Expanding technology of straight seam steel pipe:
1. Preliminary rounding stage: the fan-shaped blocks are opened until all the fan-shaped blocks touch the inner wall of the steel pipe. At this time, the radius of each point in the inner tube of the steel pipe within the step range is almost the same, and the steel pipe is initially rounded.
2. Nominal inner diameter stage: The fan-shaped block starts to reduce the moving speed from the front position until it reaches the required position, which is the required inner circumference position of the finished tube.
3. Springback compensation stage: The sector block starts to move at a lower speed in the second stage until it reaches the required position. This position is the inner circumference position of the steel pipe before the spring back required by the process design.
4. Stable pressure holding stage: the fan-shaped block remains stationary for some time in the inner circumference of the steel pipe before springing back. This is the pressure holding and stable stage required by the equipment and diameter expansion process.
5. Unloading and return stage: the sector block starts to retract rapidly from the inner circumference of the steel pipe before springing back until it reaches the initial diameter expansion position, which is the minimum shrinkage diameter of the sector block required by the diameter expansion process
Common detection methods for straight seam steel pipes:
1. In the test results of straight seam steel pipes, if a certain item does not meet the requirements of the product standard, the unqualified ones should be picked out, and double the number of samples should be randomly taken from the same batch of straight seam steel pipes to check the unqualified items. recheck. If the re-inspection result is unqualified, the batch of straight seam steel pipes shall not be delivered. For the following inspection items, if the initial inspection fails, re-inspection is not allowed.
2. For straight seam steel pipes that fail the re-inspection results, the supplier can submit them for acceptance one by one; or conduct heat treatment again, and submit a new batch for acceptance.
3. If there is no special regulation in the product standard, the chemical composition of the straight seam steel pipe shall be checked and accepted according to the melting composition.
4. The inspection and acceptance of straight seam steel pipes shall be carried out by the technical supervision department of the supplier.
5. The supplier guarantees that the delivery of straight seam steel pipes complies with the provisions of the corresponding product standards. The buyer has the right to inspect and accept the products according to the corresponding product standards.
6. Straight seam steel pipes should be submitted for acceptance in batches, and the batching rules should comply with the provisions of the corresponding product standards.
7. The inspection items, sampling quantity, sampling location, and test method of straight seam steel pipe shall be by the provisions of the corresponding product standards.
Post time: Dec-14-2022