Foreword
The use temperature of the hot rolling furnace is not high, and the design and material selection of the refractory material are set according to the use temperature. The preheating section, the heating section and the soaking section are generally in accordance with 800~900 °C, 1150~1400 °C, 1200~1300 °C. The temperature range is controlled, and there is no national standard or industry standard to limit the refractory of the furnace. There are two heating furnaces in the hot rolling mill and three hot rolling mills of WISCO Hot Rolling Plant for rolling steels that require high temperature heating. Due to the sticking of the walking beams and columns, it is often necessary to periodically shut down the furnace to clean the slag. Overhaul is not only time consuming but also increases costs.
In order to study the cause of the lining of the lining, and solve the problem of the influence of the walking beam and the slag of the column, during the inspection of the hot rolling and shutdown, the damage of the walking beam and the column in each heating furnace was investigated, and the parts were analyzed. The performance and structure of the lining material were analyzed and discussed.
Performance and erosion analysis of refractory materials for columns and walking beams
From the basic situation of the refractory materials for the walking beam and the column of the three hot rolling furnace, the material is mainly castable, and the repair is mainly made of plastic. The chemical composition of the walking beam and column refractory is shown in Table 1. 
Table 1 Chemical composition of casting material for walking beam and column of heating furnace /%
As shown in Fig. 1 and Fig. 2, in the heating furnace, the walking beam and the column are heavily slag, and the slag layer with iron oxide as the main component is formed along both sides of the walking beam, which is column-shaped or waterfall-like, which affects the furnace. Air distribution and temperature distribution. The column, especially the column of the movable beam, becomes thicker due to the slag, which in turn affects the stroke of the walking beam and hinders the normal production. Severe slag also leads to poor slagging, resulting in accumulation of slag in the furnace. Finally, it is necessary to stop the slag cleaning, resulting in shortened maintenance period and increased cost. Table 2 lists the performance of the caster for the walking beam and column of the furnace.
Table 2 Performance of castables for walking beam and column of heating furnace
Figure 1 shows the situation of the slag and the sticky iron oxide phase walking beam in the heating furnace
(a) slag formation; (b) walking beam with iron oxide as the main phase
Figure 3 shows the microstructure of the residual refractory material of the column in the heating furnace. The outermost layer of the lining is a magnetite belt, which is mainly composed of granular magnetite. The magnetite crystal has a gray bonding phase and is porous. 3(a)]; The main aggregate of the original brick belt is corundum or alumina particles, mullite, and other particles, and there are a small number of pores in the sample [Fig. 3(b)].
Figure 2 Status of the column and walking beam in the hot rolling furnace
Figure 3 Microstructure of the residual brick of the heating furnace column
The structure and composition of the residual samples of the column were analyzed by using electron probe and energy spectrum technique, as shown in Fig. 4. The magnetite composition shown in Fig. 4(a) after partial enlargement is: w(Al2O3) 14.97%, w(FeO) 85.03%. The composition of one part in Fig. 4(a) is: w(SiO2) 68.81%, w(Al2O3) 23.28%, w(Na2O)1.17%, w(CaO) 6.74%; the dark black portion is composed of a single SiO2. Figure 4(b) shows the structure between the slag and the refractory interface. The white phase is similar to magnetite, but one of the components is: w(SiO2)69.88%, w(Al2O3) 18.26%, w(Na2O) ) 1.09%, w(K2O) 2.58%, w(CaO) 3.61%, w(FeO) 4.59%. Whether the alumina dissolved in the iron oxide slag phase is dissolved from the refractory material or enters by other means is worth considering. When the slag is severely slag, the aluminized slag is used, but from the structural analysis, the alumina in the lining is more easily dissolved into the iron oxide phase, and the silicon oxide and the calcium oxide are not easily eutectic with the iron oxide. There are more possibilities for technology.
Figure 4 Structure and composition of residual bricks in heating furnace columns
Figure 5 is the microstructure of the refractory residual sample of the walking beam in the heating furnace. The outermost layer of the lining is a magnetite belt [Fig. 5(a)]; the main aggregate of the original brick belt is corundum, mullite, and Other particles, the aggregate and the matrix are densely bonded [Fig. 5(b)].
