Problems and solutions of hot rolled strip steel

In actual production, in the specific steel processing stage, the defects that affect the quality of hot-rolled strip steel are explored and researched, and the technical problems and the ways to solve the problems are found. The technology improves and reduces 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 steel 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 reasons for the formation of scale. It is divided into primary scale pressing and secondary scale pressing. The first is the specific situation of the formation of primary iron oxide scale, which is formed during the heating process in the heating furnace.
After the slab is rolled, there will be more spots, some of which are larger 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 the subsequent production cooling will be much less 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.

Solutions and methods for 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 avoid situations such as too high temperature and too long heating time. In addition, the heating environment should be controlled as a micro-oxidation 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. Reasonable speed control.
Finally, in response to 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 the working time of finishing rolling should be shortened 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

For the problem of strip thickness, the main problem is that the thickness of the finished product is uneven, which can be 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 strip steel, rolls will be used for rolling. The rolls are severely worn due to long-term rolling work, plus they have to withstand high temperatures, etc., which will affect the thermal crown and roll surface quality of the working rolls. Have a big impact. This in turn affects the rolling quality of strip steel.
The appearance of damage and unevenness on the surface of the roll directly leads to the indentation and uneven thickness of the steel plate surface. In view of this situation, the corresponding staff must regularly check the rolls, and timely understand the wear problems of the rolls used, and 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 quality of the processing will be greatly reduced, and the roll shape and ellipticity will not meet the needs, which will cause the roll gap of the roll itself to change, which will affect the thickness of the strip and the entire finished product. the quality of. In particular, the cyclical changes among them lead to the cyclical changes of strip steel and cause 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. It is especially important 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 enterprises, 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 curve

Among the practical problems of hot-rolled strip quality defects, sickle bend is the most common phenomenon. And its quality problems often lead to difficulties in the subsequent welding work, difficulty in uncoiling and threading. Due to the environmental problems of the work site, the production process of the sickle bend has many factors that will greatly affect the specific rolling working parameters.

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; the temperature difference between the transmission side and the operation side of the roll; the wiper plate of the work roll may also have water leakage, which causes the temperature deviation on both sides. In addition, the premature boiling of the descaled water in the finishing rolling will cause the head to be too cold, the rolling force fluctuation of the same pass will become larger, the rolling is unstable, and the sickle bend may also occur.

The influence of blank wedge

Due to the uneven thickness in the width direction of the blank, 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.

Conclusion

In summary, 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 steel 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.

Author: Metallurgical Management Ma Yintao

Source: China Strip Steel Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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References:

  • [1] Wang Longtao. Cause analysis and treatment of scratch defects in hot-rolled strip steel[J]. Metallurgical Dynamics\ Force, 2018,000(004):65-67,70.
  • [2] Zhang Hongbin, Chen Jiantai, Wang Weidong, et al. Analysis of the causes of hot-rolled strip surface printing and solutions [C]//Proceedings of the 11th China Iron and Steel Annual Conference-S03. Rolling and Heat Treatment. 2017.
  • [3] Wang Zhangling, Tian Guichang, Liu Hongming, et al. Analysis of the causes of folding defects of hot-rolled thin gauge steel strips and discussion of measures[J]. China Metallurgy, 2018, 28(002): 48-51. [4] Du Hongzhi, Wang Yafen, Wang Yadong .Analysis of the causes of oxide scale on the surface of hot rolled strip steel and its solutions[J].China Metal Bulletin,2016(9):109-110.
  • [5] Zhang Junjie. Common quality defects and control measures of hot-rolled strip steel[J]. Engineering Technology (Abstract Edition)·Architecture, 2016(8): 00241-00241.

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problems and solutions of hot rolled strip steel - Problems and solutions of hot rolled strip steel
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Problems and solutions of hot rolled strip steel
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This article will specifically discuss the quality defects and technical improvement of hot-rolled strip steel in actual production.
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