Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. It is usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe and so on. The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe, and the welded pipe with a larger diameter can be produced with a narrower billet, and welded pipes with different diameters can be produced with the same width billet. But compared with the straight seam pipe of the same length, the weld length is increased by 30~100%, and the production speed is lower.
Straight seam steel pipe inspection steps:
1. 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.
2. The inspection items, sampling quantity, sampling location and test method of straight seam steel pipe shall be in accordance with the provisions of the corresponding product standards. With the consent of the purchaser, hot-rolled seamless straight seam steel pipes can be sampled in batches according to the number of rolling roots.
3. 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 for inspection of unqualified items. 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. The following inspection items, if the preliminary inspection fails, re-inspection is not allowed: 1) There are white spots in the low-magnification structure; 2) Microstructure.
4. 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.
5. 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
Straight seam steel pipe derusting method:
1. Cleaning: Solvents and emulsions are used to clean the steel surface to remove oil, grease, dust, lubricants and similar organic matter, but it cannot remove rust, scale, welding flux, etc. on the steel surface, so it is only used in anti-corrosion operations. Auxiliary means.
2. Pickling: Chemical and electrolytic pickling are used for pickling treatment. Only chemical pickling is used for pipeline anticorrosion, which can remove scale, rust, and old coatings. Sometimes it can be used as retreatment after sandblasting and rust removal. Although chemical cleaning can achieve the cleanliness and roughness of the surface, its anchor pattern is shallow and it is easy to pollute the surrounding environment.
3. Tool derusting: Use wire brushes and other tools to polish the steel surface to remove loose scale, rust, welding slag, etc. Hand tool derusting can reach Sa2 level, and power tool derusting can reach Sa3 level. If the iron oxide scale is firmly attached to the surface of the steel, the derusting effect of the tool is not ideal, and the anchor pattern depth required for anti-corrosion construction cannot be reached.
4. Spray rust removal: Rust removal is driven by a high-power motor to rotate the spray blades at high speed, so that steel shot, steel sand, iron wire segment, minerals and other abrasives are sprayed on the surface of the straight seam steel pipe under the powerful centrifugal force of the motor, not only Oxide, rust and dirt can be eliminated, and the straight seam steel pipe can still achieve the required uniform roughness under the action of violent impact and friction of abrasives.
After spray derusting, not only the physical adsorption on the surface of the pipe can be expanded, but also the mechanical adhesion between the anti-corrosion layer and the surface of the pipe can be enhanced. Therefore, spray rust removal is an ideal rust removal method for pipeline corrosion. Generally speaking, shot blasting is mainly used for inner surface treatment of pipes, and shot blasting is mainly used for outer surface treatment of straight seam steel pipes.
Post time: Mar-27-2023