Defects and Solutions in Section Steel Straightening
The most common defects encountered during the straightening of section steel include overall bending, twisting, waviness, and surface marks. In actual production, the following measures are primarily adopted to resolve these issues:
1. Overall Bending
Bending is categorized into vertical bending (up and down) and lateral bending (left and right). According to specifications, the bending degree of section steel must be ≤3mm per meter, and the total bending degree must be ≤0.3% of the total length. Exceeding this range renders the material unqualified. Through long-term production practice, it has been found that the primary causes of vertical bending are: inappropriate pressure distribution among the upper and lower roller sets, and insufficient pressure on the first and second upper rollers. When the pressure fails to exceed the yield strength of the steel, the material retains its original curvature after straightening. The corresponding measures are to adjust the pressure distribution of the upper five rollers, increase the pressure on the first and second upper rollers, and thereby enhance the straightening force. The main cause of lateral bending is the misalignment of the straightening grooves. The solution is to adjust the upper and lower roller grooves to ensure perfect alignment.
2. Twisting
Twisting in the straightened steel is mainly caused by insufficient pressure distribution in the upper roller set and the misalignment of the straightening grooves. The adopted measures include appropriately increasing the upper roller pressure and frequently checking the alignment of the upper and lower roller grooves to prevent misalignment.
3. Waviness
Waviness is divided into web waviness and flange waviness. The primary causes of web waviness include: a significant difference in the working diameters of adjacent straightening rollers; inaccurate machining of the straightening grooves, leading to out-of-round rollers or excessive assembly clearance, which causes the rollers to wobble during rotation; and unreasonable pressure distribution in the upper roller set. Common measures include inspecting the condition of the straightening rollers, verifying the diameter deviations, appropriately adjusting the roller positions, or directly replacing non-compliant rollers, while simultaneously readjusting the upper roller pressure. The main causes of flange waviness are the misalignment of the straightening roller grooves and excessive axial displacement. The general measures are to realign the straightening rollers and check whether the equipment installation complies with process specifications to eliminate axial displacement.
4. Surface Marks (Straightening Damage)
Surface marks refer to the unqualified surface quality of the finished steel caused by the straightening process. The main causes include: excessive wear of the straightening grooves without timely replacement, deteriorating the surface quality; foreign objects (such as steel slag or scale) adhering to the contact surfaces of the rollers, which get pressed into the steel during straightening, causing scabbing defects; and groove misalignment, which leaves obvious straightening marks on the steel surface. To prevent these defects, measures such as promptly replacing straightening rollers, frequently inspecting the roller surfaces for foreign objects, and regularly realigning the grooves must be implemented.
