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2022

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Formation Defects of Rolled Parts and Preventive Measures


  Formation Defects of Rolled Parts and Preventive Measures

  Roll forming process is a very complex process, if the design is not reasonable, there will be defects such as side waves, longitudinal bending, cracks and deformation, these problems are often found in the process of production debugging. Rolls with asymmetric cross-sections will inevitably have deformation defects such as longitudinal bending, transverse bending and deformation. Defects such as side waves and cracks are also common.

Rolled parts

  Transverse side waves (side waves) are mainly caused by longitudinal extensions beyond the elastic limit of the material. The thinner the steel plate, the easier it is to produce edge waves during rolling. In order to reduce the weight of the part, the thickness of the steel plate of the rolled part will be significantly reduced, and the difficulty of the rolling process will increase a lot; another key issue is that the edge is an important installation datum, and it is a position that has strict requirements on the difference between shape and position; therefore, Solving the problem of edge wave of ultra-high strength steel roll is one of its key technologies.

 

  Longitudinal bending occurs in the XY plane (i.e., the vertical plane of the roll), which is caused by unbalanced longitudinal membrane strains of the side legs and web sections. The longitudinal membrane strain of the upper leg is a tensile strain, and the longitudinal membrane strain of the web is a compressive strain. The compression of the web is caused by the elongation of the upper leg during bending. This is determined by the characteristics of the rolling process. Proper use of the downhill method can alleviate longitudinal curvature, but cannot completely eradicate it.

 

  The outlet adopts a straightening machine to eliminate longitudinal bending. There is a straightening device at the exit of the roll forming machine, which exerts downward pressure on the products rolled out from the end. Longitudinal bending is eliminated by applying a moment on the product section.

 

  Lateral bending occurs in the XZ plane (horizontal plane during rolling). The lateral bending of rolled parts depends on its asymmetry, and the greater the asymmetry, the more serious the lateral bending deformation of the material. To eliminate side bending, the straightener can be used to produce side bending in the opposite direction to the material type, so that the length of the shorter inner arc is extended, and the length of the arcs on both sides is equal, so as to achieve the purpose of eliminating side bending.

 

  Another way to eliminate side bending is to adjust the roller pad in the last pass to realize the axial movement of the roller. Using this method, you need to pay attention to whether it will affect the width of the section.

 

  The way to eliminate deformation is to place the straightening device at the exit of the roll forming machine, and apply a reverse rotational force to the product rolled out from the end. Apply a counterclockwise torque on the product section to remove distortion.

 

  For asymmetric cross-section materials with edge bending, torsion, and bending defects, if you want to straighten the product, you usually remove the edge bending first, and then remove the deformation and bending. This adjustment method seems simple, but it is not easy. This is because, after removing the side bending deformation, when the next adjustment is made to remove the deformation, the eliminated side bending will reappear, and the state of "pressing the gourd and floating the gourd" will continue. In short, there is no other way but to eliminate deformation down-to-earth.