Practice of accelerated rolling in ultra-thin tropical production
For ultra-thin specification products, the thinner the thickness, the greater the temperature drop during rolling. Increasing the speed of rolling is one of the effective methods to ensure reasonable final rolling temperature and control the excessive temperature drop in the rolling process. Speed up rolling can be achieved by adopting large rolling down on the first stand and fine-tuning the rolling down on the last few mills.
The characteristics of accelerated rolling are: 1) the thickness and tension of the plate are reduced at the same time when the speed is increased; 2) Increased rolling load of the first frame plays a major role; 3) The optimization of the distribution of pressure can achieve accelerated rolling.
Speed up rolling needs attention:
1) In order to ensure the final rolling temperature, the finishing mill should adopt the FTC function, that is, according to the rolling speed to adjust the cooling water between the racks to ensure the final rolling temperature.
2) The cooling capacity of the layer should be considered when accelerating. In order to ensure a reasonable coiling temperature, the cooling water of the layer after accelerating is larger than the normal state.
3) After speeding up, due to the high threading speed, it is not conducive to the operator's timely control of the bad shape of the plate, so low speed rolling should be adopted, and the speed should be increased after the coiler is fed with steel.
4) When cutting the head, the rolling piece should be reduced to the shear speed, and the rolling piece should be increased after cutting. At this time, the sudden load change of the roughing rolling motor has a greater impact on the equipment.
5) When the distribution rate of the first and second frames is large, it is easy to slip or overload, so semi-headless rolling technology should be used.
The accelerated rolling was realized on the R1, R2, F1, F2, F3, F4, F5, 7 racks of the hot rolled sheet mill of Tangsteel in China.
The results are:
1) Taking 85×1510×24000mm accelerated rolling of 5.7×1500mm sheet as an example, the F5 outlet speed is increased from 5.11m/s to 6.21m/s, and the single roll pure rolling time is saved by 21s.
2) The production of the class has been improved, ranking first in the similar production line.
3) Energy is saved. After the speed increase, the annual consumption of steel gas per ton in 2006 was about 10% less than that in 2005.
4) Benefit increase. After the accelerated rolling, 3.01 million t of coil was completed in 2006, exceeding the design by 20%, if it is difficult to complete these volumes before the speed is increased, the efficiency is significantly improved.
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