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YUAN HUI

YUAN HUI

LMM GROUP main products focus on the cold and hot plate & wide strip mill rolls and heavy section mill rolls and big casting & forging pieces.

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Hot rolled strip steel problems and solutions

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In actual production, in the specific steel processing stage, the defects that affect the quality of hot-rolled strip are explored and researched, and the technical problems and the ways to solve the problems are found, which will improve the overall production quality of the steel industry. Corresponding costs and improving the qualification rate have very obvious effects. Therefore, this article will specifically discuss the quality defects and technical improvement of hot-rolled strip in actual production.

The reason for the pressing of iron oxide scale and the corresponding solutions

  • Research on the specific reasons for the formation of iron oxide scale

In considering the specific production process, according to the reason for the formation of scale. It is divided into primary scale pressing and secondary scale pressing. The first is the specific situation of the primary scale formation by pressing in. The primary scale is formed during the heating process in the heating furnace. After the slab is rolled, there will be more spots, some of which are relatively large and streaks are arranged randomly on the strip. If the primary oxide scale produced cannot be cleaned up well before entering the roughing mill for further production, the hardness of the hot billet after cooling in the subsequent production will be much smaller than the hardness after cooling, and it will also be produced in the subsequent rolling process. Very serious quality defect problem. This is the specific situation and quality problem of the formation of iron oxide scale. The formation of secondary oxide scale is mainly affected by the environment and other aspects. The problems caused by the secondary iron oxide scale are mainly concentrated on the pattern of ripples, stains, and streamlined particles on the surface of the steel plate. In short, it will seriously affect the quality of the strip surface.

  • Measures and methods to solve the formation of iron oxide scale

Specific measures for the situation of primary oxide scale. First, when putting the slab into the furnace for heating, the heating temperature must be strictly controlled, and the heating time must also be monitored to prevent the temperature from being too high and the heating time being too long. In addition, the heating environment should be controlled as a slightly oxidized environment as much as possible. In fact, the method of segmented heating can also be incorporated into the heating process in the heating furnace, so that the primary scale can be removed in the descaling machine. Then there is the problem of rough rolling descaling. For the specific descaling process, the amount of dephosphorization water and dephosphorization pressure must be sufficient, and the angle of the dephosphorization nozzle is reasonable. For slabs that have passed through the descaler, according to the rough rolling starting temperature Reasonable speed control. Finally, in view of the problem of secondary oxide scale, for the formation of secondary oxide scale, when performing specific work, it is required to set a reasonable final rolling temperature and shorten the working time of finishing rolling as much as possible. This is to reduce air The contact time between moisture, etc. and the rolled piece, thereby controlling the formation of secondary scale.

Causes of excessive strip thickness and solutions

As for the problem of strip thickness, the main problem is that the thickness of the finished product is uneven, which is divided into horizontal and vertical directions. In the actual production process, whether it is the problem of uneven thickness in the transverse direction or the problem of uneven thickness in the longitudinal direction, the problem will appear. In the process of rolling the strip steel, rolls are used for rolling. The rolls are severely worn due to long-term rolling work, and they have to withstand high temperatures, which will affect the thermal crown and roll surface quality of the working rolls. Have a big impact. This affects the rolling quality of strip steel. The appearance of damage and unevenness on the surface of the roll directly leads to problems such as indentation and uneven thickness on the surface of the steel sheet. In response to this situation, the corresponding staff must regularly inspect the rolls, and timely understand the wear problems of the rolls used to prevent the occurrence of uneven thickness of the strip. In addition, it is the problem of the roll itself. If the processing accuracy is insufficient, the processing quality will be greatly compromised, and the roll shape and ellipticity will not meet the requirements, which will lead to changes in the roll gap itself, which will affect the thickness of the strip and the entire finished product. the quality of. In particular, the cyclical changes among them cause the cyclical changes of strip steel, causing serious quality problems such as excessive batch thickness deviation.

Therefore, the accuracy of the roll itself is also a core link that requires strict control. In addition, the rolling force of the stand is too large, and the entire rolling force of the stand is too large. The thickness of the strip is difficult to control due to the temperature change during the specific strip rolling process, and the required thickness cannot be obtained. In the specific production process, the thickness of the strip and the fluctuating width of the strip are carefully explored and analyzed. There are also some ways to help better solve the actual problems. It is possible to organize various data according to the specific production situation, and especially to grasp the reduction situation, reasonably allocate the reduction of each stand, control the rolling force of each stand, and ensure the thickness accuracy of the strip. Meet the needs of strip steel production, improve work efficiency, reduce production costs, improve the competitive advantage of steel companies, achieve better benefits and promote the development of the entire industry, and establish a sound and better steel manufacturing market.

The specific causes of sickle bend defects and their solutions

The specific situation of the sickle bend.

Among the practical problems of hot-rolled strip quality defects, the sickle bend is the most common phenomenon. And its quality problems often lead to difficulties in the subsequent welding work, difficulty in uncoiling and tape threading. In the process of producing the sickle bend, due to the environmental problems of the work site, there are many factors that will have a great impact on the working parameters of the specific rolling.

For the sickle bend, there are mainly the following reasons leading to its defects:

  • The influence of temperature

There is a temperature difference between the transmission side and the operation side of the slab; there is a difference in the temperature between the transmission side and the operation side of the roll; the wiper of the work roll may also have water leakage, resulting in temperature deviations on both sides. In addition, the premature boiling of the descaled water in the finishing rolling will cause the head to be too cold, and the rolling force fluctuations in the same pass will become larger, rolling is unstable, and sickle bends may occur

  • The effect of blank wedge

Due to the uneven thickness in the width direction of the billet, the reduction of the two sides of the strip is different, so that the bounce on both sides of the rolling mill is different, and the thickness of the exit on both sides of the strip is inconsistent. As the length of the strip increases, this phenomenon becomes more and more. obvious. The appearance of this sickle bend is not easy to adjust

The conclusion

To sum up, steel is the most indispensable raw material in current production and life, and the increasingly competitive steel industry also puts forward more requirements on production technology and quality. There is also a need for enterprises in related industries to further reduce production costs and improve product quality. In view of the quality defects of hot-rolled strip steel, further analysis and detailed solutions to specific problems, so as to produce more and better high-quality strip products that meet the needs of social production, promote more comprehensive development of the steel industry, and improve production technology Level and promote the national steel manufacturing level

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The world No. 1 in crude steel production steel plant, over 70% of the HSS for bar and wire are from us.

LMM high-speed steel rolls have higher steel passing per groove (times) due to their good wear resistance, which saves roll changing time, improves rolling mill operation rate, reduces roll consumption, and improve the overall efficiency of the factory.
Generally, the amount of steel passing in a single groove (times) is 3 to 5 times that of cast iron rolls.

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