After the steel sheet is opened, it must be rolled to form a welded longitudinal joint. Therefore, the quality of the rounding step is directly related to the quality of the welded pair. Since the steel sheet is directly cooled into a cylindrical structure in a two-dimensional plane, it faces the metal fatigue characteristics caused by various tensile deformations of the metal, and it is critical to adopt suitable coil parameters and processes. Today, I will introduce the precautions for the roll of the container.
Before the coiling machine is rolled
Pre-bend the sheet before the coiler performs the coiling. Especially when using a three-roller symmetrical bending machine, the portion of the sheet that cannot be directly bent at both ends is approximately equal to half the center distance of the lower roll, which can be pre-bent using a hydraulic press.
When the coiler is feeding
When feeding the coiler, the sheet should always be kept at the axis of the roller. The upper roller is pressed downward to press the steel plate, and can be bent multiple times according to experience to avoid less damage to the machine. After each pressing of the steel plate, the upper roller must stop pressing down, start the main motor, and use the two lower rollers to rotate left and right to shape the steel plate. The upper roller is pressed down again, and the amount of pressing is determined according to the thickness of the steel plate and the diameter of the cylinder. It must not be pressed down once, which is prone to slippage.
The barrel forms a butt weld in the coil
When the barrel is formed into a butt weld at the coil, it is necessary to use intermediate reinforcement point welding to spread the contraction force of the longitudinal joint from the middle to both sides. The length of the barrel on both sides cannot be warped in the head and the middle is distorted.
Before the coiler removes the board
Before removing the plate from the coiler, first turn the left handwheel to press the right end of the upper roller with a balancing device to maintain balance. The tilt frame is then tilted approximately 90 degrees, at which point the rolled sheet can be removed.
Stainless steel coiling and calibration
The rolling and rounding of stainless steel shall be carried out on a special coiling machine; if the thickness of the coil exceeds the capacity of the coiling machine, the application shall be rolled on a large coiling machine, but the rotating roller shall be cleaned before rolling.
Under normal circumstances, it can be rolled directly without pre-bending. According to the thickness, the straight section is controlled to be about 150mm, and the welding is completed to the required arc after welding.
Pre-bending with a template
On the lower roll of the three-roller, place a pre-bent formwork (the thickness of the formwork is more than twice the thickness of the bent steel plate, the length is slightly wider than the width of the bent steel plate) and place the steel plate to be bent in the formwork. Above, roll together on the coiling machine, the pre-bending length of each end is about 200~300mm.
According to the material of the steel plate and the amount of welding deformation, the amount of deformation is reasonably controlled according to the steel plate material and the amount of welding deformation; if the barrel joint is welded with internal welding, the external welding head after welding, the curvature requirement is slightly larger than the curvature of the cylinder section, and the external single-sided welding is used for double-sided forming. The curvature of the welding process can be the same as the barrel section.
The center line of the steel plate is ejected, and the distance between the upper and lower rolls of the bending machine is adjusted.
Use a crane to place the board between the upper and lower rolls and align the center line of the steel plate with the center line of the lower roll
Pressing the upper roller down, starting the roller bed, starting to wind the plate; when the steel plate is rolled to the end, it should be checked whether the reference line at the end is parallel with the center line of the shaft roller, and if there is deviation, it is corrected;
Each time the steel plate is rolled, the upper roll can be gradually reduced by 5~10mm according to the thickness of the steel plate. The thicker the steel plate, the lower the degree of decline, and vice versa.
During the rolling process, the test sample is often used to check the curvature to avoid excessive rolling.