, which provides a scientific basis for the calculation of the contact pressure between the lining and the furnace shell and the calculation of the thermal stress and thermal deformation of the lining and the design of the converter.

(2) The expansion gap is set in the lining, which causes the contact pressure between the lining and the furnace shell to be different. Therefore, the distribution of the contact pressure between the lining and the furnace shell is adjusted by providing different expansion gaps.

On the contrary, by solving the distribution of the contact pressure between the lining and the furnace shell, it can be indirectly determined whether the expansion gap setting of the lining is reasonable. In order to maintain the stability of the lining, it is desirable that the contact pressure between the lining and the furnace shell exists when the converter is operated at a high temperature. At the same time, in order to reduce the "pressure concentration" of the contact pressure of the transition portion of the furnace shell, the stress concentration of the lining of the portion is caused, and the "soft filler layer" should be filled at the portion to reduce the damage of the lining.

Dinning Room Furniture,Furniture Dining ,White Dining Furniture,Modern Furniture

BOSA FURNITURE CO.,LTD. , https://www.bosafurniture.com