Figure 5 Microstructure of the residual brick of the walking beam of the heating furnace
The structure and composition of the residual sample of the walking beam were analyzed by using electron probe and energy spectrum technique, as shown in Fig. 6. The composition of the white magnetite in Fig. 6(a) is: w(Al2O3) 12.08%, w(FeO) 87.92%; the composition at 1 is: w(SiO2) 51.34%, w(Al2O3) 14.67%, w(Na2O) 1.09%, w(CaO) 16.35%, w(FeO) 5.09%, w(P2O5) 11.47%; the dark black portion is composed of a single SiO2. However, from the results of water slag slag analysis, as shown in Figure 6(b), the composition at one location is: w(Na2O) 0.56%, w(MgO) 0.61%, and w(FeO) 98.83%. The results of this analysis show that under the slag phase corrosion of the main component of iron oxide in the furnace, alumina is more likely to form a eutectic phase with iron oxide, and the viscosity may be increased because the melting point of alumina is high, thereby reducing the slag. fluidity.
Figure 6. Microstructure of the residual beam of the walking beam of the heating furnace observed by EPMA
It can be seen from Table 2 that the load softening start temperature deformation of the column and the walking beam is 1319 °C when the temperature deformation starts 0.6%, and the deformation is only 1342 °C when the deformation amount reaches 2%. This temperature range is very narrow, and the deformation is very small. Large, this will create a soft surface, increased liquid phase, easy to bond the iron oxide under the billet flow, and easily react with the iron oxide skin to form a thick slag.
At present, there is no national standard for refractory materials for heating furnaces. The design and construction basis is based on product industry standards. For example, high-strength castables (JC/T498-96) can be used in heating furnaces. It only specifies alumina, silica, and calcium oxide. The content is divided into two grades; the performance specifies the compressive strength, flexural strength, post-fire line change rate, bulk density, and refractoriness after treatment at 110 ° C, 1100 ° C, and 1500 ° C, but these indicators also do not explain the actual lining Effect. Analysis of the composition, structure and performance of the column and the walking beam can provide a basis for future material selection.
Conclusion
1) For the characteristics that the refractory materials for the walking beam and the column of the heating furnace cannot meet the requirements of the process, it is recommended to increase the softening temperature to 1400 °C or more in the second heating section and the soaking section, and the deformation of the refractory used is 0.6%. The 2% softening temperature is increased to above 1500 °C to reduce the slag of the lining, and at the same time reduce the reactivity of the scale and the lining, reduce the alumina content in the slag, and control the adhesion of the slag.
2) In the heating furnace, the refractory material for the walking beam and the column is used, the slag layer of the iron oxide is more likely to form a eutectic phase with the alumina in the lining, and the impurities such as silicon oxide and calcium oxide tend to form a bond. phase. To solve the problem of sticking slag, it is necessary to comprehensively consider the composition of the slag and the composition of the lining to avoid the close adhesion of the slag.
Xu Guotao, Li Jiyu, Zhang Honglei, He Mingsheng
Research Institute of Resources and Environment, Wuhan Iron and Steel Group Corporation
ABS Ceiling Fan
The Ceiling Fan is beautiful in appearance, equipped with durable fan blades and lighting of different colors and styles, and has functions such as lighting, cooling, and decoration.There are much more Led Ceiling Fan styles in our website,such as DC Ceiling Fan ,Iron ceiling fan,Wooden Blades Ceiling Fan With Bulbs,Retractable Ceiling Fan Light,Simple Ceiling Fan Lamp,and best decoration Plywood Led Ceiling Fan.And there are more items are not showing on the website,please feel free to contact us directly for more information.
Led Ceiling Fan,Ceiling Fan,Ceiling Fan Abs Blade,Ceiling Fan With Remote Control,Decorative Ceiling Fan
JIANGMEN ESCLIGHTING TECHNOLOGY LIMITED , https://www.jmesclightingfan.com