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Analysis and research on wear laws of section steel rolling rolls

Description:This paper main writes how to find the cause of roll wear and how to improve it from the law of wear

Title:Analysis and research on wear laws of section steel rolling rolls

Keyword:Rolling roll, rolling roll wear, steel rolling rolls

 

The wear of the profile steel pass is directly related to the production efficiency of the rolling line and the quality of the product. At the same time, it has a great impact on the adjustment of the mill profile and the control of the negative difference. Therefore, by understanding and mastering the wear pattern of each pass in the rolling process, the material type can be adjusted and the rolling groove replaced in time, and corresponding measures can be taken to achieve the purpose of stable production, improving the rolling groove tonnage and product quality. The results show that: in the process of rolling angle steel, measures such as improving the material of the roll, modifying the finished pass, optimizing the slope of the side wall of the rolling groove before the finished product, improving the processing accuracy of the roll, formulating a reasonable rolling groove tonnage and reduction system, etc. Reducing the degree of wear and unevenness of the rolling groove has played a key role, so as to achieve the purpose of improving the rolling tonnage and the quality of the finished product.

 

Rolling roll is a direct tool for metal deformation during rolling. Therefore, grasping the law of rolling roll wear and taking corresponding measures can achieve the purpose of reducing roll consumption, increasing operation rate, improving product quality, and reducing labor intensity of employees. Because of the special-shaped pass used in the rolling of section steel, the force of the rolling groove is uneven, and the wear conditions are also different. The study of the wear law of the section steel rolling groove is very important for guiding production.

  • Study on the law of rolling roll wear

Since the profile operation area of a steel rolling plant of HBIS Xuangang was put into operation, it has successfully developed 8#~20# angle steel (national standard, European standard, etc.), some channel steel specifications, round steel φ50mm~φ110mm, and some mining U-shaped steel specifications. In this paper, when studying the wear of the rolls, the angle steel specifications are selected for follow-up investigation. The wear data collected through production over a period of time reflects some of the relationship between roll wear and rolling tonnage, and also reflects the rough-rolled pass, the butterfly hole before the finished product,The

finished hole wears out with the use of the rolling groove,and the amount of wear.

 

Wear of rough rolling pass:

Through the measurement of the wear of the off-line rolls, the wear of each rack of rough rolling is relatively uniform, and it is basically proportional to the rolling tonnage, as shown in Figure 1.

Wear condition of butterfly hole:

Angle steel finish-rolled pass adopts butterfly hole as shown in figure 2. Due to the different work roll diameters of the roll at each point in the pass, the pressure of the rolled piece at each point in the pass is different, and the amount of roll wear is quite different. Therefore, unevenness is the most obvious feature of roll wear in section steel rolling.

Figure 2 shows the roller matching diagram of the angle steel butterfly hole. The roll wear was analyzed and compared by the opportunity of the roll reloading, and the roll wear curve in Fig. 3 was formed.

The wear of the upper and lower rollers in Figure 3 shows that the wear of the angle steel butterfly pass shows great unevenness.

Due to the different rolling specifications and pass design dimensions, the wear condition of each pass is also different. But the general trend is that as the diameter of the work roll at each point of the pass decreases, the amount of wear increases. The maximum wear of the hole pattern occurs at the top corner. The upper roller leg end of the lower opening butterfly hole and the lower roller leg end of the upper opening have a large amount of wear due to the pressure brought by the side wall. The straight line and arc parts have relatively little wear due to the close hole design.

Finished pass wear:

In the angle steel rolling process, the deformation of the finished product is the most severe, so the wear of the finished groove is very uneven, which affects the rolling tonnage and product quality. Table 1 shows the wear of the finished roll of 125 gauge steel.

It can be seen from the above data that the wear of the upper roller in the finished angle steel hole is relatively small, and the lower roller presents a law of wear that is the largest at the leg end from the vertex angle 1/2 to 2/3 of the leg width, and then gradually decreases. The wear of the finished hole is mainly concentrated in the severely deformed arc area. Since the top angle of the previous rolling piece is close to 90°, the wear of the top corner is not large.

  • Wear analysis and countermeasures

The roll hardness is not uniform.

