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 stabilizing 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.
The roll is a direct tool for metal deformation during the rolling process. Therefore, grasping the law of roll wear and taking corresponding measures can achieve the purpose of reducing roll consumption, increasing operation rate, improving product quality, and reducing employee labor intensity. 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 of great significance for guiding production.
Research on the Law of Roll Wear
Since the profile operation area of the No. 1 Steel Rolling Plant of HBIS was put into production, it has successfully developed 8 # ～ 20 # angle steel (national standard, European standard, etc.), some channel steel specifications, round steel φ 50 mm～φ110 mm and some mines. U-shaped steel specifications are used. In this paper, when studying the wear of 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 rolling pass, the butterfly hole before the finished product, and the finished hole wear with the use of the rolling groove. The location and 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:
The angle steel finish-rolled pass adopts butterfly hole as shown in Figure 2. Due to the different work roll diameters of the rolls 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 varies greatly. Therefore, unevenness is the most obvious feature of roll wear in section steel rolling.
Figure 2 shows the roll 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 larger amount of wear due to the pressure brought by the side wall, other 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.
From the above data, it can be seen that the wear of the upper roller in the finished angle steel hole is relatively small, and the lower roller exhibits a law of wear that is the largest at the leg end from the vertex angle of 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 difference is not large. However, the pass of the section steel is a special-shaped hole, and the depth of the rolling groove is relatively large. In addition, the reason for the need to configure the upper and lower pressures 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 crystal grains of the quenched layer, strengthens the metal surface layer, and makes the metal surface have high wear resistance. By adopting this technology, the hardness of each point of the pass is nearly 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.
Unreasonable hole design
Angle steel rolling mostly uses butterfly holes. If the parameters are selected unreasonably, it will accelerate the wear of the rolling groove, increase the difficulty of adjustment, and cause unstable production. Due to the special-shaped section, during the rolling process, the rolled piece does not contact the roll at the same time, resulting in not all parts of the rolled piece sliding 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 rolling piece, the backward slip occurs. Such different sliding values result in poor friction, resulting in uneven wear of the hole pattern. If the pass design parameters are unreasonably selected, the clamping force of the sidewall of the rolled piece will increase, and the wear will be accelerated, while the difficulty of degrooving will occur, which will 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 big difference between the maximum and minimum diameters of the bottom rolling groove of the finished hole. 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, the wear intensifies, and the 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 modified waist thickness, and Hz is the increase of the modified waist thickness, so you get
Hy= Hb+ Hz, according to the measured data in Table 1, the range of Hz= 0.2 to 0.5 mm can be obtained. 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 means:
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 wear of the rolling groove of the rear 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. General turning processing is used. The lathe itself has low accuracy. Manual grinding of the turning tool causes the processing accuracy to be low. Therefore, the use of CNC machining can reduce the uneven wear of the rolling groove.
In conclusion
The rolling groove wear of section steel has its particularity. The sidewalls and arcs 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, factors such as 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, etc., all cause uneven roll wear. the reason.
By analyzing 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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