Acceptance of straight seam steel pipe:
1. The inspection and acceptance of straight seam steel pipes shall be carried out by the technical supervision department of the supplier.
2. 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.
3. 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.
4. 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.
5. In the test results of straight seam 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 straight seam steel pipes, and the unqualified items should be checked. recheck. If the re-inspection result (including any index required by the project test) 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: 1) There are white spots in low-magnification tissues. 2) Microstructure.
6. For the straight seam steel pipes whose re-inspection results are unqualified (including the unqualified microstructure of the initial inspection results and items that are not allowed to be re-inspected), the supplier can submit them for acceptance one by one; or re-heat treatment (the number of re-heat treatments shall not exceed two times) ), to submit a new batch for acceptance.
7. 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.
Treatment measures for common problems in pre-welding of straight seam steel pipes
1. Wrong side. This is a common problem in pre-welding, and the wrong side is out of tolerance, which directly leads to the degradation or scrapping of the steel pipe. Therefore, it is required to strictly control the misalignment amount during pre-welding. When the whole or more than half of the steel tube blanks have misaligned sides, it is generally because 1) the opening seam is not adjusted in place; 2) the joint pressure roller is not adjusted in place (the circumferential angle of the pressure roller is wrong, or the center of the tube blank The line is the axis, the left and right pressure rollers are asymmetrical, or the radial elongation of the relative pressure rollers is inconsistent), there is no rounding; 3) The pre-bending edge is not pre-bent in place, and the edge of the plate is caused by the phenomenon of straight edge. When the head or tail of the tube blank has a wrong edge and is out of tolerance, it is generally due to: 1) The position of the inlet and outlet rollers being wrong; 2) The center of the ring frame being wrong; Roller position deviation; 4) Poor forming (the height difference between the two sides of the formed tube blank is large; 5) The opening slit width is above 150mm); 6) Due to pressure fluctuations in the hydraulic system;
2. Welding bumps and burn-through on the back. If the welding bump on the back is time-consuming, it will affect the normal production process; no, it will affect the welding shape of the inner welding and the tracking of the inner welding seam. Burn-through affects internal and external welding and needs to be filled. The causes of back weld bumps and burn-through are generally ① not tight joints, or the pressure of the hydraulic system may be too low; ② poor forming and large deviation of roundness; ③ improper selection of pre-welding process parameters. The welding current and arc voltage should be matched with an appropriate welding speed. If the line energy is too large or the welding speed is too low, it is easy to produce back welding bumps and burn through.
3. Stomata. Porosity in pre-welded welds causes internal defects in internal and external welds. Pores in pre-welded welds are generally caused by ① poor shielding gas, such as moisture content, insufficient pressure flow, etc.; ② partial blockage of the welding torch, resulting in uneven gas shields and harmful gases; ③ rust on the groove, Oil pollution, etc.
4. Poor weld formation. Poor weld formation affects subsequent internal and external welding tracking, affects the stability of the welding process, and thus affects welding. Welding seam formation is closely related to line energy, welding current, arc voltage, welding speed increase, weld penetration depth, and fusion width decrease, resulting in poor weld formation. Poor weld formation often occurs when porosity occurs in the weld.
5. Splash. Splash during pre-welding is easy to burn the surface or groove of the steel pipe, thus affecting the welding and the outer surface of the steel pipe. The main reason for splashing is that the protective gas composition is incorrect or the process parameters are incorrect, and the proportion of argon in the protective gas should be adjusted.
Post time: Apr-17-2023