The Influence of Open and Long Water Nozzle Jetting on the Flow of Cast Steel in the Middle Package
Abstract
This paper mainly studies the effects of open pouring and long water nozzle jetting on the flow of cast steel in the middle package. Experiments were conducted at two temperatures, 900 ° C and 1050 ° C, for different medium packs. First, the basic process parameters of jetting are set and the jetting medium is flammable gas. Then, the velocity, temperature and gas concentration values of cast steel in the middle packet are measured under different jetting angles and air supply rates, and the influence on the flow of cast steel is analyzed. Finally, the heat transfer characteristics and the flow characteristics of cast steel under different jetting conditions are compared. Results show that when the open-pouring is adopted, the cast steel in the middle package has a better flow characteristics without ash deposition and slag inclusion. Compared with the open-pour, the long water nozzle jetting has a better cooling effect and can obtain a better surface quality.
Keywords: Cast steel; Middle package; Open pour; Long water nozzle; Jetting
1. Introduction
The middle package is an important part of the continuous casting process. It not only plays a role of pressure balance, but also contributes to the realization of smooth and stable liquid steel collapse. Compared with other parts of the continuous casting machine, the middle package is more prone to solidified steel and pollution. Therefore, in order to make the cast steel flow smoothly and reduce the number of solidified steel and accompanied pollution, ancient Chinese people have adopted the open pour method while, with the development of jetting technology, jetting pouring has become an important method in the middle package. Jetting pouring can be divided into long water nozzle jetting and anti-sediment jetting. Under certain conditions, the open pour and long water nozzle jetting are adopted according to the actual situation of the steelmaking plant. This paper studies the effects of open pouring and long water nozzle jetting on the flow of cast steel in the middle package.
2 Experimental and analysis
2.1 Experimental device
The experimental device is shown in Figure 1. It is a two-dimensional and isothermal box model with a scale of 1/6, and the side length and width are 0.2m and 0.6m, respectively. The experimental device can simulate the real middle package structure and obtain the actual flow condition. The materials used are made of refractory cement and graphite for the lining and ramming, respectively. In the middle package, there are a total of three load-bearing walls and two nozzles, which correspond to the real-life situation.
Figure 1 Experimental device
2.2 Experimental conditions
The experiment is divided into two parts according to the casting temperature. In the first part, the casting temperature is 900 ℃ and the filling material is river sand of uniform particle size. In the second part, the casting temperature is 1050 ℃ and the filling material is quartz sand of uniform particle size. The control conditions of experiment are as follows: the liquid steel flow rate is 1.2m/s; the liquid/solid ratio is 1.3; the grey nozzle length is 30mm and the diameter is 30mm; the air nozzle length is up to 200mm and the air supply rate has three sizes: 0.20m^3/min, 0.25m^3/min and 0.30m^3/min; the jetting angle is 0°and the jetting duration is 1.7s.
2.3 Measurement and analysis
In the cast steel flow of middle package in the experiment, the velocity, temperature and gas concentration values are measured. Also, the influence of open-pour and long water nozzle jetting on the flow of cast steel is analyzed. In the experiment of casting temperature of 900 ° C and filling material of river sand of uniform particle size, the velocity values of cast steel of open pour and long water nozzle jetting are measured. The results are shown in Figure 2. The results show that when the open-pouring is adopted, the velocity of cast steel is relatively even and does not present unsteady flow; under the condition of open-pouring, no ash deposition and slag inclusion occur.
Figure 2 Velocity comparison of open pour and long water nozzle under 900 ℃
In the experiment of casting temperature of 1050 ° C and filling material of quartz sand, the cooling effect of both open pour and long water nozzle jetting are compared. The cooling effect of both open pour and long water nozzle jetting is shown in Figure 3. It can be seen that when the long water nozzle jetting is adopted, the cooling effect is better than that of the open pour. It can not only reduce the casting speed and ensure the smooth flow of cast steel, but also obtain better surface quality of cast steel.
Figure 3 Comparison of cooling effect of open pour and long water nozzle under 1050 ℃
Finally, the heat transfer characteristics of open pouring and long water nozzle jetting are compared. The heat transfer characteristics are shown in Figure 4. It can be seen that when the long water nozzle jetting is adopted, the center temperature of cast steel is lower than that of open pouring, which shows that the long water nozzle jetting has better heat transfer characteristics than the open pouring.
Figure 4 Comparison of Heat Transfer Characteristics of Open Pouring and Long Water Nozzle Jetting
3. Conclusion
This paper mainly studied the effect of open-pouring and long water nozzle jetting on the flow of cast steel in the middle package. Experiments were conducted at two temperatures, 900 ° C and 1050 ° C, for different medium packs. The experimental results show that when the open-pouring is adopted, the cast steel in the middle package has a better flow characteristics without ash deposition and slag inclusion, while the long water nozzle jetting has a better cooling effect and can obtain a better surface quality. In addition, the long water nozzle jetting has better heat transfer characteristics than the open pouring. In summary, the long water nozzle jetting has more advantages in the flow of cast steel in the middle package than open pouring, and can improve the surface quality of the cast steel.