The heat-treated roll has a certain depth of working layer, and the relative hardness is not much different. However, the pass shape of the section steel is a special-shaped hole, and the depth of the rolling groove is large. In addition, the reason why the upper and lower pressures need to be configured for the rolling of the section steel. Layer, and the other part is in the working layer, causing the hardness drop of the entire rolling groove to increase, and the unevenness of wear is more obvious.

Laser surface strengthening technology has developed rapidly in recent years. Its most important feature is the extremely fast heating and cooling speed, which is conducive to the remarkable refinement of the grains of the quenched layer, strengthens the metal surface layer, and makes the metal surface have high wear resistance. Through the use of this technology, the hardness of each point of the pass is close to the same, which greatly reduces the uneven wear caused by the uneven hardness of the roll, and the tonnage of the groove is increased to more than twice the original.

The hole design is unreasonable.

Angle steel rolling mostly uses butterfly holes. If the parameters are selected unreasonably, it will accelerate the wear of the rolling groove, and increase the difficulty of adjustment, resulting in unstable production. Due to the special-shaped section, the rolled piece does not contact the roll at the same time during the rolling process, which causes not all parts of the rolled piece to slide forward. With the increase of the roll diameter, the forward slip value decreases, and when the speed of the roll exceeds the speed of the rolled piece, the backward slip occurs. Such different sliding values ​​lead to uneven friction and cause uneven wear of the hole pattern. If the pass design parameters are unreasonably selected, it will increase the clamping force of the sidewall of the rolled piece, accelerate the wear and make it difficult to go out of the groove, cause the rolled piece to warp at the exit, and cause a production accident. In the butterfly hole design, under normal circumstances, the side wall slope is gradually reduced from 20% to 10%, the arc of each frame side wall is appropriately increased, and the design concept of large slope and large arc is adopted. By optimizing these parameters, the degrooving of the rolled piece is easier, and the arc fullness of the leg end is better, which not only reduces the wear of the groove, but also improves the product quality and reduces the process accidents. There is a large difference between the maximum and minimum diameters of the bottom rolling groove of the finished hole, and the rolling piece slides relative to the metal at the end of the leg at the inner arc of the pass, which causes the wear rate of the rolling groove to increase, and the wear at the arc is the fastest, and As the rolling tonnage increases, wear intensifies, and metal accumulates at the inner corners of the arc, which is not conducive to negative differential rolling. According to this feature, we can make appropriate modifications to the leg of the finished angle steel hole as shown in Figure 4. Among them, Hb is the standard leg thickness, Hy is the waist thickness after the change, and Hz is the increase in the waist thickness after the change, so Hy=Hb+Hz is obtained. According to the measured data in Table 1, Hz=0.2~0.5mm Range. Through the modification of the pass, the problem of the reduction of tonnage caused by the wear of the rolling groove, the uneven thickness of the rolled leg, and the difficulty of controlling the negative difference are solved.

Other methods:

Other methods can also effectively compensate for various problems caused by groove wear. The first is to formulate a reasonable reduction adjustment and roll change and groove change system. According to the actual production, adjust and replace the material type of each rack in time to avoid the abrasion of the rolling groove of the later rack due to the irregular material type of this rack. The second is the use of CNC lathes for roll processing. Shaped steel rolling adopts special-shaped pass, which is difficult to process. It is processed by ordinary turning. The accuracy of the lathe itself is low. The processing accuracy of manual grinding of the turning tool is not high. Therefore, the use of CNC machining can reduce the uneven wear of the rolling groove.

Conclusion

The wear of the rolling groove of the profile steel has its particularity. The sidewall and arc of the finishing pass have more wear than other parts, which fully reflects the unevenness of the groove wear.

Through the analysis of the actual groove wear data, the selection of roll material, pass design parameters, the relative sliding of the rolling piece and the roll, the processing accuracy of the roll, the formulation of the roll change and groove change system and other factors all cause uneven roll wear. reason.

Through the analysis of the causes and taking corresponding countermeasures, such as laser surface strengthening technology, optimization of pass parameters, etc., it can effectively reduce the speed and unevenness of roll wear, stabilize production, and improve product quality.

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