In the last article we described the finite element simulation of the 4-roll plate rolling machine, today we will conduct the actual plate rolling test
In order to verify the accuracy of the simulation results, an experimental study was carried out using a 4-roll plate rolling machine.
The size of the rolling test metal plate is 60 mm × 7850 mm × 1200 mm, the material is Q345R, the yield strength is 345 MPa, the elastic modulus is 210 GPa, the relative strengthening coefficient is 14.9, and the pre-rolled inner diameter is 2440 mm.
The rolling test of the steel plate was carried out in accordance with the steps of feeding, sheet centering, end pre-bending, and continuous rolling. The rolling process and results are as follows:
According to the requirements of the coiling process, the pre-bending of the plate is completed, and after the roll is changed, the forming arc section must be able to overlap with the non-pre-bending roll, otherwise a straight line section will appear in the middle of the metal plate.
According to the simulation results, the radius of curvature of the arc segment was measured after the pre-bending roller was raised to 500 mm. When the pre-bending roll is raised to 660 mm, the inner diameter of the finished product is close to the target inner diameter, but after the pre-bending is completed and the roll is changed, the plate cannot contact the non-pre-bending roll, and slipping also occurs.
According to the existing plate rolling process and roll displacement calculation model of the four-roll plate rolling machine, the roll displacement of the non-pre-bending roll should be 656 mm when rolling the plate to round. In the test, when the first feed reaches 645 mm, the actual inner diameter of the arc obtained is too small, and then adjusted to 620 mm, the inner diameter of the arc obtained is too large, and after adjustment, when it reaches 640 mm, the inner diameter of the rolled arc The inner diameter is Φ2430 mm, which is close to the target inner diameter Φ2440 mm, which meets the test requirements and the rolling effect is better.
From the results of this test, it can be seen that the test results and simulation results are in good agreement, and the error in the rounding stage is only 2.3%, which shows that the simulation model established in the previous article is correct.
As for the reasons for the large difference between the test displacement and the simulated displacement in the pre-bending stage:
- One is that the formed plate may be overbent due to the excessive feed of the pre-bending roller;
- The second is that the pressure between the upper and lower rolls is not enough. When the pre-bending roll is lowered, the end steel plate is warped due to gravity, and the upper roll is more bent, resulting in the inability to contact the non-pre-bending roll.
During the pre-bending stage, the plate cannot be pre-bent directly to the target inner diameter, otherwise it will not only easily cause overbending, which will cause the plate to become a waste product, but also a straight line will appear in the middle of the plate. Therefore, the displacement of the pre-bending rolls should not be too large, but it must be ensured that after the pre-bending rolls are changed, the non-pre-bending rolls can touch the edge of the formed circular arc section. After the pre-bending is completed, the pre-bending rolls should be lowered by 30~ 50 mm, and then roll forward for a section to realize the transition between the pre-bending section and the rolling section.