With the development of science and technology and the improvement of living standards, residents have increasingly studied cars as one of the means of transportation, and their performance requirements have also increased. At this stage, China advocates energy conservation and emission reduction, so corresponding research and development have also been carried out in the automotive field. The new idea for the design of new vehicles is to make appropriate adjustments to the weight of vehicle panels and strengthen the design of vehicle structures. According to the material selection data of major automotive companies, the most popular automotive plate materials currently are electrogalvanized steel plate, alloyed hot-dip galvanized steel plate, and non alloyed hot-dip galvanized steel plate.
Definition of surface roughness
Surface roughness refers to a geometric shape in a microscopic state where there are very small gaps on the surface of the processed object, but there are some slight peak valley irregularities. The smoother the surface, the smaller the roughness. The reasons for producing surface roughness are improper processing methods or friction between the part and the cutting tool. Due to different reasons for producing roughness, the resulting micro geometry and density vary.
Method for measuring the surface roughness of automobile plates and rollers
2.1 Traditional measurement methods
There are two methods for measuring the surface roughness of automotive panels, traditional and online. The traditional measurement method is to randomly select an appropriate amount of templates from each production node based on the actual production line of the factory, and measure the roughness of these templates. The commonly used measurement method is offline measurement. The method is to measure the roughness of the roller that needs to be rolled before it is rolled on the machine to become the original roughness. After the roller is rolled on the machine for one cycle, its roughness is measured again. Based on the change in the surface roughness of the automobile plate, the change in the roughness of the leveling roller after rolling is inferred and judged.
Although there are two methods for measuring surface roughness: contact and non contact, traditional measurement methods tend to use contact measurement more often. The measurement method where the measuring part of the device for detecting the surface roughness of the roller can directly contact the surface of the roller to be measured is contact measurement, which can more intuitively reflect the information of the surface of the object to be measured.
2.2 Online measurement method
Due to the fact that surface roughness is a quality indicator of automotive plates and rollers, with the continuous improvement of technical means, online measurement and control technology is currently required as a key research direction for automotive enterprises when conducting product research and development work.
The non-contact measurement method mentioned above is commonly used in online measurement of roller surface roughness. It is a measurement method that does not affect the shape and smoothness of the roller surface, and indirectly reflects the roller surface roughness through new technological means. The most important feature of this measurement method is that the detection part of the measurement device does not have any direct contact with the surface of the roller to be measured, which not only protects the detection device, To avoid damage during use, it can also effectively prevent the occurrence of errors caused by direct contact measurement methods due to contact.
Variation law of surface roughness of roller 3
Based on the changes in the surface roughness of automobile panels and the conversion rate of steel, the changes in the surface roughness of rollers and the change cycle are reasonably estimated.
Changing the surface roughness of the roller can also be said to wear the roller surface. According to previous research on the wear of the surface roughness of the work roll of a cold strip mill, it has been found that under stable and constant pressure, there is friction between the friction layer and the surface of the work roll, which will lead to particle shedding in some structures on the surface of the work roll, which is the process of roughening the surface of the work roll. However, different pressure values have different wear levels on the surface of the work roller. In the actual wear process, there are three wear stages, namely, the primary stage, the intermediate stage, and the advanced stage. The primary stage is the initial stage of wear, while the intermediate stage is a stable wear period for the work roller. The advanced stage will cause severe wear on the work roller.
Control Technology for Surface Roughness of Automobile Plate and Roll
Due to the importance of surface roughness for automotive panels, it is necessary to have high requirements for the quality of surface roughness of automotive panels based on the high requirements of users. According to actual production experience, the factors that can effectively control the surface roughness of automotive panels and rollers include reduction rate, rolling force, service cycle, etc. Therefore, in order to produce finished automotive panels that meet customer requirements and production needs, the surface roughness of automotive panels can be controlled in several aspects.
4.1 Adjusting the reduction rate
In the actual production process, the original roughness and service life of the last stand work roll are preset parameters that cannot be arbitrarily changed during production, but the reduction rate can be adjusted online.
4.2 Shortening the service cycle of roller
Generally speaking, designers need to design a rolling plan in advance and roll the roughness of the surface of automotive panels. After a pair of work rollers are put on the machine, technicians need to calculate the offline time based on the rolling plan designed by the previous designers and the requirements for the surface roughness of automotive panels, combined with the roll roughness attenuation model.
4.3 Selection of appropriate rolling force
The purpose of rolling steel is to obtain a surface roughness that meets the needs of users. If in actual operation, the previously designed rolling plan cannot meet the requirements, the method of optimizing the rolling force can be used to make appropriate adjustments. If the rolling force is appropriately increased at the end frame of the flatness section, it can effectively change the surface roughness of automotive panels. In other words, if the rolling force is reduced, the surface roughness will be reduced.
4.4 Reasonable adjustment of rolling sequence
During initial rolling, some automobile plates with low roughness transfer rate can be selected for rolling, while those with high roughness transfer rate can be arranged for rolling at the later stage of rolling. This can effectively ensure that the surface roughness of the strip steel rolled by the work roller during the service cycle meets the specifications and user requirements. Combining the transfer rate of rolled materials with the requirements for surface roughness, scientifically and reasonably arrange the rolling sequence of rolled steel to maximize the requirements for surface roughness of automotive panels.
5 Conclusion
In summary, based on the above statement on the surface roughness of automobile plates and rollers, it can be concluded that the surface roughness of automobile plates and rollers can be appropriately predicted and changed according to specific requirements. Appropriate adjustments are made to the reduction ratio, roll service cycle, rolling force, and rolling sequence according to the specific requirements of users. Moreover, due to the different research and experimental periods set by different researchers, the variation rules of the surface roughness of automobile plates and rollers obtained are also different. In addition to the different research periods, they are also closely related to the complexity of actual working conditions in the production process. Therefore, it is necessary to establish prediction models to provide important information for the formulation of roughness and flatness control measures.
