1.What causes uneven thickness along the longitudinal direction? How can it be resolved?
Uneven properties of hot-rolled incoming materials: Inconsistent properties and hardness along the length of hot-rolled coils lead to fluctuations in rolling force during cold rolling, which is a major cause of excessive thickness at both ends.
Optimize hot rolling process: Control the shape of hot-rolled strip, optimize laminar flow cooling (e.g., using U-shaped cooling), ensure uniform cooling along the entire length of the strip, and improve the uniformity of incoming material properties.
• Strengthen incoming material inspection: Conduct random checks on the hardness and thickness of hot-rolled coils to control the process from the source.
2.What are the causes of lateral thickness differences (same-plate thickness differences)? How can they be resolved?
Inappropriate roll profile: The original roll profile crown of the work roll or intermediate roll does not match the incoming material cross-section, or the rolls wear unevenly, causing changes in the roll gap shape during rolling.
• Optimize roll profile curves: Design and adopt more reasonable roll profiles (such as improving the end roll shape of intermediate rolls) according to product specifications to better control strip edge thinning and lateral thickness difference.
• Manage roll wear: Rationally schedule roll change cycles, monitor roll wear, and perform timely grinding.
3.How to inspect the quality of incoming materials?
This is the most easily overlooked yet crucial aspect. The uniformity of the microstructure and cross-sectional shape of the hot-rolled coil directly determines the ceiling for cold-rolled thickness control. For difficult-to-roll varieties such as high-strength steel, special attention must be paid to the performance differences between the beginning and end of the incoming material.
4.How to make good use of automatic thickness control systems?
Feedforward AGC: Adjusts the roll gap in advance based on the incoming material thickness deviation detected by the inlet thickness gauge before the rolling force is disturbed; this is a "predictive" adjustment.
Feedback AGC: Adjusts the roll gap laggingly based on the actual thickness deviation detected by the outlet thickness gauge; this is a "corrective" adjustment.
Flow rate AGC: Utilizes laser velocimeters and thickness gauges at the inlet and outlet, based on the principle that the metal flow rate per second is equal. It can calculate and control the instantaneous thickness deviation more quickly and accurately, and is currently the mainstream advanced control method.
5.How to manage rolling mill rolls with precision?
Roll profile is fundamental: Ensure the ground roll profile curve meets process requirements.
Uniform cooling is essential: Ensure the roll cooling system functions properly, providing uniform cooling along the roll length to maintain a stable hot roll profile.
Roll changing strategy: Strictly adhere to the roll changing procedure based on rolling mileage and product precision requirements.