Large-diameter steel pipes are steel pipes with an outer diameter of 1000MM or more. Large-diameter steel pipes are mainly completed by tension reduction and continuous rolling of hollow base metals without mandrels. On the premise of determining the welded pipe, the whole welded steel pipe is heated to a high temperature above 950°C, and then rolled into seamless steel pipes of various specifications through a tension reducing machine.
Inspection and acceptance of large-diameter steel pipes?
1. The inspection items, sampling quantity, sampling location and test method of large-diameter steel pipes shall be in accordance with the provisions of the corresponding product standards
2. The quality inspection and acceptance of large-diameter steel pipes should be carried out by the technical quality supervision department of the supplier.
3. Large-diameter steel pipes should be submitted for acceptance in batches, and the batching rules should comply with the provisions of the corresponding product standards.
4. Test results of large-diameter steel pipes. When 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 large-diameter steel pipes for re-inspection of unqualified items. If the re-inspection results (including any index required by the project test) are unqualified, the batch of large-diameter steel pipes cannot be delivered.
5. For the large-diameter steel pipes whose re-inspection results are unqualified (including those whose microstructure is unqualified in the initial inspection and re-inspection is not allowed), the supplier can submit them for acceptance one by one. Or re-heat treatment (the number of re-heat treatment can not exceed twice), and submit a new batch for acceptance.
6. The supplier needs to confirm that the delivery of large-diameter steel pipes meets the requirements of the corresponding product standards. The buyer has the right to inspect and accept the products according to the corresponding product standards.
7. If there is no special provision in the product standard, the chemical composition of the large-diameter steel pipe shall be checked and accepted according to the melting composition.
Before the non-destructive testing of large-diameter steel pipes, the appearance of the welds should meet the requirements. The general requirements for the appearance of large-diameter steel pipe welds and the surface quality of welded joints are as follows:
1. The appearance of welding should be well formed, and the width should be 2mm over the edge of the groove on each side.
2. The height of the fillet weld leg should comply with the design rules, and the shape should be steeply transitioned.
3. Cracks, incomplete fusion, pores, slag inclusions, and splashes are not allowed on the surface of welded joints.
4. The surface of the weld seam of pipes with a planning temperature lower than -29 degrees, stainless steel and alloy steel pipes with a large tendency to harden should not have undercuts.
5. The weld seam undercut of other material pipelines should be greater than 0.5mm, the length of the continuous undercut should not be greater than 100mm, and the total length of the weld seam undercut at both ends should not exceed 10% of the total length of the weld seam.
The weld surface must not be lower than the pipe surface. Weld seam reinforcement, and not greater than 3mm, (for the maximum width of the groove after welding joint assembly). The misalignment of welded joints should not be greater than 10% of the wall thickness, and not greater than 2mm. Surface non-destructive testing Principles for surface non-destructive testing of large-diameter steel pipes: For ferromagnetic steel pipes, magnetic particle testing should be used; for non-ferromagnetic steel pipes, penetrant testing should be used.
Inspection and acceptance of large-diameter steel pipes?
1. The inspection items, sampling quantity, sampling location and test method of large-diameter steel pipes shall be in accordance with the provisions of the corresponding product standards
2. The quality inspection and acceptance of large-diameter steel pipes should be carried out by the technical quality supervision department of the supplier.
3. Large-diameter steel pipes should be submitted for acceptance in batches, and the batching rules should comply with the provisions of the corresponding product standards.
4. Test results of large-diameter steel pipes. When 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 large-diameter steel pipes for re-inspection of unqualified items. If the re-inspection results (including any index required by the project test) are unqualified, the batch of large-diameter steel pipes cannot be delivered.
5. For the large-diameter steel pipes whose re-inspection results are unqualified (including those whose microstructure is unqualified in the initial inspection and re-inspection is not allowed), the supplier can submit them for acceptance one by one. Or re-heat treatment (the number of re-heat treatment can not exceed twice), and submit a new batch for acceptance.
6. The supplier needs to confirm that the delivery of large-diameter steel pipes meets the requirements of the corresponding product standards. The buyer has the right to inspect and accept the products according to the corresponding product standards.
7. If there is no special provision in the product standard, the chemical composition of the large-diameter steel pipe shall be checked and accepted according to the melting composition.
Before the non-destructive testing of large-diameter steel pipes, the appearance of the welds should meet the requirements. The general requirements for the appearance of large-diameter steel pipe welds and the surface quality of welded joints are as follows:
1. The appearance of welding should be well formed, and the width should be 2mm over the edge of the groove on each side.
2. The height of the fillet weld leg should comply with the design rules, and the shape should be steeply transitioned.
3. Cracks, incomplete fusion, pores, slag inclusions, and splashes are not allowed on the surface of welded joints.
4. The surface of the weld seam of pipes with a planning temperature lower than -29 degrees, stainless steel and alloy steel pipes with a large tendency to harden should not have undercuts.
5. The weld seam undercut of other material pipelines should be greater than 0.5mm, the length of the continuous undercut should not be greater than 100mm, and the total length of the weld seam undercut at both ends should not exceed 10% of the total length of the weld seam.
The weld surface must not be lower than the pipe surface. Weld seam reinforcement, and not greater than 3mm, (for the maximum width of the groove after welding joint assembly). The misalignment of welded joints should not be greater than 10% of the wall thickness, and not greater than 2mm. Surface non-destructive testing Principles for surface non-destructive testing of large-diameter steel pipes: For ferromagnetic steel pipes, magnetic particle testing should be used; for non-ferromagnetic steel pipes, penetrant testing should be used.
